[Devel] [PATCH 4/4] bcache: fix cache_set_flush() NULL pointer dereference on OOM

[Andrey Ryabinin]

From: Eric Wheeler <git at linux.ewheeler.net>

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>
Cc: stable at vger.kernel.org

https://jira.sw.ru/browse/PSBM-106785
(cherry picked from commit f8b11260a445169989d01df75d35af0f56178f95)
Signed-off-by: Andrey Ryabinin <aryabinin at virtuozzo.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 88a008577dc0..f06212f856c6 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);
-- 
2.26.2