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=-10.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,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 2B9D7C43441 for ; Thu, 29 Nov 2018 14:27:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E6F192146D for ; Thu, 29 Nov 2018 14:27:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="EiNY8igL" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E6F192146D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733219AbeK3BdD (ORCPT ); Thu, 29 Nov 2018 20:33:03 -0500 Received: from mail.kernel.org ([198.145.29.99]:33396 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731824AbeK3BdC (ORCPT ); Thu, 29 Nov 2018 20:33:02 -0500 Received: from localhost (5356596B.cm-6-7b.dynamic.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 65F1A2133F; Thu, 29 Nov 2018 14:27:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1543501649; bh=hKgTb9/F6g1je62aL9KVwQJfL/CJgMIbmO9zgTTZ/Yc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=EiNY8igLm4VpX1IpOEcgEs0+MiK1B77w2WyjsPqWqh/sAN0TUKawMei83ubC8OXuk WoHyMFXA1TpHmISzok92dv3JPN/ywMDy+ZX/faRbNgFqQBftBHsJX23gY1PdN/0cLe rvq3nfFzCPoHFxYAm1KggrNZ4yTg2g6PKsCy7BWs= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Omar Sandoval , Jens Axboe , Sasha Levin Subject: [PATCH 4.14 051/100] floppy: fix race condition in __floppy_read_block_0() Date: Thu, 29 Nov 2018 15:12:21 +0100 Message-Id: <20181129140103.612671151@linuxfoundation.org> X-Mailer: git-send-email 2.19.2 In-Reply-To: <20181129140058.768942700@linuxfoundation.org> References: <20181129140058.768942700@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ [ Upstream commit de7b75d82f70c5469675b99ad632983c50b6f7e7 ] LKP recently reported a hang at bootup in the floppy code: [ 245.678853] INFO: task mount:580 blocked for more than 120 seconds. [ 245.679906] Tainted: G T 4.19.0-rc6-00172-ga9f38e1 #1 [ 245.680959] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 245.682181] mount D 6372 580 1 0x00000004 [ 245.683023] Call Trace: [ 245.683425] __schedule+0x2df/0x570 [ 245.683975] schedule+0x2d/0x80 [ 245.684476] schedule_timeout+0x19d/0x330 [ 245.685090] ? wait_for_common+0xa5/0x170 [ 245.685735] wait_for_common+0xac/0x170 [ 245.686339] ? do_sched_yield+0x90/0x90 [ 245.686935] wait_for_completion+0x12/0x20 [ 245.687571] __floppy_read_block_0+0xfb/0x150 [ 245.688244] ? floppy_resume+0x40/0x40 [ 245.688844] floppy_revalidate+0x20f/0x240 [ 245.689486] check_disk_change+0x43/0x60 [ 245.690087] floppy_open+0x1ea/0x360 [ 245.690653] __blkdev_get+0xb4/0x4d0 [ 245.691212] ? blkdev_get+0x1db/0x370 [ 245.691777] blkdev_get+0x1f3/0x370 [ 245.692351] ? path_put+0x15/0x20 [ 245.692871] ? lookup_bdev+0x4b/0x90 [ 245.693539] blkdev_get_by_path+0x3d/0x80 [ 245.694165] mount_bdev+0x2a/0x190 [ 245.694695] squashfs_mount+0x10/0x20 [ 245.695271] ? squashfs_alloc_inode+0x30/0x30 [ 245.695960] mount_fs+0xf/0x90 [ 245.696451] vfs_kern_mount+0x43/0x130 [ 245.697036] do_mount+0x187/0xc40 [ 245.697563] ? memdup_user+0x28/0x50 [ 245.698124] ksys_mount+0x60/0xc0 [ 245.698639] sys_mount+0x19/0x20 [ 245.699167] do_int80_syscall_32+0x61/0x130 [ 245.699813] entry_INT80_32+0xc7/0xc7 showing that we never complete that read request. The reason is that the completion setup is racy - it initializes the completion event AFTER submitting the IO, which means that the IO could complete before/during the init. If it does, we are passing garbage to complete() and we may sleep forever waiting for the event to occur. Fixes: 7b7b68bba5ef ("floppy: bail out in open() if drive is not responding to block0 read") Reviewed-by: Omar Sandoval Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- drivers/block/floppy.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c index 3d0287e212fe..a7f212ea17bf 100644 --- a/drivers/block/floppy.c +++ b/drivers/block/floppy.c @@ -4146,10 +4146,11 @@ static int __floppy_read_block_0(struct block_device *bdev, int drive) bio.bi_end_io = floppy_rb0_cb; bio_set_op_attrs(&bio, REQ_OP_READ, 0); + init_completion(&cbdata.complete); + submit_bio(&bio); process_fd_request(); - init_completion(&cbdata.complete); wait_for_completion(&cbdata.complete); __free_page(page); -- 2.17.1