btrfs: prevent to set invalid default subvolid

`btrfs sub set-default` succeeds to set an ID which isn't corresponding to any fs/file tree. If such the bad ID is set to a filesystem, we can't mount this filesystem without specifying `subvol` or `subvolid` mount options. Fixes: 6ef5ed0 ("Btrfs: add ioctl and incompat flag to set the default mount subvol") Cc: <[email protected]> Signed-off-by: Satoru Takeuchi <[email protected]> Reviewed-by: Qu Wenruo <[email protected]> Reviewed-by: David Sterba <[email protected]> Signed-off-by: David Sterba <[email protected]>
cail · Sep 26, 2017 · 6d6d282 · 6d6d282
1 parent ca6842b
commit 6d6d282
Showing 1 changed file with 4 additions and 0 deletions.
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
@@ -4057,6 +4057,10 @@ static long btrfs_ioctl_default_subvol(struct file *file, void __user *argp)
 		ret = PTR_ERR(new_root);
 		goto out;
 	}
+	if (!is_fstree(new_root->objectid)) {
+		ret = -ENOENT;
+		goto out;
+	}
 
 	path = btrfs_alloc_path();
 	if (!path) {