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=-2.3 required=3.0 tests=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 E75BDC2D0CE for ; Fri, 24 Jan 2020 07:03:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A99BC2071A for ; Fri, 24 Jan 2020 07:03:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727496AbgAXHDK (ORCPT ); Fri, 24 Jan 2020 02:03:10 -0500 Received: from relay.sw.ru ([185.231.240.75]:53108 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726657AbgAXHDK (ORCPT ); Fri, 24 Jan 2020 02:03:10 -0500 Received: from vvs-ws.sw.ru ([172.16.24.21]) by relay.sw.ru with esmtp (Exim 4.92.3) (envelope-from ) id 1iuszF-00085a-V4; Fri, 24 Jan 2020 10:02:38 +0300 From: Vasily Averin Subject: [PATCH 0/7] seq_file .next functions should increase position index To: linux-kernel@vger.kernel.org Cc: Andrew Morton , NeilBrown , Waiman Long , Steven Rostedt , Ingo Molnar , Peter Oberparleiter Message-ID: <244674e5-760c-86bd-d08a-047042881748@virtuozzo.com> Date: Fri, 24 Jan 2020 10:02:36 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 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 In Aug 2018 NeilBrown noticed commit 1f4aace60b0e ("fs/seq_file.c: simplify seq_file iteration code and interface") "Some ->next functions do not increment *pos when they return NULL... Note that such ->next functions are buggy and should be fixed. A simple demonstration is dd if=/proc/swaps bs=1000 skip=1 Choose any block size larger than the size of /proc/swaps. This will always show the whole last line of /proc/swaps" Described problem is still actual. If you make lseek into middle of last output line following read will output end of last line and whole last line once again. $ dd if=/proc/swaps bs=1 # usual output Filename Type Size Used Priority /dev/dm-0 partition 4194812 97536 -2 104+0 records in 104+0 records out 104 bytes copied $ dd if=/proc/swaps bs=40 skip=1 # last line was generated twice dd: /proc/swaps: cannot skip to specified offset v/dm-0 partition 4194812 97536 -2 /dev/dm-0 partition 4194812 97536 -2 3+1 records in 3+1 records out 131 bytes copied There are lot of other affected files, I've found 30+ including /proc/net/ip_tables_matches and /proc/sysvipc/* I've sent patches into maillists of affected subsystems already, this patch-set fixes the problem in files related to pstore, tracing, gcov, sysvipc and other subsystems processed via linux-kernel@ mailing list directly https://bugzilla.kernel.org/show_bug.cgi?id=206283 Vasily Averin (7): pstore_ftrace_seq_next should increase position index gcov_seq_next should increase position index t_next should increase position index fpid_next should increase position index eval_map_next should increase position index trigger_next should increase position index sysvipc_find_ipc should increase position index fs/pstore/inode.c | 2 +- ipc/util.c | 2 +- kernel/gcov/fs.c | 2 +- kernel/trace/ftrace.c | 9 ++++++--- kernel/trace/trace.c | 4 +--- kernel/trace/trace_events_trigger.c | 5 +++-- 6 files changed, 13 insertions(+), 11 deletions(-) -- 1.8.3.1