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 unsigned long move_page_tables(struct vm_area_struct *vma,
 195                 unsigned long old_addr, struct vm_area_struct *new_vma,
 196                 unsigned long new_addr, unsigned long len,
 197                 bool need_rmap_locks)
 198 {
 199         unsigned long extent, next, old_end;
 200         pmd_t *old_pmd, *new_pmd;
 201         unsigned long mmun_start;       /* For mmu_notifiers */
 202         unsigned long mmun_end;         /* For mmu_notifiers */
 203
 204         old_end = old_addr + len;
 205         flush_cache_range(vma, old_addr, old_end);
 206
 207         mmun_start = old_addr;
 208         mmun_end   = old_end;
 209         mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
 210
 211         for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
 212                 cond_resched();
 213                 next = (old_addr + PMD_SIZE) & PMD_MASK;
 214                 /* even if next overflowed, extent below will be ok */
 215                 extent = next - old_addr;
 216                 if (extent > old_end - old_addr)
 217                         extent = old_end - old_addr;
 218                 old_pmd = get_old_pmd(vma->vm_mm, old_addr);
 219                 if (!old_pmd)
 220                         continue;
 221                 new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr);
 222                 if (!new_pmd)
 223                         break;
 224                 if (is_swap_pmd(*old_pmd) || pmd_trans_huge(*old_pmd)) {
 225                         if (extent == HPAGE_PMD_SIZE) {
 226                                 bool moved;
 227                                 /* See comment in move_ptes() */
 228                                 if (need_rmap_locks)
 229                                         take_rmap_locks(vma);
 230                                 moved = move_huge_pmd(vma, old_addr, new_addr,
 231                                                     old_end, old_pmd, new_pmd);
 232                                 if (need_rmap_locks)
 233                                         drop_rmap_locks(vma);
 234                                 if (moved)
 235                                         continue;
 236                         }
 237                         split_huge_pmd(vma, old_pmd, old_addr);
 238                         if (pmd_trans_unstable(old_pmd))
 239                                 continue;
 240                 }
 241                 if (pte_alloc(new_vma->vm_mm, new_pmd, new_addr))
 242                         break;
 243                 next = (new_addr + PMD_SIZE) & PMD_MASK;
 244                 if (extent > next - new_addr)
 245                         extent = next - new_addr;
 246                 move_ptes(vma, old_pmd, old_addr, old_addr + extent, new_vma,
 247                           new_pmd, new_addr, need_rmap_locks);
 248         }
 249
 250         mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
 251
 252         return len + old_addr - old_end;        /* how much done */
 253 }
 254
 255 static unsigned long move_vma(struct vm_area_struct *vma,
 256                 unsigned long old_addr, unsigned long old_len,
 257                 unsigned long new_len, unsigned long new_addr,
 258                 bool *locked, struct vm_userfaultfd_ctx *uf,
 259                 struct list_head *uf_unmap)
 260 {
 261         struct mm_struct *mm = vma->vm_mm;
 262         struct vm_area_struct *new_vma;
 263         unsigned long vm_flags = vma->vm_flags;
 264         unsigned long new_pgoff;
 265         unsigned long moved_len;
 266         unsigned long excess = 0;
 267         unsigned long hiwater_vm;
 268         int split = 0;
 269         int err;
 270         bool need_rmap_locks;
 271
 272         /*
 273          * We'd prefer to avoid failure later on in do_munmap:
 274          * which may split one vma into three before unmapping.
 275          */
 276         if (mm->map_count >= sysctl_max_map_count - 3)
 277                 return -ENOMEM;
 278
 279         /*
 280          * Advise KSM to break any KSM pages in the area to be moved:
 281          * it would be confusing if they were to turn up at the new
 282          * location, where they happen to coincide with different KSM
 283          * pages recently unmapped.  But leave vma->vm_flags as it was,
 284          * so KSM can come around to merge on vma and new_vma afterwards.
 285          */
 286         err = ksm_madvise(vma, old_addr, old_addr + old_len,
 287                                                 MADV_UNMERGEABLE, &vm_flags);
 288         if (err)
 289                 return err;
 290
 291         new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
 292         new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff,
 293                            &need_rmap_locks);
 294         if (!new_vma)
 295                 return -ENOMEM;
 296
 297         moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len,
 298                                      need_rmap_locks);
 299         if (moved_len < old_len) {
 300                 err = -ENOMEM;
 301         } else if (vma->vm_ops && vma->vm_ops->mremap) {
 302                 err = vma->vm_ops->mremap(new_vma);
 303         }
 304
 305         if (unlikely(err)) {
 306                 /*
 307                  * On error, move entries back from new area to old,
 308                  * which will succeed since page tables still there,
 309                  * and then proceed to unmap new area instead of old.
 310                  */
 311                 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len,
 312                                  true);
 313                 vma = new_vma;
 314                 old_len = new_len;
 315                 old_addr = new_addr;
 316                 new_addr = err;
 317         } else {
 318                 mremap_userfaultfd_prep(new_vma, uf);
 319                 arch_remap(mm, old_addr, old_addr + old_len,
 320                            new_addr, new_addr + new_len);
 321         }
 322
 323         /* Conceal VM_ACCOUNT so old reservation is not undone */
 324         if (vm_flags & VM_ACCOUNT) {
 325                 vma->vm_flags &= ~VM_ACCOUNT;
 326                 excess = vma->vm_end - vma->vm_start - old_len;
 327                 if (old_addr > vma->vm_start &&
 328                     old_addr + old_len < vma->vm_end)
 329                         split = 1;
 330         }
 331
 332         /*
 333          * If we failed to move page tables we still do total_vm increment
 334          * since do_munmap() will decrement it by old_len == new_len.
 335          *
 336          * Since total_vm is about to be raised artificially high for a
 337          * moment, we need to restore high watermark afterwards: if stats
 338          * are taken meanwhile, total_vm and hiwater_vm appear too high.
 339          * If this were a serious issue, we'd add a flag to do_munmap().
 340          */
 341         hiwater_vm = mm->hiwater_vm;
 342         vm_stat_account(mm, vma->vm_flags, new_len >> PAGE_SHIFT);
 343
 344         /* Tell pfnmap has moved from this vma */
 345         if (unlikely(vma->vm_flags & VM_PFNMAP))
 346                 untrack_pfn_moved(vma);
 347
 348         if (do_munmap(mm, old_addr, old_len, uf_unmap) < 0) {
 349                 /* OOM: unable to split vma, just get accounts right */
 350                 vm_unacct_memory(excess >> PAGE_SHIFT);
 351                 excess = 0;
 352         }
 353         mm->hiwater_vm = hiwater_vm;
 354
 355         /* Restore VM_ACCOUNT if one or two pieces of vma left */
 356         if (excess) {
 357                 vma->vm_flags |= VM_ACCOUNT;
 358                 if (split)
 359                         vma->vm_next->vm_flags |= VM_ACCOUNT;
 360         }
 361
 362         if (vm_flags & VM_LOCKED) {
 363                 mm->locked_vm += new_len >> PAGE_SHIFT;
 364                 *locked = true;
 365         }
 366
 367         return new_addr;
 368 }
 369
 370 static struct vm_area_struct *vma_to_resize(unsigned long addr,
 371         unsigned long old_len, unsigned long new_len, unsigned long *p)
 372 {
 373         struct mm_struct *mm = current->mm;
 374         struct vm_area_struct *vma = find_vma(mm, addr);
 375         unsigned long pgoff;
 376
 377         if (!vma || vma->vm_start > addr)
 378                 return ERR_PTR(-EFAULT);
 379
 380         /*
 381          * !old_len is a special case where an attempt is made to 'duplicate'
 382          * a mapping.  This makes no sense for private mappings as it will
 383          * instead create a fresh/new mapping unrelated to the original.  This
 384          * is contrary to the basic idea of mremap which creates new mappings
 385          * based on the original.  There are no known use cases for this
 386          * behavior.  As a result, fail such attempts.
 387          */
 388         if (!old_len && !(vma->vm_flags & (VM_SHARED | VM_MAYSHARE))) {
 389                 pr_warn_once("%s (%d): attempted to duplicate a private mapping with mremap.  This is not supported.\n", current->comm, current->pid);
 390                 return ERR_PTR(-EINVAL);
 391         }
 392
 393         if (is_vm_hugetlb_page(vma))
 394                 return ERR_PTR(-EINVAL);
 395
 396         /* We can't remap across vm area boundaries */
 397         if (old_len > vma->vm_end - addr)
 398                 return ERR_PTR(-EFAULT);
 399
 400         if (new_len == old_len)
 401                 return vma;
 402
 403         /* Need to be careful about a growing mapping */
 404         pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
 405         pgoff += vma->vm_pgoff;
 406         if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
 407                 return ERR_PTR(-EINVAL);
 408
 409         if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
 410                 return ERR_PTR(-EFAULT);
 411
 412         if (vma->vm_flags & VM_LOCKED) {
 413                 unsigned long locked, lock_limit;
 414                 locked = mm->locked_vm << PAGE_SHIFT;
 415                 lock_limit = rlimit(RLIMIT_MEMLOCK);
 416                 locked += new_len - old_len;
 417                 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
 418                         return ERR_PTR(-EAGAIN);
 419         }
 420
 421         if (!may_expand_vm(mm, vma->vm_flags,
 422                                 (new_len - old_len) >> PAGE_SHIFT))
 423                 return ERR_PTR(-ENOMEM);
 424
 425         if (vma->vm_flags & VM_ACCOUNT) {
 426                 unsigned long charged = (new_len - old_len) >> PAGE_SHIFT;
 427                 if (security_vm_enough_memory_mm(mm, charged))
 428                         return ERR_PTR(-ENOMEM);
 429                 *p = charged;
 430         }
 431
 432         return vma;
 433 }
 434
 435 static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
 436                 unsigned long new_addr, unsigned long new_len, bool *locked,
 437                 struct vm_userfaultfd_ctx *uf,
 438                 struct list_head *uf_unmap_early,
 439                 struct list_head *uf_unmap)
 440 {
 441         struct mm_struct *mm = current->mm;
 442         struct vm_area_struct *vma;
 443         unsigned long ret = -EINVAL;
 444         unsigned long charged = 0;
 445         unsigned long map_flags;
 446
 447         if (offset_in_page(new_addr))
 448                 goto out;
 449
 450         if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
 451                 goto out;
 452
 453         /* Ensure the old/new locations do not overlap */
 454         if (addr + old_len > new_addr && new_addr + new_len > addr)
 455                 goto out;
 456
 457         ret = do_munmap(mm, new_addr, new_len, uf_unmap_early);
 458         if (ret)
 459                 goto out;
 460
 461         if (old_len >= new_len) {
 462                 ret = do_munmap(mm, addr+new_len, old_len - new_len, uf_unmap);
 463                 if (ret && old_len != new_len)
 464                         goto out;
 465                 old_len = new_len;
 466         }
 467
 468         vma = vma_to_resize(addr, old_len, new_len, &charged);
 469         if (IS_ERR(vma)) {
 470                 ret = PTR_ERR(vma);
 471                 goto out;
 472         }
 473
 474         map_flags = MAP_FIXED;
 475         if (vma->vm_flags & VM_MAYSHARE)
 476                 map_flags |= MAP_SHARED;
 477
 478         ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff +
 479                                 ((addr - vma->vm_start) >> PAGE_SHIFT),
 480                                 map_flags);
 481         if (offset_in_page(ret))
 482                 goto out1;
 483
 484         ret = move_vma(vma, addr, old_len, new_len, new_addr, locked, uf,
 485                        uf_unmap);
 486         if (!(offset_in_page(ret)))
 487                 goto out;
 488 out1:
 489         vm_unacct_memory(charged);
 490
 491 out:
 492         return ret;
 493 }
 494
 495 static int vma_expandable(struct vm_area_struct *vma, unsigned long delta)
 496 {
 497         unsigned long end = vma->vm_end + delta;
 498         if (end < vma->vm_end) /* overflow */
 499                 return 0;
 500         if (vma->vm_next && vma->vm_next->vm_start < end) /* intersection */
 501                 return 0;
 502         if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start,
 503                               0, MAP_FIXED) & ~PAGE_MASK)
 504                 return 0;
 505         return 1;
 506 }
 507
 508 /*
 509  * Expand (or shrink) an existing mapping, potentially moving it at the
 510  * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
 511  *
 512  * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
 513  * This option implies MREMAP_MAYMOVE.
 514  */
 515 SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
 516                 unsigned long, new_len, unsigned long, flags,
 517                 unsigned long, new_addr)
 518 {
 519         struct mm_struct *mm = current->mm;
 520         struct vm_area_struct *vma;
 521         unsigned long ret = -EINVAL;
 522         unsigned long charged = 0;
 523         bool locked = false;
 524         bool downgraded = false;
 525         struct vm_userfaultfd_ctx uf = NULL_VM_UFFD_CTX;
 526         LIST_HEAD(uf_unmap_early);
 527         LIST_HEAD(uf_unmap);
 528
 529         if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
 530                 return ret;
 531
 532         if (flags & MREMAP_FIXED && !(flags & MREMAP_MAYMOVE))
 533                 return ret;
 534
 535         if (offset_in_page(addr))
 536                 return ret;
 537
 538         old_len = PAGE_ALIGN(old_len);
 539         new_len = PAGE_ALIGN(new_len);
 540
 541         /*
 542          * We allow a zero old-len as a special case
 543          * for DOS-emu "duplicate shm area" thing. But
 544          * a zero new-len is nonsensical.
 545          */
 546         if (!new_len)
 547                 return ret;
 548
 549         if (down_write_killable(&current->mm->mmap_sem))
 550                 return -EINTR;
 551
 552         if (flags & MREMAP_FIXED) {
 553                 ret = mremap_to(addr, old_len, new_addr, new_len,
 554                                 &locked, &uf, &uf_unmap_early, &uf_unmap);
 555                 goto out;
 556         }
 557
 558         /*
 559          * Always allow a shrinking remap: that just unmaps
 560          * the unnecessary pages..
 561          * __do_munmap does all the needed commit accounting, and
 562          * downgrades mmap_sem to read if so directed.
 563          */
 564         if (old_len >= new_len) {
 565                 int retval;
 566
 567                 retval = __do_munmap(mm, addr+new_len, old_len - new_len,
 568                                   &uf_unmap, true);
 569                 if (retval < 0 && old_len != new_len) {
 570                         ret = retval;
 571                         goto out;
 572                 /* Returning 1 indicates mmap_sem is downgraded to read. */
 573                 } else if (retval == 1)
 574                         downgraded = true;
 575                 ret = addr;
 576                 goto out;
 577         }
 578
 579         /*
 580          * Ok, we need to grow..
 581          */
 582         vma = vma_to_resize(addr, old_len, new_len, &charged);
 583         if (IS_ERR(vma)) {
 584                 ret = PTR_ERR(vma);
 585                 goto out;
 586         }
 587
 588         /* old_len exactly to the end of the area..
 589          */
 590         if (old_len == vma->vm_end - addr) {
 591                 /* can we just expand the current mapping? */
 592                 if (vma_expandable(vma, new_len - old_len)) {
 593                         int pages = (new_len - old_len) >> PAGE_SHIFT;
 594
 595                         if (vma_adjust(vma, vma->vm_start, addr + new_len,
 596                                        vma->vm_pgoff, NULL)) {
 597                                 ret = -ENOMEM;
 598                                 goto out;
 599                         }
 600
 601                         vm_stat_account(mm, vma->vm_flags, pages);
 602                         if (vma->vm_flags & VM_LOCKED) {
 603                                 mm->locked_vm += pages;
 604                                 locked = true;
 605                                 new_addr = addr;
 606                         }
 607                         ret = addr;
 608                         goto out;
 609                 }
 610         }
 611
 612         /*
 613          * We weren't able to just expand or shrink the area,
 614          * we need to create a new one and move it..
 615          */
 616         ret = -ENOMEM;
 617         if (flags & MREMAP_MAYMOVE) {
 618                 unsigned long map_flags = 0;
 619                 if (vma->vm_flags & VM_MAYSHARE)
 620                         map_flags |= MAP_SHARED;
 621
 622                 new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
 623                                         vma->vm_pgoff +
 624                                         ((addr - vma->vm_start) >> PAGE_SHIFT),
 625                                         map_flags);
 626                 if (offset_in_page(new_addr)) {
 627                         ret = new_addr;
 628                         goto out;
 629                 }
 630
 631                 ret = move_vma(vma, addr, old_len, new_len, new_addr,
 632                                &locked, &uf, &uf_unmap);
 633         }
 634 out:
 635         if (offset_in_page(ret)) {
 636                 vm_unacct_memory(charged);
 637                 locked = 0;
 638         }
 639         if (downgraded)
 640                 up_read(&current->mm->mmap_sem);
 641         else
 642                 up_write(&current->mm->mmap_sem);
 643         if (locked && new_len > old_len)
 644                 mm_populate(new_addr + old_len, new_len - old_len);
 645         userfaultfd_unmap_complete(mm, &uf_unmap_early);
 646         mremap_userfaultfd_complete(&uf, addr, new_addr, old_len);
 647         userfaultfd_unmap_complete(mm, &uf_unmap);
 648         return ret;
 649 }