Messages in this thread | | | From | Zheng Hacker <> | Date | Fri, 14 Apr 2023 00:46:08 +0800 | Subject | Re: [PATCH] misc: hisi_hikey_usb: Fix use after free bug in hisi_hikey_usb_remove due to race condition |
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Greg KH <gregkh@linuxfoundation.org> 于2023年4月13日周四 23:56写道: > > On Thu, Apr 13, 2023 at 11:35:17PM +0800, Zheng Hacker wrote: > > Greg KH <gregkh@linuxfoundation.org> 于2023年4月13日周四 20:48写道: > > > > > > On Thu, Apr 13, 2023 at 07:12:07PM +0800, Zheng Hacker wrote: > > > > Yongqin Liu <yongqin.liu@linaro.org> 于2023年4月13日周四 18:55写道: > > > > > > > > > > Hi, Zheng > > > > > > > > > > On Thu, 13 Apr 2023 at 16:08, Zheng Hacker <hackerzheng666@gmail.com> wrote: > > > > > > > > > > > > Friendly ping about the bug. > > > > > > > > > > Sorry, wasn't aware of this message before, > > > > > > > > > > Could you please help share the instructions to reproduce the problem > > > > > this change fixes? > > > > > > > > > > > > > Hi Yongqin, > > > > > > > > Thanks for your reply. This bug is found by static analysis. There is no PoC. > > > > > > > > >From my personal experience, triggering race condition bugs stably in > > > > the kernel needs some tricks. > > > > For example, you can insert some sleep-time code to slow down the > > > > thread until the related object is freed. > > > > Besides, you can use gdb to control the time window. Also, there are > > > > some other tricks as [1] said. > > > > > > > > As for the reproduction, this attack vector requires that the attacker > > > > can physically access the device. > > > > When he/she unplugs the usb, the remove function is triggered, and if > > > > the set callback is invoked, there might be a race condition. > > > > > > How does the removal of the USB device trigger a platform device > > > removal? > > > > Sorry I made a mistake. The USB device usually calls disconnect > > callback when it's unpluged. > > Yes, but you are changing the platform device disconnect, not the USB > device disconnect. > > > What I want to express here is When the driver-related device(here > > it's USB GPIO Hub) was removed, the remove function is triggered. > > And is this a patform device on a USB device? If so, that's a bigger > problem that we need to fix as that is not allowed.
No this is not a platform device on a USB device.
> > But in looking at the code, it does not seem to be that at all, this is > just a "normal" platform device. So how can it ever be removed from the > system? (and no, unloading the driver doesn't count, that can never > happen on a normal machine.) >
Yes, I finally figured out your meaning. I know it's hard to unplug the platform device directly. All I want to express is that it's a theoretical method except rmmod. I think it's better to fix the bug. But if the developers think it's practically impossible, I think there's no need to take further action.
Sorry for wasting your time and thanks for your explanation.
Best regards, Zheng
> thanks, > > greg k-h
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