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=-0.9 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 A4FFCC04EB8 for ; Mon, 10 Dec 2018 14:01:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5D74220870 for ; Mon, 10 Dec 2018 14:01:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5D74220870 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=i-love.sakura.ne.jp Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727878AbeLJOBt (ORCPT ); Mon, 10 Dec 2018 09:01:49 -0500 Received: from www262.sakura.ne.jp ([202.181.97.72]:19838 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727056AbeLJOBs (ORCPT ); Mon, 10 Dec 2018 09:01:48 -0500 Received: from fsav105.sakura.ne.jp (fsav105.sakura.ne.jp [27.133.134.232]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id wBAE1kNg089294; Mon, 10 Dec 2018 23:01:46 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav105.sakura.ne.jp (F-Secure/fsigk_smtp/530/fsav105.sakura.ne.jp); Mon, 10 Dec 2018 23:01:46 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/530/fsav105.sakura.ne.jp) Received: from [192.168.1.8] (softbank126126163036.bbtec.net [126.126.163.36]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id wBAE1fXx089253 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NO); Mon, 10 Dec 2018 23:01:46 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Subject: Re: [PATCH] printk: Add caller information to printk() output. To: Petr Mladek Cc: Dmitry Vyukov , Sergey Senozhatsky , Sergey Senozhatsky , Steven Rostedt , Linus Torvalds , Andrew Morton , LKML , syzkaller References: <1543045075-3008-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> <20181130154024.ls3mntfdr4zvluub@pathway.suse.cz> <20181203150603.cdqii263e4kmmibo@pathway.suse.cz> <20181204152724.ypk44mi4a56nrud4@pathway.suse.cz> <459018db-763b-9520-ead2-2c0d5975fbf3@i-love.sakura.ne.jp> <20181210130930.bas4fozjhe3dc5nu@pathway.suse.cz> From: Tetsuo Handa Message-ID: Date: Mon, 10 Dec 2018 23:01:39 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.3.3 MIME-Version: 1.0 In-Reply-To: <20181210130930.bas4fozjhe3dc5nu@pathway.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2018/12/10 22:09, Petr Mladek wrote: >> +#ifdef CONFIG_PRINTK_FROM >> +#define PREFIX_FROM_MAX 16 >> +#define PREFIX_MAX (32 + PREFIX_FROM_MAX) >> +#define LOG_LINE_MAX (1024 - 32) > > This looks suspicious. We either need to limit LOG_LINE_MAX > by the real PREFIX_MAX (48). Or we must make sure that > the code is able to handle an eventual overflow. Reducing LOG_LINE_MAX makes devkmsg_write() to return -EINVAL. Is such user visible change acceptable? > BTW: The limit 48 looks right. If I count correctly, the longest > prefix might be: > > <2048>[4294967296,xxxxxx][T4294967296] > > 38 = 6+19+13 Theoretical max (based on variable's bit width) is 6 + 20 + 13 + 1 (for space) + 1 (for '\0') = 41. We allocate 32 for "<2047>[18446744073.709551] ". Thus, I chose 48 for "<2047>[18446744073.709551][T4294967295] ".