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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 96788C43603 for ; Mon, 16 Dec 2019 18:03:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5EC9E20700 for ; Mon, 16 Dec 2019 18:03:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1576519424; bh=Ed1Hq/HQhuS0e/QvE5n80m20YwTftllcPIv26wDuKiY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=E0r2IOwhmcXDs+2adcbJVFj9xGgNIGRS30nw4taIwu3pItFbO2/axUuQY/AmpXrzW lHiR0mYriBUAnF6ZvgbEjQw4BodLmlpp2evljuVS6KiW06bQHA0B0IlCu1/TG1IX80 7Ygiyq0iSDJtXFCTHQOV3RhfntkWQOWnfw3oE+7s= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729051AbfLPSDn (ORCPT ); Mon, 16 Dec 2019 13:03:43 -0500 Received: from mail.kernel.org ([198.145.29.99]:40570 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729534AbfLPSDj (ORCPT ); Mon, 16 Dec 2019 13:03:39 -0500 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 99AF421835; Mon, 16 Dec 2019 18:03:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1576519419; bh=Ed1Hq/HQhuS0e/QvE5n80m20YwTftllcPIv26wDuKiY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YUhGpeIw3nisJU1SotmZk9odFNu5eLSM8deehAVdXavVm2Ca9YAtwd0D1LFQ8NmIt 66EWMSyCucW1Rm3l2wmp3y7IjHf5KgYPhcnrip1a5IXZiw9ioGaiFJ/z5ddkhCvnFn 2G27OFpSRC+mvDV7EZ1B3N08O0leu6iPI7gQ9+v0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Ming Lei , Jens Axboe Subject: [PATCH 4.19 059/140] blk-mq: avoid sysfs buffer overflow with too many CPU cores Date: Mon, 16 Dec 2019 18:48:47 +0100 Message-Id: <20191216174804.176499341@linuxfoundation.org> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20191216174747.111154704@linuxfoundation.org> References: <20191216174747.111154704@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Ming Lei commit 8962842ca5abdcf98e22ab3b2b45a103f0408b95 upstream. It is reported that sysfs buffer overflow can be triggered if the system has too many CPU cores(>841 on 4K PAGE_SIZE) when showing CPUs of hctx via /sys/block/$DEV/mq/$N/cpu_list. Use snprintf to avoid the potential buffer overflow. This version doesn't change the attribute format, and simply stops showing CPU numbers if the buffer is going to overflow. Cc: stable@vger.kernel.org Fixes: 676141e48af7("blk-mq: don't dump CPU -> hw queue map on driver load") Signed-off-by: Ming Lei Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- block/blk-mq-sysfs.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) --- a/block/blk-mq-sysfs.c +++ b/block/blk-mq-sysfs.c @@ -151,20 +151,25 @@ static ssize_t blk_mq_hw_sysfs_nr_reserv static ssize_t blk_mq_hw_sysfs_cpus_show(struct blk_mq_hw_ctx *hctx, char *page) { + const size_t size = PAGE_SIZE - 1; unsigned int i, first = 1; - ssize_t ret = 0; + int ret = 0, pos = 0; for_each_cpu(i, hctx->cpumask) { if (first) - ret += sprintf(ret + page, "%u", i); + ret = snprintf(pos + page, size - pos, "%u", i); else - ret += sprintf(ret + page, ", %u", i); + ret = snprintf(pos + page, size - pos, ", %u", i); + + if (ret >= size - pos) + break; first = 0; + pos += ret; } - ret += sprintf(ret + page, "\n"); - return ret; + ret = snprintf(pos + page, size - pos, "\n"); + return pos + ret; } static struct attribute *default_ctx_attrs[] = {