mm/mremap.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *      mm/mremap.c
   4  *
   5  *      (C) Copyright 1996 Linus Torvalds
   6  *
   7  *      Address space accounting code   <alan@lxorguk.ukuu.org.uk>
   8  *      (C) Copyright 2002 Red Hat Inc, All Rights Reserved
   9  */
  10
  11 #include <linux/mm.h>
  12 #include <linux/hugetlb.h>
  13 #include <linux/shm.h>
  14 #include <linux/ksm.h>
  15 #include <linux/mman.h>
  16 #include <linux/swap.h>
  17 #include <linux/capability.h>
  18 #include <linux/fs.h>
  19 #include <linux/swapops.h>
  20 #include <linux/highmem.h>
  21 #include <linux/security.h>
  22 #include <linux/syscalls.h>
  23 #include <linux/mmu_notifier.h>
  24 #include <linux/uaccess.h>
  25 #include <linux/mm-arch-hooks.h>
  26 #include <linux/userfaultfd_k.h>
  27
  28 #include <asm/cacheflush.h>
  29 #include <asm/tlbflush.h>
  30
  31 #include "internal.h"
  32
  33 static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr)
  34 {
  35         pgd_t *pgd;
  36         p4d_t *p4d;
  37         pud_t *pud;
  38         pmd_t *pmd;
  39
  40         pgd = pgd_offset(mm, addr);
  41         if (pgd_none_or_clear_bad(pgd))
  42                 return NULL;
  43
  44         p4d = p4d_offset(pgd, addr);
  45         if (p4d_none_or_clear_bad(p4d))
  46                 return NULL;
  47
  48         pud = pud_offset(p4d, addr);
  49         if (pud_none_or_clear_bad(pud))
  50                 return NULL;
  51
  52         pmd = pmd_offset(pud, addr);
  53         if (pmd_none(*pmd))
  54                 return NULL;
  55
  56         return pmd;
  57 }
  58
  59 static pmd_t *alloc_new_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
  60                             unsigned long addr)
  61 {
  62         pgd_t *pgd;
  63         p4d_t *p4d;
  64         pud_t *pud;
  65         pmd_t *pmd;
  66
  67         pgd = pgd_offset(mm, addr);
  68         p4d = p4d_alloc(mm, pgd, addr);
  69         if (!p4d)
  70                 return NULL;
  71         pud = pud_alloc(mm, p4d, addr);
  72         if (!pud)
  73                 return NULL;
  74
  75         pmd = pmd_alloc(mm, pud, addr);
  76         if (!pmd)
  77                 return NULL;
  78
  79         VM_BUG_ON(pmd_trans_huge(*pmd));
  80
  81         return pmd;
  82 }
  83
  84 static void take_rmap_locks(struct vm_area_struct *vma)
  85 {
  86         if (vma->vm_file)
  87                 i_mmap_lock_write(vma->vm_file->f_mapping);
  88         if (vma->anon_vma)
  89                 anon_vma_lock_write(vma->anon_vma);
  90 }
  91
  92 static void drop_rmap_locks(struct vm_area_struct *vma)
  93 {
  94         if (vma->anon_vma)
  95                 anon_vma_unlock_write(vma->anon_vma);
  96         if (vma->vm_file)
  97                 i_mmap_unlock_write(vma->vm_file->f_mapping);
  98 }
  99
 100 static pte_t move_soft_dirty_pte(pte_t pte)
 101 {
 102         /*
 103          * Set soft dirty bit so we can notice
 104          * in userspace the ptes were moved.
 105          */
 106 #ifdef CONFIG_MEM_SOFT_DIRTY
 107         if (pte_present(pte))
 108                 pte = pte_mksoft_dirty(pte);
 109         else if (is_swap_pte(pte))
 110                 pte = pte_swp_mksoft_dirty(pte);
 111 #endif
 112         return pte;
 113 }
 114
 115 static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
 116                 unsigned long old_addr, unsigned long old_end,
 117                 struct vm_area_struct *new_vma, pmd_t *new_pmd,
 118                 unsigned long new_addr, bool need_rmap_locks)
 119 {
 120         struct mm_struct *mm = vma->vm_mm;
 121         pte_t *old_pte, *new_pte, pte;
 122         spinlock_t *old_ptl, *new_ptl;
 123         bool force_flush = false;
 124         unsigned long len = old_end - old_addr;
 125
 126         /*
 127          * When need_rmap_locks is true, we take the i_mmap_rwsem and anon_vma
 128          * locks to ensure that rmap will always observe either the old or the
 129          * new ptes. This is the easiest way to avoid races with
 130          * truncate_pagecache(), page migration, etc...
 131          *
 132          * When need_rmap_locks is false, we use other ways to avoid
 133          * such races:
 134          *
 135          * - During exec() shift_arg_pages(), we use a specially tagged vma
 136          *   which rmap call sites look for using is_vma_temporary_stack().
 137          *
 138          * - During mremap(), new_vma is often known to be placed after vma
 139          *   in rmap traversal order. This ensures rmap will always observe
 140          *   either the old pte, or the new pte, or both (the page table locks
 141          *   serialize access to individual ptes, but only rmap traversal
 142          *   order guarantees that we won't miss both the old and new ptes).
 143          */
 144         if (need_rmap_locks)
 145                 take_rmap_locks(vma);
 146
 147         /*
 148          * We don't have to worry about the ordering of src and dst
 149          * pte locks because exclusive mmap_sem prevents deadlock.
 150          */
 151         old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl);
 152         new_pte = pte_offset_map(new_pmd, new_addr);
 153         new_ptl = pte_lockptr(mm, new_pmd);
 154         if (new_ptl != old_ptl)
 155                 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
 156         flush_tlb_batched_pending(vma->vm_mm);
 157         arch_enter_lazy_mmu_mode();
 158
 159         for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE,
 160                                    new_pte++, new_addr += PAGE_SIZE) {
 161                 if (pte_none(*old_pte))
 162                         continue;
 163
 164                 pte = ptep_get_and_clear(mm, old_addr, old_pte);
 165                 /*
 166                  * If we are remapping a valid PTE, make sure
 167                  * to flush TLB before we drop the PTL for the
 168                  * PTE.
 169                  *
 170                  * NOTE! Both old and new PTL matter: the old one
 171                  * for racing with page_mkclean(), the new one to
 172                  * make sure the physical page stays valid until
 173                  * the TLB entry for the old mapping has been
 174                  * flushed.
 175                  */
 176                 if (pte_present(pte))
 177                         force_flush = true;
 178                 pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr);
 179                 pte = move_soft_dirty_pte(pte);
 180                 set_pte_at(mm, new_addr, new_pte, pte);
 181         }
 182
 183         arch_leave_lazy_mmu_mode();
 184         if (force_flush)
 185                 flush_tlb_range(vma, old_end - len, old_end);
 186         if (new_ptl != old_ptl)
 187                 spin_unlock(new_ptl);
 188         pte_unmap(new_pte - 1);
 189         pte_unmap_unlock(old_pte - 1, old_ptl);
 190         if (need_rmap_locks)
 191                 drop_rmap_locks(vma);
 192 }
 193
 194 #define LATENCY_LIMIT   (64 * PAGE_SIZE)
 195
 196 unsigned long move_page_tables(struct vm_area_struct *vma,
 197                 unsigned long old_addr, struct vm_area_struct *new_vma,
 198                 unsigned long new_addr, unsigned long len,
 199                 bool need_rmap_locks)
 200 {
 201         unsigned long extent, next, old_end;
 202         pmd_t *old_pmd, *new_pmd;
 203         unsigned long mmun_start;       /* For mmu_notifiers */
 204         unsigned long mmun_end;         /* For mmu_notifiers */
 205
 206         if (!len)
 207                 return 0;
 208
 209         old_end = old_addr + len;
 210         flush_cache_range(vma, old_addr, old_end);
 211
 212         mmun_start = old_addr;
 213         mmun_end   = old_end;
 214         mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
 215
 216         for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
 217                 cond_resched();
 218                 next = (old_addr + PMD_SIZE) & PMD_MASK;
 219                 /* even if next overflowed, extent below will be ok */
 220                 extent = next - old_addr;
 221                 if (extent > old_end - old_addr)
 222                         extent = old_end - old_addr;
 223                 old_pmd = get_old_pmd(vma->vm_mm, old_addr);
 224                 if (!old_pmd)
 225                         continue;
 226                 new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr);
 227                 if (!new_pmd)
 228                         break;
 229                 if (is_swap_pmd(*old_pmd) || pmd_trans_huge(*old_pmd) || pmd_devmap(*old_pmd)) {
 230                         if (extent == HPAGE_PMD_SIZE) {
 231                                 bool moved;
 232                                 /* See comment in move_ptes() */
 233                                 if (need_rmap_locks)
 234                                         take_rmap_locks(vma);
 235                                 moved = move_huge_pmd(vma, old_addr, new_addr,
 236                                                     old_end, old_pmd, new_pmd);
 237                                 if (need_rmap_locks)
 238                                         drop_rmap_locks(vma);
 239                                 if (moved)
 240                                         continue;
 241                         }
 242                         split_huge_pmd(vma, old_pmd, old_addr);
 243                         if (pmd_trans_unstable(old_pmd))
 244                                 continue;
 245                 }
 246                 if (pte_alloc(new_vma->vm_mm, new_pmd, new_addr))
 247                         break;
 248                 next = (new_addr + PMD_SIZE) & PMD_MASK;
 249                 if (extent > next - new_addr)
 250                         extent = next - new_addr;
 251                 if (extent > LATENCY_LIMIT)
 252                         extent = LATENCY_LIMIT;
 253                 move_ptes(vma, old_pmd, old_addr, old_addr + extent, new_vma,
 254                           new_pmd, new_addr, need_rmap_locks);
 255         }
 256
 257         mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
 258
 259         return len + old_addr - old_end;        /* how much done */
 260 }
 261
 262 static unsigned long move_vma(struct vm_area_struct *vma,
 263                 unsigned long old_addr, unsigned long old_len,
 264                 unsigned long new_len, unsigned long new_addr,
 265                 bool *locked, struct vm_userfaultfd_ctx *uf,
 266                 struct list_head *uf_unmap)
 267 {
 268         struct mm_struct *mm = vma->vm_mm;
 269         struct vm_area_struct *new_vma;
 270         unsigned long vm_flags = vma->vm_flags;
 271         unsigned long new_pgoff;
 272         unsigned long moved_len;
 273         unsigned long excess = 0;
 274         unsigned long hiwater_vm;
 275         int split = 0;
 276         int err;
 277         bool need_rmap_locks;
 278
 279         /*
 280          * We'd prefer to avoid failure later on in do_munmap:
 281          * which may split one vma into three before unmapping.
 282          */
 283         if (mm->map_count >= sysctl_max_map_count - 3)
 284                 return -ENOMEM;
 285
 286         /*
 287          * Advise KSM to break any KSM pages in the area to be moved:
 288          * it would be confusing if they were to turn up at the new
 289          * location, where they happen to coincide with different KSM
 290          * pages recently unmapped.  But leave vma->vm_flags as it was,
 291          * so KSM can come around to merge on vma and new_vma afterwards.
 292          */
 293         err = ksm_madvise(vma, old_addr, old_addr + old_len,
 294                                                 MADV_UNMERGEABLE, &vm_flags);
 295         if (err)
 296                 return err;
 297
 298         new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
 299         new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff,
 300                            &need_rmap_locks);
 301         if (!new_vma)
 302                 return -ENOMEM;
 303
 304         moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len,
 305                                      need_rmap_locks);
 306         if (moved_len < old_len) {
 307                 err = -ENOMEM;
 308         } else if (vma->vm_ops && vma->vm_ops->mremap) {
 309                 err = vma->vm_ops->mremap(new_vma);
 310         }
 311
 312         if (unlikely(err)) {
 313                 /*
 314                  * On error, move entries back from new area to old,
 315                  * which will succeed since page tables still there,
 316                  * and then proceed to unmap new area instead of old.
 317                  */
 318                 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len,
 319                                  true);
 320                 vma = new_vma;
 321                 old_len = new_len;
 322                 old_addr = new_addr;
 323                 new_addr = err;
 324         } else {
 325                 mremap_userfaultfd_prep(new_vma, uf);
 326                 arch_remap(mm, old_addr, old_addr + old_len,
 327                            new_addr, new_addr + new_len);
 328         }
 329
 330         /* Conceal VM_ACCOUNT so old reservation is not undone */
 331         if (vm_flags & VM_ACCOUNT) {
 332                 vma->vm_flags &= ~VM_ACCOUNT;
 333                 excess = vma->vm_end - vma->vm_start - old_len;
 334                 if (old_addr > vma->vm_start &&
 335                     old_addr + old_len < vma->vm_end)
 336                         split = 1;
 337         }
 338
 339         /*
 340          * If we failed to move page tables we still do total_vm increment
 341          * since do_munmap() will decrement it by old_len == new_len.
 342          *
 343          * Since total_vm is about to be raised artificially high for a
 344          * moment, we need to restore high watermark afterwards: if stats
 345          * are taken meanwhile, total_vm and hiwater_vm appear too high.
 346          * If this were a serious issue, we'd add a flag to do_munmap().
 347          */
 348         hiwater_vm = mm->hiwater_vm;
 349         vm_stat_account(mm, vma->vm_flags, new_len >> PAGE_SHIFT);
 350
 351         /* Tell pfnmap has moved from this vma */
 352         if (unlikely(vma->vm_flags & VM_PFNMAP))
 353                 untrack_pfn_moved(vma);
 354
 355         if (do_munmap(mm, old_addr, old_len, uf_unmap) < 0) {
 356                 /* OOM: unable to split vma, just get accounts right */
 357                 vm_unacct_memory(excess >> PAGE_SHIFT);
 358                 excess = 0;
 359         }
 360         mm->hiwater_vm = hiwater_vm;
 361
 362         /* Restore VM_ACCOUNT if one or two pieces of vma left */
 363         if (excess) {
 364                 vma->vm_flags |= VM_ACCOUNT;
 365                 if (split)
 366                         vma->vm_next->vm_flags |= VM_ACCOUNT;
 367         }
 368
 369         if (vm_flags & VM_LOCKED) {
 370                 mm->locked_vm += new_len >> PAGE_SHIFT;
 371                 *locked = true;
 372         }
 373
 374         return new_addr;
 375 }
 376
 377 static struct vm_area_struct *vma_to_resize(unsigned long addr,
 378         unsigned long old_len, unsigned long new_len, unsigned long *p)
 379 {
 380         struct mm_struct *mm = current->mm;
 381         struct vm_area_struct *vma = find_vma(mm, addr);
 382         unsigned long pgoff;
 383
 384         if (!vma || vma->vm_start > addr)
 385                 return ERR_PTR(-EFAULT);
 386
 387         /*
 388          * !old_len is a special case where an attempt is made to 'duplicate'
 389          * a mapping.  This makes no sense for private mappings as it will
 390          * instead create a fresh/new mapping unrelated to the original.  This
 391          * is contrary to the basic idea of mremap which creates new mappings
 392          * based on the original.  There are no known use cases for this
 393          * behavior.  As a result, fail such attempts.
 394          */
 395         if (!old_len && !(vma->vm_flags & (VM_SHARED | VM_MAYSHARE))) {
 396                 pr_warn_once("%s (%d): attempted to duplicate a private mapping with mremap.  This is not supported.\n", current->comm, current->pid);
 397                 return ERR_PTR(-EINVAL);
 398         }
 399
 400         if (is_vm_hugetlb_page(vma))
 401                 return ERR_PTR(-EINVAL);
 402
 403         /* We can't remap across vm area boundaries */
 404         if (old_len > vma->vm_end - addr)
 405                 return ERR_PTR(-EFAULT);
 406
 407         if (new_len == old_len)
 408                 return vma;
 409
 410         /* Need to be careful about a growing mapping */
 411         pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
 412         pgoff += vma->vm_pgoff;
 413         if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
 414                 return ERR_PTR(-EINVAL);
 415
 416         if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
 417                 return ERR_PTR(-EFAULT);
 418
 419         if (vma->vm_flags & VM_LOCKED) {
 420                 unsigned long locked, lock_limit;
 421                 locked = mm->locked_vm << PAGE_SHIFT;
 422                 lock_limit = rlimit(RLIMIT_MEMLOCK);
 423                 locked += new_len - old_len;
 424                 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
 425                         return ERR_PTR(-EAGAIN);
 426         }
 427
 428         if (!may_expand_vm(mm, vma->vm_flags,
 429                                 (new_len - old_len) >> PAGE_SHIFT))
 430                 return ERR_PTR(-ENOMEM);
 431
 432         if (vma->vm_flags & VM_ACCOUNT) {
 433                 unsigned long charged = (new_len - old_len) >> PAGE_SHIFT;
 434                 if (security_vm_enough_memory_mm(mm, charged))
 435                         return ERR_PTR(-ENOMEM);
 436                 *p = charged;
 437         }
 438
 439         return vma;
 440 }
 441
 442 static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
 443                 unsigned long new_addr, unsigned long new_len, bool *locked,
 444                 struct vm_userfaultfd_ctx *uf,
 445                 struct list_head *uf_unmap_early,
 446                 struct list_head *uf_unmap)
 447 {
 448         struct mm_struct *mm = current->mm;
 449         struct vm_area_struct *vma;
 450         unsigned long ret = -EINVAL;
 451         unsigned long charged = 0;
 452         unsigned long map_flags;
 453
 454         if (offset_in_page(new_addr))
 455                 goto out;
 456
 457         if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
 458                 goto out;
 459
 460         /* Ensure the old/new locations do not overlap */
 461         if (addr + old_len > new_addr && new_addr + new_len > addr)
 462                 goto out;
 463
 464         ret = do_munmap(mm, new_addr, new_len, uf_unmap_early);
 465         if (ret)
 466                 goto out;
 467
 468         if (old_len >= new_len) {
 469                 ret = do_munmap(mm, addr+new_len, old_len - new_len, uf_unmap);
 470                 if (ret && old_len != new_len)
 471                         goto out;
 472                 old_len = new_len;
 473         }
 474
 475         vma = vma_to_resize(addr, old_len, new_len, &charged);
 476         if (IS_ERR(vma)) {
 477                 ret = PTR_ERR(vma);
 478                 goto out;
 479         }
 480
 481         map_flags = MAP_FIXED;
 482         if (vma->vm_flags & VM_MAYSHARE)
 483                 map_flags |= MAP_SHARED;
 484
 485         ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff +
 486                                 ((addr - vma->vm_start) >> PAGE_SHIFT),
 487                                 map_flags);
 488         if (offset_in_page(ret))
 489                 goto out1;
 490
 491         ret = move_vma(vma, addr, old_len, new_len, new_addr, locked, uf,
 492                        uf_unmap);
 493         if (!(offset_in_page(ret)))
 494                 goto out;
 495 out1:
 496         vm_unacct_memory(charged);
 497
 498 out:
 499         return ret;
 500 }
 501
 502 static int vma_expandable(struct vm_area_struct *vma, unsigned long delta)
 503 {
 504         unsigned long end = vma->vm_end + delta;
 505         if (end < vma->vm_end) /* overflow */
 506                 return 0;
 507         if (vma->vm_next && vma->vm_next->vm_start < end) /* intersection */
 508                 return 0;
 509         if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start,
 510                               0, MAP_FIXED) & ~PAGE_MASK)
 511                 return 0;
 512         return 1;
 513 }
 514
 515 /*
 516  * Expand (or shrink) an existing mapping, potentially moving it at the
 517  * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
 518  *
 519  * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
 520  * This option implies MREMAP_MAYMOVE.
 521  */
 522 SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
 523                 unsigned long, new_len, unsigned long, flags,
 524                 unsigned long, new_addr)
 525 {
 526         struct mm_struct *mm = current->mm;
 527         struct vm_area_struct *vma;
 528         unsigned long ret = -EINVAL;
 529         unsigned long charged = 0;
 530         bool locked = false;
 531         struct vm_userfaultfd_ctx uf = NULL_VM_UFFD_CTX;
 532         LIST_HEAD(uf_unmap_early);
 533         LIST_HEAD(uf_unmap);
 534
 535         if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
 536                 return ret;
 537
 538         if (flags & MREMAP_FIXED && !(flags & MREMAP_MAYMOVE))
 539                 return ret;
 540
 541         if (offset_in_page(addr))
 542                 return ret;
 543
 544         old_len = PAGE_ALIGN(old_len);
 545         new_len = PAGE_ALIGN(new_len);
 546
 547         /*
 548          * We allow a zero old-len as a special case
 549          * for DOS-emu "duplicate shm area" thing. But
 550          * a zero new-len is nonsensical.
 551          */
 552         if (!new_len)
 553                 return ret;
 554
 555         if (down_write_killable(&current->mm->mmap_sem))
 556                 return -EINTR;
 557
 558         if (flags & MREMAP_FIXED) {
 559                 ret = mremap_to(addr, old_len, new_addr, new_len,
 560                                 &locked, &uf, &uf_unmap_early, &uf_unmap);
 561                 goto out;
 562         }
 563
 564         /*
 565          * Always allow a shrinking remap: that just unmaps
 566          * the unnecessary pages..
 567          * do_munmap does all the needed commit accounting
 568          */
 569         if (old_len >= new_len) {
 570                 ret = do_munmap(mm, addr+new_len, old_len - new_len, &uf_unmap);
 571                 if (ret && old_len != new_len)
 572                         goto out;
 573                 ret = addr;
 574                 goto out;
 575         }
 576
 577         /*
 578          * Ok, we need to grow..
 579          */
 580         vma = vma_to_resize(addr, old_len, new_len, &charged);
 581         if (IS_ERR(vma)) {
 582                 ret = PTR_ERR(vma);
 583                 goto out;
 584         }
 585
 586         /* old_len exactly to the end of the area..
 587          */
 588         if (old_len == vma->vm_end - addr) {
 589                 /* can we just expand the current mapping? */
 590                 if (vma_expandable(vma, new_len - old_len)) {
 591                         int pages = (new_len - old_len) >> PAGE_SHIFT;
 592
 593                         if (vma_adjust(vma, vma->vm_start, addr + new_len,
 594                                        vma->vm_pgoff, NULL)) {
 595                                 ret = -ENOMEM;
 596                                 goto out;
 597                         }
 598
 599                         vm_stat_account(mm, vma->vm_flags, pages);
 600                         if (vma->vm_flags & VM_LOCKED) {
 601                                 mm->locked_vm += pages;
 602                                 locked = true;
 603                                 new_addr = addr;
 604                         }
 605                         ret = addr;
 606                         goto out;
 607                 }
 608         }
 609
 610         /*
 611          * We weren't able to just expand or shrink the area,
 612          * we need to create a new one and move it..
 613          */
 614         ret = -ENOMEM;
 615         if (flags & MREMAP_MAYMOVE) {
 616                 unsigned long map_flags = 0;
 617                 if (vma->vm_flags & VM_MAYSHARE)
 618                         map_flags |= MAP_SHARED;
 619
 620                 new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
 621                                         vma->vm_pgoff +
 622                                         ((addr - vma->vm_start) >> PAGE_SHIFT),
 623                                         map_flags);
 624                 if (offset_in_page(new_addr)) {
 625                         ret = new_addr;
 626                         goto out;
 627                 }
 628
 629                 ret = move_vma(vma, addr, old_len, new_len, new_addr,
 630                                &locked, &uf, &uf_unmap);
 631         }
 632 out:
 633         if (offset_in_page(ret)) {
 634                 vm_unacct_memory(charged);
 635                 locked = 0;
 636         }
 637         up_write(&current->mm->mmap_sem);
 638         if (locked && new_len > old_len)
 639                 mm_populate(new_addr + old_len, new_len - old_len);
 640         userfaultfd_unmap_complete(mm, &uf_unmap_early);
 641         mremap_userfaultfd_complete(&uf, addr, new_addr, old_len);
 642         userfaultfd_unmap_complete(mm, &uf_unmap);
 643         return ret;
 644 }