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mm: rmap: fix use-after-free in __put_anon_vma 

While working address sanitizer for kernel I've discovered
use-after-free bug in __put_anon_vma.

For the last anon_vma, anon_vma->root freed before child anon_vma.
Later in anon_vma_free(anon_vma) we are referencing to already freed
anon_vma->root to check rwsem.

This fixes it by freeing the child anon_vma before freeing
anon_vma->root.

Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: <stable@vger.kernel.org> # v3.0+
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andrey Ryabinin 2014-06-06 19:09:30 +04:00 committed by Linus Torvalds
parent 951e273060
commit 624483f3ea
1 changed files with 1 additions and 2 deletions
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3
mm/rmap.c
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@ -1564,10 +1564,9 @@ void __put_anon_vma(struct anon_vma *anon_vma)
{
struct anon_vma *root = anon_vma->root;
anon_vma_free(anon_vma);
if (root != anon_vma && atomic_dec_and_test(&root->refcount))
anon_vma_free(root);
anon_vma_free(anon_vma);
}
static struct anon_vma *rmap_walk_anon_lock(struct page *page,