Re: [PATCH] private mounts

Ram
2005-04-25T06:41:54Z

On Sun, 2005-04-24 at 23:00, Miklos Szeredi wrote:
> > >
> > > ... is the same as for the same question with "set of mounts" replaced
> > > with "environment variables".
> >
> > Not quite.
> >
> > After changing environment variables in .profile, you can copy them to
> > other shells using ". ~/.profile".
> >
> > There is no analogous mechanism to copy namespaces.
> >
> > I agree with you that Miklos' patch is not the right way to do it.
>
> I'm not sure that it is either. But, see bellow...
>
> > Much better is the proposal to make namespaces first-class objects,
> > that can be switched to. Then users can choose to have themselves a
> > namespace containing their private mounts, if they want it, with
> > login/libpam or even a program run from .profile switching into it.
>
> It would be good if it could be done just in libpam. But that would
> require every libpam user to call into it after the fork() or
> whatever, so unshare() and join_namespace() don't mess up the server
> running environment.
>
> If not, then it would mean modifying numerous programs, having these
> modifications integrated, then having distributions pick up the
> changes, etc. I would imagine quite a long cycle for this to be
> acutally useful.
>
> > While users can be allowed to create their own namespaces which affect
> > the path traversal of their _own_ directories, it's important that the
> > existence of such namespaces cannot affect path traversal of other
> > directories such as /etc, or /autofs/whatever - and that creation of
> > namespaces by a user cannot prevent the unmounting of a non-user
> > filesystem either.
> >
> > The way to do that is shared subtrees, or something along those lines.
>
> Yes, but we would be achieving essentially the same as my patch, just
> with more complexity. And my patch achieves what FUSE does in 2 lines
> of code, namely hide the mount from other users by returning -EACCESS
> in case fsuid does not mach the mount owner.
>

I have not yet sure how invisible mount can be used to solve the FUSE
problem.

Again my understanding of the basic requirement of FUSE is:

1. A user being able to setup his own VFS-mount environment which
is only visible to the user.
2. The same user being able to see exactly the same VFS-mount
environment from any login session.

RP

> I aggree that your solution is more flexible, but it's also hugely
> more complex. If somebody want's to implement it, fine. But don't
> expect me to do it, unless some company hires my for fs development
> (hint, hint ;)

>
> Thanks,
> Miklos
> -
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