On 3/17/23 04:09, Zheng Wang wrote:
In vudc_probe, it calls init_vudc_hw, which bound &udc->timer with v_timer.
When it calls usbip_sockfd_store, it will call v_start_timer to start the
timer work.
When we call vudc_remove to remove the driver, theremay be a sequence as
follows:
Fix it by shutdown the timer work before cleanup in vudc_remove.
Note that removing a driver is a root-only operation, and should never
happen. But the attacker can directly unplug the usb to trigger the remove
function.
CPU0 CPU1
|v_timer
vudc_remove |
kfree(udc); |
//free shost |
|udc->gadget
|//use
The udc might be removed before v_timer finished, and UAF happens.
This bug was found by Codeql static analysis and might by false positive.
This statement that this could be a false positive makes me hesitate
taking this patch.
What kind of testing have you done with this fix? Were you able to test
the scenario of unplugging usb?
thanks,
-- Shuah
