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 48CB0C61DA3 for ; Tue, 21 Feb 2023 14:08:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232986AbjBUOIJ (ORCPT ); Tue, 21 Feb 2023 09:08:09 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60242 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233656AbjBUOII (ORCPT ); Tue, 21 Feb 2023 09:08:08 -0500 Received: from msg-4.mailo.com (msg-4.mailo.com [213.182.54.15]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 94CC82A99A; Tue, 21 Feb 2023 06:07:42 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=mailo.com; s=mailo; t=1676988418; bh=oLZwRpXxfR8jKepCYgBAd0gcxoO2D6bBAKStsCYFVz8=; h=X-EA-Auth:Date:From:To:Cc:Subject:Message-ID:References: MIME-Version:Content-Type:In-Reply-To; b=ct/HGOoSPl2yfAJdpTmfbCK4kQ8qIvxaKs0L4O54Kib0xMGCCh0W34MpMfkFTJl8j VOcr/oyOReG12/EEQ5gUPB3DGFW3K01KcX6ECXSJqTVFA0yZHWook5MYdkKBMhrspq rPqb2ddx9urUVC9k78cNNCT253DHeqi8pEPTluaQ= Received: by b-3.in.mailobj.net [192.168.90.13] with ESMTP via ip-206.mailobj.net [213.182.55.206] Tue, 21 Feb 2023 15:06:58 +0100 (CET) X-EA-Auth: at9OF3ziCtOVa+pv6TzsuxHGTTSacIrTPKQNDcL9n3nWoXnaOhWUsf84g1TEAEzf2IJx/eMLezJ3x9Jg2DvqQbGUPd6TRiTO Date: Tue, 21 Feb 2023 19:36:52 +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 2/3] perf/x86/intel/pt: Use sysfs_emit() in show() callback function Message-ID: <54c16281234d057ebed1ef05bde20d2d57d70669.1676987821.git.drv@mailo.com> 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/pt.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c index 42a55794004a..d9e6d771b458 100644 --- a/arch/x86/events/intel/pt.c +++ b/arch/x86/events/intel/pt.c @@ -96,7 +96,7 @@ static ssize_t pt_cap_show(struct device *cdev, container_of(attr, struct dev_ext_attribute, attr); enum pt_capabilities cap = (long)ea->var; - return snprintf(buf, PAGE_SIZE, "%x\n", intel_pt_validate_hw_cap(cap)); + return sysfs_emit(buf, "%x\n", intel_pt_validate_hw_cap(cap)); } static struct attribute_group pt_cap_group __ro_after_init = { -- 2.34.1