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author | Andrea Arcangeli <aarcange@redhat.com> | 2016-10-08 00:01:37 (GMT) |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-10-08 01:46:29 (GMT) |
commit | 8f26e0b176f3484c49d55d88fe6083a9cf9ff443 (patch) | |
tree | 817114a7c54148b01bd4dc4327b1bf84b4f5a158 | |
parent | 86d12e471d9f152217744f2054e63e3742949879 (diff) | |
download | linux-8f26e0b176f3484c49d55d88fe6083a9cf9ff443.tar.xz |
mm: vma_merge: correct false positive from __vma_unlink->validate_mm_rb
The old code was always doing:
vma->vm_end = next->vm_end
vma_rb_erase(next) // in __vma_unlink
vma->vm_next = next->vm_next // in __vma_unlink
next = vma->vm_next
vma_gap_update(next)
The new code still does the above for remove_next == 1 and 2, but for
remove_next == 3 it has been changed and it does:
next->vm_start = vma->vm_start
vma_rb_erase(vma) // in __vma_unlink
vma_gap_update(next)
In the latter case, while unlinking "vma", validate_mm_rb() is told to
ignore "vma" that is being removed, but next->vm_start was reduced
instead. So for the new case, to avoid the false positive from
validate_mm_rb, it should be "next" that is ignored when "vma" is
being unlinked.
"vma" and "next" in the above comment, considered pre-swap().
Link: http://lkml.kernel.org/r/1474492522-2261-4-git-send-email-aarcange@redhat.com
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Tested-by: Shaun Tancheff <shaun.tancheff@seagate.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Jan Vorlicek <janvorli@microsoft.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r-- | mm/mmap.c | 59 |
1 files changed, 41 insertions, 18 deletions
@@ -402,15 +402,9 @@ static inline void vma_rb_insert(struct vm_area_struct *vma, rb_insert_augmented(&vma->vm_rb, root, &vma_gap_callbacks); } -static void vma_rb_erase(struct vm_area_struct *vma, struct rb_root *root) +static void __vma_rb_erase(struct vm_area_struct *vma, struct rb_root *root) { /* - * All rb_subtree_gap values must be consistent prior to erase, - * with the possible exception of the vma being erased. - */ - validate_mm_rb(root, vma); - - /* * Note rb_erase_augmented is a fairly large inline function, * so make sure we instantiate it only once with our desired * augmented rbtree callbacks. @@ -418,6 +412,32 @@ static void vma_rb_erase(struct vm_area_struct *vma, struct rb_root *root) rb_erase_augmented(&vma->vm_rb, root, &vma_gap_callbacks); } +static __always_inline void vma_rb_erase_ignore(struct vm_area_struct *vma, + struct rb_root *root, + struct vm_area_struct *ignore) +{ + /* + * All rb_subtree_gap values must be consistent prior to erase, + * with the possible exception of the "next" vma being erased if + * next->vm_start was reduced. + */ + validate_mm_rb(root, ignore); + + __vma_rb_erase(vma, root); +} + +static __always_inline void vma_rb_erase(struct vm_area_struct *vma, + struct rb_root *root) +{ + /* + * All rb_subtree_gap values must be consistent prior to erase, + * with the possible exception of the vma being erased. + */ + validate_mm_rb(root, vma); + + __vma_rb_erase(vma, root); +} + /* * vma has some anon_vma assigned, and is already inserted on that * anon_vma's interval trees. @@ -604,11 +624,12 @@ static void __insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma) static __always_inline void __vma_unlink_common(struct mm_struct *mm, struct vm_area_struct *vma, struct vm_area_struct *prev, - bool has_prev) + bool has_prev, + struct vm_area_struct *ignore) { struct vm_area_struct *next; - vma_rb_erase(vma, &mm->mm_rb); + vma_rb_erase_ignore(vma, &mm->mm_rb, ignore); next = vma->vm_next; if (has_prev) prev->vm_next = next; @@ -630,13 +651,7 @@ static inline void __vma_unlink_prev(struct mm_struct *mm, struct vm_area_struct *vma, struct vm_area_struct *prev) { - __vma_unlink_common(mm, vma, prev, true); -} - -static inline void __vma_unlink(struct mm_struct *mm, - struct vm_area_struct *vma) -{ - __vma_unlink_common(mm, vma, NULL, false); + __vma_unlink_common(mm, vma, prev, true, vma); } /* @@ -815,8 +830,16 @@ again: if (remove_next != 3) __vma_unlink_prev(mm, next, vma); else - /* vma is not before next if they've been swapped */ - __vma_unlink(mm, next); + /* + * vma is not before next if they've been + * swapped. + * + * pre-swap() next->vm_start was reduced so + * tell validate_mm_rb to ignore pre-swap() + * "next" (which is stored in post-swap() + * "vma"). + */ + __vma_unlink_common(mm, next, NULL, false, vma); if (file) __remove_shared_vm_struct(next, file, mapping); } else if (insert) { |