linux-kernel - Re: [PATCH] drm/gud: Use kmalloc

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Message-ID: <fda2b300-dd91-4357-8cd0-a82347907164@suse.de>
Date: Tue, 23 Sep 2025 09:06:07 +0200
From: Thomas Zimmermann <tzimmermann@...e.de>
To: Mehdi Ben Hadj Khelifa <mehdi.benhadjkhelifa@...il.com>,
 maarten.lankhorst@...ux.intel.com, mripard@...nel.org, airlied@...il.com,
 simona@...ll.ch, mingo@...nel.org, tglx@...utronix.de, jfalempe@...hat.com,
 skhan@...uxfoundation.org, david.hunter.linux@...il.com,
 Ruben Wauters <rubenru09@....com>
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
 linux-kernel-mentees@...ts.linuxfoundation.org
Subject: Re: [PATCH] drm/gud: Use kmalloc_array() instead of kmalloc()

Hi

Am 23.09.25 um 08:34 schrieb Thomas Zimmermann:
> cc Ruben
>
> Am 22.09.25 um 19:43 schrieb Mehdi Ben Hadj Khelifa:
>> Replace kmalloc with kmalloc array in drm/gud/gud_pipe.c since the
>> calculation inside kmalloc is dynamic "width * height" and added
>> u_char as the size of each element.
>>
>> Signed-off-by: Mehdi Ben Hadj Khelifa <mehdi.benhadjkhelifa@...il.com>
>> ---
>>   drivers/gpu/drm/gud/gud_pipe.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/gud/gud_pipe.c 
>> b/drivers/gpu/drm/gud/gud_pipe.c
>> index 8d548d08f127..eeea0cb4c7aa 100644
>> --- a/drivers/gpu/drm/gud/gud_pipe.c
>> +++ b/drivers/gpu/drm/gud/gud_pipe.c
>> @@ -70,7 +70,7 @@ static size_t gud_xrgb8888_to_r124(u8 *dst, const 
>> struct drm_format_info *format
>>       height = drm_rect_height(rect);
>>       len = drm_format_info_min_pitch(format, 0, width) * height;
>>   -    buf = kmalloc(width * height, GFP_KERNEL);
>> +    buf = kmalloc_array(width * height, sizeof(u_char), GFP_KERNEL);

u_char is more or less guaranteed to be 8 bit. So what's the point?

There's a potential overflow in width * height. If anything, you want to 
call kmalloc_array(height, width).

Best regards
Thomas


>>       if (!buf)
>>           return 0;
>

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)