Re: Possible bufferoverflow condition in lpr, xterm and xload

[juphoff () tarsier cv nrao edu (Jeff Uphoff)]

"MA" == Mike Acar <mike () contract kent edu> writes:

MA> Speaking of suid binaries, *why* are /bin/mount and /bin/umount suid?
MA> These shouldn't be run by anybody but the superuser.

Linux supports the concept of user-mountable filesystems (via the option
specification "user" in /etc/fstab), allowing non-root users to mount
and unmount e.g. removable media like CD-ROM's and floppies.  This
functionality is obviously not available unless mount/umount are suid
root.

One thing to note about the "user" option in Linux is that once a user
mounts one of these filesystems, *any* non-root user can unmount it
(unless it's busy).

I wrote a patch, sometime in '93, that tracked what user mounted such an
FS and only allowed that user--or root, of course--to unmount said
filesystem.  I never submitted this patch to the util. maintainers (I
used it extensively locally, however), but since it looks like
mount/umount are about to get a bit of a rewrite perhaps I should update
it and submit it....

--Up.

--
Jeff Uphoff - systems/network admin.  |  juphoff () nrao edu
National Radio Astronomy Observatory  |  juphoff () bofh org uk
Charlottesville, VA, USA              |  jeff.uphoff () linux org
    PGP key available at: http://www.cv.nrao.edu/~juphoff/