dm mpath: validate hw_handler argument count

Fix arg count parsing error in hw handlers.

Cc: stable@kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

drivers/md/dm-mpath.c

diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index d880299..f25bdeb 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -705,6 +705,11 @@
 	if (!hw_argc)
 		return 0;
 
+	if (hw_argc > as->argc) {
+		ti->error = "not enough arguments for hardware handler";
+		return -EINVAL;
+	}
+
 	m->hw_handler_name = kstrdup(shift(as), GFP_KERNEL);
 	request_module("scsi_dh_%s", m->hw_handler_name);
 	if (scsi_dh_handler_exist(m->hw_handler_name) == 0) {