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@linux.ewheeler.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>

diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 2d2915fdbf0217a661658da1dfbb085052b8d185..2a4c13af482a8c594247cd9df48263b9fa128a0b 100644 (file)
--- 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);