linux-kernel - Re: [PATCH v1] firmware: arm_scmi: Fix NULL pointer dereference in mailbox_clear

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Date:   Wed, 30 Aug 2023 10:39:02 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     Qiujun Huang <hqjagain@...il.com>
Cc:     cristian.marussi@....com, linux-arm-kernel@...ts.infradead.org,
        Sudeep Holla <sudeep.holla@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] firmware: arm_scmi: Fix NULL pointer dereference in
 mailbox_clear_channel

On Wed, Aug 30, 2023 at 01:07:47AM +0800, Qiujun Huang wrote:
> There is a race between the failure of probe and rx_callback (due to a
> delayed response).
> 
> scmi_probe
> scmi_acquire_protocal
> do_xfer
>  timeout
> mailbox_chan_free
>                                                     <--- delay response
>                                                            rx_callback
> mbox_free_channel
> cinfo->transport_info = NULL
>                                                           mailbox_clear_channel
>                                                          dereference cinfo->transport_info

It is always good to provide the kernel stacktrace which you get when a
NULL pointer is dereference. It helps for review and also to document it.

-- 
Regards,
Sudeep