[PATCH 3.16 057/204] btrfs: prevent to set invalid default subvolid

From: Ben Hutchings
Date: Thu Dec 28 2017 - 12:34:42 EST

3.16.52-rc1 review patch. If anyone has any objections, please let me know.


From: satoru takeuchi <satoru.takeuchi@xxxxxxxxx>

commit 6d6d282932d1a609e60dc4467677e0e863682f57 upstream.

`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: 6ef5ed0d386b ("Btrfs: add ioctl and incompat flag to set the default mount subvol")
Signed-off-by: Satoru Takeuchi <satoru.takeuchi@xxxxxxxxx>
Reviewed-by: Qu Wenruo <quwenruo.btrfs@xxxxxxx>
Reviewed-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
fs/btrfs/ioctl.c | 4 ++++
1 file changed, 4 insertions(+)

--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3980,6 +3980,10 @@ static long btrfs_ioctl_default_subvol(s
ret = PTR_ERR(new_root);
goto out;
+ if (!is_fstree(new_root->objectid)) {
+ ret = -ENOENT;
+ goto out;
+ }

path = btrfs_alloc_path();
if (!path) {