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=-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=unavailable 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 784A4C4338F for ; Thu, 5 Aug 2021 15:14:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 544CB60EEA for ; Thu, 5 Aug 2021 15:14:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241685AbhHEPOy (ORCPT ); Thu, 5 Aug 2021 11:14:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52640 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233201AbhHEPOx (ORCPT ); Thu, 5 Aug 2021 11:14:53 -0400 Received: from mail-lf1-x12c.google.com (mail-lf1-x12c.google.com [IPv6:2a00:1450:4864:20::12c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 84A82C061765; Thu, 5 Aug 2021 08:14:37 -0700 (PDT) Received: by mail-lf1-x12c.google.com with SMTP id g13so11764443lfj.12; Thu, 05 Aug 2021 08:14:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=IcxM4SQZ1Owp4dygHmrLmNFPgwp1t/zdZnY5NIzOZu0=; b=F/f7mAWu68gjHXLeJysy7N3Wx6VCcxwKiBK0KP0WJJtrNT9A067qrqdCCidLM0zG2M ruhMXbpNj5ZGC8wD/o6gYlpA2vTfYtdVzubcJk3uY1ICqTh+tJmAYlTtZZ4FwSKVmbCi 6miM2IjtWUiP37u+9fEwsvk2CkMU/ShdQQLBMkCDw28jlQg7oOm3RQkzVLAVQnHVEl2e KQFdwvvmZipEc/aWkwGlzTCJXs1+4Asn3+EH1RT0sGtMDVi8+aOTk+uPnBvGgkJvClKC +DRqpPG2vPcjeDU5r8VM6OsIYm47IIZ7y73xqWdci7a+B3FyJ8Qtju9srIrrd8SwVJe8 xwQg== 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:mime-version :content-transfer-encoding; bh=IcxM4SQZ1Owp4dygHmrLmNFPgwp1t/zdZnY5NIzOZu0=; b=WGm4f4+IN1r+kHbgTSD/p203uqgJeBUBVXxV9L1E/6WhYHk13cZM4u/la6Bvnaqc5A lHYKgdFKyKdG8zRDRHFgx8oMO0eSyDw65yeO8I35ruOrq3A9tCXgMgdY5aHLXoolAQQT XmVKgNgPCt3zXBOtDEas4+Yv7SlJR8iZqzxFJduI6rnbPF9SvezQNlDQ3tE26A1veDlo 3m6Y8AGHOkZmMVphx988iu4vvpsiHNX1HwdwZDQdKd8cl+rB176CzTKj/Dt0Ebn5J4vi /LHPNmjyqF91o2L4+pcKQrFzXxncGogkO2peQTNtf7uKb7uul47zHbqEVt+FPAUQPeo3 6qnw== X-Gm-Message-State: AOAM531pVaQIWdaIRG5x2JNOi+cLG3RaL8kG3csAqpN29kLTmFJODi+Y RPc83uQvQ7t7CcqonlwYp/w= X-Google-Smtp-Source: ABdhPJzQpgpdw8+dPgM2yFriEmZyNjF5sCxv74DBD7aDbc1EdfcyLviP1dqLuHxqJAD6JFeJ6RGOZg== X-Received: by 2002:a05:6512:3c96:: with SMTP id h22mr385622lfv.517.1628176475747; Thu, 05 Aug 2021 08:14:35 -0700 (PDT) Received: from localhost.localdomain ([94.103.226.235]) by smtp.gmail.com with ESMTPSA id t142sm540204lff.269.2021.08.05.08.14.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 05 Aug 2021 08:14:35 -0700 (PDT) From: Pavel Skripkin To: tytso@mit.edu, adilger.kernel@dilger.ca, johann@whamcloud.com Cc: linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, Pavel Skripkin , syzbot+c9ff4822a62eee994ea3@syzkaller.appspotmail.com Subject: [PATCH] ext4: avoid huge mmp update interval value Date: Thu, 5 Aug 2021 18:14:18 +0300 Message-Id: <20210805151418.30659-1-paskripkin@gmail.com> X-Mailer: git-send-email 2.32.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Syzbot reported task hung bug in ext4_fill_super(). The problem was in too huge mmp update interval. Syzkaller reproducer setted s_mmp_update_interval to 39785 seconds. This update interaval is unreasonable huge and it can cause tasks to hung on kthread_stop() call, since it will wait until timeout timer expires. To avoid this sutiation, I've added MIN and MAX constants for kmmp interval and clamped s_mmp_update_interval within the boundaries Reported-and-tested-by: syzbot+c9ff4822a62eee994ea3@syzkaller.appspotmail.com Fixes: c5e06d101aaf ("ext4: add support for multiple mount protection") Signed-off-by: Pavel Skripkin --- Hi, Ted and ext4 maintainers! I am not sure about min/max values for interval, so I look forward to receiving your views on these values and patch in general! With regards, Pavel Skripkin --- fs/ext4/mmp.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/fs/ext4/mmp.c b/fs/ext4/mmp.c index bc364c119af6..160abee66dce 100644 --- a/fs/ext4/mmp.c +++ b/fs/ext4/mmp.c @@ -7,6 +7,9 @@ #include "ext4.h" +#define EXT4_KMMP_MAX_INTERVAL 100 +#define EXT4_KMMP_MIN_INTERVAL 5 + /* Checksumming functions */ static __le32 ext4_mmp_csum(struct super_block *sb, struct mmp_struct *mmp) { @@ -140,6 +143,12 @@ static int kmmpd(void *data) unsigned long diff; int retval; + /* We should avoid unreasonable huge update interval, since it can cause + * task hung bug on umount or on error handling path in ext4_fill_super() + */ + mmp_update_interval = clamp(mmp_update_interval, EXT4_KMMP_MIN_INTERVAL, + EXT4_KMMP_MAX_INTERVAL); + mmp_block = le64_to_cpu(es->s_mmp_block); mmp = (struct mmp_struct *)(bh->b_data); mmp->mmp_time = cpu_to_le64(ktime_get_real_seconds()); @@ -156,6 +165,9 @@ static int kmmpd(void *data) memcpy(mmp->mmp_nodename, init_utsname()->nodename, sizeof(mmp->mmp_nodename)); + ext4_msg(sb, KERN_INFO, "Started kmmp thread with update interval = %u\n", + mmp_update_interval); + while (!kthread_should_stop() && !sb_rdonly(sb)) { if (!ext4_has_feature_mmp(sb)) { ext4_warning(sb, "kmmpd being stopped since MMP feature" -- 2.32.0