From nobody Thu Apr 9 07:56:41 2026 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 D2ED5C4332F for ; Thu, 3 Nov 2022 02:34:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231165AbiKCCeK (ORCPT ); Wed, 2 Nov 2022 22:34:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33728 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231132AbiKCCeE (ORCPT ); Wed, 2 Nov 2022 22:34:04 -0400 Received: from dggsgout11.his.huawei.com (dggsgout11.his.huawei.com [45.249.212.51]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2756013E17; Wed, 2 Nov 2022 19:34:02 -0700 (PDT) Received: from mail02.huawei.com (unknown [172.30.67.169]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTP id 4N2nnw4J2Yzl6CY; Thu, 3 Nov 2022 10:31:48 +0800 (CST) Received: from huaweicloud.com (unknown [10.175.127.227]) by APP1 (Coremail) with SMTP id cCh0CgCXcXqWKGNjpCjdBA--.38653S6; Thu, 03 Nov 2022 10:34:00 +0800 (CST) From: Yu Kuai To: hch@lst.de, axboe@kernel.dk Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, yukuai3@huawei.com, yukuai1@huaweicloud.com, yi.zhang@huawei.com Subject: [PATCH 2/2] block: fix use after free for bd_holder_dir Date: Thu, 3 Nov 2022 10:55:41 +0800 Message-Id: <20221103025541.1875809-3-yukuai1@huaweicloud.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20221103025541.1875809-1-yukuai1@huaweicloud.com> References: <20221103025541.1875809-1-yukuai1@huaweicloud.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-CM-TRANSID: cCh0CgCXcXqWKGNjpCjdBA--.38653S6 X-Coremail-Antispam: 1UD129KBjvJXoW7tr1rGFyxAFWxAFy3Ar1DKFg_yoW8KFW5pa 9IgFyrtry8GFsrZrsrt347XrWjg3W8W3W8CFya9F4IvrsxJr4vvr17AFy7WF1xKrWIvFs0 qF1UX3yFvF1vkrJanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUU9m14x267AKxVWrJVCq3wAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2048vs2IY020E87I2jVAFwI0_Jryl82xGYIkIc2 x26xkF7I0E14v26r4j6ryUM28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48ve4kI8wA2z4x0 Y4vE2Ix0cI8IcVAFwI0_tr0E3s1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI0_Gr1j6F4UJw A2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x0267AKxVW0oVCq3wAS 0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG6I80ewAv7VC0I7IYx2 IY67AKxVWUJVWUGwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFVCjc4AY6r1j6r4UM4x0 Y48IcxkI7VAKI48JM4x0x7Aq67IIx4CEVc8vx2IErcIFxwCF04k20xvY0x0EwIxGrwCFx2 IqxVCFs4IE7xkEbVWUJVW8JwC20s026c02F40E14v26r1j6r18MI8I3I0E7480Y4vE14v2 6r106r1rMI8E67AF67kF1VAFwI0_JF0_Jw1lIxkGc2Ij64vIr41lIxAIcVC0I7IYx2IY67 AKxVWUJVWUCwCI42IY6xIIjxv20xvEc7CjxVAFwI0_Gr0_Cr1lIxAIcVCF04k26cxKx2IY s7xG6r1j6r1xMIIF0xvEx4A2jsIE14v26r1j6r4UMIIF0xvEx4A2jsIEc7CjxVAFwI0_Gr 0_Gr1UYxBIdaVFxhVjvjDU0xZFpf9x0JUc6pPUUUUU= X-CM-SenderInfo: 51xn3trlr6x35dzhxuhorxvhhfrp/ X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Yu Kuai Currently, the caller of bd_link_disk_holer() get 'bdev' by blkdev_get_by_dev(), which will look up 'bdev' by inode number 'dev'. Howerver, it's possible that del_gendisk() can be called currently, and 'bd_holder_dir' can be freed before bd_link_disk_holer() access it, thus use after free is triggered. t1: t2: bdev =3D blkdev_get_by_dev del_gendisk kobject_put(bd_holder_dir) kobject_free() bd_link_disk_holder Fix the problem by checking disk is still live and grabbing a reference to 'bd_holder_dir' first in bd_link_disk_holder(). Signed-off-by: Yu Kuai --- block/holder.c | 23 ++++++++++++++++------- 1 file changed, 16 insertions(+), 7 deletions(-) diff --git a/block/holder.c b/block/holder.c index 5fc68238ce3a..1c6c5b132a92 100644 --- a/block/holder.c +++ b/block/holder.c @@ -78,19 +78,32 @@ int bd_link_disk_holder(struct block_device *bdev, stru= ct gendisk *disk) if (bdev->bd_disk =3D=3D disk) return -EINVAL; =20 - mutex_lock(&disk->open_mutex); + /* + * del_gendisk drops the initial reference to bd_holder_dir, so we + * need to keep our own here to allow for cleanup past that point. + */ + mutex_lock(&bdev->bd_disk->open_mutex); + if (!disk_live(bdev->bd_disk)) { + mutex_unlock(&bdev->bd_disk->open_mutex); + return -ENODEV; + } =20 - WARN_ON_ONCE(!bdev->bd_holder); + kobject_get(bdev->bd_holder_dir); + mutex_unlock(&bdev->bd_disk->open_mutex); =20 + mutex_lock(&disk->open_mutex); + WARN_ON_ONCE(!bdev->bd_holder); holder =3D bd_find_holder_disk(bdev, disk); if (holder) { holder->refcnt++; + kobject_put(bdev->bd_holder_dir); goto out_unlock; } =20 holder =3D kzalloc(sizeof(*holder), GFP_KERNEL); if (!holder) { ret =3D -ENOMEM; + kobject_put(bdev->bd_holder_dir); goto out_unlock; } =20 @@ -101,16 +114,12 @@ int bd_link_disk_holder(struct block_device *bdev, st= ruct gendisk *disk) ret =3D __link_disk_holder(bdev, disk); if (ret) { kfree(holder); + kobject_put(bdev->bd_holder_dir); goto out_unlock; } } =20 list_add(&holder->list, &disk->slave_bdevs); - /* - * del_gendisk drops the initial reference to bd_holder_dir, so we need - * to keep our own here to allow for cleanup past that point. - */ - kobject_get(bdev->bd_holder_dir); =20 out_unlock: mutex_unlock(&disk->open_mutex); --=20 2.31.1