From mboxrd@z Thu Jan 1 00:00:00 1970 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 87DA7C61DA3 for ; Tue, 21 Feb 2023 14:08:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232246AbjBUOIW (ORCPT ); Tue, 21 Feb 2023 09:08:22 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60400 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234307AbjBUOIU (ORCPT ); Tue, 21 Feb 2023 09:08:20 -0500 Received: from msg-2.mailo.com (msg-2.mailo.com [213.182.54.12]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2CF72DBF0; Tue, 21 Feb 2023 06:08:06 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=mailo.com; s=mailo; t=1676988458; bh=Rbss0jxu2oGKjdOiKMyt4uKTBzrOuv6xJ/DDTtxIAQM=; h=X-EA-Auth:Date:From:To:Cc:Subject:Message-ID:References: MIME-Version:Content-Type:In-Reply-To; b=jJMAjZ+wRXfZFrYdt+Xcn/ezo/9xrp/LwdbJoKl+AwbZm80cZgUsaDEbAWPJRxOBU HIM6ejsCz0X04GFUTgdxcvWy6IG+M2/nxMprwhgGlNT/3F8TJ3VgNxQBi54VdouWI9 6sBCN1q9IMevCHLOoKiHI+3JiSMc2d3w3VrlkmXc= Received: by b-4.in.mailobj.net [192.168.90.14] with ESMTP via ip-206.mailobj.net [213.182.55.206] Tue, 21 Feb 2023 15:07:38 +0100 (CET) X-EA-Auth: vqvzvLOiwMJVZ0nf4zmrjP3ujrlYSnChDzDG2lu6ZTVMp0oV+9+mMIgP7QH2LsPs0i4s9VN9g+YYQSaiMUmcCpK/f2s81Znu Date: Tue, 21 Feb 2023 19:37:33 +0530 From: Deepak R Varma To: Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Thomas Gleixner , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Saurabh Singh Sengar , Praveen Kumar , Deepak R Varma Subject: [PATCH v2 3/3] perf/x86/intel: Use sysfs_emit() in show() callback function Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-perf-users@vger.kernel.org As per C99 standard, snprintf() returns the number of bytes that would be encoded in the destination buffer when it is sufficiently large. This return value may be different from what the caller is expecting and hence may lead to potential errors in the program. Kernel release 2.6.2 introduced scnprintf() & vscnprintf() which precisely return the actual bytes encoded into the destination buffer. For the sysfs attribute show() callback functions, which returns the number of bytes to the user space, a more recent recommendation is to use sysfs_emit() or sysfs_emit_at() instead of sprintf() family of functions. This is recorded in the Documentation/filesystems/sysfs.rst Kernel documentation file. Issue identified using the coccinelle device_attr_show.cocci script. Signed-off-by: Deepak R Varma --- Changes in v2: - Revise patch log message to include details on the potential issues with current implementation and how the proposal is a better solution. Feedback provided by Peter Zijlstra arch/x86/events/intel/core.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c index bafdc2be479a..8fb1225123ef 100644 --- a/arch/x86/events/intel/core.c +++ b/arch/x86/events/intel/core.c @@ -5273,7 +5273,7 @@ static ssize_t show_sysctl_tfa(struct device *cdev, struct device_attribute *attr, char *buf) { - return snprintf(buf, 40, "%d\n", allow_tsx_force_abort); + return sysfs_emit(buf, "%d\n", allow_tsx_force_abort); } static ssize_t set_sysctl_tfa(struct device *cdev, @@ -5307,7 +5307,7 @@ static ssize_t branches_show(struct device *cdev, struct device_attribute *attr, char *buf) { - return snprintf(buf, PAGE_SIZE, "%d\n", x86_pmu.lbr_nr); + return sysfs_emit(buf, "%d\n", x86_pmu.lbr_nr); } static DEVICE_ATTR_RO(branches); @@ -5323,7 +5323,7 @@ static ssize_t pmu_name_show(struct device *cdev, struct device_attribute *attr, char *buf) { - return snprintf(buf, PAGE_SIZE, "%s\n", pmu_name_str); + return sysfs_emit(buf, "%s\n", pmu_name_str); } static DEVICE_ATTR_RO(pmu_name); -- 2.34.1