kernel/fork.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  linux/kernel/fork.c
   4  *
   5  *  Copyright (C) 1991, 1992  Linus Torvalds
   6  */
   7
   8 /*
   9  *  'fork.c' contains the help-routines for the 'fork' system call
  10  * (see also entry.S and others).
  11  * Fork is rather simple, once you get the hang of it, but the memory
  12  * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
  13  */
  14
  15 #include <linux/anon_inodes.h>
  16 #include <linux/slab.h>
  17 #include <linux/sched/autogroup.h>
  18 #include <linux/sched/mm.h>
  19 #include <linux/sched/coredump.h>
  20 #include <linux/sched/user.h>
  21 #include <linux/sched/numa_balancing.h>
  22 #include <linux/sched/stat.h>
  23 #include <linux/sched/task.h>
  24 #include <linux/sched/task_stack.h>
  25 #include <linux/sched/cputime.h>
  26 #include <linux/seq_file.h>
  27 #include <linux/rtmutex.h>
  28 #include <linux/init.h>
  29 #include <linux/unistd.h>
  30 #include <linux/module.h>
  31 #include <linux/vmalloc.h>
  32 #include <linux/completion.h>
  33 #include <linux/personality.h>
  34 #include <linux/mempolicy.h>
  35 #include <linux/sem.h>
  36 #include <linux/file.h>
  37 #include <linux/fdtable.h>
  38 #include <linux/iocontext.h>
  39 #include <linux/key.h>
  40 #include <linux/binfmts.h>
  41 #include <linux/mman.h>
  42 #include <linux/mmu_notifier.h>
  43 #include <linux/hmm.h>
  44 #include <linux/fs.h>
  45 #include <linux/mm.h>
  46 #include <linux/vmacache.h>
  47 #include <linux/nsproxy.h>
  48 #include <linux/capability.h>
  49 #include <linux/cpu.h>
  50 #include <linux/cgroup.h>
  51 #include <linux/security.h>
  52 #include <linux/hugetlb.h>
  53 #include <linux/seccomp.h>
  54 #include <linux/swap.h>
  55 #include <linux/syscalls.h>
  56 #include <linux/jiffies.h>
  57 #include <linux/futex.h>
  58 #include <linux/compat.h>
  59 #include <linux/kthread.h>
  60 #include <linux/task_io_accounting_ops.h>
  61 #include <linux/rcupdate.h>
  62 #include <linux/ptrace.h>
  63 #include <linux/mount.h>
  64 #include <linux/audit.h>
  65 #include <linux/memcontrol.h>
  66 #include <linux/ftrace.h>
  67 #include <linux/proc_fs.h>
  68 #include <linux/profile.h>
  69 #include <linux/rmap.h>
  70 #include <linux/ksm.h>
  71 #include <linux/acct.h>
  72 #include <linux/userfaultfd_k.h>
  73 #include <linux/tsacct_kern.h>
  74 #include <linux/cn_proc.h>
  75 #include <linux/freezer.h>
  76 #include <linux/delayacct.h>
  77 #include <linux/taskstats_kern.h>
  78 #include <linux/random.h>
  79 #include <linux/tty.h>
  80 #include <linux/blkdev.h>
  81 #include <linux/fs_struct.h>
  82 #include <linux/magic.h>
  83 #include <linux/perf_event.h>
  84 #include <linux/posix-timers.h>
  85 #include <linux/user-return-notifier.h>
  86 #include <linux/oom.h>
  87 #include <linux/khugepaged.h>
  88 #include <linux/signalfd.h>
  89 #include <linux/uprobes.h>
  90 #include <linux/aio.h>
  91 #include <linux/compiler.h>
  92 #include <linux/sysctl.h>
  93 #include <linux/kcov.h>
  94 #include <linux/livepatch.h>
  95 #include <linux/thread_info.h>
  96 #include <linux/stackleak.h>
  97
  98 #include <asm/pgtable.h>
  99 #include <asm/pgalloc.h>
 100 #include <linux/uaccess.h>
 101 #include <asm/mmu_context.h>
 102 #include <asm/cacheflush.h>
 103 #include <asm/tlbflush.h>
 104
 105 #include <trace/events/sched.h>
 106
 107 #define CREATE_TRACE_POINTS
 108 #include <trace/events/task.h>
 109
 110 /*
 111  * Minimum number of threads to boot the kernel
 112  */
 113 #define MIN_THREADS 20
 114
 115 /*
 116  * Maximum number of threads
 117  */
 118 #define MAX_THREADS FUTEX_TID_MASK
 119
 120 /*
 121  * Protected counters by write_lock_irq(&tasklist_lock)
 122  */
 123 unsigned long total_forks;      /* Handle normal Linux uptimes. */
 124 int nr_threads;                 /* The idle threads do not count.. */
 125
 126 static int max_threads;         /* tunable limit on nr_threads */
 127
 128 #define NAMED_ARRAY_INDEX(x)    [x] = __stringify(x)
 129
 130 static const char * const resident_page_types[] = {
 131         NAMED_ARRAY_INDEX(MM_FILEPAGES),
 132         NAMED_ARRAY_INDEX(MM_ANONPAGES),
 133         NAMED_ARRAY_INDEX(MM_SWAPENTS),
 134         NAMED_ARRAY_INDEX(MM_SHMEMPAGES),
 135 };
 136
 137 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
 138
 139 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
 140
 141 #ifdef CONFIG_PROVE_RCU
 142 int lockdep_tasklist_lock_is_held(void)
 143 {
 144         return lockdep_is_held(&tasklist_lock);
 145 }
 146 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
 147 #endif /* #ifdef CONFIG_PROVE_RCU */
 148
 149 int nr_processes(void)
 150 {
 151         int cpu;
 152         int total = 0;
 153
 154         for_each_possible_cpu(cpu)
 155                 total += per_cpu(process_counts, cpu);
 156
 157         return total;
 158 }
 159
 160 void __weak arch_release_task_struct(struct task_struct *tsk)
 161 {
 162 }
 163
 164 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
 165 static struct kmem_cache *task_struct_cachep;
 166
 167 static inline struct task_struct *alloc_task_struct_node(int node)
 168 {
 169         return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
 170 }
 171
 172 static inline void free_task_struct(struct task_struct *tsk)
 173 {
 174         kmem_cache_free(task_struct_cachep, tsk);
 175 }
 176 #endif
 177
 178 #ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR
 179
 180 /*
 181  * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
 182  * kmemcache based allocator.
 183  */
 184 # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
 185
 186 #ifdef CONFIG_VMAP_STACK
 187 /*
 188  * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
 189  * flush.  Try to minimize the number of calls by caching stacks.
 190  */
 191 #define NR_CACHED_STACKS 2
 192 static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
 193
 194 static int free_vm_stack_cache(unsigned int cpu)
 195 {
 196         struct vm_struct **cached_vm_stacks = per_cpu_ptr(cached_stacks, cpu);
 197         int i;
 198
 199         for (i = 0; i < NR_CACHED_STACKS; i++) {
 200                 struct vm_struct *vm_stack = cached_vm_stacks[i];
 201
 202                 if (!vm_stack)
 203                         continue;
 204
 205                 vfree(vm_stack->addr);
 206                 cached_vm_stacks[i] = NULL;
 207         }
 208
 209         return 0;
 210 }
 211 #endif
 212
 213 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
 214 {
 215 #ifdef CONFIG_VMAP_STACK
 216         void *stack;
 217         int i;
 218
 219         for (i = 0; i < NR_CACHED_STACKS; i++) {
 220                 struct vm_struct *s;
 221
 222                 s = this_cpu_xchg(cached_stacks[i], NULL);
 223
 224                 if (!s)
 225                         continue;
 226
 227                 /* Clear stale pointers from reused stack. */
 228                 memset(s->addr, 0, THREAD_SIZE);
 229
 230                 tsk->stack_vm_area = s;
 231                 tsk->stack = s->addr;
 232                 return s->addr;
 233         }
 234
 235         /*
 236          * Allocated stacks are cached and later reused by new threads,
 237          * so memcg accounting is performed manually on assigning/releasing
 238          * stacks to tasks. Drop __GFP_ACCOUNT.
 239          */
 240         stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN,
 241                                      VMALLOC_START, VMALLOC_END,
 242                                      THREADINFO_GFP & ~__GFP_ACCOUNT,
 243                                      PAGE_KERNEL,
 244                                      0, node, __builtin_return_address(0));
 245
 246         /*
 247          * We can't call find_vm_area() in interrupt context, and
 248          * free_thread_stack() can be called in interrupt context,
 249          * so cache the vm_struct.
 250          */
 251         if (stack) {
 252                 tsk->stack_vm_area = find_vm_area(stack);
 253                 tsk->stack = stack;
 254         }
 255         return stack;
 256 #else
 257         struct page *page = alloc_pages_node(node, THREADINFO_GFP,
 258                                              THREAD_SIZE_ORDER);
 259
 260         if (likely(page)) {
 261                 tsk->stack = page_address(page);
 262                 return tsk->stack;
 263         }
 264         return NULL;
 265 #endif
 266 }
 267
 268 static inline void free_thread_stack(struct task_struct *tsk)
 269 {
 270 #ifdef CONFIG_VMAP_STACK
 271         struct vm_struct *vm = task_stack_vm_area(tsk);
 272
 273         if (vm) {
 274                 int i;
 275
 276                 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
 277                         mod_memcg_page_state(vm->pages[i],
 278                                              MEMCG_KERNEL_STACK_KB,
 279                                              -(int)(PAGE_SIZE / 1024));
 280
 281                         memcg_kmem_uncharge(vm->pages[i], 0);
 282                 }
 283
 284                 for (i = 0; i < NR_CACHED_STACKS; i++) {
 285                         if (this_cpu_cmpxchg(cached_stacks[i],
 286                                         NULL, tsk->stack_vm_area) != NULL)
 287                                 continue;
 288
 289                         return;
 290                 }
 291
 292                 vfree_atomic(tsk->stack);
 293                 return;
 294         }
 295 #endif
 296
 297         __free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER);
 298 }
 299 # else
 300 static struct kmem_cache *thread_stack_cache;
 301
 302 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk,
 303                                                   int node)
 304 {
 305         unsigned long *stack;
 306         stack = kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
 307         tsk->stack = stack;
 308         return stack;
 309 }
 310
 311 static void free_thread_stack(struct task_struct *tsk)
 312 {
 313         kmem_cache_free(thread_stack_cache, tsk->stack);
 314 }
 315
 316 void thread_stack_cache_init(void)
 317 {
 318         thread_stack_cache = kmem_cache_create_usercopy("thread_stack",
 319                                         THREAD_SIZE, THREAD_SIZE, 0, 0,
 320                                         THREAD_SIZE, NULL);
 321         BUG_ON(thread_stack_cache == NULL);
 322 }
 323 # endif
 324 #endif
 325
 326 /* SLAB cache for signal_struct structures (tsk->signal) */
 327 static struct kmem_cache *signal_cachep;
 328
 329 /* SLAB cache for sighand_struct structures (tsk->sighand) */
 330 struct kmem_cache *sighand_cachep;
 331
 332 /* SLAB cache for files_struct structures (tsk->files) */
 333 struct kmem_cache *files_cachep;
 334
 335 /* SLAB cache for fs_struct structures (tsk->fs) */
 336 struct kmem_cache *fs_cachep;
 337
 338 /* SLAB cache for vm_area_struct structures */
 339 static struct kmem_cache *vm_area_cachep;
 340
 341 /* SLAB cache for mm_struct structures (tsk->mm) */
 342 static struct kmem_cache *mm_cachep;
 343
 344 struct vm_area_struct *vm_area_alloc(struct mm_struct *mm)
 345 {
 346         struct vm_area_struct *vma;
 347
 348         vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 349         if (vma)
 350                 vma_init(vma, mm);
 351         return vma;
 352 }
 353
 354 struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
 355 {
 356         struct vm_area_struct *new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 357
 358         if (new) {
 359                 *new = *orig;
 360                 INIT_LIST_HEAD(&new->anon_vma_chain);
 361         }
 362         return new;
 363 }
 364
 365 void vm_area_free(struct vm_area_struct *vma)
 366 {
 367         kmem_cache_free(vm_area_cachep, vma);
 368 }
 369
 370 static void account_kernel_stack(struct task_struct *tsk, int account)
 371 {
 372         void *stack = task_stack_page(tsk);
 373         struct vm_struct *vm = task_stack_vm_area(tsk);
 374
 375         BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);
 376
 377         if (vm) {
 378                 int i;
 379
 380                 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
 381
 382                 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
 383                         mod_zone_page_state(page_zone(vm->pages[i]),
 384                                             NR_KERNEL_STACK_KB,
 385                                             PAGE_SIZE / 1024 * account);
 386                 }
 387         } else {
 388                 /*
 389                  * All stack pages are in the same zone and belong to the
 390                  * same memcg.
 391                  */
 392                 struct page *first_page = virt_to_page(stack);
 393
 394                 mod_zone_page_state(page_zone(first_page), NR_KERNEL_STACK_KB,
 395                                     THREAD_SIZE / 1024 * account);
 396
 397                 mod_memcg_obj_state(stack, MEMCG_KERNEL_STACK_KB,
 398                                     account * (THREAD_SIZE / 1024));
 399         }
 400 }
 401
 402 static int memcg_charge_kernel_stack(struct task_struct *tsk)
 403 {
 404 #ifdef CONFIG_VMAP_STACK
 405         struct vm_struct *vm = task_stack_vm_area(tsk);
 406         int ret;
 407
 408         if (vm) {
 409                 int i;
 410
 411                 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
 412                         /*
 413                          * If memcg_kmem_charge() fails, page->mem_cgroup
 414                          * pointer is NULL, and both memcg_kmem_uncharge()
 415                          * and mod_memcg_page_state() in free_thread_stack()
 416                          * will ignore this page. So it's safe.
 417                          */
 418                         ret = memcg_kmem_charge(vm->pages[i], GFP_KERNEL, 0);
 419                         if (ret)
 420                                 return ret;
 421
 422                         mod_memcg_page_state(vm->pages[i],
 423                                              MEMCG_KERNEL_STACK_KB,
 424                                              PAGE_SIZE / 1024);
 425                 }
 426         }
 427 #endif
 428         return 0;
 429 }
 430
 431 static void release_task_stack(struct task_struct *tsk)
 432 {
 433         if (WARN_ON(tsk->state != TASK_DEAD))
 434                 return;  /* Better to leak the stack than to free prematurely */
 435
 436         account_kernel_stack(tsk, -1);
 437         free_thread_stack(tsk);
 438         tsk->stack = NULL;
 439 #ifdef CONFIG_VMAP_STACK
 440         tsk->stack_vm_area = NULL;
 441 #endif
 442 }
 443
 444 #ifdef CONFIG_THREAD_INFO_IN_TASK
 445 void put_task_stack(struct task_struct *tsk)
 446 {
 447         if (refcount_dec_and_test(&tsk->stack_refcount))
 448                 release_task_stack(tsk);
 449 }
 450 #endif
 451
 452 void free_task(struct task_struct *tsk)
 453 {
 454 #ifndef CONFIG_THREAD_INFO_IN_TASK
 455         /*
 456          * The task is finally done with both the stack and thread_info,
 457          * so free both.
 458          */
 459         release_task_stack(tsk);
 460 #else
 461         /*
 462          * If the task had a separate stack allocation, it should be gone
 463          * by now.
 464          */
 465         WARN_ON_ONCE(refcount_read(&tsk->stack_refcount) != 0);
 466 #endif
 467         rt_mutex_debug_task_free(tsk);
 468         ftrace_graph_exit_task(tsk);
 469         put_seccomp_filter(tsk);
 470         arch_release_task_struct(tsk);
 471         if (tsk->flags & PF_KTHREAD)
 472                 free_kthread_struct(tsk);
 473         free_task_struct(tsk);
 474 }
 475 EXPORT_SYMBOL(free_task);
 476
 477 #ifdef CONFIG_MMU
 478 static __latent_entropy int dup_mmap(struct mm_struct *mm,
 479                                         struct mm_struct *oldmm)
 480 {
 481         struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
 482         struct rb_node **rb_link, *rb_parent;
 483         int retval;
 484         unsigned long charge;
 485         LIST_HEAD(uf);
 486
 487         uprobe_start_dup_mmap();
 488         if (down_write_killable(&oldmm->mmap_sem)) {
 489                 retval = -EINTR;
 490                 goto fail_uprobe_end;
 491         }
 492         flush_cache_dup_mm(oldmm);
 493         uprobe_dup_mmap(oldmm, mm);
 494         /*
 495          * Not linked in yet - no deadlock potential:
 496          */
 497         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
 498
 499         /* No ordering required: file already has been exposed. */
 500         RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
 501
 502         mm->total_vm = oldmm->total_vm;
 503         mm->data_vm = oldmm->data_vm;
 504         mm->exec_vm = oldmm->exec_vm;
 505         mm->stack_vm = oldmm->stack_vm;
 506
 507         rb_link = &mm->mm_rb.rb_node;
 508         rb_parent = NULL;
 509         pprev = &mm->mmap;
 510         retval = ksm_fork(mm, oldmm);
 511         if (retval)
 512                 goto out;
 513         retval = khugepaged_fork(mm, oldmm);
 514         if (retval)
 515                 goto out;
 516
 517         prev = NULL;
 518         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
 519                 struct file *file;
 520
 521                 if (mpnt->vm_flags & VM_DONTCOPY) {
 522                         vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
 523                         continue;
 524                 }
 525                 charge = 0;
 526                 /*
 527                  * Don't duplicate many vmas if we've been oom-killed (for
 528                  * example)
 529                  */
 530                 if (fatal_signal_pending(current)) {
 531                         retval = -EINTR;
 532                         goto out;
 533                 }
 534                 if (mpnt->vm_flags & VM_ACCOUNT) {
 535                         unsigned long len = vma_pages(mpnt);
 536
 537                         if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
 538                                 goto fail_nomem;
 539                         charge = len;
 540                 }
 541                 tmp = vm_area_dup(mpnt);
 542                 if (!tmp)
 543                         goto fail_nomem;
 544                 retval = vma_dup_policy(mpnt, tmp);
 545                 if (retval)
 546                         goto fail_nomem_policy;
 547                 tmp->vm_mm = mm;
 548                 retval = dup_userfaultfd(tmp, &uf);
 549                 if (retval)
 550                         goto fail_nomem_anon_vma_fork;
 551                 if (tmp->vm_flags & VM_WIPEONFORK) {
 552                         /* VM_WIPEONFORK gets a clean slate in the child. */
 553                         tmp->anon_vma = NULL;
 554                         if (anon_vma_prepare(tmp))
 555                                 goto fail_nomem_anon_vma_fork;
 556                 } else if (anon_vma_fork(tmp, mpnt))
 557                         goto fail_nomem_anon_vma_fork;
 558                 tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT);
 559                 tmp->vm_next = tmp->vm_prev = NULL;
 560                 file = tmp->vm_file;
 561                 if (file) {
 562                         struct inode *inode = file_inode(file);
 563                         struct address_space *mapping = file->f_mapping;
 564
 565                         get_file(file);
 566                         if (tmp->vm_flags & VM_DENYWRITE)
 567                                 atomic_dec(&inode->i_writecount);
 568                         i_mmap_lock_write(mapping);
 569                         if (tmp->vm_flags & VM_SHARED)
 570                                 atomic_inc(&mapping->i_mmap_writable);
 571                         flush_dcache_mmap_lock(mapping);
 572                         /* insert tmp into the share list, just after mpnt */
 573                         vma_interval_tree_insert_after(tmp, mpnt,
 574                                         &mapping->i_mmap);
 575                         flush_dcache_mmap_unlock(mapping);
 576                         i_mmap_unlock_write(mapping);
 577                 }
 578
 579                 /*
 580                  * Clear hugetlb-related page reserves for children. This only
 581                  * affects MAP_PRIVATE mappings. Faults generated by the child
 582                  * are not guaranteed to succeed, even if read-only
 583                  */
 584                 if (is_vm_hugetlb_page(tmp))
 585                         reset_vma_resv_huge_pages(tmp);
 586
 587                 /*
 588                  * Link in the new vma and copy the page table entries.
 589                  */
 590                 *pprev = tmp;
 591                 pprev = &tmp->vm_next;
 592                 tmp->vm_prev = prev;
 593                 prev = tmp;
 594
 595                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
 596                 rb_link = &tmp->vm_rb.rb_right;
 597                 rb_parent = &tmp->vm_rb;
 598
 599                 mm->map_count++;
 600                 if (!(tmp->vm_flags & VM_WIPEONFORK))
 601                         retval = copy_page_range(mm, oldmm, mpnt);
 602
 603                 if (tmp->vm_ops && tmp->vm_ops->open)
 604                         tmp->vm_ops->open(tmp);
 605
 606                 if (retval)
 607                         goto out;
 608         }
 609         /* a new mm has just been created */
 610         retval = arch_dup_mmap(oldmm, mm);
 611 out:
 612         up_write(&mm->mmap_sem);
 613         flush_tlb_mm(oldmm);
 614         up_write(&oldmm->mmap_sem);
 615         dup_userfaultfd_complete(&uf);
 616 fail_uprobe_end:
 617         uprobe_end_dup_mmap();
 618         return retval;
 619 fail_nomem_anon_vma_fork:
 620         mpol_put(vma_policy(tmp));
 621 fail_nomem_policy:
 622         vm_area_free(tmp);
 623 fail_nomem:
 624         retval = -ENOMEM;
 625         vm_unacct_memory(charge);
 626         goto out;
 627 }
 628
 629 static inline int mm_alloc_pgd(struct mm_struct *mm)
 630 {
 631         mm->pgd = pgd_alloc(mm);
 632         if (unlikely(!mm->pgd))
 633                 return -ENOMEM;
 634         return 0;
 635 }
 636
 637 static inline void mm_free_pgd(struct mm_struct *mm)
 638 {
 639         pgd_free(mm, mm->pgd);
 640 }
 641 #else
 642 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 643 {
 644         down_write(&oldmm->mmap_sem);
 645         RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
 646         up_write(&oldmm->mmap_sem);
 647         return 0;
 648 }
 649 #define mm_alloc_pgd(mm)        (0)
 650 #define mm_free_pgd(mm)
 651 #endif /* CONFIG_MMU */
 652
 653 static void check_mm(struct mm_struct *mm)
 654 {
 655         int i;
 656
 657         BUILD_BUG_ON_MSG(ARRAY_SIZE(resident_page_types) != NR_MM_COUNTERS,
 658                          "Please make sure 'struct resident_page_types[]' is updated as well");
 659
 660         for (i = 0; i < NR_MM_COUNTERS; i++) {
 661                 long x = atomic_long_read(&mm->rss_stat.count[i]);
 662
 663                 if (unlikely(x))
 664                         pr_alert("BUG: Bad rss-counter state mm:%p type:%s val:%ld\n",
 665                                  mm, resident_page_types[i], x);
 666         }
 667
 668         if (mm_pgtables_bytes(mm))
 669                 pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n",
 670                                 mm_pgtables_bytes(mm));
 671
 672 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
 673         VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
 674 #endif
 675 }
 676
 677 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
 678 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
 679
 680 /*
 681  * Called when the last reference to the mm
 682  * is dropped: either by a lazy thread or by
 683  * mmput. Free the page directory and the mm.
 684  */
 685 void __mmdrop(struct mm_struct *mm)
 686 {
 687         BUG_ON(mm == &init_mm);
 688         WARN_ON_ONCE(mm == current->mm);
 689         WARN_ON_ONCE(mm == current->active_mm);
 690         mm_free_pgd(mm);
 691         destroy_context(mm);
 692         mmu_notifier_mm_destroy(mm);
 693         check_mm(mm);
 694         put_user_ns(mm->user_ns);
 695         free_mm(mm);
 696 }
 697 EXPORT_SYMBOL_GPL(__mmdrop);
 698
 699 static void mmdrop_async_fn(struct work_struct *work)
 700 {
 701         struct mm_struct *mm;
 702
 703         mm = container_of(work, struct mm_struct, async_put_work);
 704         __mmdrop(mm);
 705 }
 706
 707 static void mmdrop_async(struct mm_struct *mm)
 708 {
 709         if (unlikely(atomic_dec_and_test(&mm->mm_count))) {
 710                 INIT_WORK(&mm->async_put_work, mmdrop_async_fn);
 711                 schedule_work(&mm->async_put_work);
 712         }
 713 }
 714
 715 static inline void free_signal_struct(struct signal_struct *sig)
 716 {
 717         taskstats_tgid_free(sig);
 718         sched_autogroup_exit(sig);
 719         /*
 720          * __mmdrop is not safe to call from softirq context on x86 due to
 721          * pgd_dtor so postpone it to the async context
 722          */
 723         if (sig->oom_mm)
 724                 mmdrop_async(sig->oom_mm);
 725         kmem_cache_free(signal_cachep, sig);
 726 }
 727
 728 static inline void put_signal_struct(struct signal_struct *sig)
 729 {
 730         if (refcount_dec_and_test(&sig->sigcnt))
 731                 free_signal_struct(sig);
 732 }
 733
 734 void __put_task_struct(struct task_struct *tsk)
 735 {
 736         WARN_ON(!tsk->exit_state);
 737         WARN_ON(refcount_read(&tsk->usage));
 738         WARN_ON(tsk == current);
 739
 740         cgroup_free(tsk);
 741         task_numa_free(tsk, true);
 742         security_task_free(tsk);
 743         exit_creds(tsk);
 744         delayacct_tsk_free(tsk);
 745         put_signal_struct(tsk->signal);
 746
 747         if (!profile_handoff_task(tsk))
 748                 free_task(tsk);
 749 }
 750 EXPORT_SYMBOL_GPL(__put_task_struct);
 751
 752 void __init __weak arch_task_cache_init(void) { }
 753
 754 /*
 755  * set_max_threads
 756  */
 757 static void set_max_threads(unsigned int max_threads_suggested)
 758 {
 759         u64 threads;
 760         unsigned long nr_pages = totalram_pages();
 761
 762         /*
 763          * The number of threads shall be limited such that the thread
 764          * structures may only consume a small part of the available memory.
 765          */
 766         if (fls64(nr_pages) + fls64(PAGE_SIZE) > 64)
 767                 threads = MAX_THREADS;
 768         else
 769                 threads = div64_u64((u64) nr_pages * (u64) PAGE_SIZE,
 770                                     (u64) THREAD_SIZE * 8UL);
 771
 772         if (threads > max_threads_suggested)
 773                 threads = max_threads_suggested;
 774
 775         max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
 776 }
 777
 778 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
 779 /* Initialized by the architecture: */
 780 int arch_task_struct_size __read_mostly;
 781 #endif
 782
 783 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
 784 static void task_struct_whitelist(unsigned long *offset, unsigned long *size)
 785 {
 786         /* Fetch thread_struct whitelist for the architecture. */
 787         arch_thread_struct_whitelist(offset, size);
 788
 789         /*
 790          * Handle zero-sized whitelist or empty thread_struct, otherwise
 791          * adjust offset to position of thread_struct in task_struct.
 792          */
 793         if (unlikely(*size == 0))
 794                 *offset = 0;
 795         else
 796                 *offset += offsetof(struct task_struct, thread);
 797 }
 798 #endif /* CONFIG_ARCH_TASK_STRUCT_ALLOCATOR */
 799
 800 void __init fork_init(void)
 801 {
 802         int i;
 803 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
 804 #ifndef ARCH_MIN_TASKALIGN
 805 #define ARCH_MIN_TASKALIGN      0
 806 #endif
 807         int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN);
 808         unsigned long useroffset, usersize;
 809
 810         /* create a slab on which task_structs can be allocated */
 811         task_struct_whitelist(&useroffset, &usersize);
 812         task_struct_cachep = kmem_cache_create_usercopy("task_struct",
 813                         arch_task_struct_size, align,
 814                         SLAB_PANIC|SLAB_ACCOUNT,
 815                         useroffset, usersize, NULL);
 816 #endif
 817
 818         /* do the arch specific task caches init */
 819         arch_task_cache_init();
 820
 821         set_max_threads(MAX_THREADS);
 822
 823         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
 824         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
 825         init_task.signal->rlim[RLIMIT_SIGPENDING] =
 826                 init_task.signal->rlim[RLIMIT_NPROC];
 827
 828         for (i = 0; i < UCOUNT_COUNTS; i++) {
 829                 init_user_ns.ucount_max[i] = max_threads/2;
 830         }
 831
 832 #ifdef CONFIG_VMAP_STACK
 833         cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache",
 834                           NULL, free_vm_stack_cache);
 835 #endif
 836
 837         lockdep_init_task(&init_task);
 838         uprobes_init();
 839 }
 840
 841 int __weak arch_dup_task_struct(struct task_struct *dst,
 842                                                struct task_struct *src)
 843 {
 844         *dst = *src;
 845         return 0;
 846 }
 847
 848 void set_task_stack_end_magic(struct task_struct *tsk)
 849 {
 850         unsigned long *stackend;
 851
 852         stackend = end_of_stack(tsk);
 853         *stackend = STACK_END_MAGIC;    /* for overflow detection */
 854 }
 855
 856 static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
 857 {
 858         struct task_struct *tsk;
 859         unsigned long *stack;
 860         struct vm_struct *stack_vm_area __maybe_unused;
 861         int err;
 862
 863         if (node == NUMA_NO_NODE)
 864                 node = tsk_fork_get_node(orig);
 865         tsk = alloc_task_struct_node(node);
 866         if (!tsk)
 867                 return NULL;
 868
 869         stack = alloc_thread_stack_node(tsk, node);
 870         if (!stack)
 871                 goto free_tsk;
 872
 873         if (memcg_charge_kernel_stack(tsk))
 874                 goto free_stack;
 875
 876         stack_vm_area = task_stack_vm_area(tsk);
 877
 878         err = arch_dup_task_struct(tsk, orig);
 879
 880         /*
 881          * arch_dup_task_struct() clobbers the stack-related fields.  Make
 882          * sure they're properly initialized before using any stack-related
 883          * functions again.
 884          */
 885         tsk->stack = stack;
 886 #ifdef CONFIG_VMAP_STACK
 887         tsk->stack_vm_area = stack_vm_area;
 888 #endif
 889 #ifdef CONFIG_THREAD_INFO_IN_TASK
 890         refcount_set(&tsk->stack_refcount, 1);
 891 #endif
 892
 893         if (err)
 894                 goto free_stack;
 895
 896 #ifdef CONFIG_SECCOMP
 897         /*
 898          * We must handle setting up seccomp filters once we're under
 899          * the sighand lock in case orig has changed between now and
 900          * then. Until then, filter must be NULL to avoid messing up
 901          * the usage counts on the error path calling free_task.
 902          */
 903         tsk->seccomp.filter = NULL;
 904 #endif
 905
 906         setup_thread_stack(tsk, orig);
 907         clear_user_return_notifier(tsk);
 908         clear_tsk_need_resched(tsk);
 909         set_task_stack_end_magic(tsk);
 910
 911 #ifdef CONFIG_STACKPROTECTOR
 912         tsk->stack_canary = get_random_canary();
 913 #endif
 914         if (orig->cpus_ptr == &orig->cpus_mask)
 915                 tsk->cpus_ptr = &tsk->cpus_mask;
 916
 917         /*
 918          * One for the user space visible state that goes away when reaped.
 919          * One for the scheduler.
 920          */
 921         refcount_set(&tsk->rcu_users, 2);
 922         /* One for the rcu users */
 923         refcount_set(&tsk->usage, 1);
 924 #ifdef CONFIG_BLK_DEV_IO_TRACE
 925         tsk->btrace_seq = 0;
 926 #endif
 927         tsk->splice_pipe = NULL;
 928         tsk->task_frag.page = NULL;
 929         tsk->wake_q.next = NULL;
 930
 931         account_kernel_stack(tsk, 1);
 932
 933         kcov_task_init(tsk);
 934
 935 #ifdef CONFIG_FAULT_INJECTION
 936         tsk->fail_nth = 0;
 937 #endif
 938
 939 #ifdef CONFIG_BLK_CGROUP
 940         tsk->throttle_queue = NULL;
 941         tsk->use_memdelay = 0;
 942 #endif
 943
 944 #ifdef CONFIG_MEMCG
 945         tsk->active_memcg = NULL;
 946 #endif
 947         return tsk;
 948
 949 free_stack:
 950         free_thread_stack(tsk);
 951 free_tsk:
 952         free_task_struct(tsk);
 953         return NULL;
 954 }
 955
 956 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
 957
 958 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
 959
 960 static int __init coredump_filter_setup(char *s)
 961 {
 962         default_dump_filter =
 963                 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
 964                 MMF_DUMP_FILTER_MASK;
 965         return 1;
 966 }
 967
 968 __setup("coredump_filter=", coredump_filter_setup);
 969
 970 #include <linux/init_task.h>
 971
 972 static void mm_init_aio(struct mm_struct *mm)
 973 {
 974 #ifdef CONFIG_AIO
 975         spin_lock_init(&mm->ioctx_lock);
 976         mm->ioctx_table = NULL;
 977 #endif
 978 }
 979
 980 static __always_inline void mm_clear_owner(struct mm_struct *mm,
 981                                            struct task_struct *p)
 982 {
 983 #ifdef CONFIG_MEMCG
 984         if (mm->owner == p)
 985                 WRITE_ONCE(mm->owner, NULL);
 986 #endif
 987 }
 988
 989 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
 990 {
 991 #ifdef CONFIG_MEMCG
 992         mm->owner = p;
 993 #endif
 994 }
 995
 996 static void mm_init_uprobes_state(struct mm_struct *mm)
 997 {
 998 #ifdef CONFIG_UPROBES
 999         mm->uprobes_state.xol_area = NULL;
1000 #endif
1001 }
1002
1003 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
1004         struct user_namespace *user_ns)
1005 {
1006         mm->mmap = NULL;
1007         mm->mm_rb = RB_ROOT;
1008         mm->vmacache_seqnum = 0;
1009         atomic_set(&mm->mm_users, 1);
1010         atomic_set(&mm->mm_count, 1);
1011         init_rwsem(&mm->mmap_sem);
1012         INIT_LIST_HEAD(&mm->mmlist);
1013         mm->core_state = NULL;
1014         mm_pgtables_bytes_init(mm);
1015         mm->map_count = 0;
1016         mm->locked_vm = 0;
1017         atomic64_set(&mm->pinned_vm, 0);
1018         memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
1019         spin_lock_init(&mm->page_table_lock);
1020         spin_lock_init(&mm->arg_lock);
1021         mm_init_cpumask(mm);
1022         mm_init_aio(mm);
1023         mm_init_owner(mm, p);
1024         RCU_INIT_POINTER(mm->exe_file, NULL);
1025         mmu_notifier_mm_init(mm);
1026         init_tlb_flush_pending(mm);
1027 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
1028         mm->pmd_huge_pte = NULL;
1029 #endif
1030         mm_init_uprobes_state(mm);
1031         hugetlb_count_init(mm);
1032
1033         if (current->mm) {
1034                 mm->flags = current->mm->flags & MMF_INIT_MASK;
1035                 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
1036         } else {
1037                 mm->flags = default_dump_filter;
1038                 mm->def_flags = 0;
1039         }
1040
1041         if (mm_alloc_pgd(mm))
1042                 goto fail_nopgd;
1043
1044         if (init_new_context(p, mm))
1045                 goto fail_nocontext;
1046
1047         mm->user_ns = get_user_ns(user_ns);
1048         return mm;
1049
1050 fail_nocontext:
1051         mm_free_pgd(mm);
1052 fail_nopgd:
1053         free_mm(mm);
1054         return NULL;
1055 }
1056
1057 /*
1058  * Allocate and initialize an mm_struct.
1059  */
1060 struct mm_struct *mm_alloc(void)
1061 {
1062         struct mm_struct *mm;
1063
1064         mm = allocate_mm();
1065         if (!mm)
1066                 return NULL;
1067
1068         memset(mm, 0, sizeof(*mm));
1069         return mm_init(mm, current, current_user_ns());
1070 }
1071
1072 static inline void __mmput(struct mm_struct *mm)
1073 {
1074         VM_BUG_ON(atomic_read(&mm->mm_users));
1075
1076         uprobe_clear_state(mm);
1077         exit_aio(mm);
1078         ksm_exit(mm);
1079         khugepaged_exit(mm); /* must run before exit_mmap */
1080         exit_mmap(mm);
1081         mm_put_huge_zero_page(mm);
1082         set_mm_exe_file(mm, NULL);
1083         if (!list_empty(&mm->mmlist)) {
1084                 spin_lock(&mmlist_lock);
1085                 list_del(&mm->mmlist);
1086                 spin_unlock(&mmlist_lock);
1087         }
1088         if (mm->binfmt)
1089                 module_put(mm->binfmt->module);
1090         mmdrop(mm);
1091 }
1092
1093 /*
1094  * Decrement the use count and release all resources for an mm.
1095  */
1096 void mmput(struct mm_struct *mm)
1097 {
1098         might_sleep();
1099
1100         if (atomic_dec_and_test(&mm->mm_users))
1101                 __mmput(mm);
1102 }
1103 EXPORT_SYMBOL_GPL(mmput);
1104
1105 #ifdef CONFIG_MMU
1106 static void mmput_async_fn(struct work_struct *work)
1107 {
1108         struct mm_struct *mm = container_of(work, struct mm_struct,
1109                                             async_put_work);
1110
1111         __mmput(mm);
1112 }
1113
1114 void mmput_async(struct mm_struct *mm)
1115 {
1116         if (atomic_dec_and_test(&mm->mm_users)) {
1117                 INIT_WORK(&mm->async_put_work, mmput_async_fn);
1118                 schedule_work(&mm->async_put_work);
1119         }
1120 }
1121 #endif
1122
1123 /**
1124  * set_mm_exe_file - change a reference to the mm's executable file
1125  *
1126  * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
1127  *
1128  * Main users are mmput() and sys_execve(). Callers prevent concurrent
1129  * invocations: in mmput() nobody alive left, in execve task is single
1130  * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the
1131  * mm->exe_file, but does so without using set_mm_exe_file() in order
1132  * to do avoid the need for any locks.
1133  */
1134 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
1135 {
1136         struct file *old_exe_file;
1137
1138         /*
1139          * It is safe to dereference the exe_file without RCU as
1140          * this function is only called if nobody else can access
1141          * this mm -- see comment above for justification.
1142          */
1143         old_exe_file = rcu_dereference_raw(mm->exe_file);
1144
1145         if (new_exe_file)
1146                 get_file(new_exe_file);
1147         rcu_assign_pointer(mm->exe_file, new_exe_file);
1148         if (old_exe_file)
1149                 fput(old_exe_file);
1150 }
1151
1152 /**
1153  * get_mm_exe_file - acquire a reference to the mm's executable file
1154  *
1155  * Returns %NULL if mm has no associated executable file.
1156  * User must release file via fput().
1157  */
1158 struct file *get_mm_exe_file(struct mm_struct *mm)
1159 {
1160         struct file *exe_file;
1161
1162         rcu_read_lock();
1163         exe_file = rcu_dereference(mm->exe_file);
1164         if (exe_file && !get_file_rcu(exe_file))
1165                 exe_file = NULL;
1166         rcu_read_unlock();
1167         return exe_file;
1168 }
1169 EXPORT_SYMBOL(get_mm_exe_file);
1170
1171 /**
1172  * get_task_exe_file - acquire a reference to the task's executable file
1173  *
1174  * Returns %NULL if task's mm (if any) has no associated executable file or
1175  * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
1176  * User must release file via fput().
1177  */
1178 struct file *get_task_exe_file(struct task_struct *task)
1179 {
1180         struct file *exe_file = NULL;
1181         struct mm_struct *mm;
1182
1183         task_lock(task);
1184         mm = task->mm;
1185         if (mm) {
1186                 if (!(task->flags & PF_KTHREAD))
1187                         exe_file = get_mm_exe_file(mm);
1188         }
1189         task_unlock(task);
1190         return exe_file;
1191 }
1192 EXPORT_SYMBOL(get_task_exe_file);
1193
1194 /**
1195  * get_task_mm - acquire a reference to the task's mm
1196  *
1197  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
1198  * this kernel workthread has transiently adopted a user mm with use_mm,
1199  * to do its AIO) is not set and if so returns a reference to it, after
1200  * bumping up the use count.  User must release the mm via mmput()
1201  * after use.  Typically used by /proc and ptrace.
1202  */
1203 struct mm_struct *get_task_mm(struct task_struct *task)
1204 {
1205         struct mm_struct *mm;
1206
1207         task_lock(task);
1208         mm = task->mm;
1209         if (mm) {
1210                 if (task->flags & PF_KTHREAD)
1211                         mm = NULL;
1212                 else
1213                         mmget(mm);
1214         }
1215         task_unlock(task);
1216         return mm;
1217 }
1218 EXPORT_SYMBOL_GPL(get_task_mm);
1219
1220 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
1221 {
1222         struct mm_struct *mm;
1223         int err;
1224
1225         err =  down_read_killable(&task->signal->exec_update_lock);
1226         if (err)
1227                 return ERR_PTR(err);
1228
1229         mm = get_task_mm(task);
1230         if (mm && mm != current->mm &&
1231                         !ptrace_may_access(task, mode)) {
1232                 mmput(mm);
1233                 mm = ERR_PTR(-EACCES);
1234         }
1235         up_read(&task->signal->exec_update_lock);
1236
1237         return mm;
1238 }
1239
1240 static void complete_vfork_done(struct task_struct *tsk)
1241 {
1242         struct completion *vfork;
1243
1244         task_lock(tsk);
1245         vfork = tsk->vfork_done;
1246         if (likely(vfork)) {
1247                 tsk->vfork_done = NULL;
1248                 complete(vfork);
1249         }
1250         task_unlock(tsk);
1251 }
1252
1253 static int wait_for_vfork_done(struct task_struct *child,
1254                                 struct completion *vfork)
1255 {
1256         int killed;
1257
1258         freezer_do_not_count();
1259         cgroup_enter_frozen();
1260         killed = wait_for_completion_killable(vfork);
1261         cgroup_leave_frozen(false);
1262         freezer_count();
1263
1264         if (killed) {
1265                 task_lock(child);
1266                 child->vfork_done = NULL;
1267                 task_unlock(child);
1268         }
1269
1270         put_task_struct(child);
1271         return killed;
1272 }
1273
1274 /* Please note the differences between mmput and mm_release.
1275  * mmput is called whenever we stop holding onto a mm_struct,
1276  * error success whatever.
1277  *
1278  * mm_release is called after a mm_struct has been removed
1279  * from the current process.
1280  *
1281  * This difference is important for error handling, when we
1282  * only half set up a mm_struct for a new process and need to restore
1283  * the old one.  Because we mmput the new mm_struct before
1284  * restoring the old one. . .
1285  * Eric Biederman 10 January 1998
1286  */
1287 static void mm_release(struct task_struct *tsk, struct mm_struct *mm)
1288 {
1289         uprobe_free_utask(tsk);
1290
1291         /* Get rid of any cached register state */
1292         deactivate_mm(tsk, mm);
1293
1294         /*
1295          * Signal userspace if we're not exiting with a core dump
1296          * because we want to leave the value intact for debugging
1297          * purposes.
1298          */
1299         if (tsk->clear_child_tid) {
1300                 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) &&
1301                     atomic_read(&mm->mm_users) > 1) {
1302                         /*
1303                          * We don't check the error code - if userspace has
1304                          * not set up a proper pointer then tough luck.
1305                          */
1306                         put_user(0, tsk->clear_child_tid);
1307                         do_futex(tsk->clear_child_tid, FUTEX_WAKE,
1308                                         1, NULL, NULL, 0, 0);
1309                 }
1310                 tsk->clear_child_tid = NULL;
1311         }
1312
1313         /*
1314          * All done, finally we can wake up parent and return this mm to him.
1315          * Also kthread_stop() uses this completion for synchronization.
1316          */
1317         if (tsk->vfork_done)
1318                 complete_vfork_done(tsk);
1319 }
1320
1321 void exit_mm_release(struct task_struct *tsk, struct mm_struct *mm)
1322 {
1323         futex_exit_release(tsk);
1324         mm_release(tsk, mm);
1325 }
1326
1327 void exec_mm_release(struct task_struct *tsk, struct mm_struct *mm)
1328 {
1329         futex_exec_release(tsk);
1330         mm_release(tsk, mm);
1331 }
1332
1333 /**
1334  * dup_mm() - duplicates an existing mm structure
1335  * @tsk: the task_struct with which the new mm will be associated.
1336  * @oldmm: the mm to duplicate.
1337  *
1338  * Allocates a new mm structure and duplicates the provided @oldmm structure
1339  * content into it.
1340  *
1341  * Return: the duplicated mm or NULL on failure.
1342  */
1343 static struct mm_struct *dup_mm(struct task_struct *tsk,
1344                                 struct mm_struct *oldmm)
1345 {
1346         struct mm_struct *mm;
1347         int err;
1348
1349         mm = allocate_mm();
1350         if (!mm)
1351                 goto fail_nomem;
1352
1353         memcpy(mm, oldmm, sizeof(*mm));
1354
1355         if (!mm_init(mm, tsk, mm->user_ns))
1356                 goto fail_nomem;
1357
1358         err = dup_mmap(mm, oldmm);
1359         if (err)
1360                 goto free_pt;
1361
1362         mm->hiwater_rss = get_mm_rss(mm);
1363         mm->hiwater_vm = mm->total_vm;
1364
1365         if (mm->binfmt && !try_module_get(mm->binfmt->module))
1366                 goto free_pt;
1367
1368         return mm;
1369
1370 free_pt:
1371         /* don't put binfmt in mmput, we haven't got module yet */
1372         mm->binfmt = NULL;
1373         mm_init_owner(mm, NULL);
1374         mmput(mm);
1375
1376 fail_nomem:
1377         return NULL;
1378 }
1379
1380 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
1381 {
1382         struct mm_struct *mm, *oldmm;
1383         int retval;
1384
1385         tsk->min_flt = tsk->maj_flt = 0;
1386         tsk->nvcsw = tsk->nivcsw = 0;
1387 #ifdef CONFIG_DETECT_HUNG_TASK
1388         tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
1389         tsk->last_switch_time = 0;
1390 #endif
1391
1392         tsk->mm = NULL;
1393         tsk->active_mm = NULL;
1394
1395         /*
1396          * Are we cloning a kernel thread?
1397          *
1398          * We need to steal a active VM for that..
1399          */
1400         oldmm = current->mm;
1401         if (!oldmm)
1402                 return 0;
1403
1404         /* initialize the new vmacache entries */
1405         vmacache_flush(tsk);
1406
1407         if (clone_flags & CLONE_VM) {
1408                 mmget(oldmm);
1409                 mm = oldmm;
1410                 goto good_mm;
1411         }
1412
1413         retval = -ENOMEM;
1414         mm = dup_mm(tsk, current->mm);
1415         if (!mm)
1416                 goto fail_nomem;
1417
1418 good_mm:
1419         tsk->mm = mm;
1420         tsk->active_mm = mm;
1421         return 0;
1422
1423 fail_nomem:
1424         return retval;
1425 }
1426
1427 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
1428 {
1429         struct fs_struct *fs = current->fs;
1430         if (clone_flags & CLONE_FS) {
1431                 /* tsk->fs is already what we want */
1432                 spin_lock(&fs->lock);
1433                 if (fs->in_exec) {
1434                         spin_unlock(&fs->lock);
1435                         return -EAGAIN;
1436                 }
1437                 fs->users++;
1438                 spin_unlock(&fs->lock);
1439                 return 0;
1440         }
1441         tsk->fs = copy_fs_struct(fs);
1442         if (!tsk->fs)
1443                 return -ENOMEM;
1444         return 0;
1445 }
1446
1447 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
1448 {
1449         struct files_struct *oldf, *newf;
1450         int error = 0;
1451
1452         /*
1453          * A background process may not have any files ...
1454          */
1455         oldf = current->files;
1456         if (!oldf)
1457                 goto out;
1458
1459         if (clone_flags & CLONE_FILES) {
1460                 atomic_inc(&oldf->count);
1461                 goto out;
1462         }
1463
1464         newf = dup_fd(oldf, &error);
1465         if (!newf)
1466                 goto out;
1467
1468         tsk->files = newf;
1469         error = 0;
1470 out:
1471         return error;
1472 }
1473
1474 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
1475 {
1476 #ifdef CONFIG_BLOCK
1477         struct io_context *ioc = current->io_context;
1478         struct io_context *new_ioc;
1479
1480         if (!ioc)
1481                 return 0;
1482         /*
1483          * Share io context with parent, if CLONE_IO is set
1484          */
1485         if (clone_flags & CLONE_IO) {
1486                 ioc_task_link(ioc);
1487                 tsk->io_context = ioc;
1488         } else if (ioprio_valid(ioc->ioprio)) {
1489                 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
1490                 if (unlikely(!new_ioc))
1491                         return -ENOMEM;
1492
1493                 new_ioc->ioprio = ioc->ioprio;
1494                 put_io_context(new_ioc);
1495         }
1496 #endif
1497         return 0;
1498 }
1499
1500 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1501 {
1502         struct sighand_struct *sig;
1503
1504         if (clone_flags & CLONE_SIGHAND) {
1505                 refcount_inc(&current->sighand->count);
1506                 return 0;
1507         }
1508         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1509         rcu_assign_pointer(tsk->sighand, sig);
1510         if (!sig)
1511                 return -ENOMEM;
1512
1513         refcount_set(&sig->count, 1);
1514         spin_lock_irq(&current->sighand->siglock);
1515         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1516         spin_unlock_irq(&current->sighand->siglock);
1517         return 0;
1518 }
1519
1520 void __cleanup_sighand(struct sighand_struct *sighand)
1521 {
1522         if (refcount_dec_and_test(&sighand->count)) {
1523                 signalfd_cleanup(sighand);
1524                 /*
1525                  * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it
1526                  * without an RCU grace period, see __lock_task_sighand().
1527                  */
1528                 kmem_cache_free(sighand_cachep, sighand);
1529         }
1530 }
1531
1532 /*
1533  * Initialize POSIX timer handling for a thread group.
1534  */
1535 static void posix_cpu_timers_init_group(struct signal_struct *sig)
1536 {
1537         struct posix_cputimers *pct = &sig->posix_cputimers;
1538         unsigned long cpu_limit;
1539
1540         cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1541         posix_cputimers_group_init(pct, cpu_limit);
1542 }
1543
1544 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1545 {
1546         struct signal_struct *sig;
1547
1548         if (clone_flags & CLONE_THREAD)
1549                 return 0;
1550
1551         sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1552         tsk->signal = sig;
1553         if (!sig)
1554                 return -ENOMEM;
1555
1556         sig->nr_threads = 1;
1557         atomic_set(&sig->live, 1);
1558         refcount_set(&sig->sigcnt, 1);
1559
1560         /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1561         sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1562         tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1563
1564         init_waitqueue_head(&sig->wait_chldexit);
1565         sig->curr_target = tsk;
1566         init_sigpending(&sig->shared_pending);
1567         INIT_HLIST_HEAD(&sig->multiprocess);
1568         seqlock_init(&sig->stats_lock);
1569         prev_cputime_init(&sig->prev_cputime);
1570
1571 #ifdef CONFIG_POSIX_TIMERS
1572         INIT_LIST_HEAD(&sig->posix_timers);
1573         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1574         sig->real_timer.function = it_real_fn;
1575 #endif
1576
1577         task_lock(current->group_leader);
1578         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1579         task_unlock(current->group_leader);
1580
1581         posix_cpu_timers_init_group(sig);
1582
1583         tty_audit_fork(sig);
1584         sched_autogroup_fork(sig);
1585
1586         sig->oom_score_adj = current->signal->oom_score_adj;
1587         sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1588
1589         mutex_init(&sig->cred_guard_mutex);
1590         init_rwsem(&sig->exec_update_lock);
1591
1592         return 0;
1593 }
1594
1595 static void copy_seccomp(struct task_struct *p)
1596 {
1597 #ifdef CONFIG_SECCOMP
1598         /*
1599          * Must be called with sighand->lock held, which is common to
1600          * all threads in the group. Holding cred_guard_mutex is not
1601          * needed because this new task is not yet running and cannot
1602          * be racing exec.
1603          */
1604         assert_spin_locked(&current->sighand->siglock);
1605
1606         /* Ref-count the new filter user, and assign it. */
1607         get_seccomp_filter(current);
1608         p->seccomp = current->seccomp;
1609
1610         /*
1611          * Explicitly enable no_new_privs here in case it got set
1612          * between the task_struct being duplicated and holding the
1613          * sighand lock. The seccomp state and nnp must be in sync.
1614          */
1615         if (task_no_new_privs(current))
1616                 task_set_no_new_privs(p);
1617
1618         /*
1619          * If the parent gained a seccomp mode after copying thread
1620          * flags and between before we held the sighand lock, we have
1621          * to manually enable the seccomp thread flag here.
1622          */
1623         if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1624                 set_tsk_thread_flag(p, TIF_SECCOMP);
1625 #endif
1626 }
1627
1628 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1629 {
1630         current->clear_child_tid = tidptr;
1631
1632         return task_pid_vnr(current);
1633 }
1634
1635 static void rt_mutex_init_task(struct task_struct *p)
1636 {
1637         raw_spin_lock_init(&p->pi_lock);
1638 #ifdef CONFIG_RT_MUTEXES
1639         p->pi_waiters = RB_ROOT_CACHED;
1640         p->pi_top_task = NULL;
1641         p->pi_blocked_on = NULL;
1642 #endif
1643 }
1644
1645 static inline void init_task_pid_links(struct task_struct *task)
1646 {
1647         enum pid_type type;
1648
1649         for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1650                 INIT_HLIST_NODE(&task->pid_links[type]);
1651         }
1652 }
1653
1654 static inline void
1655 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1656 {
1657         if (type == PIDTYPE_PID)
1658                 task->thread_pid = pid;
1659         else
1660                 task->signal->pids[type] = pid;
1661 }
1662
1663 static inline void rcu_copy_process(struct task_struct *p)
1664 {
1665 #ifdef CONFIG_PREEMPT_RCU
1666         p->rcu_read_lock_nesting = 0;
1667         p->rcu_read_unlock_special.s = 0;
1668         p->rcu_blocked_node = NULL;
1669         INIT_LIST_HEAD(&p->rcu_node_entry);
1670 #endif /* #ifdef CONFIG_PREEMPT_RCU */
1671 #ifdef CONFIG_TASKS_RCU
1672         p->rcu_tasks_holdout = false;
1673         INIT_LIST_HEAD(&p->rcu_tasks_holdout_list);
1674         p->rcu_tasks_idle_cpu = -1;
1675 #endif /* #ifdef CONFIG_TASKS_RCU */
1676 }
1677
1678 struct pid *pidfd_pid(const struct file *file)
1679 {
1680         if (file->f_op == &pidfd_fops)
1681                 return file->private_data;
1682
1683         return ERR_PTR(-EBADF);
1684 }
1685
1686 static int pidfd_release(struct inode *inode, struct file *file)
1687 {
1688         struct pid *pid = file->private_data;
1689
1690         file->private_data = NULL;
1691         put_pid(pid);
1692         return 0;
1693 }
1694
1695 #ifdef CONFIG_PROC_FS
1696 static void pidfd_show_fdinfo(struct seq_file *m, struct file *f)
1697 {
1698         struct pid_namespace *ns = proc_pid_ns(file_inode(m->file));
1699         struct pid *pid = f->private_data;
1700
1701         seq_put_decimal_ull(m, "Pid:\t", pid_nr_ns(pid, ns));
1702         seq_putc(m, '\n');
1703 }
1704 #endif
1705
1706 /*
1707  * Poll support for process exit notification.
1708  */
1709 static __poll_t pidfd_poll(struct file *file, struct poll_table_struct *pts)
1710 {
1711         struct task_struct *task;
1712         struct pid *pid = file->private_data;
1713         __poll_t poll_flags = 0;
1714
1715         poll_wait(file, &pid->wait_pidfd, pts);
1716
1717         rcu_read_lock();
1718         task = pid_task(pid, PIDTYPE_PID);
1719         /*
1720          * Inform pollers only when the whole thread group exits.
1721          * If the thread group leader exits before all other threads in the
1722          * group, then poll(2) should block, similar to the wait(2) family.
1723          */
1724         if (!task || (task->exit_state && thread_group_empty(task)))
1725                 poll_flags = EPOLLIN | EPOLLRDNORM;
1726         rcu_read_unlock();
1727
1728         return poll_flags;
1729 }
1730
1731 const struct file_operations pidfd_fops = {
1732         .release = pidfd_release,
1733         .poll = pidfd_poll,
1734 #ifdef CONFIG_PROC_FS
1735         .show_fdinfo = pidfd_show_fdinfo,
1736 #endif
1737 };
1738
1739 static void __delayed_free_task(struct rcu_head *rhp)
1740 {
1741         struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
1742
1743         free_task(tsk);
1744 }
1745
1746 static __always_inline void delayed_free_task(struct task_struct *tsk)
1747 {
1748         if (IS_ENABLED(CONFIG_MEMCG))
1749                 call_rcu(&tsk->rcu, __delayed_free_task);
1750         else
1751                 free_task(tsk);
1752 }
1753
1754 static void copy_oom_score_adj(u64 clone_flags, struct task_struct *tsk)
1755 {
1756         /* Skip if kernel thread */
1757         if (!tsk->mm)
1758                 return;
1759
1760         /* Skip if spawning a thread or using vfork */
1761         if ((clone_flags & (CLONE_VM | CLONE_THREAD | CLONE_VFORK)) != CLONE_VM)
1762                 return;
1763
1764         /* We need to synchronize with __set_oom_adj */
1765         mutex_lock(&oom_adj_mutex);
1766         set_bit(MMF_MULTIPROCESS, &tsk->mm->flags);
1767         /* Update the values in case they were changed after copy_signal */
1768         tsk->signal->oom_score_adj = current->signal->oom_score_adj;
1769         tsk->signal->oom_score_adj_min = current->signal->oom_score_adj_min;
1770         mutex_unlock(&oom_adj_mutex);
1771 }
1772
1773 /*
1774  * This creates a new process as a copy of the old one,
1775  * but does not actually start it yet.
1776  *
1777  * It copies the registers, and all the appropriate
1778  * parts of the process environment (as per the clone
1779  * flags). The actual kick-off is left to the caller.
1780  */
1781 static __latent_entropy struct task_struct *copy_process(
1782                                         struct pid *pid,
1783                                         int trace,
1784                                         int node,
1785                                         struct kernel_clone_args *args)
1786 {
1787         int pidfd = -1, retval;
1788         struct task_struct *p;
1789         struct multiprocess_signals delayed;
1790         struct file *pidfile = NULL;
1791         u64 clone_flags = args->flags;
1792
1793         /*
1794          * Don't allow sharing the root directory with processes in a different
1795          * namespace
1796          */
1797         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1798                 return ERR_PTR(-EINVAL);
1799
1800         if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1801                 return ERR_PTR(-EINVAL);
1802
1803         /*
1804          * Thread groups must share signals as well, and detached threads
1805          * can only be started up within the thread group.
1806          */
1807         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1808                 return ERR_PTR(-EINVAL);
1809
1810         /*
1811          * Shared signal handlers imply shared VM. By way of the above,
1812          * thread groups also imply shared VM. Blocking this case allows
1813          * for various simplifications in other code.
1814          */
1815         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1816                 return ERR_PTR(-EINVAL);
1817
1818         /*
1819          * Siblings of global init remain as zombies on exit since they are
1820          * not reaped by their parent (swapper). To solve this and to avoid
1821          * multi-rooted process trees, prevent global and container-inits
1822          * from creating siblings.
1823          */
1824         if ((clone_flags & CLONE_PARENT) &&
1825                                 current->signal->flags & SIGNAL_UNKILLABLE)
1826                 return ERR_PTR(-EINVAL);
1827
1828         /*
1829          * If the new process will be in a different pid or user namespace
1830          * do not allow it to share a thread group with the forking task.
1831          */
1832         if (clone_flags & CLONE_THREAD) {
1833                 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1834                     (task_active_pid_ns(current) !=
1835                                 current->nsproxy->pid_ns_for_children))
1836                         return ERR_PTR(-EINVAL);
1837         }
1838
1839         if (clone_flags & CLONE_PIDFD) {
1840                 /*
1841                  * - CLONE_DETACHED is blocked so that we can potentially
1842                  *   reuse it later for CLONE_PIDFD.
1843                  * - CLONE_THREAD is blocked until someone really needs it.
1844                  */
1845                 if (clone_flags & (CLONE_DETACHED | CLONE_THREAD))
1846                         return ERR_PTR(-EINVAL);
1847         }
1848
1849         /*
1850          * Force any signals received before this point to be delivered
1851          * before the fork happens.  Collect up signals sent to multiple
1852          * processes that happen during the fork and delay them so that
1853          * they appear to happen after the fork.
1854          */
1855         sigemptyset(&delayed.signal);
1856         INIT_HLIST_NODE(&delayed.node);
1857
1858         spin_lock_irq(&current->sighand->siglock);
1859         if (!(clone_flags & CLONE_THREAD))
1860                 hlist_add_head(&delayed.node, &current->signal->multiprocess);
1861         recalc_sigpending();
1862         spin_unlock_irq(&current->sighand->siglock);
1863         retval = -ERESTARTNOINTR;
1864         if (signal_pending(current))
1865                 goto fork_out;
1866
1867         retval = -ENOMEM;
1868         p = dup_task_struct(current, node);
1869         if (!p)
1870                 goto fork_out;
1871
1872         /*
1873          * This _must_ happen before we call free_task(), i.e. before we jump
1874          * to any of the bad_fork_* labels. This is to avoid freeing
1875          * p->set_child_tid which is (ab)used as a kthread's data pointer for
1876          * kernel threads (PF_KTHREAD).
1877          */
1878         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? args->child_tid : NULL;
1879         /*
1880          * Clear TID on mm_release()?
1881          */
1882         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? args->child_tid : NULL;
1883
1884         ftrace_graph_init_task(p);
1885
1886         rt_mutex_init_task(p);
1887
1888 #ifdef CONFIG_PROVE_LOCKING
1889         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1890         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1891 #endif
1892         retval = -EAGAIN;
1893         if (atomic_read(&p->real_cred->user->processes) >=
1894                         task_rlimit(p, RLIMIT_NPROC)) {
1895                 if (p->real_cred->user != INIT_USER &&
1896                     !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
1897                         goto bad_fork_free;
1898         }
1899         current->flags &= ~PF_NPROC_EXCEEDED;
1900
1901         retval = copy_creds(p, clone_flags);
1902         if (retval < 0)
1903                 goto bad_fork_free;
1904
1905         /*
1906          * If multiple threads are within copy_process(), then this check
1907          * triggers too late. This doesn't hurt, the check is only there
1908          * to stop root fork bombs.
1909          */
1910         retval = -EAGAIN;
1911         if (nr_threads >= max_threads)
1912                 goto bad_fork_cleanup_count;
1913
1914         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1915         p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE);
1916         p->flags |= PF_FORKNOEXEC;
1917         INIT_LIST_HEAD(&p->children);
1918         INIT_LIST_HEAD(&p->sibling);
1919         rcu_copy_process(p);
1920         p->vfork_done = NULL;
1921         spin_lock_init(&p->alloc_lock);
1922
1923         init_sigpending(&p->pending);
1924
1925         p->utime = p->stime = p->gtime = 0;
1926 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
1927         p->utimescaled = p->stimescaled = 0;
1928 #endif
1929         prev_cputime_init(&p->prev_cputime);
1930
1931 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1932         seqcount_init(&p->vtime.seqcount);
1933         p->vtime.starttime = 0;
1934         p->vtime.state = VTIME_INACTIVE;
1935 #endif
1936
1937 #if defined(SPLIT_RSS_COUNTING)
1938         memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1939 #endif
1940
1941         p->default_timer_slack_ns = current->timer_slack_ns;
1942
1943 #ifdef CONFIG_PSI
1944         p->psi_flags = 0;
1945 #endif
1946
1947         task_io_accounting_init(&p->ioac);
1948         acct_clear_integrals(p);
1949
1950         posix_cputimers_init(&p->posix_cputimers);
1951
1952         p->io_context = NULL;
1953         audit_set_context(p, NULL);
1954         cgroup_fork(p);
1955 #ifdef CONFIG_NUMA
1956         p->mempolicy = mpol_dup(p->mempolicy);
1957         if (IS_ERR(p->mempolicy)) {
1958                 retval = PTR_ERR(p->mempolicy);
1959                 p->mempolicy = NULL;
1960                 goto bad_fork_cleanup_threadgroup_lock;
1961         }
1962 #endif
1963 #ifdef CONFIG_CPUSETS
1964         p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1965         p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1966         seqcount_init(&p->mems_allowed_seq);
1967 #endif
1968 #ifdef CONFIG_TRACE_IRQFLAGS
1969         p->irq_events = 0;
1970         p->hardirqs_enabled = 0;
1971         p->hardirq_enable_ip = 0;
1972         p->hardirq_enable_event = 0;
1973         p->hardirq_disable_ip = _THIS_IP_;
1974         p->hardirq_disable_event = 0;
1975         p->softirqs_enabled = 1;
1976         p->softirq_enable_ip = _THIS_IP_;
1977         p->softirq_enable_event = 0;
1978         p->softirq_disable_ip = 0;
1979         p->softirq_disable_event = 0;
1980         p->hardirq_context = 0;
1981         p->softirq_context = 0;
1982 #endif
1983
1984         p->pagefault_disabled = 0;
1985
1986 #ifdef CONFIG_LOCKDEP
1987         lockdep_init_task(p);
1988 #endif
1989
1990 #ifdef CONFIG_DEBUG_MUTEXES
1991         p->blocked_on = NULL; /* not blocked yet */
1992 #endif
1993 #ifdef CONFIG_BCACHE
1994         p->sequential_io        = 0;
1995         p->sequential_io_avg    = 0;
1996 #endif
1997
1998         /* Perform scheduler related setup. Assign this task to a CPU. */
1999         retval = sched_fork(clone_flags, p);
2000         if (retval)
2001                 goto bad_fork_cleanup_policy;
2002
2003         retval = perf_event_init_task(p);
2004         if (retval)
2005                 goto bad_fork_cleanup_policy;
2006         retval = audit_alloc(p);
2007         if (retval)
2008                 goto bad_fork_cleanup_perf;
2009         /* copy all the process information */
2010         shm_init_task(p);
2011         retval = security_task_alloc(p, clone_flags);
2012         if (retval)
2013                 goto bad_fork_cleanup_audit;
2014         retval = copy_semundo(clone_flags, p);
2015         if (retval)
2016                 goto bad_fork_cleanup_security;
2017         retval = copy_files(clone_flags, p);
2018         if (retval)
2019                 goto bad_fork_cleanup_semundo;
2020         retval = copy_fs(clone_flags, p);
2021         if (retval)
2022                 goto bad_fork_cleanup_files;
2023         retval = copy_sighand(clone_flags, p);
2024         if (retval)
2025                 goto bad_fork_cleanup_fs;
2026         retval = copy_signal(clone_flags, p);
2027         if (retval)
2028                 goto bad_fork_cleanup_sighand;
2029         retval = copy_mm(clone_flags, p);
2030         if (retval)
2031                 goto bad_fork_cleanup_signal;
2032         retval = copy_namespaces(clone_flags, p);
2033         if (retval)
2034                 goto bad_fork_cleanup_mm;
2035         retval = copy_io(clone_flags, p);
2036         if (retval)
2037                 goto bad_fork_cleanup_namespaces;
2038         retval = copy_thread_tls(clone_flags, args->stack, args->stack_size, p,
2039                                  args->tls);
2040         if (retval)
2041                 goto bad_fork_cleanup_io;
2042
2043         stackleak_task_init(p);
2044
2045         if (pid != &init_struct_pid) {
2046                 pid = alloc_pid(p->nsproxy->pid_ns_for_children);
2047                 if (IS_ERR(pid)) {
2048                         retval = PTR_ERR(pid);
2049                         goto bad_fork_cleanup_thread;
2050                 }
2051         }
2052
2053         /*
2054          * This has to happen after we've potentially unshared the file
2055          * descriptor table (so that the pidfd doesn't leak into the child
2056          * if the fd table isn't shared).
2057          */
2058         if (clone_flags & CLONE_PIDFD) {
2059                 retval = get_unused_fd_flags(O_RDWR | O_CLOEXEC);
2060                 if (retval < 0)
2061                         goto bad_fork_free_pid;
2062
2063                 pidfd = retval;
2064
2065                 pidfile = anon_inode_getfile("[pidfd]", &pidfd_fops, pid,
2066                                               O_RDWR | O_CLOEXEC);
2067                 if (IS_ERR(pidfile)) {
2068                         put_unused_fd(pidfd);
2069                         retval = PTR_ERR(pidfile);
2070                         goto bad_fork_free_pid;
2071                 }
2072                 get_pid(pid);   /* held by pidfile now */
2073
2074                 retval = put_user(pidfd, args->pidfd);
2075                 if (retval)
2076                         goto bad_fork_put_pidfd;
2077         }
2078
2079 #ifdef CONFIG_BLOCK
2080         p->plug = NULL;
2081 #endif
2082         futex_init_task(p);
2083
2084         /*
2085          * sigaltstack should be cleared when sharing the same VM
2086          */
2087         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
2088                 sas_ss_reset(p);
2089
2090         /*
2091          * Syscall tracing and stepping should be turned off in the
2092          * child regardless of CLONE_PTRACE.
2093          */
2094         user_disable_single_step(p);
2095         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
2096 #ifdef TIF_SYSCALL_EMU
2097         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
2098 #endif
2099         clear_tsk_latency_tracing(p);
2100
2101         /* ok, now we should be set up.. */
2102         p->pid = pid_nr(pid);
2103         if (clone_flags & CLONE_THREAD) {
2104                 p->group_leader = current->group_leader;
2105                 p->tgid = current->tgid;
2106         } else {
2107                 p->group_leader = p;
2108                 p->tgid = p->pid;
2109         }
2110
2111         p->nr_dirtied = 0;
2112         p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
2113         p->dirty_paused_when = 0;
2114
2115         p->pdeath_signal = 0;
2116         INIT_LIST_HEAD(&p->thread_group);
2117         p->task_works = NULL;
2118
2119         cgroup_threadgroup_change_begin(current);
2120         /*
2121          * Ensure that the cgroup subsystem policies allow the new process to be
2122          * forked. It should be noted the the new process's css_set can be changed
2123          * between here and cgroup_post_fork() if an organisation operation is in
2124          * progress.
2125          */
2126         retval = cgroup_can_fork(p);
2127         if (retval)
2128                 goto bad_fork_cgroup_threadgroup_change_end;
2129
2130         /*
2131          * From this point on we must avoid any synchronous user-space
2132          * communication until we take the tasklist-lock. In particular, we do
2133          * not want user-space to be able to predict the process start-time by
2134          * stalling fork(2) after we recorded the start_time but before it is
2135          * visible to the system.
2136          */
2137
2138         p->start_time = ktime_get_ns();
2139         p->real_start_time = ktime_get_boottime_ns();
2140
2141         /*
2142          * Make it visible to the rest of the system, but dont wake it up yet.
2143          * Need tasklist lock for parent etc handling!
2144          */
2145         write_lock_irq(&tasklist_lock);
2146
2147         /* CLONE_PARENT re-uses the old parent */
2148         if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
2149                 p->real_parent = current->real_parent;
2150                 p->parent_exec_id = current->parent_exec_id;
2151                 if (clone_flags & CLONE_THREAD)
2152                         p->exit_signal = -1;
2153                 else
2154                         p->exit_signal = current->group_leader->exit_signal;
2155         } else {
2156                 p->real_parent = current;
2157                 p->parent_exec_id = current->self_exec_id;
2158                 p->exit_signal = args->exit_signal;
2159         }
2160
2161         klp_copy_process(p);
2162
2163         spin_lock(&current->sighand->siglock);
2164
2165         /*
2166          * Copy seccomp details explicitly here, in case they were changed
2167          * before holding sighand lock.
2168          */
2169         copy_seccomp(p);
2170
2171         rseq_fork(p, clone_flags);
2172
2173         /* Don't start children in a dying pid namespace */
2174         if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) {
2175                 retval = -ENOMEM;
2176                 goto bad_fork_cancel_cgroup;
2177         }
2178
2179         /* Let kill terminate clone/fork in the middle */
2180         if (fatal_signal_pending(current)) {
2181                 retval = -EINTR;
2182                 goto bad_fork_cancel_cgroup;
2183         }
2184
2185         init_task_pid_links(p);
2186         if (likely(p->pid)) {
2187                 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
2188
2189                 init_task_pid(p, PIDTYPE_PID, pid);
2190                 if (thread_group_leader(p)) {
2191                         init_task_pid(p, PIDTYPE_TGID, pid);
2192                         init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
2193                         init_task_pid(p, PIDTYPE_SID, task_session(current));
2194
2195                         if (is_child_reaper(pid)) {
2196                                 ns_of_pid(pid)->child_reaper = p;
2197                                 p->signal->flags |= SIGNAL_UNKILLABLE;
2198                         }
2199                         p->signal->shared_pending.signal = delayed.signal;
2200                         p->signal->tty = tty_kref_get(current->signal->tty);
2201                         /*
2202                          * Inherit has_child_subreaper flag under the same
2203                          * tasklist_lock with adding child to the process tree
2204                          * for propagate_has_child_subreaper optimization.
2205                          */
2206                         p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper ||
2207                                                          p->real_parent->signal->is_child_subreaper;
2208                         list_add_tail(&p->sibling, &p->real_parent->children);
2209                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
2210                         attach_pid(p, PIDTYPE_TGID);
2211                         attach_pid(p, PIDTYPE_PGID);
2212                         attach_pid(p, PIDTYPE_SID);
2213                         __this_cpu_inc(process_counts);
2214                 } else {
2215                         current->signal->nr_threads++;
2216                         atomic_inc(&current->signal->live);
2217                         refcount_inc(&current->signal->sigcnt);
2218                         task_join_group_stop(p);
2219                         list_add_tail_rcu(&p->thread_group,
2220                                           &p->group_leader->thread_group);
2221                         list_add_tail_rcu(&p->thread_node,
2222                                           &p->signal->thread_head);
2223                 }
2224                 attach_pid(p, PIDTYPE_PID);
2225                 nr_threads++;
2226         }
2227         total_forks++;
2228         hlist_del_init(&delayed.node);
2229         spin_unlock(&current->sighand->siglock);
2230         syscall_tracepoint_update(p);
2231         write_unlock_irq(&tasklist_lock);
2232
2233         if (pidfile)
2234                 fd_install(pidfd, pidfile);
2235
2236         proc_fork_connector(p);
2237         cgroup_post_fork(p);
2238         cgroup_threadgroup_change_end(current);
2239         perf_event_fork(p);
2240
2241         trace_task_newtask(p, clone_flags);
2242         uprobe_copy_process(p, clone_flags);
2243
2244         copy_oom_score_adj(clone_flags, p);
2245
2246         return p;
2247
2248 bad_fork_cancel_cgroup:
2249         spin_unlock(&current->sighand->siglock);
2250         write_unlock_irq(&tasklist_lock);
2251         cgroup_cancel_fork(p);
2252 bad_fork_cgroup_threadgroup_change_end:
2253         cgroup_threadgroup_change_end(current);
2254 bad_fork_put_pidfd:
2255         if (clone_flags & CLONE_PIDFD) {
2256                 fput(pidfile);
2257                 put_unused_fd(pidfd);
2258         }
2259 bad_fork_free_pid:
2260         if (pid != &init_struct_pid)
2261                 free_pid(pid);
2262 bad_fork_cleanup_thread:
2263         exit_thread(p);
2264 bad_fork_cleanup_io:
2265         if (p->io_context)
2266                 exit_io_context(p);
2267 bad_fork_cleanup_namespaces:
2268         exit_task_namespaces(p);
2269 bad_fork_cleanup_mm:
2270         if (p->mm) {
2271                 mm_clear_owner(p->mm, p);
2272                 mmput(p->mm);
2273         }
2274 bad_fork_cleanup_signal:
2275         if (!(clone_flags & CLONE_THREAD))
2276                 free_signal_struct(p->signal);
2277 bad_fork_cleanup_sighand:
2278         __cleanup_sighand(p->sighand);
2279 bad_fork_cleanup_fs:
2280         exit_fs(p); /* blocking */
2281 bad_fork_cleanup_files:
2282         exit_files(p); /* blocking */
2283 bad_fork_cleanup_semundo:
2284         exit_sem(p);
2285 bad_fork_cleanup_security:
2286         security_task_free(p);
2287 bad_fork_cleanup_audit:
2288         audit_free(p);
2289 bad_fork_cleanup_perf:
2290         perf_event_free_task(p);
2291 bad_fork_cleanup_policy:
2292         lockdep_free_task(p);
2293 #ifdef CONFIG_NUMA
2294         mpol_put(p->mempolicy);
2295 bad_fork_cleanup_threadgroup_lock:
2296 #endif
2297         delayacct_tsk_free(p);
2298 bad_fork_cleanup_count:
2299         atomic_dec(&p->cred->user->processes);
2300         exit_creds(p);
2301 bad_fork_free:
2302         p->state = TASK_DEAD;
2303         put_task_stack(p);
2304         delayed_free_task(p);
2305 fork_out:
2306         spin_lock_irq(&current->sighand->siglock);
2307         hlist_del_init(&delayed.node);
2308         spin_unlock_irq(&current->sighand->siglock);
2309         return ERR_PTR(retval);
2310 }
2311
2312 static inline void init_idle_pids(struct task_struct *idle)
2313 {
2314         enum pid_type type;
2315
2316         for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
2317                 INIT_HLIST_NODE(&idle->pid_links[type]); /* not really needed */
2318                 init_task_pid(idle, type, &init_struct_pid);
2319         }
2320 }
2321
2322 struct task_struct *fork_idle(int cpu)
2323 {
2324         struct task_struct *task;
2325         struct kernel_clone_args args = {
2326                 .flags = CLONE_VM,
2327         };
2328
2329         task = copy_process(&init_struct_pid, 0, cpu_to_node(cpu), &args);
2330         if (!IS_ERR(task)) {
2331                 init_idle_pids(task);
2332                 init_idle(task, cpu);
2333         }
2334
2335         return task;
2336 }
2337
2338 struct mm_struct *copy_init_mm(void)
2339 {
2340         return dup_mm(NULL, &init_mm);
2341 }
2342
2343 /*
2344  *  Ok, this is the main fork-routine.
2345  *
2346  * It copies the process, and if successful kick-starts
2347  * it and waits for it to finish using the VM if required.
2348  *
2349  * args->exit_signal is expected to be checked for sanity by the caller.
2350  */
2351 long _do_fork(struct kernel_clone_args *args)
2352 {
2353         u64 clone_flags = args->flags;
2354         struct completion vfork;
2355         struct pid *pid;
2356         struct task_struct *p;
2357         int trace = 0;
2358         long nr;
2359
2360         /*
2361          * Determine whether and which event to report to ptracer.  When
2362          * called from kernel_thread or CLONE_UNTRACED is explicitly
2363          * requested, no event is reported; otherwise, report if the event
2364          * for the type of forking is enabled.
2365          */
2366         if (!(clone_flags & CLONE_UNTRACED)) {
2367                 if (clone_flags & CLONE_VFORK)
2368                         trace = PTRACE_EVENT_VFORK;
2369                 else if (args->exit_signal != SIGCHLD)
2370                         trace = PTRACE_EVENT_CLONE;
2371                 else
2372                         trace = PTRACE_EVENT_FORK;
2373
2374                 if (likely(!ptrace_event_enabled(current, trace)))
2375                         trace = 0;
2376         }
2377
2378         p = copy_process(NULL, trace, NUMA_NO_NODE, args);
2379         add_latent_entropy();
2380
2381         if (IS_ERR(p))
2382                 return PTR_ERR(p);
2383
2384         /*
2385          * Do this prior waking up the new thread - the thread pointer
2386          * might get invalid after that point, if the thread exits quickly.
2387          */
2388         trace_sched_process_fork(current, p);
2389
2390         pid = get_task_pid(p, PIDTYPE_PID);
2391         nr = pid_vnr(pid);
2392
2393         if (clone_flags & CLONE_PARENT_SETTID)
2394                 put_user(nr, args->parent_tid);
2395
2396         if (clone_flags & CLONE_VFORK) {
2397                 p->vfork_done = &vfork;
2398                 init_completion(&vfork);
2399                 get_task_struct(p);
2400         }
2401
2402         wake_up_new_task(p);
2403
2404         /* forking complete and child started to run, tell ptracer */
2405         if (unlikely(trace))
2406                 ptrace_event_pid(trace, pid);
2407
2408         if (clone_flags & CLONE_VFORK) {
2409                 if (!wait_for_vfork_done(p, &vfork))
2410                         ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
2411         }
2412
2413         put_pid(pid);
2414         return nr;
2415 }
2416
2417 bool legacy_clone_args_valid(const struct kernel_clone_args *kargs)
2418 {
2419         /* clone(CLONE_PIDFD) uses parent_tidptr to return a pidfd */
2420         if ((kargs->flags & CLONE_PIDFD) &&
2421             (kargs->flags & CLONE_PARENT_SETTID))
2422                 return false;
2423
2424         return true;
2425 }
2426
2427 #ifndef CONFIG_HAVE_COPY_THREAD_TLS
2428 /* For compatibility with architectures that call do_fork directly rather than
2429  * using the syscall entry points below. */
2430 long do_fork(unsigned long clone_flags,
2431               unsigned long stack_start,
2432               unsigned long stack_size,
2433               int __user *parent_tidptr,
2434               int __user *child_tidptr)
2435 {
2436         struct kernel_clone_args args = {
2437                 .flags          = (lower_32_bits(clone_flags) & ~CSIGNAL),
2438                 .pidfd          = parent_tidptr,
2439                 .child_tid      = child_tidptr,
2440                 .parent_tid     = parent_tidptr,
2441                 .exit_signal    = (lower_32_bits(clone_flags) & CSIGNAL),
2442                 .stack          = stack_start,
2443                 .stack_size     = stack_size,
2444         };
2445
2446         if (!legacy_clone_args_valid(&args))
2447                 return -EINVAL;
2448
2449         return _do_fork(&args);
2450 }
2451 #endif
2452
2453 /*
2454  * Create a kernel thread.
2455  */
2456 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
2457 {
2458         struct kernel_clone_args args = {
2459                 .flags          = ((lower_32_bits(flags) | CLONE_VM |
2460                                     CLONE_UNTRACED) & ~CSIGNAL),
2461                 .exit_signal    = (lower_32_bits(flags) & CSIGNAL),
2462                 .stack          = (unsigned long)fn,
2463                 .stack_size     = (unsigned long)arg,
2464         };
2465
2466         return _do_fork(&args);
2467 }
2468
2469 #ifdef __ARCH_WANT_SYS_FORK
2470 SYSCALL_DEFINE0(fork)
2471 {
2472 #ifdef CONFIG_MMU
2473         struct kernel_clone_args args = {
2474                 .exit_signal = SIGCHLD,
2475         };
2476
2477         return _do_fork(&args);
2478 #else
2479         /* can not support in nommu mode */
2480         return -EINVAL;
2481 #endif
2482 }
2483 #endif
2484
2485 #ifdef __ARCH_WANT_SYS_VFORK
2486 SYSCALL_DEFINE0(vfork)
2487 {
2488         struct kernel_clone_args args = {
2489                 .flags          = CLONE_VFORK | CLONE_VM,
2490                 .exit_signal    = SIGCHLD,
2491         };
2492
2493         return _do_fork(&args);
2494 }
2495 #endif
2496
2497 #ifdef __ARCH_WANT_SYS_CLONE
2498 #ifdef CONFIG_CLONE_BACKWARDS
2499 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2500                  int __user *, parent_tidptr,
2501                  unsigned long, tls,
2502                  int __user *, child_tidptr)
2503 #elif defined(CONFIG_CLONE_BACKWARDS2)
2504 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
2505                  int __user *, parent_tidptr,
2506                  int __user *, child_tidptr,
2507                  unsigned long, tls)
2508 #elif defined(CONFIG_CLONE_BACKWARDS3)
2509 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
2510                 int, stack_size,
2511                 int __user *, parent_tidptr,
2512                 int __user *, child_tidptr,
2513                 unsigned long, tls)
2514 #else
2515 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2516                  int __user *, parent_tidptr,
2517                  int __user *, child_tidptr,
2518                  unsigned long, tls)
2519 #endif
2520 {
2521         struct kernel_clone_args args = {
2522                 .flags          = (lower_32_bits(clone_flags) & ~CSIGNAL),
2523                 .pidfd          = parent_tidptr,
2524                 .child_tid      = child_tidptr,
2525                 .parent_tid     = parent_tidptr,
2526                 .exit_signal    = (lower_32_bits(clone_flags) & CSIGNAL),
2527                 .stack          = newsp,
2528                 .tls            = tls,
2529         };
2530
2531         if (!legacy_clone_args_valid(&args))
2532                 return -EINVAL;
2533
2534         return _do_fork(&args);
2535 }
2536 #endif
2537
2538 #ifdef __ARCH_WANT_SYS_CLONE3
2539
2540 /*
2541  * copy_thread implementations handle CLONE_SETTLS by reading the TLS value from
2542  * the registers containing the syscall arguments for clone. This doesn't work
2543  * with clone3 since the TLS value is passed in clone_args instead.
2544  */
2545 #ifndef CONFIG_HAVE_COPY_THREAD_TLS
2546 #error clone3 requires copy_thread_tls support in arch
2547 #endif
2548
2549 noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
2550                                               struct clone_args __user *uargs,
2551                                               size_t usize)
2552 {
2553         int err;
2554         struct clone_args args;
2555
2556         if (unlikely(usize > PAGE_SIZE))
2557                 return -E2BIG;
2558         if (unlikely(usize < CLONE_ARGS_SIZE_VER0))
2559                 return -EINVAL;
2560
2561         err = copy_struct_from_user(&args, sizeof(args), uargs, usize);
2562         if (err)
2563                 return err;
2564
2565         /*
2566          * Verify that higher 32bits of exit_signal are unset and that
2567          * it is a valid signal
2568          */
2569         if (unlikely((args.exit_signal & ~((u64)CSIGNAL)) ||
2570                      !valid_signal(args.exit_signal)))
2571                 return -EINVAL;
2572
2573         *kargs = (struct kernel_clone_args){
2574                 .flags          = args.flags,
2575                 .pidfd          = u64_to_user_ptr(args.pidfd),
2576                 .child_tid      = u64_to_user_ptr(args.child_tid),
2577                 .parent_tid     = u64_to_user_ptr(args.parent_tid),
2578                 .exit_signal    = args.exit_signal,
2579                 .stack          = args.stack,
2580                 .stack_size     = args.stack_size,
2581                 .tls            = args.tls,
2582         };
2583
2584         return 0;
2585 }
2586
2587 /**
2588  * clone3_stack_valid - check and prepare stack
2589  * @kargs: kernel clone args
2590  *
2591  * Verify that the stack arguments userspace gave us are sane.
2592  * In addition, set the stack direction for userspace since it's easy for us to
2593  * determine.
2594  */
2595 static inline bool clone3_stack_valid(struct kernel_clone_args *kargs)
2596 {
2597         if (kargs->stack == 0) {
2598                 if (kargs->stack_size > 0)
2599                         return false;
2600         } else {
2601                 if (kargs->stack_size == 0)
2602                         return false;
2603
2604                 if (!access_ok((void __user *)kargs->stack, kargs->stack_size))
2605                         return false;
2606
2607 #if !defined(CONFIG_STACK_GROWSUP) && !defined(CONFIG_IA64)
2608                 kargs->stack += kargs->stack_size;
2609 #endif
2610         }
2611
2612         return true;
2613 }
2614
2615 static bool clone3_args_valid(struct kernel_clone_args *kargs)
2616 {
2617         /*
2618          * All lower bits of the flag word are taken.
2619          * Verify that no other unknown flags are passed along.
2620          */
2621         if (kargs->flags & ~CLONE_LEGACY_FLAGS)
2622                 return false;
2623
2624         /*
2625          * - make the CLONE_DETACHED bit reuseable for clone3
2626          * - make the CSIGNAL bits reuseable for clone3
2627          */
2628         if (kargs->flags & (CLONE_DETACHED | CSIGNAL))
2629                 return false;
2630
2631         if ((kargs->flags & (CLONE_THREAD | CLONE_PARENT)) &&
2632             kargs->exit_signal)
2633                 return false;
2634
2635         if (!clone3_stack_valid(kargs))
2636                 return false;
2637
2638         return true;
2639 }
2640
2641 /**
2642  * clone3 - create a new process with specific properties
2643  * @uargs: argument structure
2644  * @size:  size of @uargs
2645  *
2646  * clone3() is the extensible successor to clone()/clone2().
2647  * It takes a struct as argument that is versioned by its size.
2648  *
2649  * Return: On success, a positive PID for the child process.
2650  *         On error, a negative errno number.
2651  */
2652 SYSCALL_DEFINE2(clone3, struct clone_args __user *, uargs, size_t, size)
2653 {
2654         int err;
2655
2656         struct kernel_clone_args kargs;
2657
2658         err = copy_clone_args_from_user(&kargs, uargs, size);
2659         if (err)
2660                 return err;
2661
2662         if (!clone3_args_valid(&kargs))
2663                 return -EINVAL;
2664
2665         return _do_fork(&kargs);
2666 }
2667 #endif
2668
2669 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data)
2670 {
2671         struct task_struct *leader, *parent, *child;
2672         int res;
2673
2674         read_lock(&tasklist_lock);
2675         leader = top = top->group_leader;
2676 down:
2677         for_each_thread(leader, parent) {
2678                 list_for_each_entry(child, &parent->children, sibling) {
2679                         res = visitor(child, data);
2680                         if (res) {
2681                                 if (res < 0)
2682                                         goto out;
2683                                 leader = child;
2684                                 goto down;
2685                         }
2686 up:
2687                         ;
2688                 }
2689         }
2690
2691         if (leader != top) {
2692                 child = leader;
2693                 parent = child->real_parent;
2694                 leader = parent->group_leader;
2695                 goto up;
2696         }
2697 out:
2698         read_unlock(&tasklist_lock);
2699 }
2700
2701 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
2702 #define ARCH_MIN_MMSTRUCT_ALIGN 0
2703 #endif
2704
2705 static void sighand_ctor(void *data)
2706 {
2707         struct sighand_struct *sighand = data;
2708
2709         spin_lock_init(&sighand->siglock);
2710         init_waitqueue_head(&sighand->signalfd_wqh);
2711 }
2712
2713 void __init proc_caches_init(void)
2714 {
2715         unsigned int mm_size;
2716
2717         sighand_cachep = kmem_cache_create("sighand_cache",
2718                         sizeof(struct sighand_struct), 0,
2719                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU|
2720                         SLAB_ACCOUNT, sighand_ctor);
2721         signal_cachep = kmem_cache_create("signal_cache",
2722                         sizeof(struct signal_struct), 0,
2723                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2724                         NULL);
2725         files_cachep = kmem_cache_create("files_cache",
2726                         sizeof(struct files_struct), 0,
2727                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2728                         NULL);
2729         fs_cachep = kmem_cache_create("fs_cache",
2730                         sizeof(struct fs_struct), 0,
2731                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2732                         NULL);
2733
2734         /*
2735          * The mm_cpumask is located at the end of mm_struct, and is
2736          * dynamically sized based on the maximum CPU number this system
2737          * can have, taking hotplug into account (nr_cpu_ids).
2738          */
2739         mm_size = sizeof(struct mm_struct) + cpumask_size();
2740
2741         mm_cachep = kmem_cache_create_usercopy("mm_struct",
2742                         mm_size, ARCH_MIN_MMSTRUCT_ALIGN,
2743                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2744                         offsetof(struct mm_struct, saved_auxv),
2745                         sizeof_field(struct mm_struct, saved_auxv),
2746                         NULL);
2747         vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
2748         mmap_init();
2749         nsproxy_cache_init();
2750 }
2751
2752 /*
2753  * Check constraints on flags passed to the unshare system call.
2754  */
2755 static int check_unshare_flags(unsigned long unshare_flags)
2756 {
2757         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
2758                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
2759                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
2760                                 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP))
2761                 return -EINVAL;
2762         /*
2763          * Not implemented, but pretend it works if there is nothing
2764          * to unshare.  Note that unsharing the address space or the
2765          * signal handlers also need to unshare the signal queues (aka
2766          * CLONE_THREAD).
2767          */
2768         if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
2769                 if (!thread_group_empty(current))
2770                         return -EINVAL;
2771         }
2772         if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
2773                 if (refcount_read(&current->sighand->count) > 1)
2774                         return -EINVAL;
2775         }
2776         if (unshare_flags & CLONE_VM) {
2777                 if (!current_is_single_threaded())
2778                         return -EINVAL;
2779         }
2780
2781         return 0;
2782 }
2783
2784 /*
2785  * Unshare the filesystem structure if it is being shared
2786  */
2787 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
2788 {
2789         struct fs_struct *fs = current->fs;
2790
2791         if (!(unshare_flags & CLONE_FS) || !fs)
2792                 return 0;
2793
2794         /* don't need lock here; in the worst case we'll do useless copy */
2795         if (fs->users == 1)
2796                 return 0;
2797
2798         *new_fsp = copy_fs_struct(fs);
2799         if (!*new_fsp)
2800                 return -ENOMEM;
2801
2802         return 0;
2803 }
2804
2805 /*
2806  * Unshare file descriptor table if it is being shared
2807  */
2808 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
2809 {
2810         struct files_struct *fd = current->files;
2811         int error = 0;
2812
2813         if ((unshare_flags & CLONE_FILES) &&
2814             (fd && atomic_read(&fd->count) > 1)) {
2815                 *new_fdp = dup_fd(fd, &error);
2816                 if (!*new_fdp)
2817                         return error;
2818         }
2819
2820         return 0;
2821 }
2822
2823 /*
2824  * unshare allows a process to 'unshare' part of the process
2825  * context which was originally shared using clone.  copy_*
2826  * functions used by do_fork() cannot be used here directly
2827  * because they modify an inactive task_struct that is being
2828  * constructed. Here we are modifying the current, active,
2829  * task_struct.
2830  */
2831 int ksys_unshare(unsigned long unshare_flags)
2832 {
2833         struct fs_struct *fs, *new_fs = NULL;
2834         struct files_struct *fd, *new_fd = NULL;
2835         struct cred *new_cred = NULL;
2836         struct nsproxy *new_nsproxy = NULL;
2837         int do_sysvsem = 0;
2838         int err;
2839
2840         /*
2841          * If unsharing a user namespace must also unshare the thread group
2842          * and unshare the filesystem root and working directories.
2843          */
2844         if (unshare_flags & CLONE_NEWUSER)
2845                 unshare_flags |= CLONE_THREAD | CLONE_FS;
2846         /*
2847          * If unsharing vm, must also unshare signal handlers.
2848          */
2849         if (unshare_flags & CLONE_VM)
2850                 unshare_flags |= CLONE_SIGHAND;
2851         /*
2852          * If unsharing a signal handlers, must also unshare the signal queues.
2853          */
2854         if (unshare_flags & CLONE_SIGHAND)
2855                 unshare_flags |= CLONE_THREAD;
2856         /*
2857          * If unsharing namespace, must also unshare filesystem information.
2858          */
2859         if (unshare_flags & CLONE_NEWNS)
2860                 unshare_flags |= CLONE_FS;
2861
2862         err = check_unshare_flags(unshare_flags);
2863         if (err)
2864                 goto bad_unshare_out;
2865         /*
2866          * CLONE_NEWIPC must also detach from the undolist: after switching
2867          * to a new ipc namespace, the semaphore arrays from the old
2868          * namespace are unreachable.
2869          */
2870         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
2871                 do_sysvsem = 1;
2872         err = unshare_fs(unshare_flags, &new_fs);
2873         if (err)
2874                 goto bad_unshare_out;
2875         err = unshare_fd(unshare_flags, &new_fd);
2876         if (err)
2877                 goto bad_unshare_cleanup_fs;
2878         err = unshare_userns(unshare_flags, &new_cred);
2879         if (err)
2880                 goto bad_unshare_cleanup_fd;
2881         err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
2882                                          new_cred, new_fs);
2883         if (err)
2884                 goto bad_unshare_cleanup_cred;
2885
2886         if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
2887                 if (do_sysvsem) {
2888                         /*
2889                          * CLONE_SYSVSEM is equivalent to sys_exit().
2890                          */
2891                         exit_sem(current);
2892                 }
2893                 if (unshare_flags & CLONE_NEWIPC) {
2894                         /* Orphan segments in old ns (see sem above). */
2895                         exit_shm(current);
2896                         shm_init_task(current);
2897                 }
2898
2899                 if (new_nsproxy)
2900                         switch_task_namespaces(current, new_nsproxy);
2901
2902                 task_lock(current);
2903
2904                 if (new_fs) {
2905                         fs = current->fs;
2906                         spin_lock(&fs->lock);
2907                         current->fs = new_fs;
2908                         if (--fs->users)
2909                                 new_fs = NULL;
2910                         else
2911                                 new_fs = fs;
2912                         spin_unlock(&fs->lock);
2913                 }
2914
2915                 if (new_fd) {
2916                         fd = current->files;
2917                         current->files = new_fd;
2918                         new_fd = fd;
2919                 }
2920
2921                 task_unlock(current);
2922
2923                 if (new_cred) {
2924                         /* Install the new user namespace */
2925                         commit_creds(new_cred);
2926                         new_cred = NULL;
2927                 }
2928         }
2929
2930         perf_event_namespaces(current);
2931
2932 bad_unshare_cleanup_cred:
2933         if (new_cred)
2934                 put_cred(new_cred);
2935 bad_unshare_cleanup_fd:
2936         if (new_fd)
2937                 put_files_struct(new_fd);
2938
2939 bad_unshare_cleanup_fs:
2940         if (new_fs)
2941                 free_fs_struct(new_fs);
2942
2943 bad_unshare_out:
2944         return err;
2945 }
2946
2947 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
2948 {
2949         return ksys_unshare(unshare_flags);
2950 }
2951
2952 /*
2953  *      Helper to unshare the files of the current task.
2954  *      We don't want to expose copy_files internals to
2955  *      the exec layer of the kernel.
2956  */
2957
2958 int unshare_files(struct files_struct **displaced)
2959 {
2960         struct task_struct *task = current;
2961         struct files_struct *copy = NULL;
2962         int error;
2963
2964         error = unshare_fd(CLONE_FILES, &copy);
2965         if (error || !copy) {
2966                 *displaced = NULL;
2967                 return error;
2968         }
2969         *displaced = task->files;
2970         task_lock(task);
2971         task->files = copy;
2972         task_unlock(task);
2973         return 0;
2974 }
2975
2976 int sysctl_max_threads(struct ctl_table *table, int write,
2977                        void __user *buffer, size_t *lenp, loff_t *ppos)
2978 {
2979         struct ctl_table t;
2980         int ret;
2981         int threads = max_threads;
2982         int min = 1;
2983         int max = MAX_THREADS;
2984
2985         t = *table;
2986         t.data = &threads;
2987         t.extra1 = &min;
2988         t.extra2 = &max;
2989
2990         ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
2991         if (ret || !write)
2992                 return ret;
2993
2994         max_threads = threads;
2995
2996         return 0;
2997 }