releases/2.6.34.15/mm-bugfix-set-current-reclaim_state-to-NULL-while-re.patch

From 7d3406a32b112d9590ce276c5b122feccf48dbe6 Mon Sep 17 00:00:00 2001
From: Takamori Yamaguchi <takamori.yamaguchi@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()

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@jp.sony.com>
Signed-off-by: Aaditya Kumar <aaditya.kumar@ap.sony.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---
 mm/vmscan.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 5c4620600333..365a899bcae0 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2341,6 +2341,8 @@ static int kswapd(void *p)
 		if (!ret)
 			balance_pgdat(pgdat, order);
 	}
+
+	current->reclaim_state = NULL;
 	return 0;
 }
 
-- 
1.8.5.2