Re: [PATCH v13 5/9] drm/i915: Check for integer truncation on scatterlist creation

[Gwan-gyeong Mun]

On 9/28/22 11:51 AM, Jani Nikula wrote:
> On Wed, 28 Sep 2022, Gwan-gyeong Mun <gwan-gyeong.mun@xxxxxxxxx> wrote:
> > diff --git a/drivers/gpu/drm/i915/i915_scatterlist.h b/drivers/gpu/drm/i915/i915_scatterlist.h
> > index 9ddb3e743a3e..1d1802beb42b 100644
> > --- a/drivers/gpu/drm/i915/i915_scatterlist.h
> > +++ b/drivers/gpu/drm/i915/i915_scatterlist.h
> > @@ -220,4 +220,15 @@ struct i915_refct_sgt *i915_rsgt_from_buddy_resource(struct ttm_resource *res,
> >   						     u64 region_start,
> >   						     u32 page_alignment);
> >   
> > +/* Wrap scatterlist.h to sanity check for integer truncation */
> > +typedef unsigned int __sg_size_t; /* see linux/scatterlist.h */
> > +#define sg_alloc_table(sgt, nents, gfp) \
> > +	overflows_type(nents, __sg_size_t) ? -E2BIG \
> > +		: ((sg_alloc_table)(sgt, (__sg_size_t)(nents), gfp))
> > +
> > +#define sg_alloc_table_from_pages_segment(sgt, pages, npages, offset, size, max_segment, gfp) \
> > +	overflows_type(npages, __sg_size_t) ? -E2BIG \
> > +		: ((sg_alloc_table_from_pages_segment)(sgt, pages, (__sg_size_t)(npages), offset, \
> > +						       size, max_segment, gfp))
> > +
> >   #endif
>
> No. I don't think we should shadow sg_alloc_table() and
> sg_alloc_table_from_pages_segment().
>
> Either get this in scatterlist.h (preferred) or prefix with i915_ or
> whatever to indicate it's our local thing.
>
> i915_scatterlist.h already has too much scatterlist "namespace" abuse
> that I'd rather see gone than violated more.
Hi Jani,
Thanks for you comments.

I will update this patch by removing the shadowing of 
sg_alloc_table_from_pages_segment() / sg_alloc_table(), so that the 
caller checks when overflow checking is required.

Br,
G.G.

> BR,
> Jani.