From patchwork Fri Jan 22 11:03:40 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Xin Long X-Patchwork-Id: 12038997 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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 B4DD3C433E0 for ; Fri, 22 Jan 2021 11:06:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 713E72376F for ; Fri, 22 Jan 2021 11:06:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727423AbhAVLGN (ORCPT ); Fri, 22 Jan 2021 06:06:13 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36222 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727955AbhAVLEl (ORCPT ); Fri, 22 Jan 2021 06:04:41 -0500 Received: from mail-pg1-x535.google.com (mail-pg1-x535.google.com [IPv6:2607:f8b0:4864:20::535]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0B28AC061793 for ; Fri, 22 Jan 2021 03:03:50 -0800 (PST) Received: by mail-pg1-x535.google.com with SMTP id n10so3445860pgl.10 for ; Fri, 22 Jan 2021 03:03:50 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id; bh=8Cv1OFV4PqWqs9OFGtdzGJdasAixNkXlyH3Z+SOrD2s=; b=BJiJsu3jZE45SKsE//wnDRYUoE66mojERC6nqj+RXSMJq8L+sAWvy+Ek/eY6X7iXnQ 7HRii0Cn+94pI4Tk41+twVE5idKl5uXF8luTbId76mulGeB2KsJOuYNFE4ZsQE+itwfO bNA0qeRJv5ijMl9BekVDecCGmm2Ce8kP7diBZkM7j4+N9OM1Pfv00OjZ0+sScXRY6ETW w99BkWAm4PMJRR414OVcaFZ/fK94ewRt9f9SKoWoUkHtMbZJby3VDvUinrywWCBQEYVQ nv8DReuPmIZ597uGVMZQsYIijzcCOPAQCQD8iVP0ORqZrNf0nOcgUyDU5JxhhzCNY9Gv JnQQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=8Cv1OFV4PqWqs9OFGtdzGJdasAixNkXlyH3Z+SOrD2s=; b=MOE+KzJ89y+ClgjNXodV9xgtfX38xSbs60/dzhoKoHFCGeJlPAEvk9FwofTZ9JX5p6 JoxZ0QDz+9FibG05eM/5owDWEsR8sKR7oypblIO/Fj+kjrIRNNP2TZHqrBUFQHqg96gy 2GHII0h3plDcDoN9roSLNi1UwKZc9SG/+xtrROO7h2o5PQakKm0iQQt/PuhDhIe1jDGo QBDYTDmwE9cUnGPDT9I7+mK1vlS/uISX5tfnUkyAyi1Rhl3r61KLB8AapfWvnnbS3phO f3Rd5YIxU+dgtyNJvv2nAvXxvcR+bU3LytmHJdADeGUIn1me/n0iFlI/df01NZQIxiUh lORg== X-Gm-Message-State: AOAM5332eAzfFt3dUnUIaMssURxFxQKQHR6WJQTk5sb1TpKOHQNvfgFu 8ntkabZ2s0PmnI3lMo7vQjiW92LXxGzCEw== X-Google-Smtp-Source: ABdhPJwR4JqPoRoXyEluavVlTxcnJ79QUlGMEikjpUDWhjKyaOyL+fE+3pOmyoD1A9wUV+Lx8yB51g== X-Received: by 2002:aa7:88c3:0:b029:1b4:ca2f:2074 with SMTP id k3-20020aa788c30000b02901b4ca2f2074mr4146235pff.45.1611313429324; Fri, 22 Jan 2021 03:03:49 -0800 (PST) Received: from localhost ([209.132.188.80]) by smtp.gmail.com with ESMTPSA id c5sm8997659pjo.4.2021.01.22.03.03.47 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Fri, 22 Jan 2021 03:03:48 -0800 (PST) From: Xin Long To: linux-fsdevel@vger.kernel.org, Alexander Viro Cc: NeilBrown Subject: [PATCH] seq_read: move count check against iov_iter_count after calling op show Date: Fri, 22 Jan 2021 19:03:40 +0800 Message-Id: <91568e002fed69425485c17de223bef0ff660f3a.1611313420.git.lucien.xin@gmail.com> X-Mailer: git-send-email 2.1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org In commit 1f4aace60b0e ("fs/seq_file.c: simplify seq_file iteration code and interface"), it broke a behavior: op show() is always called when op next() returns an available obj. This caused a refcnt leak in net/sctp/proc.c, as of the seq_operations sctp_assoc_ops, transport obj is held in op next() and released in op show(). Here fix it by moving count check against iov_iter_count after calling op show() so that op show() can still be called when op next() returns an available obj. Note that m->index needs to increase so that op start() could go fetch the next obj in the next round. Fixes: 1f4aace60b0e ("fs/seq_file.c: simplify seq_file iteration code and interface") Reported-by: Prijesh Signed-off-by: Xin Long Reported-by: kernel test robot --- fs/seq_file.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/fs/seq_file.c b/fs/seq_file.c index 03a369c..da304f7 100644 --- a/fs/seq_file.c +++ b/fs/seq_file.c @@ -264,8 +264,6 @@ ssize_t seq_read_iter(struct kiocb *iocb, struct iov_iter *iter) } if (!p || IS_ERR(p)) // no next record for us break; - if (m->count >= iov_iter_count(iter)) - break; err = m->op->show(m, p); if (err > 0) { // ->show() says "skip it" m->count = offs; @@ -273,6 +271,10 @@ ssize_t seq_read_iter(struct kiocb *iocb, struct iov_iter *iter) m->count = offs; break; } + if (m->count >= iov_iter_count(iter)) { + m->index++; + break; + } } m->op->stop(m, p); n = copy_to_iter(m->buf, m->count, iter);