[PATCH] drm/gud: Use kmalloc_array() instead of kmalloc()

[PATCH] drm/gud: Use kmalloc_array() instead of kmalloc()

[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@gmail.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);
 	if (!buf)
 		return 0;
 
-- 
2.51.0

Re: [PATCH] drm/gud: Use kmalloc_array() instead of kmalloc()

[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@gmail.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);
>   	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)

Re: [PATCH] drm/gud: Use kmalloc_array() instead of kmalloc()

[Thomas Zimmermann]

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@gmail.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)

Re: [PATCH] drm/gud: Use kmalloc_array() instead of kmalloc()

[Mehdi Ben Hadj Khelifa]

On 9/23/25 8:06 AM, Thomas Zimmermann wrote:
> 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@gmail.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?

i thought it would be more "clean" to have a data type that is of 1 byte 
size to use as a reference for the size of each element here.


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

This was more apparent to me after i have sent the patch and was waiting
for a reply first. Since my initial though was that width or height 
alone couldn't be treated as a reference to "n of elements" or "size of 
each element" but your suggestion is more logical since leaving the 
calculation width * height in the kmalloc_array would defeat the purpose 
of switching from kmalloc to kmalloc_array since dynamic calculation is 
still present and overflow is still possible.

I will send a v2 patch shortly changing to your suggestion.

> Best regards
> Thomas
> 

Best Regards,
Mehdi Ben Hadj Khelifa