linux-hardening - Re: [PATCH 1/5] Compiler Attributes: Add __alloc

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Message-ID: <202108181404.B5E8739C3C@keescook>
Date:   Wed, 18 Aug 2021 14:04:31 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     linux-kernel@...r.kernel.org, Miguel Ojeda <ojeda@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        clang-built-linux@...glegroups.com,
        Andrew Morton <akpm@...ux-foundation.org>,
        Daniel Micay <danielmicay@...il.com>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Dennis Zhou <dennis@...nel.org>, Tejun Heo <tj@...nel.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>, linux-mm@...ck.org,
        linux-kbuild@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH 1/5] Compiler Attributes: Add __alloc_size() for better
 bounds checking

On Wed, Aug 18, 2021 at 11:04:32AM -0700, Nathan Chancellor wrote:
> On 8/17/2021 10:08 PM, Kees Cook wrote:
> > GCC and Clang can use the alloc_size attribute to better inform the
> > results of __builtin_object_size() (for compile-time constant values).
> > Clang can additionally use alloc_size to informt the results of
> > __builtin_dynamic_object_size() (for run-time values).
> > 
> > Additionally disables -Wno-alloc-size-larger-than since the allocators
> > already reject SIZE_MAX, and the compile-time warnings aren't helpful.
> 
> In addition to what Miguel said, it might be helpful to mention that this
> warning is GCC specific, I was a little confused at first as to why it was
> just being added in the GCC only block :)

Yes, good point. I'll call it out in particular.

> Otherwise, the attribute addition looks good to me. I will add my tag on v2.

Thanks!

-- 
Kees Cook