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

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Date:   Thu, 23 Jun 2022 11:46:41 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Duoming Zhou <duoming@....edu.cn>
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

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?

thanks,

greg k-h