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=-19.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,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 BDB47C433DB for ; Mon, 8 Feb 2021 17:46:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 766BF64E84 for ; Mon, 8 Feb 2021 17:46:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234750AbhBHRps (ORCPT ); Mon, 8 Feb 2021 12:45:48 -0500 Received: from mail.kernel.org ([198.145.29.99]:33696 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233407AbhBHPRd (ORCPT ); Mon, 8 Feb 2021 10:17:33 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id BA79564EC4; Mon, 8 Feb 2021 15:11:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1612797100; bh=wpP4i7BQ4WKIsO17uvTj70lFGzob/jQLcJhFFcwLSYw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ZKQImTk4r/Dex5qu/Ew4V09WS6+dTxfZh4QmMuDSEU6MA6a+mNLHK30o4zgEz89dW fP6uojhTZOT7Dj6j4U2NUDOTYBnpkm/1T+DvuUPirpyc+AWCMlKa2axs9kmGoAtarS 4D0tug2TEyWivGLbfBYFZqTwgA3DRtRs/hz60SSo= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, David Jeffery , Xiao Ni , Song Liu , Jack Wang Subject: [PATCH 5.4 59/65] md: Set prev_flush_start and flush_bio in an atomic way Date: Mon, 8 Feb 2021 16:01:31 +0100 Message-Id: <20210208145812.514171243@linuxfoundation.org> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210208145810.230485165@linuxfoundation.org> References: <20210208145810.230485165@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Xiao Ni commit dc5d17a3c39b06aef866afca19245a9cfb533a79 upstream. One customer reports a crash problem which causes by flush request. It triggers a warning before crash. /* new request after previous flush is completed */ if (ktime_after(req_start, mddev->prev_flush_start)) { WARN_ON(mddev->flush_bio); mddev->flush_bio = bio; bio = NULL; } The WARN_ON is triggered. We use spin lock to protect prev_flush_start and flush_bio in md_flush_request. But there is no lock protection in md_submit_flush_data. It can set flush_bio to NULL first because of compiler reordering write instructions. For example, flush bio1 sets flush bio to NULL first in md_submit_flush_data. An interrupt or vmware causing an extended stall happen between updating flush_bio and prev_flush_start. Because flush_bio is NULL, flush bio2 can get the lock and submit to underlayer disks. Then flush bio1 updates prev_flush_start after the interrupt or extended stall. Then flush bio3 enters in md_flush_request. The start time req_start is behind prev_flush_start. The flush_bio is not NULL(flush bio2 hasn't finished). So it can trigger the WARN_ON now. Then it calls INIT_WORK again. INIT_WORK() will re-initialize the list pointers in the work_struct, which then can result in a corrupted work list and the work_struct queued a second time. With the work list corrupted, it can lead in invalid work items being used and cause a crash in process_one_work. We need to make sure only one flush bio can be handled at one same time. So add spin lock in md_submit_flush_data to protect prev_flush_start and flush_bio in an atomic way. Reviewed-by: David Jeffery Signed-off-by: Xiao Ni Signed-off-by: Song Liu Signed-off-by: Jack Wang Signed-off-by: Greg Kroah-Hartman --- drivers/md/md.c | 2 ++ 1 file changed, 2 insertions(+) --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -538,8 +538,10 @@ static void md_submit_flush_data(struct * could wait for this and below md_handle_request could wait for those * bios because of suspend check */ + spin_lock_irq(&mddev->lock); mddev->last_flush = mddev->start_flush; mddev->flush_bio = NULL; + spin_unlock_irq(&mddev->lock); wake_up(&mddev->sb_wait); if (bio->bi_iter.bi_size == 0) {