From: Christian Brauner <christian.brauner@ubuntu.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Linux Containers <containers@lists.linux-foundation.org>,
Christof Meerwald <cmeerw@cmeerw.org>,
"Eric W. Biederman" <ebiederm@xmission.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] signal: Avoid corrupting si_pid and si_uid in do_notify_parent
Date: Tue, 21 Apr 2020 13:26:06 +0200 [thread overview]
Message-ID: <20200421112606.ay4cck2dphguqazb@wittgenstein> (raw)
In-Reply-To: <20200421111139.GC6787@redhat.com>
On Tue, Apr 21, 2020 at 01:11:40PM +0200, Oleg Nesterov wrote:
> Sorry Christian, I don't understand...
In my original mail, it was really just a clarification question. I
said the patch is correct from looking at the codepaths. :) I was just
trying to see whether there was a potential corner-case we're missing
where "force" could be _validly_ true.
>
> > because child subreapers can't come from outside the pid namespace. If
> > they could you could create a scenario where the signal is generated
> > from a sibling pid namespace in which case it would be correctly set to
> > true.
>
> not sure I understand, but probably the answer is "yes"...
(This is really purely academic now since it isn't possible, but for
pure amusement assume that a child subreaper could cross namespace
boundaries (which they don't). A marks itself as a subreaper and creates
a new process B in a new pid namespace <pidnsB>, process B setnses into
<pidnsC> which is a sibling pid namespace, B clones a new proces in
<pidnsC> which is now a full member of <pidnsC>, B dies and C is
reparented to A, B exits and then you'd be getting a sigchld from a pid
in a pid namespace in which you have no pid nr.)
next prev parent reply other threads:[~2020-04-21 11:26 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-19 20:13 SIGCHLD signal sometimes sent with si_pid==0 (Linux 5.6.5) Christof Meerwald
2020-04-20 17:05 ` [PATCH] signal: Avoid corrupting si_pid and si_uid in do_notify_parent Eric W. Biederman
2020-04-21 8:30 ` Christian Brauner
2020-04-21 9:28 ` Oleg Nesterov
2020-04-21 10:21 ` Christian Brauner
2020-04-21 11:11 ` Oleg Nesterov
2020-04-21 11:26 ` Christian Brauner [this message]
2020-04-21 12:17 ` Oleg Nesterov
2020-04-21 12:59 ` Christian Brauner
2020-04-21 13:42 ` Eric W. Biederman
2020-04-21 11:28 ` Oleg Nesterov
2020-04-21 11:38 ` Christian Brauner
2020-04-21 10:28 ` Christian Brauner
2020-04-21 14:57 ` Eric W. Biederman
2020-04-21 15:08 ` Christian Brauner
2020-04-21 9:04 ` Oleg Nesterov
2020-04-21 10:19 ` [PATCH] remove the no longer needed pid_alive() check in __task_pid_nr_ns() Oleg Nesterov
2020-04-21 10:50 ` Christian Brauner
2020-04-21 15:05 ` Eric W. Biederman
2020-04-24 18:05 ` Oleg Nesterov
2020-04-24 19:54 ` Eric W. Biederman
2020-04-21 14:59 ` SIGCHLD signal sometimes sent with si_pid==0 (Linux 5.6.5) Eric W. Biederman
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