linux-kernel - Re: [PATCH][next] drm/panel: fix null pointer dereference on pointer mode

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Date:   Fri, 18 Sep 2020 17:39:45 +0100
From:   Colin Ian King <colin.king@...onical.com>
To:     Guido Günther <guido.gunther@...i.sm>
Cc:     Purism Kernel Team <kernel@...i.sm>,
        Thierry Reding <thierry.reding@...il.com>,
        Sam Ravnborg <sam@...nborg.org>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH][next] drm/panel: fix null pointer dereference on pointer
 mode

On 18/09/2020 17:22, Guido Günther wrote:
> Hi,
> On Fri, Sep 18, 2020 at 04:51:36PM +0100, Colin King wrote:
>> From: Colin Ian King <colin.king@...onical.com>
>>
>> Currently a null pointer check on pointer mode is passing mode to
>> function drm_mode_vrefresh and this causes a null pointer dereference
>> on mode.  Fix this by not calling drm_mode_vrefresh since the call
>> is only required for error reporting.
>>
>> Addresses-Coverity: ("Dereference after null check")
>> Fixes: 72967d5616d3 ("drm/panel: Add panel driver for the Mantix MLAF057WE51-X DSI panel")
>> Signed-off-by: Colin Ian King <colin.king@...onical.com>
>> ---
>>  drivers/gpu/drm/panel/panel-mantix-mlaf057we51.c | 5 ++---
>>  1 file changed, 2 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/panel/panel-mantix-mlaf057we51.c b/drivers/gpu/drm/panel/panel-mantix-mlaf057we51.c
>> index 3482e28e30fc..be4761a643f9 100644
>> --- a/drivers/gpu/drm/panel/panel-mantix-mlaf057we51.c
>> +++ b/drivers/gpu/drm/panel/panel-mantix-mlaf057we51.c
>> @@ -202,9 +202,8 @@ static int mantix_get_modes(struct drm_panel *panel,
>>  
>>  	mode = drm_mode_duplicate(connector->dev, &default_mode);
>>  	if (!mode) {
>> -		dev_err(ctx->dev, "Failed to add mode %ux%u@%u\n",
>> -			default_mode.hdisplay, default_mode.vdisplay,
>> -			drm_mode_vrefresh(mode));
>> +		dev_err(ctx->dev, "Failed to add mode %ux%u\n",
>> +			default_mode.hdisplay, default_mode.vdisplay);
>>  		return -ENOMEM;
>>  	}
> 
> drm_mode_vrefresh(&default_mode) gives some more clue what's going on -
> I have had a fix queued up in my tree already but if you send a v2
> that's fine.

I'll defer to your queued up fix.
> 
> Thanks!
>  -- Guido
> 
>>  
>> -- 
>> 2.27.0
>>