linux-kernel - [PATCH 3.10 034/143] bcache: fix cache_set_flush() NULL pointer dereference on OOM

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Date:	Sun,  5 Jun 2016 12:18:57 +0200
From:	Willy Tarreau <w@....eu>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Eric Wheeler <git@...ux.ewheeler.net>,
	Eric Wheeler <bcache@...ux.ewheeler.net>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Willy Tarreau <w@....eu>
Subject: [PATCH 3.10 034/143] bcache: fix cache_set_flush() NULL pointer dereference on OOM

From: Eric Wheeler <git@...ux.ewheeler.net>

commit f8b11260a445169989d01df75d35af0f56178f95 upstream.

When bch_cache_set_alloc() fails to kzalloc the cache_set, the
asyncronous closure handling tries to dereference a cache_set that
hadn't yet been allocated inside of cache_set_flush() which is called
by __cache_set_unregister() during cleanup.  This appears to happen only
during an OOM condition on bcache_register.

Signed-off-by: Eric Wheeler <bcache@...ux.ewheeler.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Willy Tarreau <w@....eu>
---
 drivers/md/bcache/super.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 2d2915f..2a4c13a 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -1295,6 +1295,9 @@ static void cache_set_flush(struct closure *cl)
 	set_bit(CACHE_SET_STOPPING_2, &c->flags);
 	wake_up(&c->alloc_wait);
 
+	if (!c)
+		closure_return(cl);
+
 	bch_cache_accounting_destroy(&c->accounting);
 
 	kobject_put(&c->internal);
-- 
2.8.0.rc2.1.gbe9624a