From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794717340; b=C7Kq/w91IAC5moF1d3/ZEV+kY/YqJrgVV4BAN0XGuJkZGOo0cceWft0lVS5grUOVoG4o vWJJfTWaLpqGN/TFvv8mKc67OzSTNOtz9F0ScLXcasUkcD3BzoFU+6BUxnn+7H1VvOiLB SSdQIIsNeLDfxOhPWmVZ6bzezS8sJZPZbnADots1LBE2Zs+aQP16koRxT9WOHH5MOqr7C +ZVh1H2UHeGQC9K9WcxSaEFJGupr9utNRR6Evi1xQ7344nh7nyYjx4xorHRhsOMjf+M1e OcidUz/INUxzyn96S+0eGKOEb5Ti8Efmer5Kn3HfKx2KFPsM8aI9UHR01myVPXo3CfA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794717340; h=Received:DKIM-Signature:From:Date:Subject:MIME-Version:Content-Type: Content-Transfer-Encoding:Message-Id:X-B4-Tracking:X-Change-ID:To:Cc: X-Mailer:X-Developer-Signature:X-Developer-Key; bh=pge8S+uzPBjYzO9sQ/3/s+m2MnX1W31RL27i5NJe3sM=; b=xuF/DTbsPrGx9WMcKPdJHIrxCVupq0CV1hvphJmM1CnJYxpZIFBwvg7wGpoWVolJsHEh HFnie/fwFRYz8OiLmXCygkXcIUXJUuBgOA+oqIi63DVAclFwWgMqcGZVjIERpIWHdGcSy 5hLcTI/n0zyo46tc3PNybRCsKhTvxujha3fYFtNVcBtrM/sKNvjf/brYa0P97rjA0zU9b mbmOWOv0RY2L9PJoaKDIoePB3wEKoM78/j7yAqrYDSPhWkjiC2jWxcJlLKYP1ESx4EP9w cj1yURV1KuGFTaa3SUrlrJG1XXZbEOLSYr7ZNyi8xiJTmNDWB1cwclR+CrfrOuNG2hw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=TtiHk++8; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F0DC6606A323; Sun, 15 Nov 2026 04:35:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=TtiHk++8 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4589B1F000C4; Sun, 15 Nov 2026 04:35:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794717339; bh=pge8S+uzPBjYzO9sQ/3/s+m2MnX1W31RL27i5NJe3sM=; h=From:Date:Subject:To:Cc; b=TtiHk++8tQHafjcGYp/xGrHpiXXoT8vhlQVhEZ24RMB0GOQcBnhKKzpeWZEduoLew Wq5Azc/0MBnlmG3bSxy4lnfjDHVtwK4ZoK67gTNvPQvrBM9THocGbhiSudonVB4L53 8ksUFWN8vGpd3JOzX4PVyo6lu8lcXtS2rOcuZ2aBYAT2FesiG3axRIwJor13PROdoo VEUFtWoJYHhFiyny7SFc4Qx802tSL4f90aGalRboqS0aafTW9s/AuJbgBvJwLRtav+ N0Tfgm//J3rDcozU/bdq14GzFNFFAx/ofWJGcbnvUgYNUxnkM/ucUheQVz44pJ9qe1 /jws/+E8U40uw== From: Nathan Chancellor Date: Sat, 14 Nov 2026 21:35:33 -0700 Subject: [PATCH] lkdtm/bugs: Remove volatile from element_count X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261114-lkdtm-bugs-wunsequenced-v1-1-b24f15ce1328@kernel.org> X-B4-Tracking: v=1; b=H4sIAAAAAAAA/yXMwQ6CMAyA4VchPduELsSJr2I8SFexqFNXpiaEd 3fC8Tv8/wQmScVgX02Q5K2mj1hAmwr4coq9oIZicLXbElGDt2sY79jl3vCTo8krS2QJ6Jl2Tdu y856g1M8kZ/0u58NxteVuEB7/O5jnHzaJdJt7AAAA X-Change-ID: 20261114-lkdtm-bugs-wunsequenced-7c18499c2771 To: Kees Cook Cc: Arnd Bergmann , Greg Kroah-Hartman , linux-kernel@vger.kernel.org, llvm@lists.linux.dev, stable@vger.kernel.org, kernel test robot , Nathan Chancellor X-Mailer: b4 0.17-dev X-Developer-Signature: v=1; a=openpgp-sha256; l=2596; i=nathan@kernel.org; h=from:subject:message-id; bh=PXq6yOI2haGDOFCWB2rN+EDzgPLHZ2hY9ZGbOCcl0rs=; b=owGbwMvMwCUmm602sfCA1DTG02pJDFk/zaYXeDZXMzGc05ffviN0l/Kq7W0GwdPNdzQu/9Wwc PLnU6HBHaUsDGJcDLJiiizVj1WPGxrOOct449QkmDmsTCBDGLg4BWAiESEM/wyPzQyX6HvhasrI 8qa9zncJn6K8AKNuxtke8Z73iyqXP2H4H2xm5iBn0efxr8ZukcEht5tad7fd+HTqu5lRI8OEmUe X8gEA X-Developer-Key: i=nathan@kernel.org; a=openpgp; fpr=2437CB76E544CB6AB3D9DFD399739260CB6CB716 After a recent improvement in clang to warn on unsequenced accesses to volatile variables [1], an instance appears in lkdtm_FAM_BOUNDS(), which can break the build with CONFIG_WERROR=y / W=e: drivers/misc/lkdtm/bugs.c:493:31: error: unsequenced accesses to volatile qualified 'element_count' [-Werror,-Wunsequenced] 493 | inst->array[element_count] = element_count; | ~~~~~~~~~~~~~ ^ Per C11 5.1.2.3.2, accessing a volatile object is a side effect. Per C11 6.5.2, unsequenced side effects on the same scalar object are undefined behavior. Per C11 6.5.16.3, the value computations of the left and right operands of the assignment operator are unsequenced. This variable is marked volatile to hide its value from the compiler at compile time. The same thing can be accomplished with OPTIMIZER_HIDE_VAR. Drop volatile from element_count to clear up the warning. The tests still pass and there are no warnings at compile time. Cc: stable@vger.kernel.org Fixes: 5d207e83ca41 ("lkdtm: Add FAM_BOUNDS test for __counted_by") Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202611140405.wMowxoPE-lkp@intel.com/ Closes: https://github.com/ClangBuiltLinux/linux/issues/2194 Link: https://github.com/llvm/llvm-project/commit/955715460eaf9188c241c74750637fc82dfcc423 [1] Signed-off-by: Nathan Chancellor --- drivers/misc/lkdtm/bugs.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/misc/lkdtm/bugs.c b/drivers/misc/lkdtm/bugs.c index 2761685cf4f8..7c799fef89a8 100644 --- a/drivers/misc/lkdtm/bugs.c +++ b/drivers/misc/lkdtm/bugs.c @@ -472,12 +472,14 @@ struct lkdtm_cb_fam { int array[] __counted_by(count); }; -static volatile int element_count = 4; +static int element_count = 4; static void lkdtm_FAM_BOUNDS(void) { struct lkdtm_cb_fam *inst; + OPTIMIZER_HIDE_VAR(element_count); + inst = kzalloc_flex(*inst, array, element_count + 1); if (!inst) { pr_err("FAIL: could not allocate test struct!\n"); @@ -534,6 +536,8 @@ static void lkdtm_PTR_BOUNDS(void) { struct lkdtm_cb_ptr *inst; + OPTIMIZER_HIDE_VAR(element_count); + inst = kzalloc_obj(*inst); if (!inst) { pr_err("FAIL: could not allocate struct lkdtm_cb_ptr!\n"); --- base-commit: 7475ea8b58616b33c04afb976cf0fbaad9dd63fb base-tree: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master change-id: 20261114-lkdtm-bugs-wunsequenced-7c18499c2771 Best regards, -- Cheers, Nathan