Commit 32c39e8a authored by Yu Kuai's avatar Yu Kuai Committed by Zheng Zengkai
Browse files

block: fix use after free for bd_holder_dir 

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I60Q98
CVE: NA

--------------------------------

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 = 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().

Link: https://lore.kernel.org/all/20221103025541.1875809-3-yukuai1@huaweicloud.com/


Signed-off-by: default avatarYu Kuai <yukuai3@huawei.com>
Reviewed-by: default avatarJason Yan <yanaijie@huawei.com>
Signed-off-by: default avatarZheng Zengkai <zhengzengkai@huawei.com>
parent 1f4bac39

fs/block_dev.c

+19 −7
Original line number Diff line number Diff line
@@ -1264,16 +1264,31 @@ int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk) 
	struct bd_holder_disk *holder;

	int ret = 0;



	mutex_lock(&bdev->bd_mutex);

	/*

	 * bdev could be deleted beneath us which would implicitly destroy

	 * the holder directory.  Hold on to it.

	 */

	down_read(&bdev->bd_disk->lookup_sem);

	if (!(disk->flags & GENHD_FL_UP)) {

		up_read(&bdev->bd_disk->lookup_sem);

		return -ENODEV;

	}



	kobject_get(bdev->bd_part->holder_dir);

	up_read(&bdev->bd_disk->lookup_sem);



	mutex_lock(&bdev->bd_mutex);

	WARN_ON_ONCE(!bdev->bd_holder);



	/* FIXME: remove the following once add_disk() handles errors */

	if (WARN_ON(!disk->slave_dir || !bdev->bd_part->holder_dir))

	if (WARN_ON(!disk->slave_dir || !bdev->bd_part->holder_dir)) {

		kobject_put(bdev->bd_part->holder_dir);

		goto out_unlock;

	}



	holder = bd_find_holder_disk(bdev, disk);

	if (holder) {

		kobject_put(bdev->bd_part->holder_dir);

		holder->refcnt++;

		goto out_unlock;

	}
@@ -1295,11 +1310,6 @@ int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk) 
	ret = add_symlink(bdev->bd_part->holder_dir, &disk_to_dev(disk)->kobj);

	if (ret)

		goto out_del;

	/*

	 * bdev could be deleted beneath us which would implicitly destroy

	 * the holder directory.  Hold on to it.

	 */

	kobject_get(bdev->bd_part->holder_dir);



	list_add(&holder->list, &bdev->bd_holder_disks);

	goto out_unlock;
@@ -1310,6 +1320,8 @@ int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk) 
	kfree(holder);

out_unlock:

	mutex_unlock(&bdev->bd_mutex);

	if (ret)

		kobject_put(bdev->bd_part->holder_dir);

	return ret;

}

EXPORT_SYMBOL_GPL(bd_link_disk_holder);