dm raid: fix a couple integer overflows

My static checker complains that if "num_raid_params" is UINT_MAX then
the "if (num_raid_params + 1 > argc) {" check doesn't work as intended.

The other change is that I moved the "if (argc != (num_raid_devs * 2))"
condition forward a few lines so it was before the call to
context_alloc(). If we had an integer overflow inside that function
then it would lead to an immediate crash.

Signed-off-by: Dan Carpenter <[e-mail]>
Signed-off-by: Mike Snitzer <[e-mail]>

drivers/md/dm-raid.c

···
 	argv++;
 
 	/* Skip over RAID params for now and find out # of devices */
-	if (num_raid_params + 1 > argc) {
+	if (num_raid_params >= argc) {
 		ti->error = "Arguments do not agree with counts given";
 		return -EINVAL;
 	}
···
 	if ((kstrtoul(argv[num_raid_params], 10, &num_raid_devs) < 0) ||
 	    (num_raid_devs >= INT_MAX)) {
 		ti->error = "Cannot understand number of raid devices";
+		return -EINVAL;
+	}
+
+	argc -= num_raid_params + 1; /* +1: we already have num_raid_devs */
+	if (argc != (num_raid_devs * 2)) {
+		ti->error = "Supplied RAID devices does not match the count given";
 		return -EINVAL;
 	}
 
···
 	if (ret)
 		goto bad;
 
-	ret = -EINVAL;
-
-	argc -= num_raid_params + 1; /* +1: we already have num_raid_devs */
 	argv += num_raid_params + 1;
-
-	if (argc != (num_raid_devs * 2)) {
-		ti->error = "Supplied RAID devices does not match the count given";
-		goto bad;
-	}
 
 	ret = dev_parms(rs, argv);
 	if (ret)