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=-9.0 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,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 C4512C10F11 for ; Wed, 24 Apr 2019 17:19:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 914462190A for ; Wed, 24 Apr 2019 17:19:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556126370; bh=DNzbvR+6HvBRWcXAHVIlIVv77H2hy4Iarg1JpF0HhhY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=hgH2WvxP2v+JUystsSYZLbZRzYFLPCoJgJz+sKhnKzvwoHpq1C4Nq/JeDO7uSRhrt RILA7895kCY9Bd6L/k+bd77/mdTmt5JxwbljhpN55YPV0Eq0ox2ljeIa9Fd+ObWfYv bzdim9ETYp5eoAdmC7GIKBIEgyw5VKjNvTqHQKIM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389003AbfDXRT3 (ORCPT ); Wed, 24 Apr 2019 13:19:29 -0400 Received: from mail.kernel.org ([198.145.29.99]:44632 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388594AbfDXRTY (ORCPT ); Wed, 24 Apr 2019 13:19:24 -0400 Received: from localhost (62-193-50-229.as16211.net [62.193.50.229]) (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 8674C20835; Wed, 24 Apr 2019 17:19:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556126364; bh=DNzbvR+6HvBRWcXAHVIlIVv77H2hy4Iarg1JpF0HhhY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=U9wfRbDUJWo7e8B24R+1oXK8uzIWP1bAhI3FWygWnk2QH2HT0/Jk40KTs5LVEL09Z GArr7QpBCx4Ru9U8P1ijMbjdggIjDIT0DbPF8bOcQXHj+1MsMwKhrkXbcyb5pq+sgL HkjCuD4bQbOvW1VMrMo9dwfivwqXqfP17U226FfY= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Guenter Roeck , Jens Axboe , Sasha Levin Subject: [PATCH 4.4 050/168] cdrom: Fix race condition in cdrom_sysctl_register Date: Wed, 24 Apr 2019 19:08:14 +0200 Message-Id: <20190424170926.759700328@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190424170923.452349382@linuxfoundation.org> References: <20190424170923.452349382@linuxfoundation.org> User-Agent: quilt/0.66 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 [ Upstream commit f25191bb322dec8fa2979ecb8235643aa42470e1 ] The following traceback is sometimes seen when booting an image in qemu: [ 54.608293] cdrom: Uniform CD-ROM driver Revision: 3.20 [ 54.611085] Fusion MPT base driver 3.04.20 [ 54.611877] Copyright (c) 1999-2008 LSI Corporation [ 54.616234] Fusion MPT SAS Host driver 3.04.20 [ 54.635139] sysctl duplicate entry: /dev/cdrom//info [ 54.639578] CPU: 0 PID: 266 Comm: kworker/u4:5 Not tainted 5.0.0-rc5 #1 [ 54.639578] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 [ 54.641273] Workqueue: events_unbound async_run_entry_fn [ 54.641273] Call Trace: [ 54.641273] dump_stack+0x67/0x90 [ 54.641273] __register_sysctl_table+0x50b/0x570 [ 54.641273] ? rcu_read_lock_sched_held+0x6f/0x80 [ 54.641273] ? kmem_cache_alloc_trace+0x1c7/0x1f0 [ 54.646814] __register_sysctl_paths+0x1c8/0x1f0 [ 54.646814] cdrom_sysctl_register.part.7+0xc/0x5f [ 54.646814] register_cdrom.cold.24+0x2a/0x33 [ 54.646814] sr_probe+0x4bd/0x580 [ 54.646814] ? __driver_attach+0xd0/0xd0 [ 54.646814] really_probe+0xd6/0x260 [ 54.646814] ? __driver_attach+0xd0/0xd0 [ 54.646814] driver_probe_device+0x4a/0xb0 [ 54.646814] ? __driver_attach+0xd0/0xd0 [ 54.646814] bus_for_each_drv+0x73/0xc0 [ 54.646814] __device_attach+0xd6/0x130 [ 54.646814] bus_probe_device+0x9a/0xb0 [ 54.646814] device_add+0x40c/0x670 [ 54.646814] ? __pm_runtime_resume+0x4f/0x80 [ 54.646814] scsi_sysfs_add_sdev+0x81/0x290 [ 54.646814] scsi_probe_and_add_lun+0x888/0xc00 [ 54.646814] ? scsi_autopm_get_host+0x21/0x40 [ 54.646814] __scsi_add_device+0x116/0x130 [ 54.646814] ata_scsi_scan_host+0x93/0x1c0 [ 54.646814] async_run_entry_fn+0x34/0x100 [ 54.646814] process_one_work+0x237/0x5e0 [ 54.646814] worker_thread+0x37/0x380 [ 54.646814] ? rescuer_thread+0x360/0x360 [ 54.646814] kthread+0x118/0x130 [ 54.646814] ? kthread_create_on_node+0x60/0x60 [ 54.646814] ret_from_fork+0x3a/0x50 The only sensible explanation is that cdrom_sysctl_register() is called twice, once from the module init function and once from register_cdrom(). cdrom_sysctl_register() is not mutex protected and may happily execute twice if the second call is made before the first call is complete. Use a static atomic to ensure that the function is executed exactly once. Signed-off-by: Guenter Roeck Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- drivers/cdrom/cdrom.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/drivers/cdrom/cdrom.c b/drivers/cdrom/cdrom.c index d203940203b6..aee23092f50e 100644 --- a/drivers/cdrom/cdrom.c +++ b/drivers/cdrom/cdrom.c @@ -265,6 +265,7 @@ /* #define ERRLOGMASK (CD_WARNING|CD_OPEN|CD_COUNT_TRACKS|CD_CLOSE) */ /* #define ERRLOGMASK (CD_WARNING|CD_REG_UNREG|CD_DO_IOCTL|CD_OPEN|CD_CLOSE|CD_COUNT_TRACKS) */ +#include #include #include #include @@ -3677,9 +3678,9 @@ static struct ctl_table_header *cdrom_sysctl_header; static void cdrom_sysctl_register(void) { - static int initialized; + static atomic_t initialized = ATOMIC_INIT(0); - if (initialized == 1) + if (!atomic_add_unless(&initialized, 1, 1)) return; cdrom_sysctl_header = register_sysctl_table(cdrom_root_table); @@ -3690,8 +3691,6 @@ static void cdrom_sysctl_register(void) cdrom_sysctl_settings.debug = debug; cdrom_sysctl_settings.lock = lockdoor; cdrom_sysctl_settings.check = check_media_type; - - initialized = 1; } static void cdrom_sysctl_unregister(void) -- 2.19.1