dm mpath: validate table argument count

The parser reads the argument count as a number but doesn't check that
sufficient arguments are supplied. This command triggers the bug:

dmsetup create mpath --table "0 `blockdev --getsize /dev/mapper/cr0`
    multipath 0 0 2 1 round-robin 1000 0 1 1 /dev/mapper/cr0
    round-robin 0 1 1 /dev/mapper/cr1 1000"
kernel BUG at drivers/md/dm-mpath.c:530!

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

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index 6a386ab4f7e..d880299334e 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -553,6 +553,12 @@ static int parse_path_selector(struct arg_set *as, struct priority_group *pg,
                 return -EINVAL;
         }
 
+        if (ps_argc > as->argc) {
+                dm_put_path_selector(pst);
+                ti->error = "not enough arguments for path selector";
+                return -EINVAL;
+        }
+
         r = pst->create(&pg->ps, ps_argc, as->argv);
         if (r) {
                 dm_put_path_selector(pst);