1 // SPDX-License-Identifier: GPL-2.0
5 * (C) Copyright 1996 Linus Torvalds
7 * Address space accounting code <alan@lxorguk.ukuu.org.uk>
8 * (C) Copyright 2002 Red Hat Inc, All Rights Reserved
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>
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/userfaultfd_k.h>
27 #include <asm/cacheflush.h>
29 #include <asm/pgalloc.h>
33 static pud_t
*get_old_pud(struct mm_struct
*mm
, unsigned long addr
)
39 pgd
= pgd_offset(mm
, addr
);
40 if (pgd_none_or_clear_bad(pgd
))
43 p4d
= p4d_offset(pgd
, addr
);
44 if (p4d_none_or_clear_bad(p4d
))
47 pud
= pud_offset(p4d
, addr
);
48 if (pud_none_or_clear_bad(pud
))
54 static pmd_t
*get_old_pmd(struct mm_struct
*mm
, unsigned long addr
)
59 pud
= get_old_pud(mm
, addr
);
63 pmd
= pmd_offset(pud
, addr
);
70 static pud_t
*alloc_new_pud(struct mm_struct
*mm
, struct vm_area_struct
*vma
,
76 pgd
= pgd_offset(mm
, addr
);
77 p4d
= p4d_alloc(mm
, pgd
, addr
);
81 return pud_alloc(mm
, p4d
, addr
);
84 static pmd_t
*alloc_new_pmd(struct mm_struct
*mm
, struct vm_area_struct
*vma
,
90 pud
= alloc_new_pud(mm
, vma
, addr
);
94 pmd
= pmd_alloc(mm
, pud
, addr
);
98 VM_BUG_ON(pmd_trans_huge(*pmd
));
103 static void take_rmap_locks(struct vm_area_struct
*vma
)
106 i_mmap_lock_write(vma
->vm_file
->f_mapping
);
108 anon_vma_lock_write(vma
->anon_vma
);
111 static void drop_rmap_locks(struct vm_area_struct
*vma
)
114 anon_vma_unlock_write(vma
->anon_vma
);
116 i_mmap_unlock_write(vma
->vm_file
->f_mapping
);
119 static pte_t
move_soft_dirty_pte(pte_t pte
)
122 * Set soft dirty bit so we can notice
123 * in userspace the ptes were moved.
125 #ifdef CONFIG_MEM_SOFT_DIRTY
126 if (pte_present(pte
))
127 pte
= pte_mksoft_dirty(pte
);
128 else if (is_swap_pte(pte
))
129 pte
= pte_swp_mksoft_dirty(pte
);
134 static void move_ptes(struct vm_area_struct
*vma
, pmd_t
*old_pmd
,
135 unsigned long old_addr
, unsigned long old_end
,
136 struct vm_area_struct
*new_vma
, pmd_t
*new_pmd
,
137 unsigned long new_addr
, bool need_rmap_locks
)
139 struct mm_struct
*mm
= vma
->vm_mm
;
140 pte_t
*old_pte
, *new_pte
, pte
;
141 spinlock_t
*old_ptl
, *new_ptl
;
142 bool force_flush
= false;
143 unsigned long len
= old_end
- old_addr
;
146 * When need_rmap_locks is true, we take the i_mmap_rwsem and anon_vma
147 * locks to ensure that rmap will always observe either the old or the
148 * new ptes. This is the easiest way to avoid races with
149 * truncate_pagecache(), page migration, etc...
151 * When need_rmap_locks is false, we use other ways to avoid
154 * - During exec() shift_arg_pages(), we use a specially tagged vma
155 * which rmap call sites look for using vma_is_temporary_stack().
157 * - During mremap(), new_vma is often known to be placed after vma
158 * in rmap traversal order. This ensures rmap will always observe
159 * either the old pte, or the new pte, or both (the page table locks
160 * serialize access to individual ptes, but only rmap traversal
161 * order guarantees that we won't miss both the old and new ptes).
164 take_rmap_locks(vma
);
167 * We don't have to worry about the ordering of src and dst
168 * pte locks because exclusive mmap_lock prevents deadlock.
170 old_pte
= pte_offset_map_lock(mm
, old_pmd
, old_addr
, &old_ptl
);
171 new_pte
= pte_offset_map(new_pmd
, new_addr
);
172 new_ptl
= pte_lockptr(mm
, new_pmd
);
173 if (new_ptl
!= old_ptl
)
174 spin_lock_nested(new_ptl
, SINGLE_DEPTH_NESTING
);
175 flush_tlb_batched_pending(vma
->vm_mm
);
176 arch_enter_lazy_mmu_mode();
178 for (; old_addr
< old_end
; old_pte
++, old_addr
+= PAGE_SIZE
,
179 new_pte
++, new_addr
+= PAGE_SIZE
) {
180 if (pte_none(*old_pte
))
183 pte
= ptep_get_and_clear(mm
, old_addr
, old_pte
);
185 * If we are remapping a valid PTE, make sure
186 * to flush TLB before we drop the PTL for the
189 * NOTE! Both old and new PTL matter: the old one
190 * for racing with page_mkclean(), the new one to
191 * make sure the physical page stays valid until
192 * the TLB entry for the old mapping has been
195 if (pte_present(pte
))
197 pte
= move_pte(pte
, new_vma
->vm_page_prot
, old_addr
, new_addr
);
198 pte
= move_soft_dirty_pte(pte
);
199 set_pte_at(mm
, new_addr
, new_pte
, pte
);
202 arch_leave_lazy_mmu_mode();
204 flush_tlb_range(vma
, old_end
- len
, old_end
);
205 if (new_ptl
!= old_ptl
)
206 spin_unlock(new_ptl
);
207 pte_unmap(new_pte
- 1);
208 pte_unmap_unlock(old_pte
- 1, old_ptl
);
210 drop_rmap_locks(vma
);
213 #ifndef arch_supports_page_table_move
214 #define arch_supports_page_table_move arch_supports_page_table_move
215 static inline bool arch_supports_page_table_move(void)
217 return IS_ENABLED(CONFIG_HAVE_MOVE_PMD
) ||
218 IS_ENABLED(CONFIG_HAVE_MOVE_PUD
);
222 #ifdef CONFIG_HAVE_MOVE_PMD
223 static bool move_normal_pmd(struct vm_area_struct
*vma
, unsigned long old_addr
,
224 unsigned long new_addr
, pmd_t
*old_pmd
, pmd_t
*new_pmd
)
226 spinlock_t
*old_ptl
, *new_ptl
;
227 struct mm_struct
*mm
= vma
->vm_mm
;
230 if (!arch_supports_page_table_move())
233 * The destination pmd shouldn't be established, free_pgtables()
234 * should have released it.
236 * However, there's a case during execve() where we use mremap
237 * to move the initial stack, and in that case the target area
238 * may overlap the source area (always moving down).
240 * If everything is PMD-aligned, that works fine, as moving
241 * each pmd down will clear the source pmd. But if we first
242 * have a few 4kB-only pages that get moved down, and then
243 * hit the "now the rest is PMD-aligned, let's do everything
244 * one pmd at a time", we will still have the old (now empty
245 * of any 4kB pages, but still there) PMD in the page table
248 * Warn on it once - because we really should try to figure
249 * out how to do this better - but then say "I won't move
252 * One alternative might be to just unmap the target pmd at
253 * this point, and verify that it really is empty. We'll see.
255 if (WARN_ON_ONCE(!pmd_none(*new_pmd
)))
259 * We don't have to worry about the ordering of src and dst
260 * ptlocks because exclusive mmap_lock prevents deadlock.
262 old_ptl
= pmd_lock(vma
->vm_mm
, old_pmd
);
263 new_ptl
= pmd_lockptr(mm
, new_pmd
);
264 if (new_ptl
!= old_ptl
)
265 spin_lock_nested(new_ptl
, SINGLE_DEPTH_NESTING
);
271 VM_BUG_ON(!pmd_none(*new_pmd
));
273 pmd_populate(mm
, new_pmd
, pmd_pgtable(pmd
));
274 flush_tlb_range(vma
, old_addr
, old_addr
+ PMD_SIZE
);
275 if (new_ptl
!= old_ptl
)
276 spin_unlock(new_ptl
);
277 spin_unlock(old_ptl
);
282 static inline bool move_normal_pmd(struct vm_area_struct
*vma
,
283 unsigned long old_addr
, unsigned long new_addr
, pmd_t
*old_pmd
,
290 #if CONFIG_PGTABLE_LEVELS > 2 && defined(CONFIG_HAVE_MOVE_PUD)
291 static bool move_normal_pud(struct vm_area_struct
*vma
, unsigned long old_addr
,
292 unsigned long new_addr
, pud_t
*old_pud
, pud_t
*new_pud
)
294 spinlock_t
*old_ptl
, *new_ptl
;
295 struct mm_struct
*mm
= vma
->vm_mm
;
298 if (!arch_supports_page_table_move())
301 * The destination pud shouldn't be established, free_pgtables()
302 * should have released it.
304 if (WARN_ON_ONCE(!pud_none(*new_pud
)))
308 * We don't have to worry about the ordering of src and dst
309 * ptlocks because exclusive mmap_lock prevents deadlock.
311 old_ptl
= pud_lock(vma
->vm_mm
, old_pud
);
312 new_ptl
= pud_lockptr(mm
, new_pud
);
313 if (new_ptl
!= old_ptl
)
314 spin_lock_nested(new_ptl
, SINGLE_DEPTH_NESTING
);
320 VM_BUG_ON(!pud_none(*new_pud
));
322 pud_populate(mm
, new_pud
, pud_pgtable(pud
));
323 flush_tlb_range(vma
, old_addr
, old_addr
+ PUD_SIZE
);
324 if (new_ptl
!= old_ptl
)
325 spin_unlock(new_ptl
);
326 spin_unlock(old_ptl
);
331 static inline bool move_normal_pud(struct vm_area_struct
*vma
,
332 unsigned long old_addr
, unsigned long new_addr
, pud_t
*old_pud
,
339 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
340 static bool move_huge_pud(struct vm_area_struct
*vma
, unsigned long old_addr
,
341 unsigned long new_addr
, pud_t
*old_pud
, pud_t
*new_pud
)
343 spinlock_t
*old_ptl
, *new_ptl
;
344 struct mm_struct
*mm
= vma
->vm_mm
;
348 * The destination pud shouldn't be established, free_pgtables()
349 * should have released it.
351 if (WARN_ON_ONCE(!pud_none(*new_pud
)))
355 * We don't have to worry about the ordering of src and dst
356 * ptlocks because exclusive mmap_lock prevents deadlock.
358 old_ptl
= pud_lock(vma
->vm_mm
, old_pud
);
359 new_ptl
= pud_lockptr(mm
, new_pud
);
360 if (new_ptl
!= old_ptl
)
361 spin_lock_nested(new_ptl
, SINGLE_DEPTH_NESTING
);
367 VM_BUG_ON(!pud_none(*new_pud
));
369 /* Set the new pud */
370 /* mark soft_ditry when we add pud level soft dirty support */
371 set_pud_at(mm
, new_addr
, new_pud
, pud
);
372 flush_pud_tlb_range(vma
, old_addr
, old_addr
+ HPAGE_PUD_SIZE
);
373 if (new_ptl
!= old_ptl
)
374 spin_unlock(new_ptl
);
375 spin_unlock(old_ptl
);
380 static bool move_huge_pud(struct vm_area_struct
*vma
, unsigned long old_addr
,
381 unsigned long new_addr
, pud_t
*old_pud
, pud_t
*new_pud
)
397 * Returns an extent of the corresponding size for the pgt_entry specified if
398 * valid. Else returns a smaller extent bounded by the end of the source and
399 * destination pgt_entry.
401 static __always_inline
unsigned long get_extent(enum pgt_entry entry
,
402 unsigned long old_addr
, unsigned long old_end
,
403 unsigned long new_addr
)
405 unsigned long next
, extent
, mask
, size
;
423 next
= (old_addr
+ size
) & mask
;
424 /* even if next overflowed, extent below will be ok */
425 extent
= next
- old_addr
;
426 if (extent
> old_end
- old_addr
)
427 extent
= old_end
- old_addr
;
428 next
= (new_addr
+ size
) & mask
;
429 if (extent
> next
- new_addr
)
430 extent
= next
- new_addr
;
435 * Attempts to speedup the move by moving entry at the level corresponding to
436 * pgt_entry. Returns true if the move was successful, else false.
438 static bool move_pgt_entry(enum pgt_entry entry
, struct vm_area_struct
*vma
,
439 unsigned long old_addr
, unsigned long new_addr
,
440 void *old_entry
, void *new_entry
, bool need_rmap_locks
)
444 /* See comment in move_ptes() */
446 take_rmap_locks(vma
);
450 moved
= move_normal_pmd(vma
, old_addr
, new_addr
, old_entry
,
454 moved
= move_normal_pud(vma
, old_addr
, new_addr
, old_entry
,
458 moved
= IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE
) &&
459 move_huge_pmd(vma
, old_addr
, new_addr
, old_entry
,
463 moved
= IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE
) &&
464 move_huge_pud(vma
, old_addr
, new_addr
, old_entry
,
474 drop_rmap_locks(vma
);
479 unsigned long move_page_tables(struct vm_area_struct
*vma
,
480 unsigned long old_addr
, struct vm_area_struct
*new_vma
,
481 unsigned long new_addr
, unsigned long len
,
482 bool need_rmap_locks
)
484 unsigned long extent
, old_end
;
485 struct mmu_notifier_range range
;
486 pmd_t
*old_pmd
, *new_pmd
;
487 pud_t
*old_pud
, *new_pud
;
492 old_end
= old_addr
+ len
;
493 flush_cache_range(vma
, old_addr
, old_end
);
495 mmu_notifier_range_init(&range
, MMU_NOTIFY_UNMAP
, 0, vma
, vma
->vm_mm
,
497 mmu_notifier_invalidate_range_start(&range
);
499 for (; old_addr
< old_end
; old_addr
+= extent
, new_addr
+= extent
) {
502 * If extent is PUD-sized try to speed up the move by moving at the
503 * PUD level if possible.
505 extent
= get_extent(NORMAL_PUD
, old_addr
, old_end
, new_addr
);
507 old_pud
= get_old_pud(vma
->vm_mm
, old_addr
);
510 new_pud
= alloc_new_pud(vma
->vm_mm
, vma
, new_addr
);
513 if (pud_trans_huge(*old_pud
) || pud_devmap(*old_pud
)) {
514 if (extent
== HPAGE_PUD_SIZE
) {
515 move_pgt_entry(HPAGE_PUD
, vma
, old_addr
, new_addr
,
516 old_pud
, new_pud
, need_rmap_locks
);
517 /* We ignore and continue on error? */
520 } else if (IS_ENABLED(CONFIG_HAVE_MOVE_PUD
) && extent
== PUD_SIZE
) {
522 if (move_pgt_entry(NORMAL_PUD
, vma
, old_addr
, new_addr
,
523 old_pud
, new_pud
, true))
527 extent
= get_extent(NORMAL_PMD
, old_addr
, old_end
, new_addr
);
528 old_pmd
= get_old_pmd(vma
->vm_mm
, old_addr
);
531 new_pmd
= alloc_new_pmd(vma
->vm_mm
, vma
, new_addr
);
534 if (is_swap_pmd(*old_pmd
) || pmd_trans_huge(*old_pmd
) ||
535 pmd_devmap(*old_pmd
)) {
536 if (extent
== HPAGE_PMD_SIZE
&&
537 move_pgt_entry(HPAGE_PMD
, vma
, old_addr
, new_addr
,
538 old_pmd
, new_pmd
, need_rmap_locks
))
540 split_huge_pmd(vma
, old_pmd
, old_addr
);
541 if (pmd_trans_unstable(old_pmd
))
543 } else if (IS_ENABLED(CONFIG_HAVE_MOVE_PMD
) &&
544 extent
== PMD_SIZE
) {
546 * If the extent is PMD-sized, try to speed the move by
547 * moving at the PMD level if possible.
549 if (move_pgt_entry(NORMAL_PMD
, vma
, old_addr
, new_addr
,
550 old_pmd
, new_pmd
, true))
554 if (pte_alloc(new_vma
->vm_mm
, new_pmd
))
556 move_ptes(vma
, old_pmd
, old_addr
, old_addr
+ extent
, new_vma
,
557 new_pmd
, new_addr
, need_rmap_locks
);
560 mmu_notifier_invalidate_range_end(&range
);
562 return len
+ old_addr
- old_end
; /* how much done */
565 static unsigned long move_vma(struct vm_area_struct
*vma
,
566 unsigned long old_addr
, unsigned long old_len
,
567 unsigned long new_len
, unsigned long new_addr
,
568 bool *locked
, unsigned long flags
,
569 struct vm_userfaultfd_ctx
*uf
, struct list_head
*uf_unmap
)
571 struct mm_struct
*mm
= vma
->vm_mm
;
572 struct vm_area_struct
*new_vma
;
573 unsigned long vm_flags
= vma
->vm_flags
;
574 unsigned long new_pgoff
;
575 unsigned long moved_len
;
576 unsigned long excess
= 0;
577 unsigned long hiwater_vm
;
580 bool need_rmap_locks
;
583 * We'd prefer to avoid failure later on in do_munmap:
584 * which may split one vma into three before unmapping.
586 if (mm
->map_count
>= sysctl_max_map_count
- 3)
589 if (vma
->vm_ops
&& vma
->vm_ops
->may_split
) {
590 if (vma
->vm_start
!= old_addr
)
591 err
= vma
->vm_ops
->may_split(vma
, old_addr
);
592 if (!err
&& vma
->vm_end
!= old_addr
+ old_len
)
593 err
= vma
->vm_ops
->may_split(vma
, old_addr
+ old_len
);
599 * Advise KSM to break any KSM pages in the area to be moved:
600 * it would be confusing if they were to turn up at the new
601 * location, where they happen to coincide with different KSM
602 * pages recently unmapped. But leave vma->vm_flags as it was,
603 * so KSM can come around to merge on vma and new_vma afterwards.
605 err
= ksm_madvise(vma
, old_addr
, old_addr
+ old_len
,
606 MADV_UNMERGEABLE
, &vm_flags
);
610 if (unlikely(flags
& MREMAP_DONTUNMAP
&& vm_flags
& VM_ACCOUNT
)) {
611 if (security_vm_enough_memory_mm(mm
, new_len
>> PAGE_SHIFT
))
615 new_pgoff
= vma
->vm_pgoff
+ ((old_addr
- vma
->vm_start
) >> PAGE_SHIFT
);
616 new_vma
= copy_vma(&vma
, new_addr
, new_len
, new_pgoff
,
619 if (unlikely(flags
& MREMAP_DONTUNMAP
&& vm_flags
& VM_ACCOUNT
))
620 vm_unacct_memory(new_len
>> PAGE_SHIFT
);
624 moved_len
= move_page_tables(vma
, old_addr
, new_vma
, new_addr
, old_len
,
626 if (moved_len
< old_len
) {
628 } else if (vma
->vm_ops
&& vma
->vm_ops
->mremap
) {
629 err
= vma
->vm_ops
->mremap(new_vma
);
634 * On error, move entries back from new area to old,
635 * which will succeed since page tables still there,
636 * and then proceed to unmap new area instead of old.
638 move_page_tables(new_vma
, new_addr
, vma
, old_addr
, moved_len
,
645 mremap_userfaultfd_prep(new_vma
, uf
);
648 /* Conceal VM_ACCOUNT so old reservation is not undone */
649 if (vm_flags
& VM_ACCOUNT
&& !(flags
& MREMAP_DONTUNMAP
)) {
650 vma
->vm_flags
&= ~VM_ACCOUNT
;
651 excess
= vma
->vm_end
- vma
->vm_start
- old_len
;
652 if (old_addr
> vma
->vm_start
&&
653 old_addr
+ old_len
< vma
->vm_end
)
658 * If we failed to move page tables we still do total_vm increment
659 * since do_munmap() will decrement it by old_len == new_len.
661 * Since total_vm is about to be raised artificially high for a
662 * moment, we need to restore high watermark afterwards: if stats
663 * are taken meanwhile, total_vm and hiwater_vm appear too high.
664 * If this were a serious issue, we'd add a flag to do_munmap().
666 hiwater_vm
= mm
->hiwater_vm
;
667 vm_stat_account(mm
, vma
->vm_flags
, new_len
>> PAGE_SHIFT
);
669 /* Tell pfnmap has moved from this vma */
670 if (unlikely(vma
->vm_flags
& VM_PFNMAP
))
671 untrack_pfn_moved(vma
);
673 if (unlikely(!err
&& (flags
& MREMAP_DONTUNMAP
))) {
674 /* We always clear VM_LOCKED[ONFAULT] on the old vma */
675 vma
->vm_flags
&= VM_LOCKED_CLEAR_MASK
;
678 * anon_vma links of the old vma is no longer needed after its page
679 * table has been moved.
681 if (new_vma
!= vma
&& vma
->vm_start
== old_addr
&&
682 vma
->vm_end
== (old_addr
+ old_len
))
683 unlink_anon_vmas(vma
);
685 /* Because we won't unmap we don't need to touch locked_vm */
689 if (do_munmap(mm
, old_addr
, old_len
, uf_unmap
) < 0) {
690 /* OOM: unable to split vma, just get accounts right */
691 if (vm_flags
& VM_ACCOUNT
&& !(flags
& MREMAP_DONTUNMAP
))
692 vm_acct_memory(old_len
>> PAGE_SHIFT
);
696 if (vm_flags
& VM_LOCKED
) {
697 mm
->locked_vm
+= new_len
>> PAGE_SHIFT
;
701 mm
->hiwater_vm
= hiwater_vm
;
703 /* Restore VM_ACCOUNT if one or two pieces of vma left */
705 vma
->vm_flags
|= VM_ACCOUNT
;
707 vma
->vm_next
->vm_flags
|= VM_ACCOUNT
;
713 static struct vm_area_struct
*vma_to_resize(unsigned long addr
,
714 unsigned long old_len
, unsigned long new_len
, unsigned long flags
,
717 struct mm_struct
*mm
= current
->mm
;
718 struct vm_area_struct
*vma
;
721 vma
= vma_lookup(mm
, addr
);
723 return ERR_PTR(-EFAULT
);
726 * !old_len is a special case where an attempt is made to 'duplicate'
727 * a mapping. This makes no sense for private mappings as it will
728 * instead create a fresh/new mapping unrelated to the original. This
729 * is contrary to the basic idea of mremap which creates new mappings
730 * based on the original. There are no known use cases for this
731 * behavior. As a result, fail such attempts.
733 if (!old_len
&& !(vma
->vm_flags
& (VM_SHARED
| VM_MAYSHARE
))) {
734 pr_warn_once("%s (%d): attempted to duplicate a private mapping with mremap. This is not supported.\n", current
->comm
, current
->pid
);
735 return ERR_PTR(-EINVAL
);
738 if ((flags
& MREMAP_DONTUNMAP
) &&
739 (vma
->vm_flags
& (VM_DONTEXPAND
| VM_PFNMAP
)))
740 return ERR_PTR(-EINVAL
);
742 if (is_vm_hugetlb_page(vma
))
743 return ERR_PTR(-EINVAL
);
745 /* We can't remap across vm area boundaries */
746 if (old_len
> vma
->vm_end
- addr
)
747 return ERR_PTR(-EFAULT
);
749 if (new_len
== old_len
)
752 /* Need to be careful about a growing mapping */
753 pgoff
= (addr
- vma
->vm_start
) >> PAGE_SHIFT
;
754 pgoff
+= vma
->vm_pgoff
;
755 if (pgoff
+ (new_len
>> PAGE_SHIFT
) < pgoff
)
756 return ERR_PTR(-EINVAL
);
758 if (vma
->vm_flags
& (VM_DONTEXPAND
| VM_PFNMAP
))
759 return ERR_PTR(-EFAULT
);
761 if (vma
->vm_flags
& VM_LOCKED
) {
762 unsigned long locked
, lock_limit
;
763 locked
= mm
->locked_vm
<< PAGE_SHIFT
;
764 lock_limit
= rlimit(RLIMIT_MEMLOCK
);
765 locked
+= new_len
- old_len
;
766 if (locked
> lock_limit
&& !capable(CAP_IPC_LOCK
))
767 return ERR_PTR(-EAGAIN
);
770 if (!may_expand_vm(mm
, vma
->vm_flags
,
771 (new_len
- old_len
) >> PAGE_SHIFT
))
772 return ERR_PTR(-ENOMEM
);
774 if (vma
->vm_flags
& VM_ACCOUNT
) {
775 unsigned long charged
= (new_len
- old_len
) >> PAGE_SHIFT
;
776 if (security_vm_enough_memory_mm(mm
, charged
))
777 return ERR_PTR(-ENOMEM
);
784 static unsigned long mremap_to(unsigned long addr
, unsigned long old_len
,
785 unsigned long new_addr
, unsigned long new_len
, bool *locked
,
786 unsigned long flags
, struct vm_userfaultfd_ctx
*uf
,
787 struct list_head
*uf_unmap_early
,
788 struct list_head
*uf_unmap
)
790 struct mm_struct
*mm
= current
->mm
;
791 struct vm_area_struct
*vma
;
792 unsigned long ret
= -EINVAL
;
793 unsigned long charged
= 0;
794 unsigned long map_flags
= 0;
796 if (offset_in_page(new_addr
))
799 if (new_len
> TASK_SIZE
|| new_addr
> TASK_SIZE
- new_len
)
802 /* Ensure the old/new locations do not overlap */
803 if (addr
+ old_len
> new_addr
&& new_addr
+ new_len
> addr
)
807 * move_vma() need us to stay 4 maps below the threshold, otherwise
808 * it will bail out at the very beginning.
809 * That is a problem if we have already unmaped the regions here
810 * (new_addr, and old_addr), because userspace will not know the
811 * state of the vma's after it gets -ENOMEM.
812 * So, to avoid such scenario we can pre-compute if the whole
813 * operation has high chances to success map-wise.
814 * Worst-scenario case is when both vma's (new_addr and old_addr) get
815 * split in 3 before unmapping it.
816 * That means 2 more maps (1 for each) to the ones we already hold.
817 * Check whether current map count plus 2 still leads us to 4 maps below
818 * the threshold, otherwise return -ENOMEM here to be more safe.
820 if ((mm
->map_count
+ 2) >= sysctl_max_map_count
- 3)
823 if (flags
& MREMAP_FIXED
) {
824 ret
= do_munmap(mm
, new_addr
, new_len
, uf_unmap_early
);
829 if (old_len
>= new_len
) {
830 ret
= do_munmap(mm
, addr
+new_len
, old_len
- new_len
, uf_unmap
);
831 if (ret
&& old_len
!= new_len
)
836 vma
= vma_to_resize(addr
, old_len
, new_len
, flags
, &charged
);
842 /* MREMAP_DONTUNMAP expands by old_len since old_len == new_len */
843 if (flags
& MREMAP_DONTUNMAP
&&
844 !may_expand_vm(mm
, vma
->vm_flags
, old_len
>> PAGE_SHIFT
)) {
849 if (flags
& MREMAP_FIXED
)
850 map_flags
|= MAP_FIXED
;
852 if (vma
->vm_flags
& VM_MAYSHARE
)
853 map_flags
|= MAP_SHARED
;
855 ret
= get_unmapped_area(vma
->vm_file
, new_addr
, new_len
, vma
->vm_pgoff
+
856 ((addr
- vma
->vm_start
) >> PAGE_SHIFT
),
858 if (IS_ERR_VALUE(ret
))
861 /* We got a new mapping */
862 if (!(flags
& MREMAP_FIXED
))
865 ret
= move_vma(vma
, addr
, old_len
, new_len
, new_addr
, locked
, flags
, uf
,
868 if (!(offset_in_page(ret
)))
872 vm_unacct_memory(charged
);
878 static int vma_expandable(struct vm_area_struct
*vma
, unsigned long delta
)
880 unsigned long end
= vma
->vm_end
+ delta
;
881 if (end
< vma
->vm_end
) /* overflow */
883 if (vma
->vm_next
&& vma
->vm_next
->vm_start
< end
) /* intersection */
885 if (get_unmapped_area(NULL
, vma
->vm_start
, end
- vma
->vm_start
,
886 0, MAP_FIXED
) & ~PAGE_MASK
)
892 * Expand (or shrink) an existing mapping, potentially moving it at the
893 * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
895 * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
896 * This option implies MREMAP_MAYMOVE.
898 SYSCALL_DEFINE5(mremap
, unsigned long, addr
, unsigned long, old_len
,
899 unsigned long, new_len
, unsigned long, flags
,
900 unsigned long, new_addr
)
902 struct mm_struct
*mm
= current
->mm
;
903 struct vm_area_struct
*vma
;
904 unsigned long ret
= -EINVAL
;
905 unsigned long charged
= 0;
907 bool downgraded
= false;
908 struct vm_userfaultfd_ctx uf
= NULL_VM_UFFD_CTX
;
909 LIST_HEAD(uf_unmap_early
);
913 * There is a deliberate asymmetry here: we strip the pointer tag
914 * from the old address but leave the new address alone. This is
915 * for consistency with mmap(), where we prevent the creation of
916 * aliasing mappings in userspace by leaving the tag bits of the
917 * mapping address intact. A non-zero tag will cause the subsequent
918 * range checks to reject the address as invalid.
920 * See Documentation/arm64/tagged-address-abi.rst for more information.
922 addr
= untagged_addr(addr
);
924 if (flags
& ~(MREMAP_FIXED
| MREMAP_MAYMOVE
| MREMAP_DONTUNMAP
))
927 if (flags
& MREMAP_FIXED
&& !(flags
& MREMAP_MAYMOVE
))
931 * MREMAP_DONTUNMAP is always a move and it does not allow resizing
934 if (flags
& MREMAP_DONTUNMAP
&&
935 (!(flags
& MREMAP_MAYMOVE
) || old_len
!= new_len
))
939 if (offset_in_page(addr
))
942 old_len
= PAGE_ALIGN(old_len
);
943 new_len
= PAGE_ALIGN(new_len
);
946 * We allow a zero old-len as a special case
947 * for DOS-emu "duplicate shm area" thing. But
948 * a zero new-len is nonsensical.
953 if (mmap_write_lock_killable(current
->mm
))
956 if (flags
& (MREMAP_FIXED
| MREMAP_DONTUNMAP
)) {
957 ret
= mremap_to(addr
, old_len
, new_addr
, new_len
,
958 &locked
, flags
, &uf
, &uf_unmap_early
,
964 * Always allow a shrinking remap: that just unmaps
965 * the unnecessary pages..
966 * __do_munmap does all the needed commit accounting, and
967 * downgrades mmap_lock to read if so directed.
969 if (old_len
>= new_len
) {
972 retval
= __do_munmap(mm
, addr
+new_len
, old_len
- new_len
,
974 if (retval
< 0 && old_len
!= new_len
) {
977 /* Returning 1 indicates mmap_lock is downgraded to read. */
978 } else if (retval
== 1)
985 * Ok, we need to grow..
987 vma
= vma_to_resize(addr
, old_len
, new_len
, flags
, &charged
);
993 /* old_len exactly to the end of the area..
995 if (old_len
== vma
->vm_end
- addr
) {
996 /* can we just expand the current mapping? */
997 if (vma_expandable(vma
, new_len
- old_len
)) {
998 int pages
= (new_len
- old_len
) >> PAGE_SHIFT
;
1000 if (vma_adjust(vma
, vma
->vm_start
, addr
+ new_len
,
1001 vma
->vm_pgoff
, NULL
)) {
1006 vm_stat_account(mm
, vma
->vm_flags
, pages
);
1007 if (vma
->vm_flags
& VM_LOCKED
) {
1008 mm
->locked_vm
+= pages
;
1018 * We weren't able to just expand or shrink the area,
1019 * we need to create a new one and move it..
1022 if (flags
& MREMAP_MAYMOVE
) {
1023 unsigned long map_flags
= 0;
1024 if (vma
->vm_flags
& VM_MAYSHARE
)
1025 map_flags
|= MAP_SHARED
;
1027 new_addr
= get_unmapped_area(vma
->vm_file
, 0, new_len
,
1029 ((addr
- vma
->vm_start
) >> PAGE_SHIFT
),
1031 if (IS_ERR_VALUE(new_addr
)) {
1036 ret
= move_vma(vma
, addr
, old_len
, new_len
, new_addr
,
1037 &locked
, flags
, &uf
, &uf_unmap
);
1040 if (offset_in_page(ret
)) {
1041 vm_unacct_memory(charged
);
1045 mmap_read_unlock(current
->mm
);
1047 mmap_write_unlock(current
->mm
);
1048 if (locked
&& new_len
> old_len
)
1049 mm_populate(new_addr
+ old_len
, new_len
- old_len
);
1050 userfaultfd_unmap_complete(mm
, &uf_unmap_early
);
1051 mremap_userfaultfd_complete(&uf
, addr
, ret
, old_len
);
1052 userfaultfd_unmap_complete(mm
, &uf_unmap
);