crypto: sig - Fix verify call

The dst SG list needs to be set to NULL for verify calls.  Do
this as otherwise the underlying algorithm may fail.

Furthermore the digest needs to be copied just like the source.

Fixes: 6cb8815f ("crypto: sig - Add interface for sign/verify")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/akcipher.c

@@ -192,12 +192,17 @@ EXPORT_SYMBOL_GPL(akcipher_register_instance);
 int crypto_akcipher_sync_prep(struct crypto_akcipher_sync_data *data)
 {
 	unsigned int reqsize = crypto_akcipher_reqsize(data->tfm);
-	unsigned int mlen = max(data->slen, data->dlen);
 	struct akcipher_request *req;
 	struct scatterlist *sg;
+	unsigned int mlen;
 	unsigned int len;
 	u8 *buf;
 
+	if (data->dst)
+		mlen = max(data->slen, data->dlen);
+	else
+		mlen = data->slen + data->dlen;
+
 	len = sizeof(*req) + reqsize + mlen;
 	if (len < mlen)
 		return -EOVERFLOW;
@@ -213,9 +218,10 @@ int crypto_akcipher_sync_prep(struct crypto_akcipher_sync_data *data)
 	data->buf = buf;
 	memcpy(buf, data->src, data->slen);
 
-	sg = data->sg;
+	sg = &data->sg;
 	sg_init_one(sg, buf, mlen);
-	akcipher_request_set_crypt(req, sg, sg, data->slen, data->dlen);
+	akcipher_request_set_crypt(req, sg, data->dst ? sg : NULL,
+				   data->slen, data->dlen);
 
 	crypto_init_wait(&data->cwait);
 	akcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP,

crypto/internal.h

@@ -44,7 +44,7 @@ struct crypto_akcipher_sync_data {
 
 	struct akcipher_request *req;
 	struct crypto_wait cwait;
-	struct scatterlist sg[2];
+	struct scatterlist sg;
 	u8 *buf;
 };
 

crypto/sig.c

@@ -128,9 +128,7 @@ int crypto_sig_verify(struct crypto_sig *tfm,
 	if (err)
 		return err;
 
-	sg_init_table(data.sg, 2);
-	sg_set_buf(&data.sg[0], src, slen);
-	sg_set_buf(&data.sg[1], digest, dlen);
+	memcpy(data.buf + slen, digest, dlen);
 
 	return crypto_akcipher_sync_post(&data,
 					 crypto_akcipher_verify(data.req));