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