[ 3.5.y.z extended stable ] Patch "mm: bugfix: set current->reclaim_state to NULL while" has been added to staging queue

[Herton Ronaldo Krzesinski]

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

    mm: bugfix: set current->reclaim_state to NULL while

to the linux-3.5.y-queue branch of the 3.5.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-3.5.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 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Herton

------

>From 7115a7b18b958293129fd2ea2d8848e4b1ecbc48 Mon Sep 17 00:00:00 2001
From: Takamori Yamaguchi <takamori.yamaguchi at jp.sony.com>
Date: Thu, 8 Nov 2012 15:53:39 -0800
Subject: [PATCH] mm: bugfix: set current->reclaim_state to NULL while
 returning from kswapd()
X-Extended-Stable: 3.5

commit b0a8cc58e6b9aaae3045752059e5e6260c0b94bc upstream.

In kswapd(), set current->reclaim_state to NULL before returning, as
current->reclaim_state holds reference to variable on kswapd()'s stack.

In rare cases, while returning from kswapd() during memory offlining,
__free_slab() and freepages() can access the dangling pointer of
current->reclaim_state.

Signed-off-by: Takamori Yamaguchi <takamori.yamaguchi at jp.sony.com>
Signed-off-by: Aaditya Kumar <aaditya.kumar at ap.sony.com>
Acked-by: David Rientjes <rientjes at google.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>
---
 mm/vmscan.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index f0f8ebb..cdfdfc5 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2835,6 +2835,8 @@ static int kswapd(void *p)
 						&balanced_classzone_idx);
 		}
 	}
+
+	current->reclaim_state = NULL;
 	return 0;
 }

--
1.7.9.5