crypto: qat - add param check for DH

Reject requests with a source buffer that is bigger than the size of the
key. This is to prevent a possible integer underflow that might happen
when copying the source scatterlist into a linear buffer.

Cc: stable@vger.kernel.org
Signed-off-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Reviewed-by: Adam Guerin <adam.guerin@intel.com>
Reviewed-by: Wojciech Ziemba <wojciech.ziemba@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/qat/qat_common/qat_asym_algs.c

@@ -235,6 +235,10 @@ static int qat_dh_compute_value(struct kpp_request *req)
 		req->dst_len = ctx->p_size;
 		return -EOVERFLOW;
 	}
+
+	if (req->src_len > ctx->p_size)
+		return -EINVAL;
+
 	memset(msg, '\0', sizeof(*msg));
 	ICP_QAT_FW_PKE_HDR_VALID_FLAG_SET(msg->pke_hdr,
 					  ICP_QAT_FW_COMN_REQ_FLAG_SET);