linux-kernel - Re: [PATCH v2] staging: rtl8192u: Fix sleep in atomic context bug in dm_fsync_timer

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Date:   Sat, 25 Jun 2022 17:21:06 +0800 (GMT+08:00)
From:   duoming@....edu.cn
To:     "Greg KH" <gregkh@...uxfoundation.org>
Cc:     linux-staging@...ts.linux.dev, davem@...emloft.net,
        alexander.deucher@....com, kuba@...nel.org, broonie@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] staging: rtl8192u: Fix sleep in atomic context bug
 in dm_fsync_timer_callback

Hello,

> > On Thu, Jun 23, 2022 at 01:59:12PM +0800, Duoming Zhou wrote:
> > > There are sleep in atomic context bugs when dm_fsync_timer_callback is
> > > executing. The root cause is that the memory allocation functions with
> > > GFP_KERNEL or GFP_NOIO parameters are called in dm_fsync_timer_callback
> > > which is a timer handler. The call paths that could trigger bugs are
> > > shown below:
> > > 
> > >     (interrupt context)
> > > dm_fsync_timer_callback
> > >   write_nic_byte
> > >     kzalloc(sizeof(data), GFP_KERNEL); //may sleep
> > >     usb_control_msg
> > >       kmalloc(.., GFP_NOIO); //may sleep
> > >   write_nic_dword
> > >     kzalloc(sizeof(data), GFP_KERNEL); //may sleep
> > >     usb_control_msg
> > >       kmalloc(.., GFP_NOIO); //may sleep
> > > 
> > > This patch uses delayed work to replace timer and moves the operations
> > > that may sleep into the delayed work in order to mitigate bugs.
> > > 
> > > Fixes: 8fc8598e61f6 ("Staging: Added Realtek rtl8192u driver to staging")
> > > Signed-off-by: Duoming Zhou <duoming@....edu.cn>
> > > ---
> > > Changes in v2:
> > >   - Use delayed work to replace timer.
> > 
> > Did you test this with real hardware to verify it still works?
> 
> I am testing this and I will give you feedback within one or two days.

Do you know what vendor id and device id use the r8192u_usb driver?
I try many hardwares, they could not trigger this code.

Thank you!

Best regards,
Duoming Zhou