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R. Silva" , linux-hardening@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] refcount: Annotated intentional signed integer wrap-around Date: Tue, 20 Feb 2024 21:16:38 -0800 Message-Id: <20240221051634.work.287-kees@kernel.org> X-Mailer: git-send-email 2.34.1 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=2035; i=keescook@chromium.org; h=from:subject:message-id; bh=cY2KqIQK1pcG7S9aS/1nKIllmRZnaU4rHJB4e+mP73E=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBl1Yc2qj2v95a8MncuEjOaS6rwqcyJ0914acvqi 04tQHzd1KGJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCZdWHNgAKCRCJcvTf3G3A JohaD/9NCQi7lx5d6xm0eljAyda1wjpSCLIW9ZrSFIcwGwuSrjOwJdCQBMVDt6CoGY3thuTRjNq y2IZey2D3DGPvnD7qvmd6HZ376YLAaslABETK5wtg8Qa0cVlmFNggME4eE8nM5lsKpOZa8cPKjq 5J8jbjXoiry5uQWQAwdLJT4yKeGN1avAV6l2YcivLs6hlQwZxDOBVKFwW8cNaSCsVO9P4fnUWwJ 756mKPpceBnLMjD/yNr6BZT1in/bbAbvV811UxhlctNROrVG41LkyiAZu2AH688nhDu9LrGl5fe z3mfF3PDrjOnoTATm70EAvMfMYQhCLfVl/Lbtihm8yYftYZa6f0pGaHVi+qei4mRDR30ScEMqYd nAiwJc1Cpl0u2s4NMV9ZMbZU+qxfd3xiKpKsLaOna45NSA1tholfS7n8iqaai60GByG+y1UwDX6 MGww115zQ2qAYwJZufEu3jpaUAlmraW52SQH+ZAOBy2nhAXAvHqz1+hTADGXu4BAIn9zPHvqUoj r13N6N3TFg6dmnKnM4a1njm+SjsLMeEbA1AeH0zd2Xq8Ilsx0cyVwwngrcVu7M+k37w1N1GU/2p gMkBPyJb8BAzuEgE1Mc/PPEorXmxLZsxMhhYYcXvV3XrhdaPpTWdsQdXzqETHvNz5ziav6HujsG DutSAQG AbCs3NlA== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Content-Transfer-Encoding: 8bit Mark the various refcount_t functions with __signed_wrap, as we depend on the wrapping behavior to detect the overflow and perform saturation. Silences warnings seen with the LKDTM REFCOUNT_* tests: UBSAN: signed-integer-overflow in ../include/linux/refcount.h:189:11 2147483647 + 1 cannot be represented in type 'int' Signed-off-by: Kees Cook --- Cc: Miguel Ojeda Cc: Will Deacon Cc: Peter Zijlstra Cc: Boqun Feng Cc: Mark Rutland Cc: "Gustavo A. R. Silva" Cc: linux-hardening@vger.kernel.org --- include/linux/refcount.h | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/include/linux/refcount.h b/include/linux/refcount.h index 85c6df0d1bef..59b3b752394d 100644 --- a/include/linux/refcount.h +++ b/include/linux/refcount.h @@ -136,7 +136,8 @@ static inline unsigned int refcount_read(const refcount_t *r) return atomic_read(&r->refs); } -static inline __must_check bool __refcount_add_not_zero(int i, refcount_t *r, int *oldp) +static inline __must_check __signed_wrap +bool __refcount_add_not_zero(int i, refcount_t *r, int *oldp) { int old = refcount_read(r); @@ -177,7 +178,8 @@ static inline __must_check bool refcount_add_not_zero(int i, refcount_t *r) return __refcount_add_not_zero(i, r, NULL); } -static inline void __refcount_add(int i, refcount_t *r, int *oldp) +static inline __signed_wrap +void __refcount_add(int i, refcount_t *r, int *oldp) { int old = atomic_fetch_add_relaxed(i, &r->refs); @@ -256,7 +258,8 @@ static inline void refcount_inc(refcount_t *r) __refcount_inc(r, NULL); } -static inline __must_check bool __refcount_sub_and_test(int i, refcount_t *r, int *oldp) +static inline __must_check __signed_wrap +bool __refcount_sub_and_test(int i, refcount_t *r, int *oldp) { int old = atomic_fetch_sub_release(i, &r->refs); -- 2.34.1