libceph: allow ceph_buffer_put() to receive a NULL ceph_buffer

BugLink: https://bugs.launchpad.net/bugs/1845374

[ Upstream commit 5c498950 ]
Signed-off-by: Luis Henriques <lhenriques@suse.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

include/linux/ceph/buffer.h

@@ -29,6 +29,7 @@ static inline struct ceph_buffer *ceph_buffer_get(struct ceph_buffer *b)
 
 static inline void ceph_buffer_put(struct ceph_buffer *b)
 {
+	if (b)
 		kref_put(&b->kref, ceph_buffer_release);
 }