From 3f874ecc49208f3635e29c3a08ade01778ad85e4 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: 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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 mm/vmscan.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index e989ee22f100..e6ca5051c021 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3128,6 +3128,8 @@ static int kswapd(void *p)
 						&balanced_classzone_idx);
 		}
 	}
+
+	current->reclaim_state = NULL;
 	return 0;
 }
 
-- 
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