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, bool *need_flush)
 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 dirty PTE, make sure
 167                  * to flush TLB before we drop the PTL for the
 168                  * old PTE or we may race with page_mkclean().
 169                  *
 170                  * This check has to be done after we removed the
 171                  * old PTE from page tables or another thread may
 172                  * dirty it after the check and before the removal.
 173                  */
 174                 if (pte_present(pte) && pte_dirty(pte))
 175                         force_flush = true;
 176                 pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr);
 177                 pte = move_soft_dirty_pte(pte);
 178                 set_pte_at(mm, new_addr, new_pte, pte);
 179         }
 180
 181         arch_leave_lazy_mmu_mode();
 182         if (new_ptl != old_ptl)
 183                 spin_unlock(new_ptl);
 184         pte_unmap(new_pte - 1);
 185         if (force_flush)
 186                 flush_tlb_range(vma, old_end - len, old_end);
 187         else
 188                 *need_flush = true;
 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         bool need_flush = false;
 204         unsigned long mmun_start;       /* For mmu_notifiers */
 205         unsigned long mmun_end;         /* For mmu_notifiers */
 206
 207         old_end = old_addr + len;
 208         flush_cache_range(vma, old_addr, old_end);
 209
 210         mmun_start = old_addr;
 211         mmun_end   = old_end;
 212         mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
 213
 214         for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
 215                 cond_resched();
 216                 next = (old_addr + PMD_SIZE) & PMD_MASK;
 217                 /* even if next overflowed, extent below will be ok */
 218                 extent = next - old_addr;
 219                 if (extent > old_end - old_addr)
 220                         extent = old_end - old_addr;
 221                 old_pmd = get_old_pmd(vma->vm_mm, old_addr);
 222                 if (!old_pmd)
 223                         continue;
 224                 new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr);
 225                 if (!new_pmd)
 226                         break;
 227                 if (is_swap_pmd(*old_pmd) || pmd_trans_huge(*old_pmd)) {
 228                         if (extent == HPAGE_PMD_SIZE) {
 229                                 bool moved;
 230                                 /* See comment in move_ptes() */
 231                                 if (need_rmap_locks)
 232                                         take_rmap_locks(vma);
 233                                 moved = move_huge_pmd(vma, old_addr, new_addr,
 234                                                     old_end, old_pmd, new_pmd,
 235                                                     &need_flush);
 236                                 if (need_rmap_locks)
 237                                         drop_rmap_locks(vma);
 238                                 if (moved)
 239                                         continue;
 240                         }
 241                         split_huge_pmd(vma, old_pmd, old_addr);
 242                         if (pmd_trans_unstable(old_pmd))
 243                                 continue;
 244                 }
 245                 if (pte_alloc(new_vma->vm_mm, new_pmd, new_addr))
 246                         break;
 247                 next = (new_addr + PMD_SIZE) & PMD_MASK;
 248                 if (extent > next - new_addr)
 249                         extent = next - new_addr;
 250                 if (extent > LATENCY_LIMIT)
 251                         extent = LATENCY_LIMIT;
 252                 move_ptes(vma, old_pmd, old_addr, old_addr + extent, new_vma,
 253                           new_pmd, new_addr, need_rmap_locks, &need_flush);
 254         }
 255         if (need_flush)
 256                 flush_tlb_range(vma, old_end-len, old_addr);
 257
 258         mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
 259
 260         return len + old_addr - old_end;        /* how much done */
 261 }
 262
 263 static unsigned long move_vma(struct vm_area_struct *vma,
 264                 unsigned long old_addr, unsigned long old_len,
 265                 unsigned long new_len, unsigned long new_addr,
 266                 bool *locked, struct vm_userfaultfd_ctx *uf,
 267                 struct list_head *uf_unmap)
 268 {
 269         struct mm_struct *mm = vma->vm_mm;
 270         struct vm_area_struct *new_vma;
 271         unsigned long vm_flags = vma->vm_flags;
 272         unsigned long new_pgoff;
 273         unsigned long moved_len;
 274         unsigned long excess = 0;
 275         unsigned long hiwater_vm;
 276         int split = 0;
 277         int err;
 278         bool need_rmap_locks;
 279
 280         /*
 281          * We'd prefer to avoid failure later on in do_munmap:
 282          * which may split one vma into three before unmapping.
 283          */
 284         if (mm->map_count >= sysctl_max_map_count - 3)
 285                 return -ENOMEM;
 286
 287         /*
 288          * Advise KSM to break any KSM pages in the area to be moved:
 289          * it would be confusing if they were to turn up at the new
 290          * location, where they happen to coincide with different KSM
 291          * pages recently unmapped.  But leave vma->vm_flags as it was,
 292          * so KSM can come around to merge on vma and new_vma afterwards.
 293          */
 294         err = ksm_madvise(vma, old_addr, old_addr + old_len,
 295                                                 MADV_UNMERGEABLE, &vm_flags);
 296         if (err)
 297                 return err;
 298
 299         new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
 300         new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff,
 301                            &need_rmap_locks);
 302         if (!new_vma)
 303                 return -ENOMEM;
 304
 305         moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len,
 306                                      need_rmap_locks);
 307         if (moved_len < old_len) {
 308                 err = -ENOMEM;
 309         } else if (vma->vm_ops && vma->vm_ops->mremap) {
 310                 err = vma->vm_ops->mremap(new_vma);
 311         }
 312
 313         if (unlikely(err)) {
 314                 /*
 315                  * On error, move entries back from new area to old,
 316                  * which will succeed since page tables still there,
 317                  * and then proceed to unmap new area instead of old.
 318                  */
 319                 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len,
 320                                  true);
 321                 vma = new_vma;
 322                 old_len = new_len;
 323                 old_addr = new_addr;
 324                 new_addr = err;
 325         } else {
 326                 mremap_userfaultfd_prep(new_vma, uf);
 327                 arch_remap(mm, old_addr, old_addr + old_len,
 328                            new_addr, new_addr + new_len);
 329         }
 330
 331         /* Conceal VM_ACCOUNT so old reservation is not undone */
 332         if (vm_flags & VM_ACCOUNT) {
 333                 vma->vm_flags &= ~VM_ACCOUNT;
 334                 excess = vma->vm_end - vma->vm_start - old_len;
 335                 if (old_addr > vma->vm_start &&
 336                     old_addr + old_len < vma->vm_end)
 337                         split = 1;
 338         }
 339
 340         /*
 341          * If we failed to move page tables we still do total_vm increment
 342          * since do_munmap() will decrement it by old_len == new_len.
 343          *
 344          * Since total_vm is about to be raised artificially high for a
 345          * moment, we need to restore high watermark afterwards: if stats
 346          * are taken meanwhile, total_vm and hiwater_vm appear too high.
 347          * If this were a serious issue, we'd add a flag to do_munmap().
 348          */
 349         hiwater_vm = mm->hiwater_vm;
 350         vm_stat_account(mm, vma->vm_flags, new_len >> PAGE_SHIFT);
 351
 352         /* Tell pfnmap has moved from this vma */
 353         if (unlikely(vma->vm_flags & VM_PFNMAP))
 354                 untrack_pfn_moved(vma);
 355
 356         if (do_munmap(mm, old_addr, old_len, uf_unmap) < 0) {
 357                 /* OOM: unable to split vma, just get accounts right */
 358                 vm_unacct_memory(excess >> PAGE_SHIFT);
 359                 excess = 0;
 360         }
 361         mm->hiwater_vm = hiwater_vm;
 362
 363         /* Restore VM_ACCOUNT if one or two pieces of vma left */
 364         if (excess) {
 365                 vma->vm_flags |= VM_ACCOUNT;
 366                 if (split)
 367                         vma->vm_next->vm_flags |= VM_ACCOUNT;
 368         }
 369
 370         if (vm_flags & VM_LOCKED) {
 371                 mm->locked_vm += new_len >> PAGE_SHIFT;
 372                 *locked = true;
 373         }
 374
 375         return new_addr;
 376 }
 377
 378 static struct vm_area_struct *vma_to_resize(unsigned long addr,
 379         unsigned long old_len, unsigned long new_len, unsigned long *p)
 380 {
 381         struct mm_struct *mm = current->mm;
 382         struct vm_area_struct *vma = find_vma(mm, addr);
 383         unsigned long pgoff;
 384
 385         if (!vma || vma->vm_start > addr)
 386                 return ERR_PTR(-EFAULT);
 387
 388         /*
 389          * !old_len is a special case where an attempt is made to 'duplicate'
 390          * a mapping.  This makes no sense for private mappings as it will
 391          * instead create a fresh/new mapping unrelated to the original.  This
 392          * is contrary to the basic idea of mremap which creates new mappings
 393          * based on the original.  There are no known use cases for this
 394          * behavior.  As a result, fail such attempts.
 395          */
 396         if (!old_len && !(vma->vm_flags & (VM_SHARED | VM_MAYSHARE))) {
 397                 pr_warn_once("%s (%d): attempted to duplicate a private mapping with mremap.  This is not supported.\n", current->comm, current->pid);
 398                 return ERR_PTR(-EINVAL);
 399         }
 400
 401         if (is_vm_hugetlb_page(vma))
 402                 return ERR_PTR(-EINVAL);
 403
 404         /* We can't remap across vm area boundaries */
 405         if (old_len > vma->vm_end - addr)
 406                 return ERR_PTR(-EFAULT);
 407
 408         if (new_len == old_len)
 409                 return vma;
 410
 411         /* Need to be careful about a growing mapping */
 412         pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
 413         pgoff += vma->vm_pgoff;
 414         if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
 415                 return ERR_PTR(-EINVAL);
 416
 417         if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
 418                 return ERR_PTR(-EFAULT);
 419
 420         if (vma->vm_flags & VM_LOCKED) {
 421                 unsigned long locked, lock_limit;
 422                 locked = mm->locked_vm << PAGE_SHIFT;
 423                 lock_limit = rlimit(RLIMIT_MEMLOCK);
 424                 locked += new_len - old_len;
 425                 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
 426                         return ERR_PTR(-EAGAIN);
 427         }
 428
 429         if (!may_expand_vm(mm, vma->vm_flags,
 430                                 (new_len - old_len) >> PAGE_SHIFT))
 431                 return ERR_PTR(-ENOMEM);
 432
 433         if (vma->vm_flags & VM_ACCOUNT) {
 434                 unsigned long charged = (new_len - old_len) >> PAGE_SHIFT;
 435                 if (security_vm_enough_memory_mm(mm, charged))
 436                         return ERR_PTR(-ENOMEM);
 437                 *p = charged;
 438         }
 439
 440         return vma;
 441 }
 442
 443 static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
 444                 unsigned long new_addr, unsigned long new_len, bool *locked,
 445                 struct vm_userfaultfd_ctx *uf,
 446                 struct list_head *uf_unmap_early,
 447                 struct list_head *uf_unmap)
 448 {
 449         struct mm_struct *mm = current->mm;
 450         struct vm_area_struct *vma;
 451         unsigned long ret = -EINVAL;
 452         unsigned long charged = 0;
 453         unsigned long map_flags;
 454
 455         if (offset_in_page(new_addr))
 456                 goto out;
 457
 458         if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
 459                 goto out;
 460
 461         /* Ensure the old/new locations do not overlap */
 462         if (addr + old_len > new_addr && new_addr + new_len > addr)
 463                 goto out;
 464
 465         ret = do_munmap(mm, new_addr, new_len, uf_unmap_early);
 466         if (ret)
 467                 goto out;
 468
 469         if (old_len >= new_len) {
 470                 ret = do_munmap(mm, addr+new_len, old_len - new_len, uf_unmap);
 471                 if (ret && old_len != new_len)
 472                         goto out;
 473                 old_len = new_len;
 474         }
 475
 476         vma = vma_to_resize(addr, old_len, new_len, &charged);
 477         if (IS_ERR(vma)) {
 478                 ret = PTR_ERR(vma);
 479                 goto out;
 480         }
 481
 482         map_flags = MAP_FIXED;
 483         if (vma->vm_flags & VM_MAYSHARE)
 484                 map_flags |= MAP_SHARED;
 485
 486         ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff +
 487                                 ((addr - vma->vm_start) >> PAGE_SHIFT),
 488                                 map_flags);
 489         if (offset_in_page(ret))
 490                 goto out1;
 491
 492         ret = move_vma(vma, addr, old_len, new_len, new_addr, locked, uf,
 493                        uf_unmap);
 494         if (!(offset_in_page(ret)))
 495                 goto out;
 496 out1:
 497         vm_unacct_memory(charged);
 498
 499 out:
 500         return ret;
 501 }
 502
 503 static int vma_expandable(struct vm_area_struct *vma, unsigned long delta)
 504 {
 505         unsigned long end = vma->vm_end + delta;
 506         if (end < vma->vm_end) /* overflow */
 507                 return 0;
 508         if (vma->vm_next && vma->vm_next->vm_start < end) /* intersection */
 509                 return 0;
 510         if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start,
 511                               0, MAP_FIXED) & ~PAGE_MASK)
 512                 return 0;
 513         return 1;
 514 }
 515
 516 /*
 517  * Expand (or shrink) an existing mapping, potentially moving it at the
 518  * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
 519  *
 520  * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
 521  * This option implies MREMAP_MAYMOVE.
 522  */
 523 SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
 524                 unsigned long, new_len, unsigned long, flags,
 525                 unsigned long, new_addr)
 526 {
 527         struct mm_struct *mm = current->mm;
 528         struct vm_area_struct *vma;
 529         unsigned long ret = -EINVAL;
 530         unsigned long charged = 0;
 531         bool locked = false;
 532         struct vm_userfaultfd_ctx uf = NULL_VM_UFFD_CTX;
 533         LIST_HEAD(uf_unmap_early);
 534         LIST_HEAD(uf_unmap);
 535
 536         if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
 537                 return ret;
 538
 539         if (flags & MREMAP_FIXED && !(flags & MREMAP_MAYMOVE))
 540                 return ret;
 541
 542         if (offset_in_page(addr))
 543                 return ret;
 544
 545         old_len = PAGE_ALIGN(old_len);
 546         new_len = PAGE_ALIGN(new_len);
 547
 548         /*
 549          * We allow a zero old-len as a special case
 550          * for DOS-emu "duplicate shm area" thing. But
 551          * a zero new-len is nonsensical.
 552          */
 553         if (!new_len)
 554                 return ret;
 555
 556         if (down_write_killable(&current->mm->mmap_sem))
 557                 return -EINTR;
 558
 559         if (flags & MREMAP_FIXED) {
 560                 ret = mremap_to(addr, old_len, new_addr, new_len,
 561                                 &locked, &uf, &uf_unmap_early, &uf_unmap);
 562                 goto out;
 563         }
 564
 565         /*
 566          * Always allow a shrinking remap: that just unmaps
 567          * the unnecessary pages..
 568          * do_munmap does all the needed commit accounting
 569          */
 570         if (old_len >= new_len) {
 571                 ret = do_munmap(mm, addr+new_len, old_len - new_len, &uf_unmap);
 572                 if (ret && old_len != new_len)
 573                         goto out;
 574                 ret = addr;
 575                 goto out;
 576         }
 577
 578         /*
 579          * Ok, we need to grow..
 580          */
 581         vma = vma_to_resize(addr, old_len, new_len, &charged);
 582         if (IS_ERR(vma)) {
 583                 ret = PTR_ERR(vma);
 584                 goto out;
 585         }
 586
 587         /* old_len exactly to the end of the area..
 588          */
 589         if (old_len == vma->vm_end - addr) {
 590                 /* can we just expand the current mapping? */
 591                 if (vma_expandable(vma, new_len - old_len)) {
 592                         int pages = (new_len - old_len) >> PAGE_SHIFT;
 593
 594                         if (vma_adjust(vma, vma->vm_start, addr + new_len,
 595                                        vma->vm_pgoff, NULL)) {
 596                                 ret = -ENOMEM;
 597                                 goto out;
 598                         }
 599
 600                         vm_stat_account(mm, vma->vm_flags, pages);
 601                         if (vma->vm_flags & VM_LOCKED) {
 602                                 mm->locked_vm += pages;
 603                                 locked = true;
 604                                 new_addr = addr;
 605                         }
 606                         ret = addr;
 607                         goto out;
 608                 }
 609         }
 610
 611         /*
 612          * We weren't able to just expand or shrink the area,
 613          * we need to create a new one and move it..
 614          */
 615         ret = -ENOMEM;
 616         if (flags & MREMAP_MAYMOVE) {
 617                 unsigned long map_flags = 0;
 618                 if (vma->vm_flags & VM_MAYSHARE)
 619                         map_flags |= MAP_SHARED;
 620
 621                 new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
 622                                         vma->vm_pgoff +
 623                                         ((addr - vma->vm_start) >> PAGE_SHIFT),
 624                                         map_flags);
 625                 if (offset_in_page(new_addr)) {
 626                         ret = new_addr;
 627                         goto out;
 628                 }
 629
 630                 ret = move_vma(vma, addr, old_len, new_len, new_addr,
 631                                &locked, &uf, &uf_unmap);
 632         }
 633 out:
 634         if (offset_in_page(ret)) {
 635                 vm_unacct_memory(charged);
 636                 locked = 0;
 637         }
 638         up_write(&current->mm->mmap_sem);
 639         if (locked && new_len > old_len)
 640                 mm_populate(new_addr + old_len, new_len - old_len);
 641         userfaultfd_unmap_complete(mm, &uf_unmap_early);
 642         mremap_userfaultfd_complete(&uf, addr, new_addr, old_len);
 643         userfaultfd_unmap_complete(mm, &uf_unmap);
 644         return ret;
 645 }