[3.11.y.z extended stable] Patch "mm: rmap: fix use-after-free in __put_anon_vma" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

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

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 910c7307a415faa21a94ed766f669d9c8243c899 Mon Sep 17 00:00:00 2001
From: Andrey Ryabinin <a.ryabinin at samsung.com>
Date: Fri, 6 Jun 2014 19:09:30 +0400
Subject: 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 at samsung.com>
Acked-by: Peter Zijlstra <peterz at infradead.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 mm/rmap.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/mm/rmap.c b/mm/rmap.c
index 54935c5c9d60..f23ea5f31a31 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1684,10 +1684,9 @@ 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
--
1.9.1