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

[Ram Pai <linuxram@us.ibm.com>]

> 
> "Serge E. Hallyn" <serue@us.ibm.com> writes:
> 
> > Quoting Miklos Szeredi (miklos@szeredi.hu):
> >> From: Miklos Szeredi <mszeredi@suse.cz>
> >> 
> >> If CLONE_NEWNS and CLONE_NEWNS_USERMNT are given to clone(2) or
> >> unshare(2), then allow user mounts within the new namespace.
> >> 
> >> This is not flexible enough, because user mounts can't be enabled
> for
> >> the initial namespace.
> >> 
> >> The remaining clone bits also getting dangerously few...
> >> 
> >> Alternatives are:
> >> 
> >>   - prctl() flag
> >>   - setting through the containers filesystem
> >
> > Sorry, I know I had mentioned it, but this is definately my least
> > favorite approach.
> >
> > Curious whether are any other suggestions/opinions from the
> containers
> > list?
> 
> Given the existence of shared subtrees allowing/denying this at the
> mount
> namespace level is silly and wrong.
> 
> If we need more than just the filesystem permission checks can we
> make it a mount flag settable with mount and remount that allows
> non-privileged users the ability to create mount points under it
> in directories they have full read/write access to.

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.

RP


> 
> I don't like the use of clone flags for this purpose but in this
> case the shared subtress are a much more fundamental reasons for not
> doing this at the namespace level.
> 
> Eric
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