__send_control_msg() publishes &portdev->cpkt as the control-out
virtqueue cookie. remove_vqs() walks every virtqueue and passes leftover
cookies to free_buf(), which treats them as struct port_buffer and
reads sgpages.
If a control message is still on c_ovq when the device is unbound,
free_buf() reads past the ports_device object.
KASAN reported slab-out-of-bounds in free_buf():
free_buf
remove_vqs
virtcons_remove
unbind_store
The object was the ports_device allocated in virtcons_probe().
Drain c_ovq without freeing. The packet lives in portdev and is released
with it.
Fixes: a7a69ec0d8 ("virtio_console: free buffers after reset")
Signed-off-by: Jia Jia <physicalmtea@gmail.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-ID: <20260819021230.292696-1-physicalmtea@gmail.com>
894f98e739