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 X-Spam-Level: X-Spam-Status: No, score=-6.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9F29DC433E2 for ; Thu, 17 Sep 2020 16:25:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 321F02075B for ; Thu, 17 Sep 2020 16:25:53 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="TXX+aC8J" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728522AbgIQQZv (ORCPT ); Thu, 17 Sep 2020 12:25:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49002 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728519AbgIQQZr (ORCPT ); Thu, 17 Sep 2020 12:25:47 -0400 Received: from mail.skyhub.de (mail.skyhub.de [IPv6:2a01:4f8:190:11c2::b:1457]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CCB52C06174A; Thu, 17 Sep 2020 09:25:46 -0700 (PDT) Received: from zn.tnic (p200300ec2f105300c872f9f06eecfc48.dip0.t-ipconnect.de [IPv6:2003:ec:2f10:5300:c872:f9f0:6eec:fc48]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 2F3811EC037C; Thu, 17 Sep 2020 18:25:45 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1600359945; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=+LoOB6O795sdQOwvXn5Msv1mKnfAxL78Pj3P3gZOa8A=; b=TXX+aC8JzokMkgVgVmzKsSntV5nSge0boT3mFFkGdBn+XUdVECmAIOpcKh2ik8JX9O2vOG ekYiANhXFnhBeTFhcm3oe9sUGXv6o6WNI07nMVU3E1uxdOflQEoCNsBZANO11UHOTPxu+1 xSbWlRCG3Npr/V0wu+SitdDrZxKzKD0= Date: Thu, 17 Sep 2020 18:25:37 +0200 From: Borislav Petkov To: Xiongfeng Wang Cc: mchehab@kernel.org, tony.luck@intel.com, linux-edac@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] EDAC/mc_sysfs: Add missing newlines when printing {max,dimm}_location Message-ID: <20200917162537.GL31960@zn.tnic> References: <1600051734-8993-1-git-send-email-wangxiongfeng2@huawei.com> <20200916170052.GO2643@zn.tnic> <591e613e-0b53-028f-08fd-3d62a35b8c4f@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <591e613e-0b53-028f-08fd-3d62a35b8c4f@huawei.com> Precedence: bulk List-ID: X-Mailing-List: linux-edac@vger.kernel.org On Thu, Sep 17, 2020 at 07:38:57PM +0800, Xiongfeng Wang wrote: > I am not sure if snprintf will return a value larger than its second input > paramter 'size'. The comment over snprintf() says * The return value is the number of characters which would be * generated for the given input, excluding the trailing null, * as per ISO C99. If the return is greater than or equal to * @size, the resulting string is truncated. And let's try it, see diff at the end. Now look what that produces: [ 2.594796] kernel_init: len: 16, str: [A lo] it returns 16 for len even though the buffer is 5 chars long. So in our patch, we'd increment by 16 which would be wrong. Now let's use scnprintf(): [ 2.700142] kernel_init: len: 4, str: [A lo] Much better. Lemme do that. > Not sure whether we need to check 'len' equals to 0. > if (len <= 0) ? Yeah, lemme fix that too, so we have now incrementally ontop: --- diff --git a/drivers/edac/edac_mc_sysfs.c b/drivers/edac/edac_mc_sysfs.c index fa0551c81e63..c56e0004b39e 100644 --- a/drivers/edac/edac_mc_sysfs.c +++ b/drivers/edac/edac_mc_sysfs.c @@ -822,18 +822,17 @@ static ssize_t mci_max_location_show(struct device *dev, int i, n; for (i = 0; i < mci->n_layers; i++) { - n = snprintf(p, len, "%s %d ", - edac_layer_name[mci->layers[i].type], - mci->layers[i].size - 1); - + n = scnprintf(p, len, "%s %d ", + edac_layer_name[mci->layers[i].type], + mci->layers[i].size - 1); len -= n; - if (len < 0) + if (len <= 0) goto out; p += n; } - p += snprintf(p, len, "\n"); + p += scnprintf(p, len, "\n"); out: return p - data; } --- Test diff: --- diff --git a/init/main.c b/init/main.c index ae78fb68d231..e2d6110d3a3d 100644 --- a/init/main.c +++ b/init/main.c @@ -1397,7 +1397,8 @@ void __weak free_initmem(void) static int __ref kernel_init(void *unused) { - int ret; + char str[5]; + int ret, len; kernel_init_freeable(); /* need to finish all async __init code before freeing the memory */ @@ -1419,6 +1420,11 @@ static int __ref kernel_init(void *unused) do_sysctl_args(); + len = snprintf(str, 5, "A longer string\n"); + + pr_info("%s: len: %d, str: [%s]\n", + __func__, len, str); + if (ramdisk_execute_command) { ret = run_init_process(ramdisk_execute_command); if (!ret) -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette