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 3686DC433EF for ; Mon, 13 Jun 2022 11:47:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1355999AbiFMLrk (ORCPT ); Mon, 13 Jun 2022 07:47:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43024 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1357284AbiFMLp4 (ORCPT ); Mon, 13 Jun 2022 07:45:56 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F38014A917; Mon, 13 Jun 2022 03:52:02 -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 dfw.source.kernel.org (Postfix) with ESMTPS id 76CF061260; Mon, 13 Jun 2022 10:52:02 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 852CDC34114; Mon, 13 Jun 2022 10:52:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1655117521; bh=TLt2ISmR0txA+0hD4ZQZypqhlcRJCmCMBvYonxUvWQg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=jY6AJd6uk1LWFvl13iaDK0iOaNB8QZdIbEgStN/CU24/vGzHrSRPmKbAooC5Fz/Ow Yhp3Tx/aMkGpZY20G2khZtUMoiuON/AMhuqnsOcID10ilYKHwachtq+L9vOLp91Op5 h6Qeyn55p8T8ZD1fxGb5L4sdHk0l3qSl2bd7eO9I= 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 5.4 393/411] nbd: fix race between nbd_alloc_config() and module removal Date: Mon, 13 Jun 2022 12:11:06 +0200 Message-Id: <20220613094940.452687698@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: stable@vger.kernel.org From: Yu Kuai [ Upstream commit c55b2b983b0fa012942c3eb16384b2b722caa810 ] When nbd module is being removing, nbd_alloc_config() may be called concurrently by nbd_genl_connect(), although try_module_get() will return false, but nbd_alloc_config() doesn't handle it. The race may lead to the leak of nbd_config and its related resources (e.g, recv_workq) and oops in nbd_read_stat() due to the unload of nbd module as shown below: BUG: kernel NULL pointer dereference, address: 0000000000000040 Oops: 0000 [#1] SMP PTI CPU: 5 PID: 13840 Comm: kworker/u17:33 Not tainted 5.14.0+ #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996) Workqueue: knbd16-recv recv_work [nbd] RIP: 0010:nbd_read_stat.cold+0x130/0x1a4 [nbd] Call Trace: recv_work+0x3b/0xb0 [nbd] process_one_work+0x1ed/0x390 worker_thread+0x4a/0x3d0 kthread+0x12a/0x150 ret_from_fork+0x22/0x30 Fixing it by checking the return value of try_module_get() in nbd_alloc_config(). As nbd_alloc_config() may return ERR_PTR(-ENODEV), assign nbd->config only when nbd_alloc_config() succeeds to ensure the value of nbd->config is binary (valid or NULL). Also adding a debug message to check the reference counter of nbd_config during module removal. Signed-off-by: Hou Tao Signed-off-by: Yu Kuai Reviewed-by: Josef Bacik Link: https://lore.kernel.org/r/20220521073749.3146892-3-yukuai3@huawei.com Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- drivers/block/nbd.c | 28 +++++++++++++++++++--------- 1 file changed, 19 insertions(+), 9 deletions(-) diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index f3425e51a54b..ef355f14ed2c 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -1457,15 +1457,20 @@ static struct nbd_config *nbd_alloc_config(void) { struct nbd_config *config; + if (!try_module_get(THIS_MODULE)) + return ERR_PTR(-ENODEV); + config = kzalloc(sizeof(struct nbd_config), GFP_NOFS); - if (!config) - return NULL; + if (!config) { + module_put(THIS_MODULE); + return ERR_PTR(-ENOMEM); + } + atomic_set(&config->recv_threads, 0); init_waitqueue_head(&config->recv_wq); init_waitqueue_head(&config->conn_wait); config->blksize = NBD_DEF_BLKSIZE; atomic_set(&config->live_connections, 0); - try_module_get(THIS_MODULE); return config; } @@ -1492,12 +1497,13 @@ static int nbd_open(struct block_device *bdev, fmode_t mode) mutex_unlock(&nbd->config_lock); goto out; } - config = nbd->config = nbd_alloc_config(); - if (!config) { - ret = -ENOMEM; + config = nbd_alloc_config(); + if (IS_ERR(config)) { + ret = PTR_ERR(config); mutex_unlock(&nbd->config_lock); goto out; } + nbd->config = config; refcount_set(&nbd->config_refs, 1); refcount_inc(&nbd->refs); mutex_unlock(&nbd->config_lock); @@ -1919,13 +1925,14 @@ static int nbd_genl_connect(struct sk_buff *skb, struct genl_info *info) nbd_put(nbd); return -EINVAL; } - config = nbd->config = nbd_alloc_config(); - if (!nbd->config) { + config = nbd_alloc_config(); + if (IS_ERR(config)) { mutex_unlock(&nbd->config_lock); nbd_put(nbd); printk(KERN_ERR "nbd: couldn't allocate config\n"); - return -ENOMEM; + return PTR_ERR(config); } + nbd->config = config; refcount_set(&nbd->config_refs, 1); set_bit(NBD_RT_BOUND, &config->runtime_flags); @@ -2461,6 +2468,9 @@ static void __exit nbd_cleanup(void) while (!list_empty(&del_list)) { nbd = list_first_entry(&del_list, struct nbd_device, list); list_del_init(&nbd->list); + if (refcount_read(&nbd->config_refs)) + printk(KERN_ERR "nbd: possibly leaking nbd_config (ref %d)\n", + refcount_read(&nbd->config_refs)); if (refcount_read(&nbd->refs) != 1) printk(KERN_ERR "nbd: possibly leaking a device\n"); nbd_put(nbd); -- 2.35.1