[Devel] Re: [patch 05/10] add "permit user mounts in new namespace" clone flag

[Miklos Szeredi]

> > > > > Also for bind-mount and remount operations the flag has to be propagated
> > > > > down its propagation tree.  Otherwise a unpriviledged mount in a shared
> > > > > mount wont get reflected in its peers and slaves, leading to unidentical
> > > > > shared-subtrees.
> > > > 
> > > > That's an interesting question.  Do we want shared mounts to be
> > > > totally identical, including mnt_flags?  It doesn't look as if
> > > > do_remount() guarantees that currently.
> > > 
> > > Depends on the semantics of each of the flags. Some flags like of the
> > > read/write flag, would not interfere with the propagation semantics
> > > AFAICT.  But this one certainly seems to interfere.
> > 
> > That depends.  Current patches check the "unprivileged submounts
> > allowed under this mount" flag only on the requested mount and not on
> > the propagated mounts.  Do you see a problem with this?
> 
> Don't see a problem if the flag is propagated to all peers and slave
> mounts. 
> 
> If not, I see a problem. What if the propagated mount has its flag set
> to not do un-priviledged mounts, whereas the requested mount has it
> allowed?

Then the mount is allowed.

It is up to the sysadmin/distro to design set up the propagations in a
way that this is not a problem.

I think it would be much less clear conceptually, if unprivileged
mounting would have to check propagations as well.

Miklos