From: Andrey Ryabinin <a.ryabinin@samsung.com>
Date: Fri, 6 Jun 2014 15:09:30 +0000 (+0400)
Subject: mm: rmap: fix use-after-free in __put_anon_vma
X-Git-Tag: v3.2.61~48
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d857054b1160cdc83ad0c3dc4db406dbabcf125b;p=pandora-kernel.git

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

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@samsung.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---

diff --git a/mm/rmap.c b/mm/rmap.c
index ae27d95072c8..f3f6fd398b32 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1671,10 +1671,9 @@ 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