dm verity: set DM_TARGET_IMMUTABLE feature flag

commit 4caae58406f8ceb741603eee460d79bacca9b1b5 upstream.

The device-mapper framework provides a mechanism to mark targets as
immutable (and hence fail table reloads that try to change the target
type). Add the DM_TARGET_IMMUTABLE flag to the dm-verity target's
feature flags to prevent switching the verity target with a different
target type.

Fixes: a4ffc15 ("dm: add verity target")
Cc: [email protected]
Signed-off-by: Sarthak Kukreti <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

drivers/md/dm-verity-target.c

@@ -1176,6 +1176,7 @@ static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv)
 
 static struct target_type verity_target = {
 	.name		= "verity",
+	.features	= DM_TARGET_IMMUTABLE,
 	.version	= {1, 4, 0},
 	.module		= THIS_MODULE,
 	.ctr		= verity_ctr,