Re: [patch] mlock-as-nonroot revisted

[Andrea Arcangeli <andrea@suse.de>]

On Tue, Aug 03, 2004 at 05:13:56PM -0400, Rik van Riel wrote:
> On Tue, 3 Aug 2004, Andrea Arcangeli wrote:
> 
> > > -	if (shmflg & SHM_HUGETLB)
> > > +	if (shmflg & SHM_HUGETLB) {
> > > +		/* hugetlb_zero_setup takes care of mlock user accounting */
> > >  		file = hugetlb_zero_setup(size);
> > > +		shp->mlock_user = current->user;
> > > +	} else {
> 
> > where do you change mlock_user in chown?
> 
> You don't.  Normal users aren't allowed to chown each
> other's files, nor are they allowed to "give away" one
> of their files to somebody else.
> 
> On unlock the quota gets deducted from the user who
> created the hugetlbfs file.
> 
> This means there shouldn't be security issues with this
> approach.  Let me know if I've overlooked one.

I agree there aren't security issues, but it's still very wrong to
charge the old user if the admin gives the locked ram to a new user.
This erratic behaviour shows how much the rlimit approch is flawed for
named fs objects that have nothing to do with the transient task that
created them.