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@xxxxxxxxxxxx>
> > ---
> >   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