open_tree(..., OPEN_TREE_NAMESPACE) and
fsmount(..., FSMOUNT_NAMESPACE, ...) currently work on non-directories,
like regular files. That's bad for two reasons:
- It ends up mounting a regular file over the inherited namespace root,
which is a directory; mounting a non-directory over a directory is
normally explicitly forbidden, see for example do_move_mount()
- It causes setns() on the new namespace to set the cwd to a regular
file, which the rest of VFS does not expect
Fix it by restricting create_new_namespace() (which is used by both of
these flags) to directories.
Leave the behavior for OPEN_TREE_CLONE as-is, that seems unproblematic.
Fixes: 9b8a0ba682 ("mount: add OPEN_TREE_NAMESPACE")
Cc: Al Viro <[email protected]>
Cc: Christian Brauner <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: [email protected]
Signed-off-by: Jann Horn <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Jann Horn
805d5a2b79