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=-8.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 51937C43461 for ; Thu, 17 Sep 2020 11:54:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 191B5221E8 for ; Thu, 17 Sep 2020 11:54:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726851AbgIQLyk (ORCPT ); Thu, 17 Sep 2020 07:54:40 -0400 Received: from szxga05-in.huawei.com ([45.249.212.191]:13233 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726695AbgIQLy2 (ORCPT ); Thu, 17 Sep 2020 07:54:28 -0400 X-Greylist: delayed 923 seconds by postgrey-1.27 at vger.kernel.org; Thu, 17 Sep 2020 07:54:27 EDT Received: from DGGEMS408-HUB.china.huawei.com (unknown [172.30.72.58]) by Forcepoint Email with ESMTP id D8C347362039763D03B9; Thu, 17 Sep 2020 19:38:59 +0800 (CST) Received: from [10.174.178.16] (10.174.178.16) by DGGEMS408-HUB.china.huawei.com (10.3.19.208) with Microsoft SMTP Server id 14.3.487.0; Thu, 17 Sep 2020 19:38:57 +0800 Subject: Re: [PATCH v2] EDAC/mc_sysfs: Add missing newlines when printing {max,dimm}_location To: Borislav Petkov CC: , , , References: <1600051734-8993-1-git-send-email-wangxiongfeng2@huawei.com> <20200916170052.GO2643@zn.tnic> From: Xiongfeng Wang Message-ID: <591e613e-0b53-028f-08fd-3d62a35b8c4f@huawei.com> Date: Thu, 17 Sep 2020 19:38:57 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <20200916170052.GO2643@zn.tnic> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.178.16] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-edac@vger.kernel.org Hi , On 2020/9/17 1:00, Borislav Petkov wrote: > On Mon, Sep 14, 2020 at 10:48:54AM +0800, Xiongfeng Wang wrote: >> @@ -813,15 +817,21 @@ static ssize_t mci_max_location_show(struct device *dev, >> char *data) >> { >> struct mem_ctl_info *mci = to_mci(dev); >> - int i; >> + int i, n; >> char *p = data; >> + unsigned int len = PAGE_SIZE; >> >> for (i = 0; i < mci->n_layers; i++) { >> - p += sprintf(p, "%s %d ", >> + n = snprintf(p, len, "%s %d ", >> edac_layer_name[mci->layers[i].type], >> mci->layers[i].size - 1); >> + p += n; >> + len -= n; > > What happens if that subtraction causes len to wrap around and become a > huge positive unsigned integer? > >> + if (!len) > > Would that test still work? I am not sure if snprintf will return a value larger than its second input paramter 'size'. But we can also check if 'len' is less than 0. It's better. > > IOW, I did this to your patch ontop. Note that I've moved the "p" > pointer incrementation after the length check so that the pointer > doesn't overflow too: Thanks. I will add it in the next version. > > --- > diff --git a/drivers/edac/edac_mc_sysfs.c b/drivers/edac/edac_mc_sysfs.c > index bf0e075fb635..fa0551c81e63 100644 > --- a/drivers/edac/edac_mc_sysfs.c > +++ b/drivers/edac/edac_mc_sysfs.c > @@ -817,19 +817,22 @@ static ssize_t mci_max_location_show(struct device *dev, > char *data) > { > struct mem_ctl_info *mci = to_mci(dev); > - int i, n; > + int len = PAGE_SIZE; > char *p = data; > - unsigned int len = PAGE_SIZE; > + 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); > - p += n; > + > len -= n; > - if (!len) > + if (len < 0) Not sure whether we need to check 'len' equals to 0. if (len <= 0) ? > goto out; > + > + p += n; > } > + > p += snprintf(p, len, "\n"); > out: > return p - data; > Thanks, XIongfeng