Btrfs: do not delete a subvolume which is in a R/O subvolume

Step to reproduce:
 # mkfs.btrfs <disk>
 # mount <disk> <mnt>
 # btrfs sub create <mnt>/subv0
 # btrfs sub snap <mnt> <mnt>/subv0/snap0
 # change <mnt>/subv0 from R/W to R/O
 # btrfs sub del <mnt>/subv0/snap0

We deleted the snapshot successfully. I think we should not be able to delete
the snapshot since the parent subvolume is R/O.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>

1 files changed, 5 insertions, 5 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index dd8e3448fe8f..5a72896bd769 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2095,13 +2095,13 @@ static noinline int btrfs_ioctl_snap_destroy(struct file *file,
                 err = inode_permission(inode, MAY_WRITE | MAY_EXEC);
                 if (err)
                         goto out_dput;
-
-                /* check if subvolume may be deleted by a non-root user */
-                err = btrfs_may_delete(dir, dentry, 1);
-                if (err)
-                        goto out_dput;
         }
 
+        /* check if subvolume may be deleted by a user */
+        err = btrfs_may_delete(dir, dentry, 1);
+        if (err)
+                goto out_dput;
+
         if (btrfs_ino(inode) != BTRFS_FIRST_FREE_OBJECTID) {
                 err = -EINVAL;
                 goto out_dput;