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=-2.2 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 D2E4FC73C7C for ; Wed, 10 Jul 2019 08:19:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A206520844 for ; Wed, 10 Jul 2019 08:19:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="f5pcFIr4" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727541AbfGJIT2 (ORCPT ); Wed, 10 Jul 2019 04:19:28 -0400 Received: from mail-pg1-f195.google.com ([209.85.215.195]:41300 "EHLO mail-pg1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726140AbfGJIT2 (ORCPT ); Wed, 10 Jul 2019 04:19:28 -0400 Received: by mail-pg1-f195.google.com with SMTP id q4so858131pgj.8 for ; Wed, 10 Jul 2019 01:19:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=N6SercxtoSKSRCScJgllC9YsDuWHEtkF2Gy5vLajuYI=; b=f5pcFIr4KEnuKujSw0PCI8+ne2ZPT/eTiNxYlV/Fjw+Q+q0Vu48E8I1wCOX1vQXJej xust2dEsnBU/pTvXSaBLTG21oarZ2Xepwu3XxlB1zEXsusT4uDJeiTo4r/JZG9KPch2Y qx84ao943+2eOxQcCjY+J34bWcbEyPxGT9yvre2IP8ZwcndXohe+JD6DrT+vScM6ndC0 dh2+0sJf0NLvFZq5iroWefzcT/bIm00EpY1cBiEsBQ0jiE0FP9Mkj0V831eO3Bqsa99r 9PicD7cGit2+UXfs/qVeNN7PYuDeIlfXWYSQP9nx1NMvYQ8nNGWusHe+seyTprY7EOlN IWZQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=N6SercxtoSKSRCScJgllC9YsDuWHEtkF2Gy5vLajuYI=; b=IGsPNDLN0czgkiqsuQAJUw3Pzz7OJ2e45ms1We4ydN85mZfyCnx0fgXvlXrruYtbRR 27pWK/WeUX8JrVNreD15kz8ZEkVAnYJ+ScMaaDIO+47shAGJ8qgDtBJ+WxXvK29CsVcV hLp0iIlkL5tVccwNaMj9YLz48ia59CiCX6ca6/olD0sFzJB9Ro5Oje0TW0rSjLztg481 ZY3TwW7ha5uelGOiohhFgce75FK0iOw/gz0f8zr/P/0TPfsEbHUZpA4mKwghHNjG6ISC FQSxxLw4nMkLLBh+s0OujqKfyS3IlMBzQgsrZ94rTADops+uY85gWEN9p36//FtH7+J/ gRBA== X-Gm-Message-State: APjAAAXLC13jP2P1ylo0NY+k9QTWyPP6K5En0WXgCZHXQuN6XFb/6oF0 5Oq9wuTb7qCAq+tdgM7TSjc= X-Google-Smtp-Source: APXvYqwbWG/EgQGeyQs7s7Fp/DdmsOs7K4ad8V6aBkUpsRLK8b9OdhhMxuEWNxE1nlhfrWj4c0gUcg== X-Received: by 2002:a17:90a:9505:: with SMTP id t5mr5443039pjo.96.1562746767357; Wed, 10 Jul 2019 01:19:27 -0700 (PDT) Received: from localhost ([175.223.19.33]) by smtp.gmail.com with ESMTPSA id j15sm2809810pfn.150.2019.07.10.01.19.25 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Wed, 10 Jul 2019 01:19:26 -0700 (PDT) Date: Wed, 10 Jul 2019 17:19:22 +0900 From: Sergey Senozhatsky To: Vincent Whitchurch Cc: Petr Mladek , Sergey Senozhatsky , "sergey.senozhatsky@gmail.com" , "rostedt@goodmis.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] printk: Do not lose last line in kmsg dump Message-ID: <20190710081922.GA7020@jagdpanzerIV> References: <20190709081042.31551-1-vincent.whitchurch@axis.com> <20190709101230.GA16909@jagdpanzerIV> <20190709142939.luqhbd6x6bzdkydr@pathway.suse.cz> <20190710080402.ab3f4qfnvez6dhtc@axis.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190710080402.ab3f4qfnvez6dhtc@axis.com> User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (07/10/19 10:04), Vincent Whitchurch wrote: > > > [..] > > > > > > > @@ -1318,7 +1318,7 @@ static size_t msg_print_text(const struct printk_log *msg, bool syslog, > > > > } > > > > > > > > if (buf) { > > > > - if (prefix_len + text_len + 1 >= size - len) > > > > + if (prefix_len + text_len + 1 > size - len) > > > > break; > > > > > > So with this patch the last byte of the buffer is 0xA. It's a bit > > > uncomfortable that `len', which we return from msg_print_text(), > > > now points one byte beyond the buffer: > > > > > > buf[len++] = '\n'; > > > return len; > > > > > > This is not very common. Not sure what usually happens to kmsg_dump > > > buffers, but anyone who'd do a rather innocent > > > > > > kmsg_dump(buf, &len); > > > buf[len] = 0x00; > > > > > > will write to something which is not a kmsg buffer (in some cases). [..] > arch/powerpc/xmon/xmon.c > 2836: while (kmsg_dump_get_line_nolock(&dumper, false, buf, sizeof(buf), &len)) { > 2837- buf[len] = '\0'; > > arch/um/kernel/kmsg_dump.c > 29: while (kmsg_dump_get_line(dumper, true, line, sizeof(line), &len)) { > 30- line[len] = '\0'; > > I guess we should fix these first and leave this patch as is? We certainly need to fix something here, and I'd say that we better handle it on the msg_print_text() side. There might be more kmsg_dump_get_line() users doing `buf[len] = '\0'' in the future. -ss