[4.2.y-ckt stable] Patch "bcache: fix cache_set_flush() NULL pointer dereference on OOM" has been added to the 4.2.y-ckt tree

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    bcache: fix cache_set_flush() NULL pointer dereference on OOM

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt7.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

---8<------------------------------------------------------------

>From bbe44fdcdaf6ac14021d7a59d60eb81d811193c7 Mon Sep 17 00:00:00 2001
From: Eric Wheeler <git at linux.ewheeler.net>
Date: Mon, 7 Mar 2016 15:17:50 -0800
Subject: bcache: fix cache_set_flush() NULL pointer dereference on OOM

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 at linux.ewheeler.net>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 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 d7ce93e..eff6144 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -1398,6 +1398,9 @@ static void cache_set_flush(struct closure *cl)
 	struct btree *b;
 	unsigned i;

+	if (!c)
+		closure_return(cl);
+
 	bch_cache_accounting_destroy(&c->accounting);

 	kobject_put(&c->internal);
--
2.7.4