crypto: algif_hash - Handle initial af_alg_make_sg error correctly

When the first call to af_alg_make_sg fails, we may return garbage
instead of the real error.  This patch fixes it by setting the error
if "copied" is zero.

Based on a patch by Jesper Juhl.
Reported-by: Jesper Juhl <jj@chaosbits.net>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/algif_hash.c

@@ -68,8 +68,10 @@ static int hash_sendmsg(struct kiocb *unused, struct socket *sock,
 			int newlen;
 
 			newlen = af_alg_make_sg(&ctx->sgl, from, len, 0);
-			if (newlen < 0)
+			if (newlen < 0) {
+				err = copied ? 0 : newlen;
 				goto unlock;
+			}
 
 			ahash_request_set_crypt(&ctx->req, ctx->sgl.sg, NULL,
 						newlen);