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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, 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 04C6EC33CB6 for ; Fri, 17 Jan 2020 11:51:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D83402083E for ; Fri, 17 Jan 2020 11:51:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727195AbgAQLvH (ORCPT ); Fri, 17 Jan 2020 06:51:07 -0500 Received: from szxga07-in.huawei.com ([45.249.212.35]:35410 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726689AbgAQLvG (ORCPT ); Fri, 17 Jan 2020 06:51:06 -0500 Received: from DGGEMS411-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id A345CB9D861EFE57526B; Fri, 17 Jan 2020 19:51:03 +0800 (CST) Received: from huawei.com (10.175.124.28) by DGGEMS411-HUB.china.huawei.com (10.3.19.211) with Microsoft SMTP Server id 14.3.439.0; Fri, 17 Jan 2020 19:50:54 +0800 From: Sun Ke To: , , CC: , , Subject: [PATCH] nbd: fix potential NULL pointer fault in connect and disconnect process Date: Fri, 17 Jan 2020 19:50:05 +0800 Message-ID: <20200117115005.37006-1-sunke32@huawei.com> X-Mailer: git-send-email 2.17.2 MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.175.124.28] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Connect and disconnect a nbd device repeatedly, will cause NULL pointer fault. It will appear by the steps: 1. Connect the nbd device and disconnect it, but now nbd device is not disconnected totally. 2. Connect the same nbd device again immediately, it will fail in nbd_start_device with a EBUSY return value. 3. Wait a second to make sure the last config_refs is reduced and run nbd_config_put to disconnect the nbd device totally. 4. Start another process to open the nbd_device, config_refs will increase and at the same time disconnect it. To fix it, add a NBD_HAS_STARTED flag. Set it in nbd_start_device_ioctl and nbd_genl_connect if nbd device is started successfully. Clear it in nbd_config_put. Test it in nbd_genl_disconnect and nbd_genl_reconfigure. Signed-off-by: Sun Ke --- drivers/block/nbd.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index b4607dd96185..ddd364e208ab 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -83,6 +83,7 @@ struct link_dead_args { #define NBD_DESTROY_ON_DISCONNECT 0 #define NBD_DISCONNECT_REQUESTED 1 +#define NBD_HAS_STARTED 2 struct nbd_config { u32 flags; @@ -1215,6 +1216,7 @@ static void nbd_config_put(struct nbd_device *nbd) nbd->disk->queue->limits.discard_alignment = 0; blk_queue_max_discard_sectors(nbd->disk->queue, UINT_MAX); blk_queue_flag_clear(QUEUE_FLAG_DISCARD, nbd->disk->queue); + clear_bit(NBD_HAS_STARTED, &nbd->flags); mutex_unlock(&nbd->config_lock); nbd_put(nbd); @@ -1290,6 +1292,8 @@ static int nbd_start_device_ioctl(struct nbd_device *nbd, struct block_device *b ret = nbd_start_device(nbd); if (ret) return ret; + else + set_bit(NBD_HAS_STARTED, &nbd->flags); if (max_part) bdev->bd_invalidated = 1; @@ -1961,6 +1965,7 @@ static int nbd_genl_connect(struct sk_buff *skb, struct genl_info *info) mutex_unlock(&nbd->config_lock); if (!ret) { set_bit(NBD_RT_HAS_CONFIG_REF, &config->runtime_flags); + set_bit(NBD_HAS_STARTED, &nbd->flags); refcount_inc(&nbd->config_refs); nbd_connect_reply(info, nbd->index); } @@ -2008,6 +2013,14 @@ static int nbd_genl_disconnect(struct sk_buff *skb, struct genl_info *info) index); return -EINVAL; } + + if (!test_bit(NBD_HAS_STARTED, &nbd->flags)) { + mutex_unlock(&nbd_index_mutex); + printk(KERN_ERR "nbd: device at index %d failed to start\n", + index); + return -EBUSY; + } + if (!refcount_inc_not_zero(&nbd->refs)) { mutex_unlock(&nbd_index_mutex); printk(KERN_ERR "nbd: device at index %d is going down\n", @@ -2049,6 +2062,14 @@ static int nbd_genl_reconfigure(struct sk_buff *skb, struct genl_info *info) index); return -EINVAL; } + + if (!test_bit(NBD_HAS_STARTED, &nbd->flags)) { + mutex_unlock(&nbd_index_mutex); + printk(KERN_ERR "nbd: device at index %d failed to start\n", + index); + return -EBUSY; + } + if (!refcount_inc_not_zero(&nbd->refs)) { mutex_unlock(&nbd_index_mutex); printk(KERN_ERR "nbd: device at index %d is going down\n", -- 2.17.2