blk-crypto: fix check for too-large dun_bytes

dun_bytes needs to be less than or equal to the IV size of the
encryption mode, not just less than or equal to BLK_CRYPTO_MAX_IV_SIZE.

Currently this doesn't matter since blk_crypto_init_key() is never
actually passed invalid values, but we might as well fix this.

Fixes: a892c8d5 ("block: Inline encryption support for blk-mq")
Signed-off-by: NEric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20210825055918.51975-1-ebiggers@kernel.orgSigned-off-by: NJens Axboe <axboe@kernel.dk>

block/blk-crypto.c

@@ -332,7 +332,7 @@ int blk_crypto_init_key(struct blk_crypto_key *blk_key, const u8 *raw_key,
 	if (mode->keysize == 0)
 		return -EINVAL;
 
-	if (dun_bytes == 0 || dun_bytes > BLK_CRYPTO_MAX_IV_SIZE)
+	if (dun_bytes == 0 || dun_bytes > mode->ivsize)
 		return -EINVAL;
 
 	if (!is_power_of_2(data_unit_size))