dm flakey: check for null arg_name in parse_features()

BugLink: https://bugs.launchpad.net/bugs/1875905

[ Upstream commit 7690e253 ]

One can crash dm-flakey by specifying more feature arguments than the
number of features supplied.  Checking for null in arg_name avoids
this.

dmsetup create flakey-test --table "0 66076080 flakey /dev/sdb9 0 0 180 2 drop_writes"
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Ian May <ian.may@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/md/dm-flakey.c

@@ -69,6 +69,11 @@ static int parse_features(struct dm_arg_set *as, struct flakey_c *fc,
 		arg_name = dm_shift_arg(as);
 		argc--;
 
+		if (!arg_name) {
+			ti->error = "Insufficient feature arguments";
+			return -EINVAL;
+		}
+
 		/*
 		 * drop_writes
 		 */