From: Andrey Ryabinin <a.ryabinin@xxxxxxxxxxx>
This patch has been added to the 3.12 stable tree. If you have any
objections, please let us know.
===============
commit 624483f3ea82598ab0f62f1bdb9177f531ab1892 upstream.
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@xxxxxxxxxxx>
Acked-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
mm/rmap.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/mm/rmap.c b/mm/rmap.c
index 6e3139835e00..91ab22878103 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1681,10 +1681,9 @@ 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);
}
#ifdef CONFIG_MIGRATION
--
2.0.0
--
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