[PATCH] drm/nouveau/nvif: use struct_size()

[PATCH] drm/nouveau/nvif: use struct_size()

[Su Hui]

Use struct_size() instead of hand writing it.
This is less verbose and more informative.

Signed-off-by: Su Hui <suhui@nfschina.com>
---
 drivers/gpu/drm/nouveau/nvif/object.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/nouveau/nvif/object.c b/drivers/gpu/drm/nouveau/nvif/object.c
index 4d1aaee8fe15..4bd693aa4ee0 100644
--- a/drivers/gpu/drm/nouveau/nvif/object.c
+++ b/drivers/gpu/drm/nouveau/nvif/object.c
@@ -65,7 +65,7 @@ nvif_object_sclass_get(struct nvif_object *object, struct nvif_sclass **psclass)
 	u32 size;
 
 	while (1) {
-		size = sizeof(*args) + cnt * sizeof(args->sclass.oclass[0]);
+		size = struct_size(args, sclass.oclass, cnt);
 		if (!(args = kmalloc(size, GFP_KERNEL)))
 			return -ENOMEM;
 		args->ioctl.version = 0;
-- 
2.30.2

Re: [PATCH] drm/nouveau/nvif: use struct_size()

[Dan Carpenter]

On Wed, May 31, 2023 at 12:38:26PM +0800, Su Hui wrote:
> Use struct_size() instead of hand writing it.
> This is less verbose and more informative.
> 
> Signed-off-by: Su Hui <suhui@nfschina.com>
> ---
>  drivers/gpu/drm/nouveau/nvif/object.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/nouveau/nvif/object.c b/drivers/gpu/drm/nouveau/nvif/object.c
> index 4d1aaee8fe15..4bd693aa4ee0 100644
> --- a/drivers/gpu/drm/nouveau/nvif/object.c
> +++ b/drivers/gpu/drm/nouveau/nvif/object.c
> @@ -65,7 +65,7 @@ nvif_object_sclass_get(struct nvif_object *object, struct nvif_sclass **psclass)
>  	u32 size;
>  
>  	while (1) {
> -		size = sizeof(*args) + cnt * sizeof(args->sclass.oclass[0]);
> +		size = struct_size(args, sclass.oclass, cnt);

This is from the original code, but now that you are using the
struct_size() macro static checkers will complain about it.  (Maybe they
don't yet?).  size is a u32.  Never save struct_size() returns to
anything except unsigned long or size_t.  (ssize_t is also fine, I
suppose).  Otherwise, you do not benefit from the integer overflow
checking.

>  		if (!(args = kmalloc(size, GFP_KERNEL)))
>  			return -ENOMEM;
>  		args->ioctl.version = 0;

regards,
dan carpenter

Re: [PATCH] drm/nouveau/nvif: use struct_size()

[Su Hui]

On 2023/5/31 16:31, Dan Carpenter wrote:
> On Wed, May 31, 2023 at 12:38:26PM +0800, Su Hui wrote:
>> Use struct_size() instead of hand writing it.
>> This is less verbose and more informative.
>>
>> Signed-off-by: Su Hui <suhui@nfschina.com>
>> ---
>>   drivers/gpu/drm/nouveau/nvif/object.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/nouveau/nvif/object.c b/drivers/gpu/drm/nouveau/nvif/object.c
>> index 4d1aaee8fe15..4bd693aa4ee0 100644
>> --- a/drivers/gpu/drm/nouveau/nvif/object.c
>> +++ b/drivers/gpu/drm/nouveau/nvif/object.c
>> @@ -65,7 +65,7 @@ nvif_object_sclass_get(struct nvif_object *object, struct nvif_sclass **psclass)
>>   	u32 size;
>>   
>>   	while (1) {
>> -		size = sizeof(*args) + cnt * sizeof(args->sclass.oclass[0]);
>> +		size = struct_size(args, sclass.oclass, cnt);
> This is from the original code, but now that you are using the
> struct_size() macro static checkers will complain about it.  (Maybe they
> don't yet?).  size is a u32.  Never save struct_size() returns to
> anything except unsigned long or size_t.  (ssize_t is also fine, I
> suppose).  Otherwise, you do not benefit from the integer overflow
> checking.
Sorry, I don't notice the issue caused by type size.
You are right, this patch is wrong because of the type mismatch.
Thanks for your reply!

Su Hui

>>   		if (!(args = kmalloc(size, GFP_KERNEL)))
>>   			return -ENOMEM;
>>   		args->ioctl.version = 0;
> regards,
> dan carpenter