From: Yu Kuai <yukuai3@xxxxxxxxxx>
If device support rename, for example dm, following concurrent scenario
is possible:
t1: mount t2: rename
mount_bdev
blkdev_get_by_path
lookup_bdev(path, &dev);
dm_rename
// change device name
blkdev_get_by_dev
...
vfs_create_mount
alloc_vfsmnt
// mnt->mnt_devname is set to old name
Test cmd:
dmsetup create test1 --table "0 100000 linear /dev/sda 0"
mkfs.ext2 -F /dev/mapper/test1
mount /dev/mapper/test1 /mnt/test &
dmsetup rename test1 test2
Test result(If the above scenario triggers):
mount will show test1 is mounted:
[root@localhost ~]# mount | grep test
/dev/mapper/test1 on /mnt/test type ext2 (rw,relatime,errors=continue,user_xattr,acl)
while lsblk show test2 is mounted:
[root@localhost ~]# lsblk /dev/sda
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 100G 0 disk
└─test2 252:0 0 48.8M 0 dm /mnt/test
Furthermore, if a new device with name test1 is created, lsblk will show
that it's mounted:
[root@localhost ~]# dmsetup create test1 --table "0 100000 linear /dev/sdb 0" && lsblk /dev/sdb
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sdb 8:16 0 10G 0 disk
└─test1 252:1 0 48.8M 0 dm /mnt/test
Fix the problem by checking dev_name again after bdev if found by
blkdev_get_by_path() in mount_bdev().
Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
---
changes in v2: rebase to latest version
fs/super.c | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
diff --git a/fs/super.c b/fs/super.c
index 734ed584a946..c738da299fc1 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -1341,6 +1341,20 @@ static int test_bdev_super(struct super_block *s, void *data)
return !(s->s_iflags & SB_I_RETIRED) && (void *)s->s_bdev == data;
}
+static int check_dev_name(struct block_device *bdev, const char *dev_name)
+{
+ dev_t dev;
+ int error = lookup_bdev(dev_name, &dev);
+
+ if (error)
+ return error;
+
+ if (dev != bdev->bd_dev)
+ return -EBUSY;
+
+ return 0;
+}
+
struct dentry *mount_bdev(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data,
int (*fill_super)(struct super_block *, void *, int))
@@ -1357,6 +1371,15 @@ struct dentry *mount_bdev(struct file_system_type *fs_type,
if (IS_ERR(bdev))
return ERR_CAST(bdev);
+ /*
+ * Some drivers support device rename, for example dm, make sure the
+ * right bdev is found, otherwise inconsistent device and mountpoint
+ * will be shown in /proc/mounts.
+ */
+ error = check_dev_name(bdev, dev_name);
+ if (error)
+ goto error_bdev;
+
/*
* once the super is inserted into the list by sget, s_umount
* will protect the lockfs code from trying to start a snapshot
--
2.31.1
