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    Subject[PATCH 4.9 223/245] virtio_console: Assure used length from device is limited
    Date
    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.

    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>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    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 4ec08c7a7b65..2632b0fdb1b5 100644
    --- a/drivers/char/virtio_console.c
    +++ b/drivers/char/virtio_console.c
    @@ -492,7 +492,7 @@ 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;
    }
    @@ -1758,7 +1758,7 @@ 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);
    --
    2.30.2


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