linux-kernel - Re: [Linux-fbdev-devel] [PATCH] drivers/video: Bad error test before a dereference

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Date:	Thu, 13 Nov 2008 09:26:46 +0100
From:	Nicolas Ferre <nicolas.ferre@...el.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Julien Brunel <brunel@...u.dk>, adaplas@...il.com,
	linux-fbdev-devel@...ts.sourceforge.net,
	kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [Linux-fbdev-devel] [PATCH] drivers/video: Bad error test	before
 a dereference

Hi Andrew,

Nicolas Ferre :
> Julien Brunel :
>> The error test that follows the call to backlight_device_register
>> semms not to concern the right variable.
>>
>> A simplified version of the semantic match that finds this problem is
>> as follows: 
>> (http://www.emn.fr/x-info/coccinelle/)
>> // <smpl>
>> @def0@
>> expression x;
>> position p0;
>> @@
>> x@p0 = backlight_device_register(...)
>>
>> @protected@
>> expression def0.x,E;
>> position def0.p0;
>> position p;
>> statement S;
>> @@
>> x@p0
>> ... when != x = E
>> if (!IS_ERR(x) && ...) {<... x@p ...>} else S
>>
>> @unprotected@
>> expression def0.x;
>> identifier fld;
>> position def0.p0;
>> position p != protected.p;
>> @@
>> x@p0
>> ... when != x = E
>> * x@p->fld
>> // </smpl>
>>
>> Signed-off-by: Julien Brunel <brunel@...u.dk>
>> Signed-off-by: Julia Lawall <julia@...u.dk>
> 
> Acked-by: Nicolas Ferre <nicolas.ferre@...el.com>

I do not know if you noticed this little patch but
I think it will be good if we can queue it for -final.

Do you want me to reformulate the submission or the
original email ok for you ?

>> ---
>>  drivers/video/atmel_lcdfb.c |    2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff -u -p a/drivers/video/atmel_lcdfb.c b/drivers/video/atmel_lcdfb.c
>> --- a/drivers/video/atmel_lcdfb.c
>> +++ b/drivers/video/atmel_lcdfb.c
>> @@ -132,7 +132,7 @@ static void init_backlight(struct atmel_
>>  
>>  	bl = backlight_device_register("backlight", &sinfo->pdev->dev,
>>  			sinfo, &atmel_lcdc_bl_ops);
>> -	if (IS_ERR(sinfo->backlight)) {
>> +	if (IS_ERR(bl)) {
>>  		dev_err(&sinfo->pdev->dev, "error %ld on backlight register\n",
>>  				PTR_ERR(bl));
>>  		return;

Thanks, regards,
-- 
Nicolas Ferre

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