crypto: algif_hash - Fix result clobbering in recvmsg

Recently an init call was added to hash_recvmsg so as to reset
the hash state in case a sendmsg call was never made.

Unfortunately this ended up clobbering the result if the previous
sendmsg was done with a MSG_MORE flag.  This patch fixes it by
excluding that case when we make the init call.

Fixes: a8348bca2944 ("algif_hash - Fix NULL hash crash with shash")
Reported-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/algif_hash.c

@@ -214,7 +214,7 @@ static int hash_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
 
 	ahash_request_set_crypt(&ctx->req, NULL, ctx->result, 0);
 
-	if (!result) {
+	if (!result && !ctx->more) {
 		err = af_alg_wait_for_completion(
 				crypto_ahash_init(&ctx->req),
 				&ctx->completion);