From patchwork Fri Jul 7 03:15:34 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: zhongjinghua X-Patchwork-Id: 13304348 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 796D2EB64D9 for ; Fri, 7 Jul 2023 03:18:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231835AbjGGDSX (ORCPT ); Thu, 6 Jul 2023 23:18:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41336 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230159AbjGGDST (ORCPT ); Thu, 6 Jul 2023 23:18:19 -0400 Received: from dggsgout12.his.huawei.com (dggsgout12.his.huawei.com [45.249.212.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 99B601BFC; Thu, 6 Jul 2023 20:18:17 -0700 (PDT) Received: from mail02.huawei.com (unknown [172.30.67.143]) by dggsgout12.his.huawei.com (SkyGuard) with ESMTP id 4Qxz9p704Hz4f3jY9; Fri, 7 Jul 2023 11:18:06 +0800 (CST) Received: from huaweicloud.com (unknown [10.175.127.227]) by APP4 (Coremail) with SMTP id gCh0CgD3mp7vg6dk0X+NNQ--.406S5; Fri, 07 Jul 2023 11:18:09 +0800 (CST) From: Zhong Jinghua To: josef@toxicpanda.com, axboe@kernel.dk Cc: linux-block@vger.kernel.org, nbd@other.debian.org, linux-kernel@vger.kernel.org, zhongjinghua@huaweicloud.com, yi.zhang@huawei.com, yukuai3@huawei.com Subject: [PATCH -next 1/3] nbd: fold nbd config initialization into nbd_alloc_config() Date: Fri, 7 Jul 2023 11:15:34 +0800 Message-Id: <20230707031536.666482-2-zhongjinghua@huaweicloud.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20230707031536.666482-1-zhongjinghua@huaweicloud.com> References: <20230707031536.666482-1-zhongjinghua@huaweicloud.com> MIME-Version: 1.0 X-CM-TRANSID: gCh0CgD3mp7vg6dk0X+NNQ--.406S5 X-Coremail-Antispam: 1UD129KBjvJXoWxXw43urWxZF48Cr1DXr4ruFg_yoW5AFy5pF 45AFWUK3y8JF4fGFWvy3s7uFy3twn7KFy7Gry7J3ZYyr9akrWakrykG34fZFWUJr9rJF15 JFWrWFyIkFyxWrUanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUU9m14x267AKxVW5JVWrJwAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2048vs2IY020E87I2jVAFwI0_Jr4l82xGYIkIc2 x26xkF7I0E14v26r1I6r4UM28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48ve4kI8wA2z4x0 Y4vE2Ix0cI8IcVAFwI0_tr0E3s1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI0_Gr1j6F4UJw A2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x0267AKxVW0oVCq3wAS 0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG6I80ewAv7VC0I7IYx2 IY67AKxVWUJVWUGwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFVCjc4AY6r1j6r4UM4x0 Y48IcxkI7VAKI48JM4x0x7Aq67IIx4CEVc8vx2IErcIFxwCF04k20xvY0x0EwIxGrwCFx2 IqxVCFs4IE7xkEbVWUJVW8JwC20s026c02F40E14v26r1j6r18MI8I3I0E7480Y4vE14v2 6r106r1rMI8E67AF67kF1VAFwI0_Jw0_GFylIxkGc2Ij64vIr41lIxAIcVC0I7IYx2IY67 AKxVWUJVWUCwCI42IY6xIIjxv20xvEc7CjxVAFwI0_Gr0_Cr1lIxAIcVCF04k26cxKx2IY s7xG6r1j6r1xMIIF0xvEx4A2jsIE14v26r1j6r4UMIIF0xvEx4A2jsIEc7CjxVAFwI0_Gr 0_Gr1UYxBIdaVFxhVjvjDU0xZFpf9x0JUqAp5UUUUU= X-CM-SenderInfo: x2kr0wpmlqwxtxd6x35dzhxuhorxvhhfrp/ X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org From: Zhong Jinghua There are no functional changes, make the code cleaner and prepare to fix null-ptr-dereference while accessing 'nbd->config'. Signed-off-by: Zhong Jinghua Reviewed-by: Yu Kuai --- drivers/block/nbd.c | 41 +++++++++++++++++++---------------------- 1 file changed, 19 insertions(+), 22 deletions(-) diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index cb38477f359f..cd6d78914954 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -1526,17 +1526,20 @@ static int nbd_ioctl(struct block_device *bdev, fmode_t mode, return error; } -static struct nbd_config *nbd_alloc_config(void) +static int nbd_alloc_and_init_config(struct nbd_device *nbd) { struct nbd_config *config; + if (WARN_ON(nbd->config)) + return -EINVAL; + if (!try_module_get(THIS_MODULE)) - return ERR_PTR(-ENODEV); + return -ENODEV; config = kzalloc(sizeof(struct nbd_config), GFP_NOFS); if (!config) { module_put(THIS_MODULE); - return ERR_PTR(-ENOMEM); + return -ENOMEM; } atomic_set(&config->recv_threads, 0); @@ -1544,7 +1547,10 @@ static struct nbd_config *nbd_alloc_config(void) init_waitqueue_head(&config->conn_wait); config->blksize_bits = NBD_DEF_BLKSIZE_BITS; atomic_set(&config->live_connections, 0); - return config; + nbd->config = config; + refcount_set(&nbd->config_refs, 1); + + return 0; } static int nbd_open(struct block_device *bdev, fmode_t mode) @@ -1563,21 +1569,17 @@ static int nbd_open(struct block_device *bdev, fmode_t mode) goto out; } if (!refcount_inc_not_zero(&nbd->config_refs)) { - struct nbd_config *config; - mutex_lock(&nbd->config_lock); if (refcount_inc_not_zero(&nbd->config_refs)) { mutex_unlock(&nbd->config_lock); goto out; } - config = nbd_alloc_config(); - if (IS_ERR(config)) { - ret = PTR_ERR(config); + ret = nbd_alloc_and_init_config(nbd); + if (ret) { 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); if (max_part) @@ -1979,22 +1981,17 @@ static int nbd_genl_connect(struct sk_buff *skb, struct genl_info *info) pr_err("nbd%d already in use\n", index); return -EBUSY; } - if (WARN_ON(nbd->config)) { - mutex_unlock(&nbd->config_lock); - nbd_put(nbd); - return -EINVAL; - } - config = nbd_alloc_config(); - if (IS_ERR(config)) { + + ret = nbd_alloc_and_init_config(nbd); + if (ret) { mutex_unlock(&nbd->config_lock); nbd_put(nbd); pr_err("couldn't allocate config\n"); - return PTR_ERR(config); + return ret; } - nbd->config = config; - refcount_set(&nbd->config_refs, 1); - set_bit(NBD_RT_BOUND, &config->runtime_flags); + config = nbd->config; + set_bit(NBD_RT_BOUND, &config->runtime_flags); ret = nbd_genl_size_set(info, nbd); if (ret) goto out; From patchwork Fri Jul 7 03:15:35 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: zhongjinghua X-Patchwork-Id: 13304347 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 078A7C001B0 for ; Fri, 7 Jul 2023 03:18:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231450AbjGGDSO (ORCPT ); Thu, 6 Jul 2023 23:18:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41300 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230159AbjGGDSN (ORCPT ); Thu, 6 Jul 2023 23:18:13 -0400 Received: from dggsgout11.his.huawei.com (dggsgout11.his.huawei.com [45.249.212.51]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5827E1BFC; Thu, 6 Jul 2023 20:18:12 -0700 (PDT) Received: from mail02.huawei.com (unknown [172.30.67.143]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTP id 4Qxz9r5JxPz4f3wR2; Fri, 7 Jul 2023 11:18:08 +0800 (CST) Received: from huaweicloud.com (unknown [10.175.127.227]) by APP4 (Coremail) with SMTP id gCh0CgD3mp7vg6dk0X+NNQ--.406S6; Fri, 07 Jul 2023 11:18:09 +0800 (CST) From: Zhong Jinghua To: josef@toxicpanda.com, axboe@kernel.dk Cc: linux-block@vger.kernel.org, nbd@other.debian.org, linux-kernel@vger.kernel.org, zhongjinghua@huaweicloud.com, yi.zhang@huawei.com, yukuai3@huawei.com Subject: [PATCH -next 2/3] nbd: factor out a helper to get nbd_config without holding 'config_lock' Date: Fri, 7 Jul 2023 11:15:35 +0800 Message-Id: <20230707031536.666482-3-zhongjinghua@huaweicloud.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20230707031536.666482-1-zhongjinghua@huaweicloud.com> References: <20230707031536.666482-1-zhongjinghua@huaweicloud.com> MIME-Version: 1.0 X-CM-TRANSID: gCh0CgD3mp7vg6dk0X+NNQ--.406S6 X-Coremail-Antispam: 1UD129KBjvJXoWxZr1xJr47Cr45CF45Ar1kZrb_yoW5tFykpF 4UAFW5KrWUGF45uFWv9397WFnxtwn2gFyxGry7G3ZYvF9xArWakF1kK34xAa17Gr97JF45 JFWrWFySka47KrUanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUU9m14x267AKxVWrJVCq3wAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2048vs2IY020E87I2jVAFwI0_Jryl82xGYIkIc2 x26xkF7I0E14v26r4j6ryUM28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48ve4kI8wA2z4x0 Y4vE2Ix0cI8IcVAFwI0_tr0E3s1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI0_Gr1j6F4UJw A2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x0267AKxVW0oVCq3wAS 0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG6I80ewAv7VC0I7IYx2 IY67AKxVWUJVWUGwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFVCjc4AY6r1j6r4UM4x0 Y48IcxkI7VAKI48JM4x0x7Aq67IIx4CEVc8vx2IErcIFxwCF04k20xvY0x0EwIxGrwCFx2 IqxVCFs4IE7xkEbVWUJVW8JwC20s026c02F40E14v26r1j6r18MI8I3I0E7480Y4vE14v2 6r106r1rMI8E67AF67kF1VAFwI0_Jw0_GFylIxkGc2Ij64vIr41lIxAIcVC0I7IYx2IY67 AKxVWUJVWUCwCI42IY6xIIjxv20xvEc7CjxVAFwI0_Gr0_Cr1lIxAIcVCF04k26cxKx2IY s7xG6r1j6r1xMIIF0xvEx4A2jsIE14v26r1j6r4UMIIF0xvEx4A2jsIEc7CjxVAFwI0_Gr 0_Gr1UYxBIdaVFxhVjvjDU0xZFpf9x0JUc6pPUUUUU= X-CM-SenderInfo: x2kr0wpmlqwxtxd6x35dzhxuhorxvhhfrp/ X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org From: Zhong Jinghua There are no functional changes, just to make code cleaner and prepare to fix null-ptr-dereference while accessing 'nbd->config'. Signed-off-by: Zhong Jinghua Reviewed-by: Yu Kuai --- drivers/block/nbd.c | 27 +++++++++++++++++++-------- 1 file changed, 19 insertions(+), 8 deletions(-) diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index cd6d78914954..7186a9a49445 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -393,6 +393,14 @@ static u32 req_to_nbd_cmd_type(struct request *req) } } +static struct nbd_config *nbd_get_config_unlocked(struct nbd_device *nbd) +{ + if (refcount_inc_not_zero(&nbd->config_refs)) + return nbd->config; + + return NULL; +} + static enum blk_eh_timer_return nbd_xmit_timeout(struct request *req) { struct nbd_cmd *cmd = blk_mq_rq_to_pdu(req); @@ -407,13 +415,13 @@ static enum blk_eh_timer_return nbd_xmit_timeout(struct request *req) return BLK_EH_DONE; } - if (!refcount_inc_not_zero(&nbd->config_refs)) { + config = nbd_get_config_unlocked(nbd); + if (!config) { cmd->status = BLK_STS_TIMEOUT; __clear_bit(NBD_CMD_INFLIGHT, &cmd->flags); mutex_unlock(&cmd->lock); goto done; } - config = nbd->config; if (config->num_connections > 1 || (config->num_connections == 1 && nbd->tag_set.timeout)) { @@ -975,12 +983,12 @@ static int nbd_handle_cmd(struct nbd_cmd *cmd, int index) struct nbd_sock *nsock; int ret; - if (!refcount_inc_not_zero(&nbd->config_refs)) { + config = nbd_get_config_unlocked(nbd); + if (!config) { dev_err_ratelimited(disk_to_dev(nbd->disk), "Socks array is empty\n"); return -EINVAL; } - config = nbd->config; if (index >= config->num_connections) { dev_err_ratelimited(disk_to_dev(nbd->disk), @@ -1556,6 +1564,7 @@ static int nbd_alloc_and_init_config(struct nbd_device *nbd) static int nbd_open(struct block_device *bdev, fmode_t mode) { struct nbd_device *nbd; + struct nbd_config *config; int ret = 0; mutex_lock(&nbd_index_mutex); @@ -1568,7 +1577,9 @@ static int nbd_open(struct block_device *bdev, fmode_t mode) ret = -ENXIO; goto out; } - if (!refcount_inc_not_zero(&nbd->config_refs)) { + + config = nbd_get_config_unlocked(nbd); + if (!config) { mutex_lock(&nbd->config_lock); if (refcount_inc_not_zero(&nbd->config_refs)) { mutex_unlock(&nbd->config_lock); @@ -1584,7 +1595,7 @@ static int nbd_open(struct block_device *bdev, fmode_t mode) mutex_unlock(&nbd->config_lock); if (max_part) set_bit(GD_NEED_PART_SCAN, &bdev->bd_disk->state); - } else if (nbd_disconnected(nbd->config)) { + } else if (nbd_disconnected(config)) { if (max_part) set_bit(GD_NEED_PART_SCAN, &bdev->bd_disk->state); } @@ -2194,7 +2205,8 @@ static int nbd_genl_reconfigure(struct sk_buff *skb, struct genl_info *info) } mutex_unlock(&nbd_index_mutex); - if (!refcount_inc_not_zero(&nbd->config_refs)) { + config = nbd_get_config_unlocked(nbd); + if (!config) { dev_err(nbd_to_dev(nbd), "not configured, cannot reconfigure\n"); nbd_put(nbd); @@ -2202,7 +2214,6 @@ static int nbd_genl_reconfigure(struct sk_buff *skb, struct genl_info *info) } mutex_lock(&nbd->config_lock); - config = nbd->config; if (!test_bit(NBD_RT_BOUND, &config->runtime_flags) || !nbd->pid) { dev_err(nbd_to_dev(nbd), From patchwork Fri Jul 7 03:15:36 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: zhongjinghua X-Patchwork-Id: 13304349 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 3D007C001B0 for ; Fri, 7 Jul 2023 03:18:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232114AbjGGDSZ (ORCPT ); Thu, 6 Jul 2023 23:18:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41352 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231911AbjGGDST (ORCPT ); Thu, 6 Jul 2023 23:18:19 -0400 Received: from dggsgout12.his.huawei.com (dggsgout12.his.huawei.com [45.249.212.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 708351FCC; Thu, 6 Jul 2023 20:18:18 -0700 (PDT) Received: from mail02.huawei.com (unknown [172.30.67.143]) by dggsgout12.his.huawei.com (SkyGuard) with ESMTP id 4Qxz9q4pV4z4f3nx7; Fri, 7 Jul 2023 11:18:07 +0800 (CST) Received: from huaweicloud.com (unknown [10.175.127.227]) by APP4 (Coremail) with SMTP id gCh0CgD3mp7vg6dk0X+NNQ--.406S7; Fri, 07 Jul 2023 11:18:09 +0800 (CST) From: Zhong Jinghua To: josef@toxicpanda.com, axboe@kernel.dk Cc: linux-block@vger.kernel.org, nbd@other.debian.org, linux-kernel@vger.kernel.org, zhongjinghua@huaweicloud.com, yi.zhang@huawei.com, yukuai3@huawei.com Subject: [PATCH -next 3/3] nbd: fix null-ptr-dereference while accessing 'nbd->config' Date: Fri, 7 Jul 2023 11:15:36 +0800 Message-Id: <20230707031536.666482-4-zhongjinghua@huaweicloud.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20230707031536.666482-1-zhongjinghua@huaweicloud.com> References: <20230707031536.666482-1-zhongjinghua@huaweicloud.com> MIME-Version: 1.0 X-CM-TRANSID: gCh0CgD3mp7vg6dk0X+NNQ--.406S7 X-Coremail-Antispam: 1UD129KBjvJXoW7ZF4kXF1fAr1fKry7Ar1UZFb_yoW8tryDpF 4UAFy5G3yUJF43GFWkA348Wr15J3Z7AryxGry7G3s5Zr9xCrySyrykK34xXF1UAr9xJF45 JFWrGa4IkFy8GFUanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUU9m14x267AKxVWrJVCq3wAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2048vs2IY020E87I2jVAFwI0_JrWl82xGYIkIc2 x26xkF7I0E14v26ryj6s0DM28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48ve4kI8wA2z4x0 Y4vE2Ix0cI8IcVAFwI0_tr0E3s1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI0_Gr1j6F4UJw A2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x0267AKxVW0oVCq3wAS 0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG6I80ewAv7VC0I7IYx2 IY67AKxVWUJVWUGwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFVCjc4AY6r1j6r4UM4x0 Y48IcxkI7VAKI48JM4x0x7Aq67IIx4CEVc8vx2IErcIFxwCF04k20xvY0x0EwIxGrwCFx2 IqxVCFs4IE7xkEbVWUJVW8JwC20s026c02F40E14v26r1j6r18MI8I3I0E7480Y4vE14v2 6r106r1rMI8E67AF67kF1VAFwI0_Jw0_GFylIxkGc2Ij64vIr41lIxAIcVC0I7IYx2IY67 AKxVWUJVWUCwCI42IY6xIIjxv20xvEc7CjxVAFwI0_Gr0_Cr1lIxAIcVCF04k26cxKx2IY s7xG6r1j6r1xMIIF0xvEx4A2jsIE14v26r1j6r4UMIIF0xvEx4A2jsIEc7CjxVAFwI0_Gr 0_Gr1UYxBIdaVFxhVjvjDU0xZFpf9x0JUd8n5UUUUU= X-CM-SenderInfo: x2kr0wpmlqwxtxd6x35dzhxuhorxvhhfrp/ X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org From: Zhong Jinghua nbd->config = config and refcount_set(&nbd->config_refs, 1) in nbd_genl_connect may be out of order, causing config_refs to be set to 1 first, and then nbd_open accessing nbd->config reports a null pointer reference. T1 T2 vfs_open do_dentry_open blkdev_open blkdev_get __blkdev_get nbd_open nbd_get_config_unlocked genl_rcv_msg genl_family_rcv_msg genl_family_rcv_msg_doit nbd_genl_connect nbd_alloc_and_init_config // out of order execution refcount_set(&nbd->config_refs, 1); // 2 nbd->config // null point nbd->config = config; // 1 Fix it by adding a cpu memory barrier to guarantee sequential execution. Signed-off-by: Zhong Jinghua Reviewed-by: Yu Kuai --- drivers/block/nbd.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index 7186a9a49445..c410cf29fb0c 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -395,8 +395,16 @@ static u32 req_to_nbd_cmd_type(struct request *req) static struct nbd_config *nbd_get_config_unlocked(struct nbd_device *nbd) { - if (refcount_inc_not_zero(&nbd->config_refs)) + if (refcount_inc_not_zero(&nbd->config_refs)) { + /* + * Add smp_mb__after_atomic to ensure that reading nbd->config_refs + * and reading nbd->config is ordered. The pair is the barrier in + * nbd_alloc_and_init_config(), avoid nbd->config_refs is set + * before nbd->config. + */ + smp_mb__after_atomic(); return nbd->config; + } return NULL; } @@ -1555,7 +1563,15 @@ static int nbd_alloc_and_init_config(struct nbd_device *nbd) init_waitqueue_head(&config->conn_wait); config->blksize_bits = NBD_DEF_BLKSIZE_BITS; atomic_set(&config->live_connections, 0); + nbd->config = config; + /* + * Order refcount_set(&nbd->config_refs, 1) and nbd->config assignment, + * its pair is the barrier in nbd_get_config_unlocked(). + * So nbd_get_config_unlocked() won't see nbd->config as null after + * refcount_inc_not_zero() succeed. + */ + smp_mb__before_atomic(); refcount_set(&nbd->config_refs, 1); return 0;