fixing busybox mount/umount to work with udisks

ralda at gmx.de ralda at gmx.de
Tue Jan 31 15:07:29 UTC 2012


Hi!

> > the uhelper (and non-root umount) stuff in a clean enough manner.
> 
>  I would really advise looking for notifications that are sent by the
> *kernel*, and add helpers there, instead of patching user-space tools.
> 
>  I'm even fairly sure mdev can be configured to do this.

May anybody be as kind to explain me which types of commands/actions
require such uhelper stuff? May be I'm doing something wrong as I never
needed such things ... as this I have no idea what kind of work shall
be done there. The only situation I stumbled about, was some NFS stuff.
Due to an unclean application solution it required some cleanup before
unmount to avoid lengthy application startup checks. After reorganizing
the application it was no more necessary.

Beside this in my opinion it is not required to have any non-root umount
stuff. Everything to unmount and cleanup can be done as root. When a
normal user requires to do an umount a simple suid wrapper may be
used. That wrapper needs to receive only a single parameter the name
of the mount point directory. That parameter may easily be
checked for validity and shall not introduce any new back doors or
security violences.

I have worked at several systems (including older Linux) where umount
was installed as suid root for this purpose. Any parameter except mount
point name was rejected if umount wasn't called as root. If either the
mount point directory was not accessible or the block device was not
read/writable by the user or the device had not been mounted with the
"user" flag the umount just denied the requests from normal users. So
no further logic/command was required to allow for user unmount. Where
has this logic gone? I missed the change in this and the reason why it
has been changed.

--
Harald


More information about the busybox mailing list