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Tue, 30 May 2023 01:41:03 -0700 (PDT) MIME-Version: 1.0 References: <20230530083911.1104336-1-glider@google.com> In-Reply-To: <20230530083911.1104336-1-glider@google.com> From: Alexander Potapenko Date: Tue, 30 May 2023 10:40:26 +0200 Message-ID: Subject: Re: [PATCH v2] string: use __builtin_memcpy() in strlcpy/strlcat To: glider@google.com, andy@kernel.org, akpm@linux-foundation.org Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, elver@google.com, dvyukov@google.com, kasan-dev@googlegroups.com, ndesaulniers@google.com, nathan@kernel.org, keescook@chromium.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 756DD8000C X-Stat-Signature: ymif7otogij6ymebf973rc3gxn5caszq X-HE-Tag: 1685436065-873721 X-HE-Meta: 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 9K5weGFG drPfjRNI3lrq8uM7/Y5HTrIrWRKd5xJP5Phqa+ynbLGkvVOG5GtcmRR84q3v57sQBO0YgIrJwsMCwrE7mNtRjNM63bK6amuopvYgxUyII4wSNWexCOe9SXbZKjmJihwa74wTXiPc+70Hd2ZrRXX4aGFclepzplKX0QPAxZoz/s9OwV2WFsDXc5nP60lqd9u89B+OeFD5FOgX4p3mGDeosx8nsX61I0xKqO8rwG+D/J+cO79Q8BgMzjA7W/GeSDw82c411BRfULokdIMvdfI9XV4ITZzU63Vn6eYGqC8gfvJkP4F3rbapExeTcWh0Adx7mxa2LSaNw4CLc47FFXAxazDHU6FnOVYBx6w+9Jq8eRYmQoSSKV+QcMjLctJKuEjZa52NClHXHgvfuuVEcyBx3jSyyImvvsJuz2B2t/qw/u92mhFf+0iasMS1hi73VCZdHTrPswWudwHQC18wx25kiyIsnq/A1OFOZSMlY 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 Tue, May 30, 2023 at 10:39=E2=80=AFAM Alexander Potapenko wrote: > > lib/string.c is built with -ffreestanding, which prevents the compiler > from replacing certain functions with calls to their library versions. > > On the other hand, this also prevents Clang and GCC from instrumenting > calls to memcpy() when building with KASAN, KCSAN or KMSAN: > - KASAN normally replaces memcpy() with __asan_memcpy() with the > additional cc-param,asan-kernel-mem-intrinsic-prefix=3D1; > - KCSAN and KMSAN replace memcpy() with __tsan_memcpy() and > __msan_memcpy() by default. > > To let the tools catch memory accesses from strlcpy/strlcat, replace > the calls to memcpy() with __builtin_memcpy(), which KASAN, KCSAN and > KMSAN are able to replace even in -ffreestanding mode. > > This preserves the behavior in normal builds (__builtin_memcpy() ends up > being replaced with memcpy()), and does not introduce new instrumentation > in unwanted places, as strlcpy/strlcat are already instrumented. > > Suggested-by: Marco Elver > Signed-off-by: Alexander Potapenko > Link: https://lore.kernel.org/all/20230224085942.1791837-1-elver@google.c= om/ Sorry, missed a "Reviewed-by: Marco Elver " from the previous thread: https://lore.kernel.org/lkml/CAG_fn=3DUzQ-jnQrxzvLE6EV37zSVCOGPmsVTxyfp1wXz= Bir4vAg@mail.gmail.com/T/ > Acked-by: Kees Cook