[PATCH 4.5 137/238] bcache: fix cache_set_flush() NULL pointer dereference on OOM

[Greg Kroah-Hartman]

4.5-stable review patch.  If anyone has any objections, please let me know.

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

From: Eric Wheeler <git@xxxxxxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/md/bcache/super.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -1373,6 +1373,9 @@ 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);