virtio_console: Assure used length from device is limited

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@bytedance.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/20210525125622.1203-1-xieyongji@bytedance.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 59dfd9c..7eaf303 100644 (file)
--- 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);