linux-kernel - Re: [PATCH v3] kernel: Conditionally support non-root users, groups and capabilities

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Message-ID: <20150210003301.GH4166@linux.vnet.ibm.com>
Date:	Mon, 9 Feb 2015 16:33:01 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	josh@...htriplett.org
Cc:	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Iulia Manda <iulia.manda21@...il.com>,
	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	Peter Zijlstra <peterz@...radead.org>,
	Michal Hocko <mhocko@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Serge Hallyn <serge.hallyn@...onical.com>,
	Darren Hart <dvhart@...ux.intel.com>,
	Tim Bird <tim.bird@...ymobile.com>
Subject: Re: [PATCH v3] kernel: Conditionally support non-root users, groups
 and capabilities

On Mon, Feb 09, 2015 at 03:42:08PM -0800, josh@...htriplett.org wrote:
> On Sun, Feb 08, 2015 at 10:05:25AM +0100, Geert Uytterhoeven wrote:
> > Thanks for the update!
> > 
> > Acked-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> 
> Thanks, Geert!
> 
> On Sun, Feb 08, 2015 at 08:02:17PM -0800, Paul E. McKenney wrote:
> > I presume that v4 will have your Signed-off-by.  ;-)
> > 
> > Testing on my rcutorture setup uncovered an additional required dependency,
> > please see patch at the end of this email.  With that fix, either separately
> > or merged into your patch:
> > 
> > Tested-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> > 
> > One question below about moving the definition of capable().  Either way:
> 
> Answer below.

And that answer makes sense to me!  Might be worth a mention in the
commit log (my apologies if it was mentioned and I missed it).

> > Reviewed-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> 
> Thanks, Paul!
> 
> Based on this feedback, as well as the feedback from others on prior
> versions that has since been addressed, once there's a v4 with the
> changes suggested by Paul (and the signoff and acks/reviews added), I'm
> going to let this patch start cooking in linux-next (after the currently
> active merge window closes, of course).  That'll help shake out any
> other potential missing dependencies or merge issues, and leave plenty
> of time for people to discuss it further before the subsequent merge
> window.

Makes sense to me!  (/me suddenly remembers to take his post-merge-window
commits out of -next...)

							Thanx, Paul

> > > --- a/kernel/capability.c
> > > +++ b/kernel/capability.c
> > > @@ -35,6 +35,7 @@ static int __init file_caps_disable(char *str)
> > >  }
> > >  __setup("no_file_caps", file_caps_disable);
> > > 
> > > +#ifdef CONFIG_MULTIUSER
> > >  /*
> > >   * More recent versions of libcap are available from:
> > >   *
> > > @@ -386,6 +387,24 @@ bool ns_capable(struct user_namespace *ns, int cap)
> > >  }
> > >  EXPORT_SYMBOL(ns_capable);
> > > 
> > > +
> > > +/**
> > > + * capable - Determine if the current task has a superior capability in effect
> > > + * @cap: The capability to be tested for
> > > + *
> > > + * Return true if the current task has the given superior capability currently
> > > + * available for use, false if not.
> > > + *
> > > + * This sets PF_SUPERPRIV on the task if the capability is available on the
> > > + * assumption that it's about to be used.
> > > + */
> > > +bool capable(int cap)
> > > +{
> > > +	return ns_capable(&init_user_ns, cap);
> > > +}
> > > +EXPORT_SYMBOL(capable);
> > > +#endif /* CONFIG_MULTIUSER */
> > > +
> > >  /**
> > >   * file_ns_capable - Determine if the file's opener had a capability in effect
> > >   * @file:  The file we want to check
> > > @@ -412,22 +431,6 @@ bool file_ns_capable(const struct file *file, struct user_namespace *ns,
> > >  EXPORT_SYMBOL(file_ns_capable);
> > > 
> > >  /**
> > > - * capable - Determine if the current task has a superior capability in effect
> > > - * @cap: The capability to be tested for
> > > - *
> > > - * Return true if the current task has the given superior capability currently
> > > - * available for use, false if not.
> > > - *
> > > - * This sets PF_SUPERPRIV on the task if the capability is available on the
> > > - * assumption that it's about to be used.
> > > - */
> > > -bool capable(int cap)
> > > -{
> > > -	return ns_capable(&init_user_ns, cap);
> > > -}
> > > -EXPORT_SYMBOL(capable);
> > > -
> > > -/**
> > 
> > OK, I'll bite...  Why are we moving capable()?
> 
> Consolidating from two ifdef blocks to one, based on feedback on the
> initial version suggesting simplification of the ifdeffery.
> 
> - Josh Triplett
> 

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