linux-kernel - Re: [PATCH] media: atomisp: Move a variable assignment behind a null pointer check in atomisp_cp_general_isp

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Date:   Sun, 16 Apr 2023 15:12:28 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Andy Shevchenko <andy@...nel.org>,
        Markus Elfring <Markus.Elfring@....de>
Cc:     kernel-janitors@...r.kernel.org, linux-media@...r.kernel.org,
        linux-staging@...ts.linux.dev,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Xiaomeng Tong <xiam0nd.tong@...il.com>, cocci@...ia.fr,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] media: atomisp: Move a variable assignment behind a null
 pointer check in atomisp_cp_general_isp_parameters()

Hi,

On 4/14/23 19:13, Andy Shevchenko wrote:
> On Thu, Apr 13, 2023 at 10:20:15PM +0200, Markus Elfring wrote:
>> Date: Thu, 13 Apr 2023 22:08:42 +0200
>>
>> The address of a data structure member was determined before
>> a corresponding null pointer check in the implementation of
>> the function “atomisp_cp_general_isp_parameters”.
>>
>> Thus avoid the risk for undefined behaviour by moving the assignment
>> for the variable “cur_config” behind the null pointer check.
> 
> I don't think this is what is happening here. The check might be removed by
> optimizer in the compiler.

Right, Markus thank you for the patch.

Instead of this patch, can you please audit the callers of this
function? I expect that you will likely find that the callers
already unconditionally deref css_param themselves, or they
guarantee a non NULL value in other ways (e.g. address of local
variable).

So I expect that the check can simply be dropped completely,
which would be a much better fix.

Regards,

Hans





> 
>> This issue was detected by using the Coccinelle software.
>>
>> Fixes: ad85094b293e40e7a2f831b0311a389d952ebd5e ("Revert 'media: staging: atomisp: Remove driver'")
> 
> Wrong tag format.
> 
> Code-wise I'm not against this, but it's up to Hans.
>