On Fri, Apr 14, 2023 at 04:06:03AM +0000, Trond Myklebust wrote: > > > > On Apr 13, 2023, at 23:51, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: > > > > On Fri, Apr 14, 2023 at 03:28:45AM +0000, Trond Myklebust wrote: > > > >> We already have support for directory file descriptors when mounting with move_mount(). Why not add a umountat() with similar support for the unmount side? > >> Then add a syscall to allow users with (e.g.) the CAP_DAC_OVERRIDE privilege to convert the mount-id into an O_PATH file descriptor. > > > > You can already do umount -l /proc/self/fd/69 if you have a descriptor. > > Converting mount-id to O_PATH... might be an interesting idea. > > A dedicated umountat() might avoid the need for the lazy flag, if it were allowed to close the descriptor on success for the special case of an empty path. No. It's a wrong abstraction layer, anyway - "close the descriptor" != "make the opened file close", nevermind that it's a very odd corner case that will cause a lot of headache down the road.
