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R. Silva" , Bill Wendling , Justin Stitt , linux-kernel@vger.kernel.org Subject: [PATCH 02/82] overflow: Introduce add_would_overflow() Date: Mon, 22 Jan 2024 16:26:37 -0800 Message-Id: <20240123002814.1396804-2-keescook@chromium.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240122235208.work.748-kees@kernel.org> References: <20240122235208.work.748-kees@kernel.org> Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1326; i=keescook@chromium.org; h=from:subject; bh=rI7XvXs0gE8oB6y5lNdVJ89YzOLiYyZbayu1rCEj/HA=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBlrwgE/Rg2DOBwpGm23xchVNBK/FIvMg7Pi7tuc hrgqGce9zOJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCZa8IBAAKCRCJcvTf3G3A JpK6D/4k9MYFmrgc6c/TYlvkWlxk7cgUas0VJ225O0PQXNgzPrwydo5r9or8JHba1AD9K1lQdyq iY/c00/ng+L0pXMnyUYZ5RlfA76Q9JVIOFl2227BDoVAwb8sQ3Xlwhz/+p860wwoMqwno5TxLPM iEVrs2M2EZZo+enpPucZmQra1oVUfjoTc4LBwgzW1f4CO87CyxlQo3WW1qqFcQKlFDx9qK0bhpw KTu3fyF0WBOF1vHOAzXRGacuCBEbmLPsDAiDI6spRQTRIheANwd4kr0s5jXyY4d32MNm8D6kCdw 6o57Cm5NgRuXHzXB1diePd8nslD5neVySw31GHfZqmj9wMhnwKXi2lEZ/wqk3TO9hQ8l3WcSa0O AtuJ/dQI0LMgGmHU9s2J6rb3+sZYro4mWaVm09UCM02cSGj62u7H1KH/vj6Zw6MMiJ3GVmZomD+ JkjQ5AmlveqxnP7sv/7BdpK866HqpW9PimFvELyrCATtMf206HO00xxjv5an7q1CRv9KGSi3Ifk lVlTmvb5GZS8sUdV+rAqL0M0E7Q+RrNmT6cRlRLqCdAdwUOiUblUXUkpg3CEifH1S3OVgJzSHbq bM1kAoa9NqEH8gQAHKfJGo01p01MIhMFhfpnhrorrnpTBOFCgnmxVLdlC8Wzo7PaLcqetog57uK SjUZaEfaNTdpghQ== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Content-Transfer-Encoding: 8bit For instances where only the overflow needs to be checked (and the sum isn't used), provide the new helper add_would_overflow(), which is a wrapper for check_add_overflow(). Cc: "Gustavo A. R. Silva" Cc: linux-hardening@vger.kernel.org Signed-off-by: Kees Cook --- include/linux/overflow.h | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/include/linux/overflow.h b/include/linux/overflow.h index 099f2e559aa8..ac088f73e0fd 100644 --- a/include/linux/overflow.h +++ b/include/linux/overflow.h @@ -108,6 +108,22 @@ static inline bool __must_check __must_check_overflow(bool overflow) __builtin_add_overflow(__filter_integral(a), b, \ __filter_ptrint(d)))) +/** + * add_would_overflow() - Check if an addition would overflow + * @a: first addend + * @b: second addend + * + * Returns true if the sum would overflow. + * + * To keep a copy of the sum when the addition doesn't overflow, use + * check_add_overflow() instead. + */ +#define add_would_overflow(a, b) \ + __must_check_overflow(({ \ + size_t __result; \ + check_add_overflow(a, b, &__result);\ + })) + /** * check_sub_overflow() - Calculate subtraction with overflow checking * @a: minuend; value to subtract from -- 2.34.1