From: "Serge E. Hallyn" <serge.hallyn@canonical.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: lkml <linux-kernel@vger.kernel.org>,
richard@nod.at, Andrew Morton <akpm@google.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Tejun Heo <tj@kernel.org>,
serge@hallyn.com
Subject: Re: [PATCH] user namespace: make signal.c respect user namespaces
Date: Tue, 20 Sep 2011 11:45:24 -0500 [thread overview]
Message-ID: <20110920164524.GA8214@sergelap> (raw)
In-Reply-To: <20110920162455.GB18891@redhat.com>
Quoting Oleg Nesterov (oleg@redhat.com):
> On 09/20, Serge Hallyn wrote:
> >
> > Quoting Oleg Nesterov (oleg@redhat.com):
> > >
> > > 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?
>
> I didn't really check, but afaics send_sigio_to_task/etc never use
> SEND_SIG_NOINFO. And they shouldn't, there is no the sending process.
(I'm sure you're right - but I'll have to take a closer look for my
own understanding)
> > 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).
>
> I think you are right right, except s/==/!=/.
Yes :)
> This is like send_signal()
> which can only send the signal down or to the same namespace.
>
> I guess ptrace_signal() can even do
>
> info->si_pid = task_pid_vnr(current->parent);
>
> if (info->si_pid) // same namespace
> info->si_uid = current_uid();
> else // can't see the tracer, we are from the sub-namespace
> info->si_uid = 0;
>
> Whatever you like more.
Except you don't have to split pid and user namespaces at the same
time.
> And just in case let me repeat, I won't argue if you use
> user_ns_map_uid/helper for consistency. Without CONFIG_USER_NS it is
> even better performance-wise (even if we add a helper I guess).
Ok. On the one hand, using your new mapping helper will make it
easier to make sure everything is right. This special code may be
more educational to the new reader, but isn't as trivial to
review.
Maybe I'll go with the mapping.
thanks,
-serge
next prev parent reply other threads:[~2011-09-20 16:45 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-19 21:45 [PATCH] user namespace: make signal.c respect user namespaces Serge E. Hallyn
2011-09-19 21:47 ` [PATCH] user namespace: usb: make usb urbs user namespace aware Serge E. Hallyn
2011-09-20 13:17 ` Oleg Nesterov
2011-09-20 13:33 ` Serge E. Hallyn
2011-09-21 5:01 ` [PATCH] user namespace: usb: make usb urbs user namespace aware (v2) Serge E. Hallyn
2011-09-21 18:31 ` Oleg Nesterov
2011-09-21 19:12 ` Serge E. Hallyn
2011-09-21 19:18 ` Greg KH
2011-09-23 1:27 ` [PATCH resend] " Serge E. Hallyn
2011-09-23 15:48 ` Alan Stern
2011-09-23 16:06 ` Serge E. Hallyn
2011-09-23 16:21 ` Alan Stern
2011-09-23 17:22 ` Serge E. Hallyn
2011-09-23 18:35 ` Alan Stern
2011-09-20 12:22 ` [PATCH] user namespace: make signal.c respect user namespaces Oleg Nesterov
2011-09-20 12:44 ` Serge E. Hallyn
2011-09-20 13:41 ` Oleg Nesterov
2011-09-20 14:39 ` [PATCH 0/2] (Was: user namespace: make signal.c respect user namespaces) Oleg Nesterov
2011-09-20 14:39 ` [PATCH 1/2] creds: kill __task_cred()->task_is_dead() check Oleg Nesterov
2011-09-20 15:14 ` drivers/staging/usbip/ abuses task_is_dead/exit_state Oleg Nesterov
2011-09-20 18:38 ` Greg KH
2012-03-06 17:39 ` ping: " Oleg Nesterov
2012-03-06 19:30 ` Tobias Klauser
2012-03-08 18:57 ` Oleg Nesterov
2012-03-13 11:45 ` Tobias Klauser
2012-03-13 18:07 ` [PATCH] staging: usbip: fix the usage of kthread_stop() Oleg Nesterov
2012-04-01 23:17 ` Oleg Nesterov
2012-04-02 8:11 ` Tobias Klauser
2011-09-20 15:28 ` [PATCH 1/2] creds: kill __task_cred()->task_is_dead() check Paul E. McKenney
2011-09-20 15:40 ` Oleg Nesterov
2011-09-20 15:48 ` Paul E. McKenney
2011-09-20 14:39 ` [PATCH 2/2] creds: __task_cred(current) doesn't need rcu_read_lock_held() Oleg Nesterov
2011-09-20 15:07 ` Serge Hallyn
2011-09-20 15:35 ` Oleg Nesterov
2011-09-20 16:19 ` David Howells
2011-09-20 16:38 ` Oleg Nesterov
2011-09-20 16:50 ` David Howells
2011-09-20 17:13 ` Oleg Nesterov
2011-09-20 16:27 ` [PATCH 1/2] creds: kill __task_cred()->task_is_dead() check David Howells
2011-09-20 15:39 ` [PATCH] user namespace: make signal.c respect user namespaces Serge Hallyn
2011-09-20 16:24 ` Oleg Nesterov
2011-09-20 16:45 ` Serge E. Hallyn [this message]
2011-09-20 18:17 ` Oleg Nesterov
2011-09-21 5:00 ` [PATCH] user namespace: make signal.c respect user namespaces (v2) Serge E. Hallyn
2011-09-20 17:48 ` [PATCH] user namespace: make signal.c respect user namespaces Oleg Nesterov
2011-09-20 18:53 ` Serge E. Hallyn
2011-09-21 17:53 ` Oleg Nesterov
2011-09-22 15:23 ` Serge Hallyn
2011-09-23 16:31 ` Serge E. Hallyn
2011-09-23 17:36 ` Oleg Nesterov
2011-09-23 21:20 ` Serge E. Hallyn
2011-09-24 16:37 ` Oleg Nesterov
2011-09-25 20:17 ` Serge E. Hallyn
2011-09-26 16:06 ` Oleg Nesterov
2011-09-27 14:28 ` Serge Hallyn
2011-09-27 14:38 ` Oleg Nesterov
2011-09-27 15:27 ` Serge Hallyn
2011-09-27 17:12 ` Oleg Nesterov
2011-10-04 17:42 ` Serge E. Hallyn
2011-10-09 19:00 ` Oleg Nesterov
2011-10-11 13:08 ` Serge E. Hallyn
2011-10-08 20:02 ` Serge E. Hallyn
2011-10-09 19:03 ` Oleg Nesterov
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