crypto: marvell/cesa - Handle zero-length skcipher requests

Do not access random memory for zero-length skcipher requests.
Just return 0.

Fixes: f63601fd61 ("crypto: marvell/cesa - add a new driver for Marvell's CESA")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/marvell/cesa/cipher.c

@@ -459,6 +459,9 @@ static int mv_cesa_skcipher_queue_req(struct skcipher_request *req,
 	struct mv_cesa_skcipher_req *creq = skcipher_request_ctx(req);
 	struct mv_cesa_engine *engine;
 
+	if (!req->cryptlen)
+		return 0;
+
 	ret = mv_cesa_skcipher_req_init(req, tmpl);
 	if (ret)
 		return ret;