Re: Upstream first policy

[ebiederm@xmission.com (Eric W. Biederman)]

Weird.  Somehow I only got a copy of this from lkml.

Alan Cox <alan@lxorguk.ukuu.org.uk> writes:

>> time.  If pathnames were not fundamentally important we could apply
>> a patch like the one below and allow unprivileged users to unshare
>> the mount namespace and mount filesystems wherever.  There is nothing
>> fundamental about those operations that require root privileges except
>> that you are manipulating the pathnames of objects.
>
> And in a purely SELinux enviromnment your patch would work out because
> you could use labels to control this stuff.
>  
>
>> -	if (!capable(CAP_SYS_ADMIN))
>> -		return -EPERM;
>> -
>
> It does raise the question about whether you can do it if you had a
> namespace property of "ignore suidness". I'm not sure thats enough
> however.

The long term plan is to change that to.

	if (nscapable(mnt_ns->user_ns, CAP_SYS_ADMIN))
		return -EPERM.

That is.
- Create a new user/credential namespace (ultimately an unprivileged operation).
- Have the root user of the new user namespace create a new mount namespace.
- Over that new mount namespace the root user of the new user namespace
  has full control.

It is a little convoluted but it maintains backwards compatibility.  Unfortunately
there is still a long ways to go before we get there.

Eric