From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752062Ab1ITPjx (ORCPT ); Tue, 20 Sep 2011 11:39:53 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:56446 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751366Ab1ITPjw (ORCPT ); Tue, 20 Sep 2011 11:39:52 -0400 Date: Tue, 20 Sep 2011 10:39:44 -0500 From: Serge Hallyn To: Oleg Nesterov Cc: lkml , richard@nod.at, Andrew Morton , "Eric W. Biederman" , Tejun Heo , serge@hallyn.com Subject: Re: [PATCH] user namespace: make signal.c respect user namespaces Message-ID: <20110920153944.GA11531@peqn> References: <20110919214531.GA18085@sergelap> <20110920122202.GA26504@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110920122202.GA26504@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Quoting Oleg Nesterov (oleg@redhat.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. > > And all of them follow the same pattern, > > > @@ -1073,7 +1074,8 @@ static int __send_signal(int sig, struct siginfo *info, struct task_struct *t, > > q->info.si_code = SI_USER; > > q->info.si_pid = task_tgid_nr_ns(current, > > task_active_pid_ns(t)); > > - q->info.si_uid = current_uid(); > > + q->info.si_uid = user_ns_map_uid(task_cred_xxx(t, user_ns), > > + current_cred(), current_uid()); > > Up to you, but may be we can add a helper? Something like > > static inline uid_t good_name(struct task_struct *from, struct task_struct *to) > { > // the caller does rcu_read_lock() if needed > const struct cred *from_cred = __task_cred(from); > return user_ns_map_uid(task_cred_xxx(to, user_ns), > from_cred, from_cred->uid); > } > > As for __send_signal() in particular, I guess we could do > > q->info.si_uid = from_ancestor_ns ? 0 : current_uid(); But wait - can't __send_signal end up being triggered through fcntl F_SETSIG+F_SETOWN to another but none-ancestor namespace? So we do actually need to call the full user_ns_map_uid() there. However, the uid sent in ptrace_signal() can (if i'm thinking right) be set using info->si_uid = (current_user_ns() == parent_user_ns()) ? 0 : current_uid(); Not much of a win performance-wise, but perhaps better by making it clear that those are the only possibilities (and overflowuid is not possible). thanks, -serge