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

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Message-ID: <87edvvzxu3.fsf@intel.com>
Date:   Wed, 28 Sep 2022 11:51:00 +0300
From:   Jani Nikula <jani.nikula@...el.com>
To:     Gwan-gyeong Mun <gwan-gyeong.mun@...el.com>,
        intel-gfx@...ts.freedesktop.org
Cc:     linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        mchehab@...nel.org, chris@...is-wilson.co.uk,
        matthew.auld@...el.com, thomas.hellstrom@...ux.intel.com,
        nirmoy.das@...el.com, airlied@...hat.com, daniel@...ll.ch,
        andi.shyti@...ux.intel.com, andrzej.hajda@...el.com,
        keescook@...omium.org, mauro.chehab@...ux.intel.com,
        linux@...musvillemoes.dk, vitor@...saru.org, dlatypov@...gle.com,
        ndesaulniers@...gle.com, trix@...hat.com, llvm@...ts.linux.dev,
        linux-hardening@...r.kernel.org, linux-sparse@...r.kernel.org,
        nathan@...nel.org, gustavoars@...nel.org,
        luc.vanoostenryck@...il.com
Subject: Re: [PATCH v13 5/9] drm/i915: Check for integer truncation on
 scatterlist creation

On Wed, 28 Sep 2022, Gwan-gyeong Mun <gwan-gyeong.mun@...el.com> 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.


BR,
Jani.



-- 
Jani Nikula, Intel Open Source Graphics Center