Messages in this thread | | | Date | Thu, 13 Apr 2023 12:01:43 -0600 | Subject | Re: [PATCH v3] usbip: vudc: Fix use after free bug in vudc_remove due to race condition | From | Shuah Khan <> |
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On 4/13/23 02:09, Zheng Hacker wrote: > Friendly ping about the issue. > Sorry that I couldn't make test about the driver. > > Thanks, > Zheng > > Zheng Hacker <hackerzheng666@gmail.com> 于2023年3月18日周六 15:39写道: >> >> Shuah Khan <skhan@linuxfoundation.org> 于2023年3月18日周六 06:53写道: >>> >>> 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? >>> >> >> Sorry I did't make a full test for I did't have the device. The >> attacking scenario if based on other cases. >>
Sorry. I really need for you test this and provide information on how it was tested.
thanks, -- Shuah
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