From: Sungho Bae <[email protected]> In virtcons_restore(), after virtio_device_ready() sets DRIVER_OK, the device becomes active. If the control receive queue (c_ivq) is populated immediately, the host can instantly deliver pending control messages (e.g., VIRTIO_CONSOLE_PORT_REMOVE).
This triggers the control_work_handler(), which can modify the portdev->ports list concurrently with the unprotected list_for_each_entry loop in virtcons_restore(), leading to list corruption or Use-After-Free. Fix this by deferring the population of the control receive queue (fill_queue for c_ivq) until after the list iteration is complete. This ensures the host cannot inject control messages during the vulnerable window. Signed-off-by: Sungho Bae <[email protected]> --- drivers/char/virtio_console.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c index 589a12261e23..dd31f7069e19 100644 --- a/drivers/char/virtio_console.c +++ b/drivers/char/virtio_console.c @@ -2164,9 +2164,6 @@ static int virtcons_restore(struct virtio_device *vdev) virtio_device_ready(portdev->vdev); - if (use_multiport(portdev)) - fill_queue(portdev->c_ivq, &portdev->c_ivq_lock); - list_for_each_entry(port, &portdev->ports, list) { port->in_vq = portdev->in_vqs[port->id]; port->out_vq = portdev->out_vqs[port->id]; @@ -2183,6 +2180,18 @@ static int virtcons_restore(struct virtio_device *vdev) if (port->guest_connected) send_control_msg(port, VIRTIO_CONSOLE_PORT_OPEN, 1); } + + /* + * Populate the control receive queue only after the list iteration + * is complete. If we fill this queue before iterating, the host could + * immediately deliver a VIRTIO_CONSOLE_PORT_REMOVE message. + * This would trigger the control workqueue, which modifies the + * portdev->ports list concurrently with the unprotected loop above, + * leading to a Use-After-Free and list corruption. + */ + if (use_multiport(portdev)) + fill_queue(portdev->c_ivq, &portdev->c_ivq_lock); + return 0; } #endif -- 2.34.1
