Re: [PATCH] gpu: drm: use struct_size() in kmalloc()

[Alex Deucher]

On Mon, May 20, 2019 at 7:19 PM Pan, Xinhui <Xinhui.Pan@xxxxxxx> wrote:
>
> Daniel, what you are talking about is totally wrong.
> 1) AFAIK, only one zero-size array can be in the end of a struct.
> 2) two struct_size will add up struct itself twice. the sum is wrong then.
>
> No offense. I can't help feeling lucky that you are in intel.

Xinhui,

Please keep things civil.  There is no need for comments like this.

Alex

>
>
> åää: Daniel Vetter <daniel.vetter@xxxxxxxx> äè Daniel Vetter <daniel@xxxxxxxx>
> åéæé: 2019å5æ21æ 0:28
> æää: Pan, Xinhui
> æé: Deucher, Alexander; Koenig, Christian; Zhou, David(ChunMing); airlied@xxxxxxxx; daniel@xxxxxxxx; Quan, Evan; xiaolinkui; amd-gfx@xxxxxxxxxxxxxxxxxxxxx; dri-devel@xxxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> äé: Re: [PATCH] gpu: drm: use struct_size() in kmalloc()
>
> [CAUTION: External Email]
>
> On Fri, May 17, 2019 at 04:44:30PM +0000, Pan, Xinhui wrote:
> > I am going to put more members which are also array after this struct,
> > not only obj[].  Looks like this struct_size did not help on multiple
> > array case. Thanks anyway.  ________________________________
>
> You can then add them up, e.g. kmalloc(struct_size()+struct_size(),
> GFP_KERNEL), so this patch here still looks like a good idea.
>
> Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
>
> Cheers, Daniel
>
> > From: xiaolinkui <xiaolinkui@xxxxxxxxxx>
> > Sent: Friday, May 17, 2019 4:46:00 PM
> > To: Deucher, Alexander; Koenig, Christian; Zhou, David(ChunMing); airlied@xxxxxxxx; daniel@xxxxxxxx; Pan, Xinhui; Quan, Evan
> > Cc: amd-gfx@xxxxxxxxxxxxxxxxxxxxx; dri-devel@xxxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; xiaolinkui@xxxxxxxxxx
> > Subject: [PATCH] gpu: drm: use struct_size() in kmalloc()
> >
> > [CAUTION: External Email]
> >
> > Use struct_size() helper to keep code simple.
> >
> > Signed-off-by: xiaolinkui <xiaolinkui@xxxxxxxxxx>
> > ---
> >  drivers/gpu/drm/amd/amdgpu/amdgpu_ras.c | 3 +--
> >  1 file changed, 1 insertion(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ras.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ras.c
> > index 22bd21e..4717a64 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ras.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ras.c
> > @@ -1375,8 +1375,7 @@ int amdgpu_ras_init(struct amdgpu_device *adev)
> >         if (con)
> >                 return 0;
> >
> > -       con = kmalloc(sizeof(struct amdgpu_ras) +
> > -                       sizeof(struct ras_manager) * AMDGPU_RAS_BLOCK_COUNT,
> > +       con = kmalloc(struct_size(con, objs, AMDGPU_RAS_BLOCK_COUNT),
> >                         GFP_KERNEL|__GFP_ZERO);
> >         if (!con)
> >                 return -ENOMEM;
> > --
> > 2.7.4
> >
> >
> >
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch
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