Re: [PATCH] misc: hisi_hikey_usb: Fix use after free bug in hisi_hikey_usb_remove due to race condition

[Greg KH]

On Thu, Apr 13, 2023 at 07:12:07PM +0800, Zheng Hacker wrote:
> Yongqin Liu <yongqin.liu@xxxxxxxxxx> 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@xxxxxxxxx> 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?

Are you sure this can be triggered by some other way other than manually
unloading the driver?

thanks,

greg k-h