Re: [PATCH 4.4 175/188] virtio_console: Assure used length from device is limited

Pavel Machek
2021-07-20T21:45:04Z

[-- Attachment #1: Type: text/plain, Size: 1239 bytes --]

Hi!

> From: Xie Yongji <xieyongji@bytedance.com>
>
> [ Upstream commit d00d8da5869a2608e97cfede094dfc5e11462a46 ]
>
> 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.

Since we are not trusting the other side, do we need to use _nospec
variants to prevent speculation attacks?

Best regards,
Pavel

> +++ b/drivers/char/virtio_console.c
> @@ -487,7 +487,7 @@ 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;
> }
> @@ -1752,7 +1752,7 @@ 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);

--
DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany

[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 181 bytes --]