dm flakey: fix a crash with invalid table line

commit 98dba02d9a93eec11bffbb93c7c51624290702d2 upstream.

This command will crash with NULL pointer dereference:
 dmsetup create flakey --table \
  "0 `blockdev --getsize /dev/ram0` flakey /dev/ram0 0 0 1 2 corrupt_bio_byte 512"

Fix the crash by checking if arg_name is non-NULL before comparing it.

Cc: stable@vger.kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/md/dm-flakey.c b/drivers/md/dm-flakey.c
index bed263267323ac1aae0d9ecd7cc399f8276b1624..967d4ad6d32cadcf3eb39618d83ba99094f250c1 100644 (file)
--- a/drivers/md/dm-flakey.c
+++ b/drivers/md/dm-flakey.c
@@ -124,9 +124,9 @@ static int parse_features(struct dm_arg_set *as, struct flakey_c *fc,
                         * Direction r or w?
                         */
                        arg_name = dm_shift_arg(as);
-                       if (!strcasecmp(arg_name, "w"))
+                       if (arg_name && !strcasecmp(arg_name, "w"))
                                fc->corrupt_bio_rw = WRITE;
-                       else if (!strcasecmp(arg_name, "r"))
+                       else if (arg_name && !strcasecmp(arg_name, "r"))
                                fc->corrupt_bio_rw = READ;
                        else {
                                ti->error = "Invalid corrupt bio direction (r or w)";