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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id f5sm687890pjo.23.2021.08.18.14.04.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Aug 2021 14:04:33 -0700 (PDT) Date: Wed, 18 Aug 2021 14:04:31 -0700 From: Kees Cook To: Nathan Chancellor Cc: linux-kernel@vger.kernel.org, Miguel Ojeda , Nick Desaulniers , clang-built-linux@googlegroups.com, Andrew Morton , Daniel Micay , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Vlastimil Babka , Dennis Zhou , Tejun Heo , Masahiro Yamada , Michal Marek , 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Authentication-Results: imf28.hostedemail.com; dkim=pass header.d=chromium.org header.s=google header.b=Zqem0CoZ; dmarc=pass (policy=none) header.from=chromium.org; spf=pass (imf28.hostedemail.com: domain of keescook@chromium.org designates 209.85.215.172 as permitted sender) smtp.mailfrom=keescook@chromium.org X-Stat-Signature: x9prmq8ga8xxjwnhzubdq933ufogeggq X-Rspamd-Queue-Id: 5E7F09004291 X-Rspamd-Server: rspam05 X-HE-Tag: 1629320675-840750 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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