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=-10.6 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,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 A6425C4727E for ; Wed, 30 Sep 2020 13:31:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5157320754 for ; Wed, 30 Sep 2020 13:31:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=suse.com header.i=@suse.com header.b="Pztg8LU1" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730268AbgI3Na7 (ORCPT ); Wed, 30 Sep 2020 09:30:59 -0400 Received: from mx2.suse.de ([195.135.220.15]:43042 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728043AbgI3Na6 (ORCPT ); Wed, 30 Sep 2020 09:30:58 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1601472656; 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: in-reply-to:in-reply-to:references:references; bh=w5l3298h/W9/vnTUaZ61CRdnwpEmCubNJa9uFrQVNgI=; b=Pztg8LU1pXMAeUTodDs+P1OjYWPTevX8KIF4wRSsw8fngOVMg5ZSP4X/1tMFdTS3E+jBdz 4/tfgEYzcLu0vp5wKM6Vmi6XPfVuatZ2jslTPCSH3zIBL1s35Cp9ErhCq2qo8dJDFTebYl hmOF0swva3Csjzcm0GMFAPaqrgBNZj8= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 39EA2ABCC; Wed, 30 Sep 2020 13:30:56 +0000 (UTC) Date: Wed, 30 Sep 2020 15:30:55 +0200 From: Petr Mladek To: John Ogness Cc: Sergey Senozhatsky , Sergey Senozhatsky , Steven Rostedt , Linus Torvalds , Greg Kroah-Hartman , Thomas Gleixner , Marek Szyprowski , linux-kernel@vger.kernel.org Subject: Re: [PATCH next v2 0/2] printk: fix reading beyond buffer Message-ID: <20200930133055.GG29288@alley> References: <20200930090134.8723-1-john.ogness@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200930090134.8723-1-john.ogness@linutronix.de> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 2020-09-30 11:07:32, John Ogness wrote: > Hello, > > Marek Szyprowski reported [0] a problem with a particular printk > usage. This particular usage performs thousands of LOG_CONT calls. > The printk.c implementation was only limiting the growing record by > the maximum size available in the ringbuffer, thus creating a record > that was several kilobytes in size. This in and of itself is not > a problem. > > However, the various readers used buffers that were about 1KB in > size. The ringbuffer would only fill the reader's 1KB buffer, but the > meta data stated that the message was actually much larger. The > reader code was not checking this and assumed its buffer contained > the full message. > > I have solved this problem by adding the necessary check to the > functions where the situation can occur and also adding an argument > when extending records so that a maximum size is specified. This > will prevent the records from growing beyond the size that we know > our readers are using. > > I did not add the check where it is certain that the reader's > buffer is large enough to contain the largest possible message. > > The 2nd patch in this series reduces the size of the initial setup > buffer. I noticed it was too big while verifying all the sizes for > this series. > > John Ogness > > [0] https://lkml.kernel.org/r/f1651593-3579-5820-6863-5f4973d2bfdc@samsung.com > > John Ogness (2): > printk: avoid and/or handle record truncation > printk: reduce setup_text_buf size to LOG_LINE_MAX The patchset is committed in printk/linux.git, branch printk-rework. Best Regards, Petr