Ronald G. Minnich wrote:
> On Fri, 23 Jul 1999, Kris Kennaway wrote:
> > On Thu, 22 Jul 1999, Ronald G. Minnich wrote:
> > > Are you saying that as an ordinary user I can mount something on top of
> > > /tmp, for example?
> > If the vfs.usermount sysctl is 1, and you have appropriate access to the
> > thing you're trying to mount (block device, etc).
>
> OK, so let's say it is 1. Let's say I have "appropriate access" to /tmp. I
> mount my own fs on /tmp. I now have read/write access to everything anyone
> writes to /tmp.
"Appropriate access" includes the idea that you need to own the mountpoint
directory. If you have a system that's so badly run that arbitrary users
own /tmp, then I'd say user mounts are the least of your problems :-)
> Or, let's say I don't have "appropriate access" to /tmp. Pick some other
> place. I mount my file system there for my files. Now everyone who wants
> can look for these user mounts and walk them at will. My private stuff is
> quite public.
Correct (unless you want your private stuff to be private, and chmod
your mountpoint's parent directory accordingly).
> But thanks for the note. I just now realized that if I add a private name
> space to v9fs (which is easy), and then turn on user mounts, user
> processes can have private name spaces on freebsd!
I can't wait to see the security problems that causes when setuid executables
assume that they only need to be worrying about one filesystem namespace.
:-)
- mark
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