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McKenney" , Josh Triplett , Lai Jiangshan , Zqiang Subject: [RFC PATCH 1/4] rcu: rcupdate.h: Add missing parentheses around macro pointer dereference Date: Wed, 3 May 2023 21:29:11 -0400 Message-Id: <20230504012914.1797355-1-mathieu.desnoyers@efficios.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org linux/rcupdate.h macros use the *p parameter without parentheses, e.g.: typeof(*p) rather than typeof(*(p)) The following test-case shows how it can generate confusion due to C operator precedence being reversed compared to the expectations: #define m(p) \ do { \ __typeof__(*p) v = 0; \ } while (0) void fct(unsigned long long *p1) { m(p1 + 1); /* works */ m(1 + p1); /* broken */ } Signed-off-by: Mathieu Desnoyers Reviewed-by: Boqun Feng Reviewed-by: Steven Rostedt Reviewed-by: Joel Fernandes (Google) Cc: "Paul E. McKenney" Cc: Joel Fernandes Cc: Josh Triplett Cc: Boqun Feng Cc: Steven Rostedt Cc: Lai Jiangshan Cc: Zqiang --- include/linux/rcupdate.h | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-) diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index dcd2cf1e8326..38e84f3d515e 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -430,16 +430,16 @@ static inline void rcu_preempt_sleep_check(void) { } #ifdef __CHECKER__ #define rcu_check_sparse(p, space) \ - ((void)(((typeof(*p) space *)p) == p)) + ((void)(((typeof(*(p)) space *)(p)) == (p))) #else /* #ifdef __CHECKER__ */ #define rcu_check_sparse(p, space) #endif /* #else #ifdef __CHECKER__ */ #define __unrcu_pointer(p, local) \ ({ \ - typeof(*p) *local = (typeof(*p) *__force)(p); \ + typeof(*(p)) *local = (typeof(*(p)) *__force)(p); \ rcu_check_sparse(p, __rcu); \ - ((typeof(*p) __force __kernel *)(local)); \ + ((typeof(*(p)) __force __kernel *)(local)); \ }) /** * unrcu_pointer - mark a pointer as not being RCU protected @@ -452,29 +452,29 @@ static inline void rcu_preempt_sleep_check(void) { } #define __rcu_access_pointer(p, local, space) \ ({ \ - typeof(*p) *local = (typeof(*p) *__force)READ_ONCE(p); \ + typeof(*(p)) *local = (typeof(*(p)) *__force)READ_ONCE(p); \ rcu_check_sparse(p, space); \ - ((typeof(*p) __force __kernel *)(local)); \ + ((typeof(*(p)) __force __kernel *)(local)); \ }) #define __rcu_dereference_check(p, local, c, space) \ ({ \ /* Dependency order vs. p above. */ \ - typeof(*p) *local = (typeof(*p) *__force)READ_ONCE(p); \ + typeof(*(p)) *local = (typeof(*(p)) *__force)READ_ONCE(p); \ RCU_LOCKDEP_WARN(!(c), "suspicious rcu_dereference_check() usage"); \ rcu_check_sparse(p, space); \ - ((typeof(*p) __force __kernel *)(local)); \ + ((typeof(*(p)) __force __kernel *)(local)); \ }) #define __rcu_dereference_protected(p, local, c, space) \ ({ \ RCU_LOCKDEP_WARN(!(c), "suspicious rcu_dereference_protected() usage"); \ rcu_check_sparse(p, space); \ - ((typeof(*p) __force __kernel *)(p)); \ + ((typeof(*(p)) __force __kernel *)(p)); \ }) #define __rcu_dereference_raw(p, local) \ ({ \ /* Dependency order vs. p above. */ \ typeof(p) local = READ_ONCE(p); \ - ((typeof(*p) __force __kernel *)(local)); \ + ((typeof(*(p)) __force __kernel *)(local)); \ }) #define rcu_dereference_raw(p) __rcu_dereference_raw(p, __UNIQUE_ID(rcu)) -- 2.25.1