crypto: mediatek - Add empty messages check in GCM mode

Currently, empty messages are not supported in GCM mode, hence add
a check to prevent producing incorrect results.
Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/mediatek/mtk-aes.c

@@ -928,8 +928,13 @@ static int mtk_aes_gcm_start(struct mtk_cryp *cryp, struct mtk_aes_rec *aes)
 static int mtk_aes_gcm_crypt(struct aead_request *req, u64 mode)
 {
 	struct mtk_aes_base_ctx *ctx = crypto_aead_ctx(crypto_aead_reqtfm(req));
+	struct mtk_aes_gcm_ctx *gctx = mtk_aes_gcm_ctx_cast(ctx);
 	struct mtk_aes_reqctx *rctx = aead_request_ctx(req);
 
+	/* Empty messages are not supported yet */
+	if (!gctx->textlen && !req->assoclen)
+		return -EINVAL;
+
 	rctx->mode = AES_FLAGS_GCM | mode;
 
 	return mtk_aes_handle_queue(ctx->cryp, !!(mode & AES_FLAGS_ENCRYPT),