linux-kernel - Re: [PATCH] user namespace: make signal.c respect user namespaces

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Message-ID: <20110923163113.GA3820@sergelap>
Date:	Fri, 23 Sep 2011 11:31:13 -0500
From:	"Serge E. Hallyn" <serge.hallyn@...onical.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	lkml <linux-kernel@...r.kernel.org>, richard@....at,
	Andrew Morton <akpm@...gle.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Tejun Heo <tj@...nel.org>, serge@...lyn.com
Subject: Re: [PATCH] user namespace: make signal.c respect user namespaces

Quoting Oleg Nesterov (oleg@...hat.com):
> On 09/20, Serge E. Hallyn wrote:
> >
> > Quoting Oleg Nesterov (oleg@...hat.com):
> > > On 09/19, Serge E. Hallyn wrote:
> > > >
> > > > __send_signal: convert the uid being sent in SI_USER to the target task's
> > > > user namespace.
> > > >
> > > > do_notify_parent and do_notify_parent_cldstop: map task's uid to parent's
> > > >  user namespace
> > > >
> > > > ptrace_signal: map parent's uid into current's user namespace before
> > > > including in signal to current.
> > >
> > > Btw, what about the other users of ->si_uid? Say, kill() or tkill().
> >
> > Well, they end up calling __send_signal().
> 
> Sure. But your patch changes only the __send_signal(SEND_SIG_NOINFO).
> Note that SEND_SIG_NOINFO is rarely used, and only by kernel.
> 
> > But you sound more alarmed than that.
> 
> I am ;)

Ok, thanks for setting me straight, Oleg.  It looks like I can fix all the
cases at send_signal() by checking whether si_fromuser(info) and
current_user_ns() != task_cred_xxx(t, user_ns), and mapping the uid if
so.

-serge
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