linux-kernel - [PATCH 3.16 080/217] bcache: fix cache_set_flush() NULL pointer dereference on OOM

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Message-ID: <lsq.1461711741.216001194@decadent.org.uk>
Date:	Wed, 27 Apr 2016 01:02:21 +0200
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Eric Wheeler" <bcache@...ux.ewheeler.net>,
	"Eric Wheeler" <git@...ux.ewheeler.net>
Subject: [PATCH 3.16 080/217] bcache: fix cache_set_flush() NULL pointer
 dereference on OOM

3.16.35-rc1 review patch.  If anyone has any objections, please let me know.

------------------

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: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/md/bcache/super.c | 3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -1385,6 +1385,9 @@ static void cache_set_flush(struct closu
 	struct btree *b;
 	unsigned i;
 
+	if (!c)
+		closure_return(cl);
+
 	bch_cache_accounting_destroy(&c->accounting);
 
 	kobject_put(&c->internal);