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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9DE7DCCA487 for ; Mon, 13 Jun 2022 11:49:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1356585AbiFMLtS (ORCPT ); Mon, 13 Jun 2022 07:49:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43198 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1357249AbiFMLpx (ORCPT ); Mon, 13 Jun 2022 07:45:53 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E98B44A3E8; Mon, 13 Jun 2022 03:51:58 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 9791FB80E93; Mon, 13 Jun 2022 10:51:57 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id F0255C34114; Mon, 13 Jun 2022 10:51:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1655117516; bh=DzOvs/gCbWtsCNT7TaafoGtLfICWxM3o9lVASQbU2Rg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=PYiznKe1zu2o3qDo5mb5Iw8ASxWVY3957sCGnWwqFVfemW4o+yONQkkebxFX2yqyV p7fKvbLPHDM7yQ1S+wPvvUigDljXSOrZnYJNDBS69kU0HjbXMoS0uhLVPzC6nxnRha 5NCo8vWPSbMD01skD4UjF8J9hmuofQQqc7AtlpKU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Hou Tao , Yu Kuai , Josef Bacik , Jens Axboe , Sasha Levin Subject: [PATCH 5.4 392/411] nbd: call genl_unregister_family() first in nbd_cleanup() Date: Mon, 13 Jun 2022 12:11:05 +0200 Message-Id: <20220613094940.424189162@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220613094928.482772422@linuxfoundation.org> References: <20220613094928.482772422@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: Yu Kuai [ Upstream commit 06c4da89c24e7023ea448cadf8e9daf06a0aae6e ] Otherwise there may be race between module removal and the handling of netlink command, which can lead to the oops as shown below: BUG: kernel NULL pointer dereference, address: 0000000000000098 Oops: 0002 [#1] SMP PTI CPU: 1 PID: 31299 Comm: nbd-client Tainted: G E 5.14.0-rc4 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996) RIP: 0010:down_write+0x1a/0x50 Call Trace: start_creating+0x89/0x130 debugfs_create_dir+0x1b/0x130 nbd_start_device+0x13d/0x390 [nbd] nbd_genl_connect+0x42f/0x748 [nbd] genl_family_rcv_msg_doit.isra.0+0xec/0x150 genl_rcv_msg+0xe5/0x1e0 netlink_rcv_skb+0x55/0x100 genl_rcv+0x29/0x40 netlink_unicast+0x1a8/0x250 netlink_sendmsg+0x21b/0x430 ____sys_sendmsg+0x2a4/0x2d0 ___sys_sendmsg+0x81/0xc0 __sys_sendmsg+0x62/0xb0 __x64_sys_sendmsg+0x1f/0x30 do_syscall_64+0x3b/0xc0 entry_SYSCALL_64_after_hwframe+0x44/0xae Modules linked in: nbd(E-) Signed-off-by: Hou Tao Signed-off-by: Yu Kuai Reviewed-by: Josef Bacik Link: https://lore.kernel.org/r/20220521073749.3146892-2-yukuai3@huawei.com Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- drivers/block/nbd.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index 510e75435c43..f3425e51a54b 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -2446,6 +2446,12 @@ static void __exit nbd_cleanup(void) struct nbd_device *nbd; LIST_HEAD(del_list); + /* + * Unregister netlink interface prior to waiting + * for the completion of netlink commands. + */ + genl_unregister_family(&nbd_genl_family); + nbd_dbg_close(); mutex_lock(&nbd_index_mutex); @@ -2461,7 +2467,6 @@ static void __exit nbd_cleanup(void) } idr_destroy(&nbd_index_idr); - genl_unregister_family(&nbd_genl_family); unregister_blkdev(NBD_MAJOR, "nbd"); } -- 2.35.1