[PATCH] drm/xe: Prefer struct_size over open coded arithmetic

[PATCH] drm/xe: Prefer struct_size over open coded arithmetic

[Erick Archer]

This is an effort to get rid of all multiplications from allocation
functions in order to prevent integer overflows [1].

As the "q" variable is a pointer to "struct xe_exec_queue" and this
structure ends in a flexible array:

struct xe_exec_queue {
	[...]
	struct xe_lrc lrc[];
};

the preferred way in the kernel is to use the struct_size() helper to
do the arithmetic instead of the argument "size + size * count" in the
kzalloc() function.

This way, the code is more readable and more safer.

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments [1]
Link: https://github.com/KSPP/linux/issues/160 [2]
Signed-off-by: Erick Archer <erick.archer@gmx.com>
---
 drivers/gpu/drm/xe/xe_exec_queue.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/xe/xe_exec_queue.c b/drivers/gpu/drm/xe/xe_exec_queue.c
index bcfc4127c7c5..f4e53cbccd04 100644
--- a/drivers/gpu/drm/xe/xe_exec_queue.c
+++ b/drivers/gpu/drm/xe/xe_exec_queue.c
@@ -44,7 +44,7 @@ static struct xe_exec_queue *__xe_exec_queue_create(struct xe_device *xe,
 	/* only kernel queues can be permanent */
 	XE_WARN_ON((flags & EXEC_QUEUE_FLAG_PERMANENT) && !(flags & EXEC_QUEUE_FLAG_KERNEL));

-	q = kzalloc(sizeof(*q) + sizeof(struct xe_lrc) * width, GFP_KERNEL);
+	q = kzalloc(struct_size(q, lrc, width), GFP_KERNEL);
 	if (!q)
 		return ERR_PTR(-ENOMEM);

--
2.25.1

Re: [PATCH] drm/xe: Prefer struct_size over open coded arithmetic

[Gustavo A. R. Silva]

On 2/10/24 08:19, Erick Archer wrote:
> This is an effort to get rid of all multiplications from allocation
> functions in order to prevent integer overflows [1].
> 
> As the "q" variable is a pointer to "struct xe_exec_queue" and this
> structure ends in a flexible array:
> 
> struct xe_exec_queue {
> 	[...]
> 	struct xe_lrc lrc[];
> };
> 
> the preferred way in the kernel is to use the struct_size() helper to
> do the arithmetic instead of the argument "size + size * count" in the
> kzalloc() function.
> 
> This way, the code is more readable and more safer.
> 
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments [1]
> Link: https://github.com/KSPP/linux/issues/160 [2]
> Signed-off-by: Erick Archer <erick.archer@gmx.com>

LGTM:

Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Thanks!
-- 
Gustavo

> ---
>   drivers/gpu/drm/xe/xe_exec_queue.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_exec_queue.c b/drivers/gpu/drm/xe/xe_exec_queue.c
> index bcfc4127c7c5..f4e53cbccd04 100644
> --- a/drivers/gpu/drm/xe/xe_exec_queue.c
> +++ b/drivers/gpu/drm/xe/xe_exec_queue.c
> @@ -44,7 +44,7 @@ static struct xe_exec_queue *__xe_exec_queue_create(struct xe_device *xe,
>   	/* only kernel queues can be permanent */
>   	XE_WARN_ON((flags & EXEC_QUEUE_FLAG_PERMANENT) && !(flags & EXEC_QUEUE_FLAG_KERNEL));
> 
> -	q = kzalloc(sizeof(*q) + sizeof(struct xe_lrc) * width, GFP_KERNEL);
> +	q = kzalloc(struct_size(q, lrc, width), GFP_KERNEL);
>   	if (!q)
>   		return ERR_PTR(-ENOMEM);
> 
> --
> 2.25.1
> 
> 

Re: Re: [PATCH] drm/xe: Prefer struct_size over open coded arithmetic

[Lucas De Marchi]

On Sat, Feb 10, 2024 at 10:49:57AM -0600, Gustavo A. R. Silva wrote:
>
>
>On 2/10/24 08:19, Erick Archer wrote:
>>This is an effort to get rid of all multiplications from allocation
>>functions in order to prevent integer overflows [1].
>>
>>As the "q" variable is a pointer to "struct xe_exec_queue" and this
>>structure ends in a flexible array:
>>
>>struct xe_exec_queue {
>>	[...]
>>	struct xe_lrc lrc[];
>>};
>>
>>the preferred way in the kernel is to use the struct_size() helper to
>>do the arithmetic instead of the argument "size + size * count" in the
>>kzalloc() function.
>>
>>This way, the code is more readable and more safer.
>>
>>Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments [1]
>>Link: https://github.com/KSPP/linux/issues/160 [2]
>>Signed-off-by: Erick Archer <erick.archer@gmx.com>
>
>LGTM:
>
>Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>

applied to drm-xe-next. Thanks for the patch and review.

Lucas De Marchi