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=-7.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 15171C433B4 for ; Tue, 13 Apr 2021 13:11:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E767961369 for ; Tue, 13 Apr 2021 13:11:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238896AbhDMNMG (ORCPT ); Tue, 13 Apr 2021 09:12:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42042 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231486AbhDMNMG (ORCPT ); Tue, 13 Apr 2021 09:12:06 -0400 Received: from mail-lj1-x229.google.com (mail-lj1-x229.google.com [IPv6:2a00:1450:4864:20::229]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DD855C061574; Tue, 13 Apr 2021 06:11:44 -0700 (PDT) Received: by mail-lj1-x229.google.com with SMTP id l14so16384104ljb.1; Tue, 13 Apr 2021 06:11:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=message-id:subject:from:to:cc:date:user-agent:mime-version :content-transfer-encoding; bh=QdLdl7ZYVcXzeYaosVMxtDawv9mtCEbRVs/6OC9JF9o=; b=CT0d7ft2eGC496UOqY7CPcm/vmeacczS8kxYMJupYLVqzF5Luq7SXqOCLpEuTKmOxN 5Fk1G14n4rLcTt3un6okLXTUpQD3o8eBq613SLQ7heYQmcrYsg4NuKfNTPEcCnBQeO78 spsQ/GSiAZFtO5OwxUoJGdWzSres2mZMMSgyblCWt4g2JOStBk80hQ6rHXeJpp8h7mEV BnzO8dFbzxclTyaMKr7jxP5K92E+SZcAyoU0FceBXtGx1IP6yp0Jr1DvRjMY5czhBiFX /47pNOfhYRjaHoSz5ykS3t2MUr2RJrBvqHVXz6hp4fPwBoYBfGtUUMg0uCX6a5UWP1Kw bdrQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:message-id:subject:from:to:cc:date:user-agent :mime-version:content-transfer-encoding; bh=QdLdl7ZYVcXzeYaosVMxtDawv9mtCEbRVs/6OC9JF9o=; b=Wvsp+SOTdwmToC3bm8SdpWgY8xRBB0b96TDFg4jyGc+x8SfR8VvQquQcVGIM6vkmz4 vpe78z3dLeOM776HXDMIV9aVmNJ3ZDKxcNz3D0AqitlZ5vGUPd/TL7snsur7jB0fLnmb af0alny6Y2f6Sphde+23yEFVKJGnzc8J4bsGU6n3qCW368uQtwljVQJ2CiZ1GacXsBjc JUUn3hOa6HpiG+QjlHa905MDSSsaiCrTSxJkgHRAr8RAp7eqmTMZOm2LDlGJQjy5H+QJ K/FJGegSPEi6e9W2lAc9B2YnUBci18iOq4lR6Y25Bi8augZWnugG1FliHobWsUbZi8LO 5GPg== X-Gm-Message-State: AOAM532d8u66ZDcJO94t5qCfeSGNtBGlX6LQ4JBMxU86nSOxq6fdjRWr 8rb7gCHcMTvvX2o8KncfiVvYljhi5+8lAg== X-Google-Smtp-Source: ABdhPJzzEAnNBu3PaFSv/V5rMsWkYmo2d4Mf6z3k/+v/uK+a8Iym35+wofwnC1KxXTZNa8IEUmZo1Q== X-Received: by 2002:a2e:b555:: with SMTP id a21mr21162925ljn.69.1618319503380; Tue, 13 Apr 2021 06:11:43 -0700 (PDT) Received: from [192.168.1.11] ([94.103.229.90]) by smtp.gmail.com with ESMTPSA id k2sm3344307lfg.107.2021.04.13.06.11.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 13 Apr 2021 06:11:42 -0700 (PDT) Message-ID: Subject: memory leak in ext4_multi_mount_protect From: Pavel Skripkin To: tytso@mit.edu, adilger.kernel@dilger.ca Cc: linux-ext4@vger.kernel.org, kernel list Date: Tue, 13 Apr 2021 16:11:41 +0300 Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.38.4 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org Hi! I've done debugging on this issue https://syzkaller.appspot.com/bug?id=420258a304e5d92cfef6b0097f87b42506e1db08 and I want to ask you about proper way of fixing it. The problem was in case sbi->s_mmp_tsk hasn’t started at the time of kthread_stop() call. In that case allocated data won't be freed. I wrote fix patch, but I am confused about it, because I didn't find any kernel code like this. I don't think, that adding new members to struct super_block is good idea, that's why I came to that decision: diff --git a/fs/ext4/super.c b/fs/ext4/super.c index b9693680463a..9c33e97bd5c5 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -5156,8 +5156,10 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent) failed_mount3: flush_work(&sbi->s_error_work); del_timer_sync(&sbi->s_err_report); - if (sbi->s_mmp_tsk) - kthread_stop(sbi->s_mmp_tsk); + if (sbi->s_mmp_tsk) { + if (kthread_stop(sbi->s_mmp_tsk) == -EINTR) + kfree(kthread_data(sbi->s_mmp_tsk)); + } failed_mount2: rcu_read_lock(); group_desc = rcu_dereference(sbi->s_group_desc); I look forward to hearing your perspective on this patch :) With regards, Pavel Skripkin