mm/mremap.c

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