Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Wed, 18 Aug 2021 14:04:31 -0700
From:   Kees Cook <keescook@chromium.org>
To:     Nathan Chancellor <nathan@kernel.org>
Cc:     linux-kernel@vger.kernel.org, Miguel Ojeda <ojeda@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        clang-built-linux@googlegroups.com,
        Andrew Morton <akpm@linux-foundation.org>,
        Daniel Micay <danielmicay@gmail.com>,
        Christoph Lameter <cl@linux.com>,
        Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Dennis Zhou <dennis@kernel.org>, Tejun Heo <tj@kernel.org>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Michal Marek <michal.lkml@markovi.net>, linux-mm@kvack.org,
        linux-kbuild@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: Re: [PATCH 1/5] Compiler Attributes: Add __alloc_size() for better
 bounds checking
Message-ID: <202108181404.B5E8739C3C@keescook>
References: <20210818050841.2226600-1-keescook@chromium.org>
 <20210818050841.2226600-2-keescook@chromium.org>
 <d326fbfc-dc96-b6e9-6fd8-31df3eb9f1cb@kernel.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <d326fbfc-dc96-b6e9-6fd8-31df3eb9f1cb@kernel.org>
Precedence: bulk

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