From nobody Thu Feb 12 01:03:04 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 56BEBC77B75 for ; Wed, 3 May 2023 20:32:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229751AbjECUct (ORCPT ); Wed, 3 May 2023 16:32:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54180 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229441AbjECUcr (ORCPT ); Wed, 3 May 2023 16:32:47 -0400 Received: from smtpout.efficios.com (unknown [IPv6:2607:5300:203:b2ee::31e5]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 835E0198C for ; Wed, 3 May 2023 13:32:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=efficios.com; s=smtpout1; t=1683145963; bh=qNB6O5mVECCPuKgtGErPGROmbcclghgZAShV5yBxuaI=; h=From:To:Cc:Subject:Date:From; b=no1YqwIX/6oqGAIE4BX0MFBH9H00tUF8S1a7Rp3ST8/qqgk+RD0qNCU6dUWy7Up55 87HM522afz/NFXZUW+wWRlNHFRjoKu6wPtnzU8W79UU1ruLrptpAMrnXdurov8Afws FFpRaOOMVqHrc02dFUXt2s5GP+hlMfx04N+XtXde07EyDIH6yTeGgBnXFdjM7N/wc/ 55DXbnsj32SPXO9VdZdvQZimthqCMNyltnUfUgnUDBBCfb97PmVSZxxv9YUrX7MlBM 5QfRdpBQl/XfS1NbqH06nNOOfAcdy8e16/fhC+MM0JURh+MeIxJ4MEUVjW2cJqaOek 7akX+418JyjWg== Received: from localhost.localdomain (192-222-143-198.qc.cable.ebox.net [192.222.143.198]) by smtpout.efficios.com (Postfix) with ESMTPSA id 4QBTCb416Dz11fW; Wed, 3 May 2023 16:32:43 -0400 (EDT) From: Mathieu Desnoyers To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, Mathieu Desnoyers , Joel Fernandes , Josh Triplett , Boqun Feng , Steven Rostedt , Lai Jiangshan , Zqiang Subject: [RFC PATCH] rcu: rcupdate.h: Add missing parentheses around macro pointer dereference Date: Wed, 3 May 2023 16:32:36 -0400 Message-Id: <20230503203236.1587590-1-mathieu.desnoyers@efficios.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" 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 =3D 0; \ } while (0) void fct(unsigned long long *p1) { m(p1 + 1); /* works */ m(1 + p1); /* broken */ } Signed-off-by: Mathieu Desnoyers Cc: "Paul E. McKenney" Cc: Joel Fernandes Cc: Josh Triplett Cc: Boqun Feng Cc: Steven Rostedt Cc: Lai Jiangshan Cc: Zqiang Reviewed-by: Boqun Feng Reviewed-by: Joel Fernandes (Google) Reviewed-by: Steven Rostedt (Google) --- 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..1565012fa47f 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -430,16 +430,16 @@ static inline void rcu_preempt_sleep_check(void) { } =20 #ifdef __CHECKER__ #define rcu_check_sparse(p, space) \ - ((void)(((typeof(*p) space *)p) =3D=3D p)) + ((void)(((typeof(*(p)) space *)p) =3D=3D p)) #else /* #ifdef __CHECKER__ */ #define rcu_check_sparse(p, space) #endif /* #else #ifdef __CHECKER__ */ =20 #define __unrcu_pointer(p, local) \ ({ \ - typeof(*p) *local =3D (typeof(*p) *__force)(p); \ + typeof(*(p)) *local =3D (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) { } =20 #define __rcu_access_pointer(p, local, space) \ ({ \ - typeof(*p) *local =3D (typeof(*p) *__force)READ_ONCE(p); \ + typeof(*(p)) *local =3D (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 =3D (typeof(*p) *__force)READ_ONCE(p); \ + typeof(*(p)) *local =3D (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 =3D 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)) =20 --=20 2.25.1