linux-kernel - [PATCH] mm: bugfix: set current->reclaim_state to NULL while returning from kswapd()

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Message-ID: <CAEtiSasbEXUeFwCNO09nT8TsEzLF-zZVyJ_pCO9V49hDPbpbAQ@mail.gmail.com>
Date:	Tue, 6 Nov 2012 01:43:12 +0530
From:	Aaditya Kumar <aaditya.kumar.30@...il.com>
To:	LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org
Cc:	kosaki.motohiro@...fujitsu.com,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	KOSAKI Motohiro <kosaki.motohiro@...il.com>,
	Mel Gorman <mel@....ul.ie>, akpm@...ux-foundation.org,
	Minchan Kim <minchan.kim@...il.com>,
	takamori.yamaguchi@...sony.com, takuzo.ohara@...sony.com,
	amit.agarwal@...sony.com, tim.bird@...sony.com,
	frank.rowand@...sony.com, kan.iibuchi@...sony.com,
	aaditya.kumar@...sony.com
Subject: [PATCH] mm: bugfix: set current->reclaim_state to NULL while
 returning from kswapd()

From: Takamori Yamaguchi <takamori.yamaguchi@...sony.com>

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 off lining,
__free_slab() can access dangling pointer of current->reclaim_state.

Signed-off-by: Takamori Yamaguchi <takamori.yamaguchi@...sony.com>
Signed-off-by: Aaditya Kumar <aaditya.kumar@...sony.com>

---
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 2624edc..8b055e9 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3017,6 +3017,8 @@ static int kswapd(void *p)
 						&balanced_classzone_idx);
 		}
 	}
+
+	current->reclaim_state = NULL;
 	return 0;
 }
--
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