[PATCH v2] virtio_console: Assure used length from device is limited

[Xie Yongji]

The buf->len might come from an untrusted device. This
ensures the value would not exceed the size of the buffer
to avoid data corruption or loss.

Signed-off-by: Xie Yongji <xieyongji@xxxxxxxxxxxxx>
Acked-by: Jason Wang <jasowang@xxxxxxxxxx>
---
 drivers/char/virtio_console.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 1c40ca6d76ba..972b0cd15b87 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -475,7 +475,7 @@ static struct port_buffer *get_inbuf(struct port *port)
 
 	buf = virtqueue_get_buf(port->in_vq, &len);
 	if (buf) {
-		buf->len = len;
+		buf->len = min_t(size_t, len, buf->size);
 		buf->offset = 0;
 		port->stats.bytes_received += len;
 	}
@@ -1709,7 +1709,7 @@ static void control_work_handler(struct work_struct *work)
 	while ((buf = virtqueue_get_buf(vq, &len))) {
 		spin_unlock(&portdev->c_ivq_lock);
 
-		buf->len = len;
+		buf->len = min_t(size_t, len, buf->size);
 		buf->offset = 0;
 
 		handle_control_message(vq->vdev, portdev, buf);
-- 
2.11.0