[Devel] [PATCH RHEL7 COMMIT] ms/bcache: fix cache_set_flush() NULL pointer dereference on OOM #PSBM-106785

[Vasily Averin]

The commit is pushed to "branch-rh7-3.10.0-1127.18.2.vz7.163.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-1127.18.2.vz7.163.21
------>
commit 8a87cd599ea56c693239b6ad7cb0d5fce4898fdd
Author: Eric Wheeler <git at linux.ewheeler.net>
Date:   Tue Sep 15 11:55:18 2020 +0300

    ms/bcache: fix cache_set_flush() NULL pointer dereference on OOM #PSBM-106785
    
    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 88a0085..f06212f 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);