fs/coredump.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/slab.h>
   3 #include <linux/file.h>
   4 #include <linux/fdtable.h>
   5 #include <linux/freezer.h>
   6 #include <linux/mm.h>
   7 #include <linux/stat.h>
   8 #include <linux/fcntl.h>
   9 #include <linux/swap.h>
  10 #include <linux/ctype.h>
  11 #include <linux/string.h>
  12 #include <linux/init.h>
  13 #include <linux/pagemap.h>
  14 #include <linux/perf_event.h>
  15 #include <linux/highmem.h>
  16 #include <linux/spinlock.h>
  17 #include <linux/key.h>
  18 #include <linux/personality.h>
  19 #include <linux/binfmts.h>
  20 #include <linux/coredump.h>
  21 #include <linux/sched/coredump.h>
  22 #include <linux/sched/signal.h>
  23 #include <linux/sched/task_stack.h>
  24 #include <linux/utsname.h>
  25 #include <linux/pid_namespace.h>
  26 #include <linux/module.h>
  27 #include <linux/namei.h>
  28 #include <linux/mount.h>
  29 #include <linux/security.h>
  30 #include <linux/syscalls.h>
  31 #include <linux/tsacct_kern.h>
  32 #include <linux/cn_proc.h>
  33 #include <linux/audit.h>
  34 #include <linux/tracehook.h>
  35 #include <linux/kmod.h>
  36 #include <linux/fsnotify.h>
  37 #include <linux/fs_struct.h>
  38 #include <linux/pipe_fs_i.h>
  39 #include <linux/oom.h>
  40 #include <linux/compat.h>
  41 #include <linux/fs.h>
  42 #include <linux/path.h>
  43 #include <linux/timekeeping.h>
  44 #include <linux/elf.h>
  45
  46 #include <linux/uaccess.h>
  47 #include <asm/mmu_context.h>
  48 #include <asm/tlb.h>
  49 #include <asm/exec.h>
  50
  51 #include <trace/events/task.h>
  52 #include "internal.h"
  53
  54 #include <trace/events/sched.h>
  55
  56 static bool dump_vma_snapshot(struct coredump_params *cprm);
  57 static void free_vma_snapshot(struct coredump_params *cprm);
  58
  59 int core_uses_pid;
  60 unsigned int core_pipe_limit;
  61 char core_pattern[CORENAME_MAX_SIZE] = "core";
  62 static int core_name_size = CORENAME_MAX_SIZE;
  63
  64 struct core_name {
  65         char *corename;
  66         int used, size;
  67 };
  68
  69 /* The maximal length of core_pattern is also specified in sysctl.c */
  70
  71 static int expand_corename(struct core_name *cn, int size)
  72 {
  73         char *corename = krealloc(cn->corename, size, GFP_KERNEL);
  74
  75         if (!corename)
  76                 return -ENOMEM;
  77
  78         if (size > core_name_size) /* racy but harmless */
  79                 core_name_size = size;
  80
  81         cn->size = ksize(corename);
  82         cn->corename = corename;
  83         return 0;
  84 }
  85
  86 static __printf(2, 0) int cn_vprintf(struct core_name *cn, const char *fmt,
  87                                      va_list arg)
  88 {
  89         int free, need;
  90         va_list arg_copy;
  91
  92 again:
  93         free = cn->size - cn->used;
  94
  95         va_copy(arg_copy, arg);
  96         need = vsnprintf(cn->corename + cn->used, free, fmt, arg_copy);
  97         va_end(arg_copy);
  98
  99         if (need < free) {
 100                 cn->used += need;
 101                 return 0;
 102         }
 103
 104         if (!expand_corename(cn, cn->size + need - free + 1))
 105                 goto again;
 106
 107         return -ENOMEM;
 108 }
 109
 110 static __printf(2, 3) int cn_printf(struct core_name *cn, const char *fmt, ...)
 111 {
 112         va_list arg;
 113         int ret;
 114
 115         va_start(arg, fmt);
 116         ret = cn_vprintf(cn, fmt, arg);
 117         va_end(arg);
 118
 119         return ret;
 120 }
 121
 122 static __printf(2, 3)
 123 int cn_esc_printf(struct core_name *cn, const char *fmt, ...)
 124 {
 125         int cur = cn->used;
 126         va_list arg;
 127         int ret;
 128
 129         va_start(arg, fmt);
 130         ret = cn_vprintf(cn, fmt, arg);
 131         va_end(arg);
 132
 133         if (ret == 0) {
 134                 /*
 135                  * Ensure that this coredump name component can't cause the
 136                  * resulting corefile path to consist of a ".." or ".".
 137                  */
 138                 if ((cn->used - cur == 1 && cn->corename[cur] == '.') ||
 139                                 (cn->used - cur == 2 && cn->corename[cur] == '.'
 140                                 && cn->corename[cur+1] == '.'))
 141                         cn->corename[cur] = '!';
 142
 143                 /*
 144                  * Empty names are fishy and could be used to create a "//" in a
 145                  * corefile name, causing the coredump to happen one directory
 146                  * level too high. Enforce that all components of the core
 147                  * pattern are at least one character long.
 148                  */
 149                 if (cn->used == cur)
 150                         ret = cn_printf(cn, "!");
 151         }
 152
 153         for (; cur < cn->used; ++cur) {
 154                 if (cn->corename[cur] == '/')
 155                         cn->corename[cur] = '!';
 156         }
 157         return ret;
 158 }
 159
 160 static int cn_print_exe_file(struct core_name *cn, bool name_only)
 161 {
 162         struct file *exe_file;
 163         char *pathbuf, *path, *ptr;
 164         int ret;
 165
 166         exe_file = get_mm_exe_file(current->mm);
 167         if (!exe_file)
 168                 return cn_esc_printf(cn, "%s (path unknown)", current->comm);
 169
 170         pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
 171         if (!pathbuf) {
 172                 ret = -ENOMEM;
 173                 goto put_exe_file;
 174         }
 175
 176         path = file_path(exe_file, pathbuf, PATH_MAX);
 177         if (IS_ERR(path)) {
 178                 ret = PTR_ERR(path);
 179                 goto free_buf;
 180         }
 181
 182         if (name_only) {
 183                 ptr = strrchr(path, '/');
 184                 if (ptr)
 185                         path = ptr + 1;
 186         }
 187         ret = cn_esc_printf(cn, "%s", path);
 188
 189 free_buf:
 190         kfree(pathbuf);
 191 put_exe_file:
 192         fput(exe_file);
 193         return ret;
 194 }
 195
 196 /* format_corename will inspect the pattern parameter, and output a
 197  * name into corename, which must have space for at least
 198  * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
 199  */
 200 static int format_corename(struct core_name *cn, struct coredump_params *cprm,
 201                            size_t **argv, int *argc)
 202 {
 203         const struct cred *cred = current_cred();
 204         const char *pat_ptr = core_pattern;
 205         int ispipe = (*pat_ptr == '|');
 206         bool was_space = false;
 207         int pid_in_pattern = 0;
 208         int err = 0;
 209
 210         cn->used = 0;
 211         cn->corename = NULL;
 212         if (expand_corename(cn, core_name_size))
 213                 return -ENOMEM;
 214         cn->corename[0] = '\0';
 215
 216         if (ispipe) {
 217                 int argvs = sizeof(core_pattern) / 2;
 218                 (*argv) = kmalloc_array(argvs, sizeof(**argv), GFP_KERNEL);
 219                 if (!(*argv))
 220                         return -ENOMEM;
 221                 (*argv)[(*argc)++] = 0;
 222                 ++pat_ptr;
 223                 if (!(*pat_ptr))
 224                         return -ENOMEM;
 225         }
 226
 227         /* Repeat as long as we have more pattern to process and more output
 228            space */
 229         while (*pat_ptr) {
 230                 /*
 231                  * Split on spaces before doing template expansion so that
 232                  * %e and %E don't get split if they have spaces in them
 233                  */
 234                 if (ispipe) {
 235                         if (isspace(*pat_ptr)) {
 236                                 if (cn->used != 0)
 237                                         was_space = true;
 238                                 pat_ptr++;
 239                                 continue;
 240                         } else if (was_space) {
 241                                 was_space = false;
 242                                 err = cn_printf(cn, "%c", '\0');
 243                                 if (err)
 244                                         return err;
 245                                 (*argv)[(*argc)++] = cn->used;
 246                         }
 247                 }
 248                 if (*pat_ptr != '%') {
 249                         err = cn_printf(cn, "%c", *pat_ptr++);
 250                 } else {
 251                         switch (*++pat_ptr) {
 252                         /* single % at the end, drop that */
 253                         case 0:
 254                                 goto out;
 255                         /* Double percent, output one percent */
 256                         case '%':
 257                                 err = cn_printf(cn, "%c", '%');
 258                                 break;
 259                         /* pid */
 260                         case 'p':
 261                                 pid_in_pattern = 1;
 262                                 err = cn_printf(cn, "%d",
 263                                               task_tgid_vnr(current));
 264                                 break;
 265                         /* global pid */
 266                         case 'P':
 267                                 err = cn_printf(cn, "%d",
 268                                               task_tgid_nr(current));
 269                                 break;
 270                         case 'i':
 271                                 err = cn_printf(cn, "%d",
 272                                               task_pid_vnr(current));
 273                                 break;
 274                         case 'I':
 275                                 err = cn_printf(cn, "%d",
 276                                               task_pid_nr(current));
 277                                 break;
 278                         /* uid */
 279                         case 'u':
 280                                 err = cn_printf(cn, "%u",
 281                                                 from_kuid(&init_user_ns,
 282                                                           cred->uid));
 283                                 break;
 284                         /* gid */
 285                         case 'g':
 286                                 err = cn_printf(cn, "%u",
 287                                                 from_kgid(&init_user_ns,
 288                                                           cred->gid));
 289                                 break;
 290                         case 'd':
 291                                 err = cn_printf(cn, "%d",
 292                                         __get_dumpable(cprm->mm_flags));
 293                                 break;
 294                         /* signal that caused the coredump */
 295                         case 's':
 296                                 err = cn_printf(cn, "%d",
 297                                                 cprm->siginfo->si_signo);
 298                                 break;
 299                         /* UNIX time of coredump */
 300                         case 't': {
 301                                 time64_t time;
 302
 303                                 time = ktime_get_real_seconds();
 304                                 err = cn_printf(cn, "%lld", time);
 305                                 break;
 306                         }
 307                         /* hostname */
 308                         case 'h':
 309                                 down_read(&uts_sem);
 310                                 err = cn_esc_printf(cn, "%s",
 311                                               utsname()->nodename);
 312                                 up_read(&uts_sem);
 313                                 break;
 314                         /* executable, could be changed by prctl PR_SET_NAME etc */
 315                         case 'e':
 316                                 err = cn_esc_printf(cn, "%s", current->comm);
 317                                 break;
 318                         /* file name of executable */
 319                         case 'f':
 320                                 err = cn_print_exe_file(cn, true);
 321                                 break;
 322                         case 'E':
 323                                 err = cn_print_exe_file(cn, false);
 324                                 break;
 325                         /* core limit size */
 326                         case 'c':
 327                                 err = cn_printf(cn, "%lu",
 328                                               rlimit(RLIMIT_CORE));
 329                                 break;
 330                         default:
 331                                 break;
 332                         }
 333                         ++pat_ptr;
 334                 }
 335
 336                 if (err)
 337                         return err;
 338         }
 339
 340 out:
 341         /* Backward compatibility with core_uses_pid:
 342          *
 343          * If core_pattern does not include a %p (as is the default)
 344          * and core_uses_pid is set, then .%pid will be appended to
 345          * the filename. Do not do this for piped commands. */
 346         if (!ispipe && !pid_in_pattern && core_uses_pid) {
 347                 err = cn_printf(cn, ".%d", task_tgid_vnr(current));
 348                 if (err)
 349                         return err;
 350         }
 351         return ispipe;
 352 }
 353
 354 static int zap_process(struct task_struct *start, int exit_code, int flags)
 355 {
 356         struct task_struct *t;
 357         int nr = 0;
 358
 359         /* ignore all signals except SIGKILL, see prepare_signal() */
 360         start->signal->flags = SIGNAL_GROUP_COREDUMP | flags;
 361         start->signal->group_exit_code = exit_code;
 362         start->signal->group_stop_count = 0;
 363
 364         for_each_thread(start, t) {
 365                 task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
 366                 if (t != current && t->mm) {
 367                         sigaddset(&t->pending.signal, SIGKILL);
 368                         signal_wake_up(t, 1);
 369                         nr++;
 370                 }
 371         }
 372
 373         return nr;
 374 }
 375
 376 static int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
 377                         struct core_state *core_state, int exit_code)
 378 {
 379         struct task_struct *g, *p;
 380         unsigned long flags;
 381         int nr = -EAGAIN;
 382
 383         spin_lock_irq(&tsk->sighand->siglock);
 384         if (!signal_group_exit(tsk->signal)) {
 385                 mm->core_state = core_state;
 386                 tsk->signal->group_exit_task = tsk;
 387                 nr = zap_process(tsk, exit_code, 0);
 388                 clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
 389         }
 390         spin_unlock_irq(&tsk->sighand->siglock);
 391         if (unlikely(nr < 0))
 392                 return nr;
 393
 394         tsk->flags |= PF_DUMPCORE;
 395         if (atomic_read(&mm->mm_users) == nr + 1)
 396                 goto done;
 397         /*
 398          * We should find and kill all tasks which use this mm, and we should
 399          * count them correctly into ->nr_threads. We don't take tasklist
 400          * lock, but this is safe wrt:
 401          *
 402          * fork:
 403          *      None of sub-threads can fork after zap_process(leader). All
 404          *      processes which were created before this point should be
 405          *      visible to zap_threads() because copy_process() adds the new
 406          *      process to the tail of init_task.tasks list, and lock/unlock
 407          *      of ->siglock provides a memory barrier.
 408          *
 409          * do_exit:
 410          *      The caller holds mm->mmap_lock. This means that the task which
 411          *      uses this mm can't pass exit_mm(), so it can't exit or clear
 412          *      its ->mm.
 413          *
 414          * de_thread:
 415          *      It does list_replace_rcu(&leader->tasks, &current->tasks),
 416          *      we must see either old or new leader, this does not matter.
 417          *      However, it can change p->sighand, so lock_task_sighand(p)
 418          *      must be used. Since p->mm != NULL and we hold ->mmap_lock
 419          *      it can't fail.
 420          *
 421          *      Note also that "g" can be the old leader with ->mm == NULL
 422          *      and already unhashed and thus removed from ->thread_group.
 423          *      This is OK, __unhash_process()->list_del_rcu() does not
 424          *      clear the ->next pointer, we will find the new leader via
 425          *      next_thread().
 426          */
 427         rcu_read_lock();
 428         for_each_process(g) {
 429                 if (g == tsk->group_leader)
 430                         continue;
 431                 if (g->flags & PF_KTHREAD)
 432                         continue;
 433
 434                 for_each_thread(g, p) {
 435                         if (unlikely(!p->mm))
 436                                 continue;
 437                         if (unlikely(p->mm == mm)) {
 438                                 lock_task_sighand(p, &flags);
 439                                 nr += zap_process(p, exit_code,
 440                                                         SIGNAL_GROUP_EXIT);
 441                                 unlock_task_sighand(p, &flags);
 442                         }
 443                         break;
 444                 }
 445         }
 446         rcu_read_unlock();
 447 done:
 448         atomic_set(&core_state->nr_threads, nr);
 449         return nr;
 450 }
 451
 452 static int coredump_wait(int exit_code, struct core_state *core_state)
 453 {
 454         struct task_struct *tsk = current;
 455         struct mm_struct *mm = tsk->mm;
 456         int core_waiters = -EBUSY;
 457
 458         init_completion(&core_state->startup);
 459         core_state->dumper.task = tsk;
 460         core_state->dumper.next = NULL;
 461
 462         if (mmap_write_lock_killable(mm))
 463                 return -EINTR;
 464
 465         if (!mm->core_state)
 466                 core_waiters = zap_threads(tsk, mm, core_state, exit_code);
 467         mmap_write_unlock(mm);
 468
 469         if (core_waiters > 0) {
 470                 struct core_thread *ptr;
 471
 472                 freezer_do_not_count();
 473                 wait_for_completion(&core_state->startup);
 474                 freezer_count();
 475                 /*
 476                  * Wait for all the threads to become inactive, so that
 477                  * all the thread context (extended register state, like
 478                  * fpu etc) gets copied to the memory.
 479                  */
 480                 ptr = core_state->dumper.next;
 481                 while (ptr != NULL) {
 482                         wait_task_inactive(ptr->task, 0);
 483                         ptr = ptr->next;
 484                 }
 485         }
 486
 487         return core_waiters;
 488 }
 489
 490 static void coredump_finish(struct mm_struct *mm, bool core_dumped)
 491 {
 492         struct core_thread *curr, *next;
 493         struct task_struct *task;
 494
 495         spin_lock_irq(&current->sighand->siglock);
 496         if (core_dumped && !__fatal_signal_pending(current))
 497                 current->signal->group_exit_code |= 0x80;
 498         current->signal->group_exit_task = NULL;
 499         current->signal->flags = SIGNAL_GROUP_EXIT;
 500         spin_unlock_irq(&current->sighand->siglock);
 501
 502         next = mm->core_state->dumper.next;
 503         while ((curr = next) != NULL) {
 504                 next = curr->next;
 505                 task = curr->task;
 506                 /*
 507                  * see exit_mm(), curr->task must not see
 508                  * ->task == NULL before we read ->next.
 509                  */
 510                 smp_mb();
 511                 curr->task = NULL;
 512                 wake_up_process(task);
 513         }
 514
 515         mm->core_state = NULL;
 516 }
 517
 518 static bool dump_interrupted(void)
 519 {
 520         /*
 521          * SIGKILL or freezing() interrupt the coredumping. Perhaps we
 522          * can do try_to_freeze() and check __fatal_signal_pending(),
 523          * but then we need to teach dump_write() to restart and clear
 524          * TIF_SIGPENDING.
 525          */
 526         return fatal_signal_pending(current) || freezing(current);
 527 }
 528
 529 static void wait_for_dump_helpers(struct file *file)
 530 {
 531         struct pipe_inode_info *pipe = file->private_data;
 532
 533         pipe_lock(pipe);
 534         pipe->readers++;
 535         pipe->writers--;
 536         wake_up_interruptible_sync(&pipe->rd_wait);
 537         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 538         pipe_unlock(pipe);
 539
 540         /*
 541          * We actually want wait_event_freezable() but then we need
 542          * to clear TIF_SIGPENDING and improve dump_interrupted().
 543          */
 544         wait_event_interruptible(pipe->rd_wait, pipe->readers == 1);
 545
 546         pipe_lock(pipe);
 547         pipe->readers--;
 548         pipe->writers++;
 549         pipe_unlock(pipe);
 550 }
 551
 552 /*
 553  * umh_pipe_setup
 554  * helper function to customize the process used
 555  * to collect the core in userspace.  Specifically
 556  * it sets up a pipe and installs it as fd 0 (stdin)
 557  * for the process.  Returns 0 on success, or
 558  * PTR_ERR on failure.
 559  * Note that it also sets the core limit to 1.  This
 560  * is a special value that we use to trap recursive
 561  * core dumps
 562  */
 563 static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
 564 {
 565         struct file *files[2];
 566         struct coredump_params *cp = (struct coredump_params *)info->data;
 567         int err = create_pipe_files(files, 0);
 568         if (err)
 569                 return err;
 570
 571         cp->file = files[1];
 572
 573         err = replace_fd(0, files[0], 0);
 574         fput(files[0]);
 575         /* and disallow core files too */
 576         current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};
 577
 578         return err;
 579 }
 580
 581 void do_coredump(const kernel_siginfo_t *siginfo)
 582 {
 583         struct core_state core_state;
 584         struct core_name cn;
 585         struct mm_struct *mm = current->mm;
 586         struct linux_binfmt * binfmt;
 587         const struct cred *old_cred;
 588         struct cred *cred;
 589         int retval = 0;
 590         int ispipe;
 591         size_t *argv = NULL;
 592         int argc = 0;
 593         struct files_struct *displaced;
 594         /* require nonrelative corefile path and be extra careful */
 595         bool need_suid_safe = false;
 596         bool core_dumped = false;
 597         static atomic_t core_dump_count = ATOMIC_INIT(0);
 598         struct coredump_params cprm = {
 599                 .siginfo = siginfo,
 600                 .regs = signal_pt_regs(),
 601                 .limit = rlimit(RLIMIT_CORE),
 602                 /*
 603                  * We must use the same mm->flags while dumping core to avoid
 604                  * inconsistency of bit flags, since this flag is not protected
 605                  * by any locks.
 606                  */
 607                 .mm_flags = mm->flags,
 608                 .vma_meta = NULL,
 609         };
 610
 611         audit_core_dumps(siginfo->si_signo);
 612
 613         binfmt = mm->binfmt;
 614         if (!binfmt || !binfmt->core_dump)
 615                 goto fail;
 616         if (!__get_dumpable(cprm.mm_flags))
 617                 goto fail;
 618
 619         cred = prepare_creds();
 620         if (!cred)
 621                 goto fail;
 622         /*
 623          * We cannot trust fsuid as being the "true" uid of the process
 624          * nor do we know its entire history. We only know it was tainted
 625          * so we dump it as root in mode 2, and only into a controlled
 626          * environment (pipe handler or fully qualified path).
 627          */
 628         if (__get_dumpable(cprm.mm_flags) == SUID_DUMP_ROOT) {
 629                 /* Setuid core dump mode */
 630                 cred->fsuid = GLOBAL_ROOT_UID;  /* Dump root private */
 631                 need_suid_safe = true;
 632         }
 633
 634         retval = coredump_wait(siginfo->si_signo, &core_state);
 635         if (retval < 0)
 636                 goto fail_creds;
 637
 638         old_cred = override_creds(cred);
 639
 640         ispipe = format_corename(&cn, &cprm, &argv, &argc);
 641
 642         if (ispipe) {
 643                 int argi;
 644                 int dump_count;
 645                 char **helper_argv;
 646                 struct subprocess_info *sub_info;
 647
 648                 if (ispipe < 0) {
 649                         printk(KERN_WARNING "format_corename failed\n");
 650                         printk(KERN_WARNING "Aborting core\n");
 651                         goto fail_unlock;
 652                 }
 653
 654                 if (cprm.limit == 1) {
 655                         /* See umh_pipe_setup() which sets RLIMIT_CORE = 1.
 656                          *
 657                          * Normally core limits are irrelevant to pipes, since
 658                          * we're not writing to the file system, but we use
 659                          * cprm.limit of 1 here as a special value, this is a
 660                          * consistent way to catch recursive crashes.
 661                          * We can still crash if the core_pattern binary sets
 662                          * RLIM_CORE = !1, but it runs as root, and can do
 663                          * lots of stupid things.
 664                          *
 665                          * Note that we use task_tgid_vnr here to grab the pid
 666                          * of the process group leader.  That way we get the
 667                          * right pid if a thread in a multi-threaded
 668                          * core_pattern process dies.
 669                          */
 670                         printk(KERN_WARNING
 671                                 "Process %d(%s) has RLIMIT_CORE set to 1\n",
 672                                 task_tgid_vnr(current), current->comm);
 673                         printk(KERN_WARNING "Aborting core\n");
 674                         goto fail_unlock;
 675                 }
 676                 cprm.limit = RLIM_INFINITY;
 677
 678                 dump_count = atomic_inc_return(&core_dump_count);
 679                 if (core_pipe_limit && (core_pipe_limit < dump_count)) {
 680                         printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n",
 681                                task_tgid_vnr(current), current->comm);
 682                         printk(KERN_WARNING "Skipping core dump\n");
 683                         goto fail_dropcount;
 684                 }
 685
 686                 helper_argv = kmalloc_array(argc + 1, sizeof(*helper_argv),
 687                                             GFP_KERNEL);
 688                 if (!helper_argv) {
 689                         printk(KERN_WARNING "%s failed to allocate memory\n",
 690                                __func__);
 691                         goto fail_dropcount;
 692                 }
 693                 for (argi = 0; argi < argc; argi++)
 694                         helper_argv[argi] = cn.corename + argv[argi];
 695                 helper_argv[argi] = NULL;
 696
 697                 retval = -ENOMEM;
 698                 sub_info = call_usermodehelper_setup(helper_argv[0],
 699                                                 helper_argv, NULL, GFP_KERNEL,
 700                                                 umh_pipe_setup, NULL, &cprm);
 701                 if (sub_info)
 702                         retval = call_usermodehelper_exec(sub_info,
 703                                                           UMH_WAIT_EXEC);
 704
 705                 kfree(helper_argv);
 706                 if (retval) {
 707                         printk(KERN_INFO "Core dump to |%s pipe failed\n",
 708                                cn.corename);
 709                         goto close_fail;
 710                 }
 711         } else {
 712                 struct inode *inode;
 713                 int open_flags = O_CREAT | O_RDWR | O_NOFOLLOW |
 714                                  O_LARGEFILE | O_EXCL;
 715
 716                 if (cprm.limit < binfmt->min_coredump)
 717                         goto fail_unlock;
 718
 719                 if (need_suid_safe && cn.corename[0] != '/') {
 720                         printk(KERN_WARNING "Pid %d(%s) can only dump core "\
 721                                 "to fully qualified path!\n",
 722                                 task_tgid_vnr(current), current->comm);
 723                         printk(KERN_WARNING "Skipping core dump\n");
 724                         goto fail_unlock;
 725                 }
 726
 727                 /*
 728                  * Unlink the file if it exists unless this is a SUID
 729                  * binary - in that case, we're running around with root
 730                  * privs and don't want to unlink another user's coredump.
 731                  */
 732                 if (!need_suid_safe) {
 733                         /*
 734                          * If it doesn't exist, that's fine. If there's some
 735                          * other problem, we'll catch it at the filp_open().
 736                          */
 737                         do_unlinkat(AT_FDCWD, getname_kernel(cn.corename));
 738                 }
 739
 740                 /*
 741                  * There is a race between unlinking and creating the
 742                  * file, but if that causes an EEXIST here, that's
 743                  * fine - another process raced with us while creating
 744                  * the corefile, and the other process won. To userspace,
 745                  * what matters is that at least one of the two processes
 746                  * writes its coredump successfully, not which one.
 747                  */
 748                 if (need_suid_safe) {
 749                         /*
 750                          * Using user namespaces, normal user tasks can change
 751                          * their current->fs->root to point to arbitrary
 752                          * directories. Since the intention of the "only dump
 753                          * with a fully qualified path" rule is to control where
 754                          * coredumps may be placed using root privileges,
 755                          * current->fs->root must not be used. Instead, use the
 756                          * root directory of init_task.
 757                          */
 758                         struct path root;
 759
 760                         task_lock(&init_task);
 761                         get_fs_root(init_task.fs, &root);
 762                         task_unlock(&init_task);
 763                         cprm.file = file_open_root(root.dentry, root.mnt,
 764                                 cn.corename, open_flags, 0600);
 765                         path_put(&root);
 766                 } else {
 767                         cprm.file = filp_open(cn.corename, open_flags, 0600);
 768                 }
 769                 if (IS_ERR(cprm.file))
 770                         goto fail_unlock;
 771
 772                 inode = file_inode(cprm.file);
 773                 if (inode->i_nlink > 1)
 774                         goto close_fail;
 775                 if (d_unhashed(cprm.file->f_path.dentry))
 776                         goto close_fail;
 777                 /*
 778                  * AK: actually i see no reason to not allow this for named
 779                  * pipes etc, but keep the previous behaviour for now.
 780                  */
 781                 if (!S_ISREG(inode->i_mode))
 782                         goto close_fail;
 783                 /*
 784                  * Don't dump core if the filesystem changed owner or mode
 785                  * of the file during file creation. This is an issue when
 786                  * a process dumps core while its cwd is e.g. on a vfat
 787                  * filesystem.
 788                  */
 789                 if (!uid_eq(inode->i_uid, current_fsuid()))
 790                         goto close_fail;
 791                 if ((inode->i_mode & 0677) != 0600)
 792                         goto close_fail;
 793                 if (!(cprm.file->f_mode & FMODE_CAN_WRITE))
 794                         goto close_fail;
 795                 if (do_truncate(cprm.file->f_path.dentry, 0, 0, cprm.file))
 796                         goto close_fail;
 797         }
 798
 799         /* get us an unshared descriptor table; almost always a no-op */
 800         retval = unshare_files(&displaced);
 801         if (retval)
 802                 goto close_fail;
 803         if (displaced)
 804                 put_files_struct(displaced);
 805         if (!dump_interrupted()) {
 806                 /*
 807                  * umh disabled with CONFIG_STATIC_USERMODEHELPER_PATH="" would
 808                  * have this set to NULL.
 809                  */
 810                 if (!cprm.file) {
 811                         pr_info("Core dump to |%s disabled\n", cn.corename);
 812                         goto close_fail;
 813                 }
 814                 if (!dump_vma_snapshot(&cprm))
 815                         goto close_fail;
 816
 817                 file_start_write(cprm.file);
 818                 core_dumped = binfmt->core_dump(&cprm);
 819                 file_end_write(cprm.file);
 820                 free_vma_snapshot(&cprm);
 821         }
 822         if (ispipe && core_pipe_limit)
 823                 wait_for_dump_helpers(cprm.file);
 824 close_fail:
 825         if (cprm.file)
 826                 filp_close(cprm.file, NULL);
 827 fail_dropcount:
 828         if (ispipe)
 829                 atomic_dec(&core_dump_count);
 830 fail_unlock:
 831         kfree(argv);
 832         kfree(cn.corename);
 833         coredump_finish(mm, core_dumped);
 834         revert_creds(old_cred);
 835 fail_creds:
 836         put_cred(cred);
 837 fail:
 838         return;
 839 }
 840
 841 /*
 842  * Core dumping helper functions.  These are the only things you should
 843  * do on a core-file: use only these functions to write out all the
 844  * necessary info.
 845  */
 846 int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
 847 {
 848         struct file *file = cprm->file;
 849         loff_t pos = file->f_pos;
 850         ssize_t n;
 851         if (cprm->written + nr > cprm->limit)
 852                 return 0;
 853
 854
 855         if (dump_interrupted())
 856                 return 0;
 857         n = __kernel_write(file, addr, nr, &pos);
 858         if (n != nr)
 859                 return 0;
 860         file->f_pos = pos;
 861         cprm->written += n;
 862         cprm->pos += n;
 863
 864         return 1;
 865 }
 866 EXPORT_SYMBOL(dump_emit);
 867
 868 int dump_skip(struct coredump_params *cprm, size_t nr)
 869 {
 870         static char zeroes[PAGE_SIZE];
 871         struct file *file = cprm->file;
 872         if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
 873                 if (dump_interrupted() ||
 874                     file->f_op->llseek(file, nr, SEEK_CUR) < 0)
 875                         return 0;
 876                 cprm->pos += nr;
 877                 return 1;
 878         } else {
 879                 while (nr > PAGE_SIZE) {
 880                         if (!dump_emit(cprm, zeroes, PAGE_SIZE))
 881                                 return 0;
 882                         nr -= PAGE_SIZE;
 883                 }
 884                 return dump_emit(cprm, zeroes, nr);
 885         }
 886 }
 887 EXPORT_SYMBOL(dump_skip);
 888
 889 #ifdef CONFIG_ELF_CORE
 890 int dump_user_range(struct coredump_params *cprm, unsigned long start,
 891                     unsigned long len)
 892 {
 893         unsigned long addr;
 894
 895         for (addr = start; addr < start + len; addr += PAGE_SIZE) {
 896                 struct page *page;
 897                 int stop;
 898
 899                 /*
 900                  * To avoid having to allocate page tables for virtual address
 901                  * ranges that have never been used yet, and also to make it
 902                  * easy to generate sparse core files, use a helper that returns
 903                  * NULL when encountering an empty page table entry that would
 904                  * otherwise have been filled with the zero page.
 905                  */
 906                 page = get_dump_page(addr);
 907                 if (page) {
 908                         void *kaddr = kmap(page);
 909
 910                         stop = !dump_emit(cprm, kaddr, PAGE_SIZE);
 911                         kunmap(page);
 912                         put_page(page);
 913                 } else {
 914                         stop = !dump_skip(cprm, PAGE_SIZE);
 915                 }
 916                 if (stop)
 917                         return 0;
 918         }
 919         return 1;
 920 }
 921 #endif
 922
 923 int dump_align(struct coredump_params *cprm, int align)
 924 {
 925         unsigned mod = cprm->pos & (align - 1);
 926         if (align & (align - 1))
 927                 return 0;
 928         return mod ? dump_skip(cprm, align - mod) : 1;
 929 }
 930 EXPORT_SYMBOL(dump_align);
 931
 932 /*
 933  * Ensures that file size is big enough to contain the current file
 934  * postion. This prevents gdb from complaining about a truncated file
 935  * if the last "write" to the file was dump_skip.
 936  */
 937 void dump_truncate(struct coredump_params *cprm)
 938 {
 939         struct file *file = cprm->file;
 940         loff_t offset;
 941
 942         if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
 943                 offset = file->f_op->llseek(file, 0, SEEK_CUR);
 944                 if (i_size_read(file->f_mapping->host) < offset)
 945                         do_truncate(file->f_path.dentry, offset, 0, file);
 946         }
 947 }
 948 EXPORT_SYMBOL(dump_truncate);
 949
 950 /*
 951  * The purpose of always_dump_vma() is to make sure that special kernel mappings
 952  * that are useful for post-mortem analysis are included in every core dump.
 953  * In that way we ensure that the core dump is fully interpretable later
 954  * without matching up the same kernel and hardware config to see what PC values
 955  * meant. These special mappings include - vDSO, vsyscall, and other
 956  * architecture specific mappings
 957  */
 958 static bool always_dump_vma(struct vm_area_struct *vma)
 959 {
 960         /* Any vsyscall mappings? */
 961         if (vma == get_gate_vma(vma->vm_mm))
 962                 return true;
 963
 964         /*
 965          * Assume that all vmas with a .name op should always be dumped.
 966          * If this changes, a new vm_ops field can easily be added.
 967          */
 968         if (vma->vm_ops && vma->vm_ops->name && vma->vm_ops->name(vma))
 969                 return true;
 970
 971         /*
 972          * arch_vma_name() returns non-NULL for special architecture mappings,
 973          * such as vDSO sections.
 974          */
 975         if (arch_vma_name(vma))
 976                 return true;
 977
 978         return false;
 979 }
 980
 981 #define DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER 1
 982
 983 /*
 984  * Decide how much of @vma's contents should be included in a core dump.
 985  */
 986 static unsigned long vma_dump_size(struct vm_area_struct *vma,
 987                                    unsigned long mm_flags)
 988 {
 989 #define FILTER(type)    (mm_flags & (1UL << MMF_DUMP_##type))
 990
 991         /* always dump the vdso and vsyscall sections */
 992         if (always_dump_vma(vma))
 993                 goto whole;
 994
 995         if (vma->vm_flags & VM_DONTDUMP)
 996                 return 0;
 997
 998         /* support for DAX */
 999         if (vma_is_dax(vma)) {
1000                 if ((vma->vm_flags & VM_SHARED) && FILTER(DAX_SHARED))
1001                         goto whole;
1002                 if (!(vma->vm_flags & VM_SHARED) && FILTER(DAX_PRIVATE))
1003                         goto whole;
1004                 return 0;
1005         }
1006
1007         /* Hugetlb memory check */
1008         if (is_vm_hugetlb_page(vma)) {
1009                 if ((vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_SHARED))
1010                         goto whole;
1011                 if (!(vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_PRIVATE))
1012                         goto whole;
1013                 return 0;
1014         }
1015
1016         /* Do not dump I/O mapped devices or special mappings */
1017         if (vma->vm_flags & VM_IO)
1018                 return 0;
1019
1020         /* By default, dump shared memory if mapped from an anonymous file. */
1021         if (vma->vm_flags & VM_SHARED) {
1022                 if (file_inode(vma->vm_file)->i_nlink == 0 ?
1023                     FILTER(ANON_SHARED) : FILTER(MAPPED_SHARED))
1024                         goto whole;
1025                 return 0;
1026         }
1027
1028         /* Dump segments that have been written to.  */
1029         if ((!IS_ENABLED(CONFIG_MMU) || vma->anon_vma) && FILTER(ANON_PRIVATE))
1030                 goto whole;
1031         if (vma->vm_file == NULL)
1032                 return 0;
1033
1034         if (FILTER(MAPPED_PRIVATE))
1035                 goto whole;
1036
1037         /*
1038          * If this is the beginning of an executable file mapping,
1039          * dump the first page to aid in determining what was mapped here.
1040          */
1041         if (FILTER(ELF_HEADERS) &&
1042             vma->vm_pgoff == 0 && (vma->vm_flags & VM_READ)) {
1043                 if ((READ_ONCE(file_inode(vma->vm_file)->i_mode) & 0111) != 0)
1044                         return PAGE_SIZE;
1045
1046                 /*
1047                  * ELF libraries aren't always executable.
1048                  * We'll want to check whether the mapping starts with the ELF
1049                  * magic, but not now - we're holding the mmap lock,
1050                  * so copy_from_user() doesn't work here.
1051                  * Use a placeholder instead, and fix it up later in
1052                  * dump_vma_snapshot().
1053                  */
1054                 return DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER;
1055         }
1056
1057 #undef  FILTER
1058
1059         return 0;
1060
1061 whole:
1062         return vma->vm_end - vma->vm_start;
1063 }
1064
1065 static struct vm_area_struct *first_vma(struct task_struct *tsk,
1066                                         struct vm_area_struct *gate_vma)
1067 {
1068         struct vm_area_struct *ret = tsk->mm->mmap;
1069
1070         if (ret)
1071                 return ret;
1072         return gate_vma;
1073 }
1074
1075 /*
1076  * Helper function for iterating across a vma list.  It ensures that the caller
1077  * will visit `gate_vma' prior to terminating the search.
1078  */
1079 static struct vm_area_struct *next_vma(struct vm_area_struct *this_vma,
1080                                        struct vm_area_struct *gate_vma)
1081 {
1082         struct vm_area_struct *ret;
1083
1084         ret = this_vma->vm_next;
1085         if (ret)
1086                 return ret;
1087         if (this_vma == gate_vma)
1088                 return NULL;
1089         return gate_vma;
1090 }
1091
1092 static void free_vma_snapshot(struct coredump_params *cprm)
1093 {
1094         if (cprm->vma_meta) {
1095                 int i;
1096                 for (i = 0; i < cprm->vma_count; i++) {
1097                         struct file *file = cprm->vma_meta[i].file;
1098                         if (file)
1099                                 fput(file);
1100                 }
1101                 kvfree(cprm->vma_meta);
1102                 cprm->vma_meta = NULL;
1103         }
1104 }
1105
1106 /*
1107  * Under the mmap_lock, take a snapshot of relevant information about the task's
1108  * VMAs.
1109  */
1110 static bool dump_vma_snapshot(struct coredump_params *cprm)
1111 {
1112         struct vm_area_struct *vma, *gate_vma;
1113         struct mm_struct *mm = current->mm;
1114         int i;
1115
1116         /*
1117          * Once the stack expansion code is fixed to not change VMA bounds
1118          * under mmap_lock in read mode, this can be changed to take the
1119          * mmap_lock in read mode.
1120          */
1121         if (mmap_write_lock_killable(mm))
1122                 return false;
1123
1124         cprm->vma_data_size = 0;
1125         gate_vma = get_gate_vma(mm);
1126         cprm->vma_count = mm->map_count + (gate_vma ? 1 : 0);
1127
1128         cprm->vma_meta = kvmalloc_array(cprm->vma_count, sizeof(*cprm->vma_meta), GFP_KERNEL);
1129         if (!cprm->vma_meta) {
1130                 mmap_write_unlock(mm);
1131                 return false;
1132         }
1133
1134         for (i = 0, vma = first_vma(current, gate_vma); vma != NULL;
1135                         vma = next_vma(vma, gate_vma), i++) {
1136                 struct core_vma_metadata *m = cprm->vma_meta + i;
1137
1138                 m->start = vma->vm_start;
1139                 m->end = vma->vm_end;
1140                 m->flags = vma->vm_flags;
1141                 m->dump_size = vma_dump_size(vma, cprm->mm_flags);
1142                 m->pgoff = vma->vm_pgoff;
1143
1144                 m->file = vma->vm_file;
1145                 if (m->file)
1146                         get_file(m->file);
1147         }
1148
1149         mmap_write_unlock(mm);
1150
1151         for (i = 0; i < cprm->vma_count; i++) {
1152                 struct core_vma_metadata *m = cprm->vma_meta + i;
1153
1154                 if (m->dump_size == DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER) {
1155                         char elfmag[SELFMAG];
1156
1157                         if (copy_from_user(elfmag, (void __user *)m->start, SELFMAG) ||
1158                                         memcmp(elfmag, ELFMAG, SELFMAG) != 0) {
1159                                 m->dump_size = 0;
1160                         } else {
1161                                 m->dump_size = PAGE_SIZE;
1162                         }
1163                 }
1164
1165                 cprm->vma_data_size += m->dump_size;
1166         }
1167
1168         return true;
1169 }