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

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Date:	Tue, 20 Sep 2011 19:48:49 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	"Serge E. Hallyn" <serge.hallyn@...onical.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

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().
Looks like, we need a lot of complications to make this correct...

As for send_signal(), may be we can simply do


	--- x/kernel/signal.c
	+++ x/kernel/signal.c
	@@ -1084,10 +1084,13 @@ static int __send_signal(int sig, struct
				break;
			default:
				copy_siginfo(&q->info, info);
	-			if (from_ancestor_ns)
	-				q->info.si_pid = 0;
				break;
			}
	+
	+		if (unlikely(from_ancestor_ns)) {
	+				q->info.si_pid = 0;
	+				q->info.si_uid = 0;
	+		}
		} else if (!is_si_special(info)) {
			if (sig >= SIGRTMIN && info->si_code != SI_USER) {
				/*

?

Yes, this "breaks" sys_rt_sigqueueinfo() evem more if it is used
to send the signal to the sub-namespace.

Oleg.

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