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

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Message-ID: <20110923212025.GA21330@sergelap>
Date:	Fri, 23 Sep 2011 16:20:25 -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 09/23, Serge E. Hallyn wrote:
> >
> > It looks like I can fix all the
> > cases
> 
> except ptrace_signal(). Although we can simply ignore this case, imho.

ptrace_signal() calls send_signal() though.

But oh, dear.  It is sending a signal on behalf of the parent, so what I was
about to send, which does the uid mapping at send_signal() using current_cred()
as the id to send, is not correct.

Which unfortunately means that I'll have to have the caller of send_signal
(when doing SI_USER) either send the signal sender's cred, or do the
mapping.  Or special-case ptrace_signal().  This is not as pretty as I'd
hoped.

> > at send_signal()
> 
> Yes, I was thinking about this too but didn't have the time to check
> if this can really work.
> 
> > by checking whether si_fromuser(info)
> 
> I am not sure... sys_rt_queueinfo() is nasty. Plus we have to handle
> the "fromkernel" case too. May be we can ignore this too.

sys_rt_tgsigqueueinfo() still seems to go through send_signal().

thanks,
-serge
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