crypto: virtio/akcipher - Fix stack overflow on memcpy

sizeof(struct virtio_crypto_akcipher_session_para) is less than
sizeof(struct virtio_crypto_op_ctrl_req::u), copying more bytes from
stack variable leads stack overflow. Clang reports this issue by
commands:
make -j CC=clang-14 mrproper >/dev/null 2>&1
make -j O=/tmp/crypto-build CC=clang-14 allmodconfig >/dev/null 2>&1
make -j O=/tmp/crypto-build W=1 CC=clang-14 drivers/crypto/virtio/
  virtio_crypto_akcipher_algs.o

Fixes: 59ca6c93 ("virtio-crypto: implement RSA algorithm")
Link: https://lore.kernel.org/all/0a194a79-e3a3-45e7-be98-83abd3e1cb7e@roeck-us.net/
Cc: <stable@vger.kernel.org>
Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
Tested-by: Nathan Chancellor <nathan@kernel.org> # build
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/virtio/virtio_crypto_akcipher_algs.c

@@ -104,7 +104,8 @@ static void virtio_crypto_dataq_akcipher_callback(struct virtio_crypto_request *
 }
 
 static int virtio_crypto_alg_akcipher_init_session(struct virtio_crypto_akcipher_ctx *ctx,
-		struct virtio_crypto_ctrl_header *header, void *para,
+		struct virtio_crypto_ctrl_header *header,
+		struct virtio_crypto_akcipher_session_para *para,
 		const uint8_t *key, unsigned int keylen)
 {
 	struct scatterlist outhdr_sg, key_sg, inhdr_sg, *sgs[3];
@@ -128,7 +129,7 @@ static int virtio_crypto_alg_akcipher_init_session(struct virtio_crypto_akcipher
 
 	ctrl = &vc_ctrl_req->ctrl;
 	memcpy(&ctrl->header, header, sizeof(ctrl->header));
-	memcpy(&ctrl->u, para, sizeof(ctrl->u));
+	memcpy(&ctrl->u.akcipher_create_session.para, para, sizeof(*para));
 	input = &vc_ctrl_req->input;
 	input->status = cpu_to_le32(VIRTIO_CRYPTO_ERR);