linux-kernel - Re: Documenting reboot(2) changes for PID namespace in 3.9

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Date:	Tue, 12 Mar 2013 00:20:52 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	mtk.manpages@...il.com
Cc:	Li Zefan <lizefan@...wei.com>,
	linux-man <linux-man@...r.kernel.org>,
	Linux Containers <containers@...ts.linux-foundation.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: Documenting reboot(2) changes for PID namespace in 3.9

"Michael Kerrisk (man-pages)" <mtk.manpages@...il.com> writes:

> Li,
>
> Regarding your commit 923c7538236564c46ee80c253a416705321f13e3 , I
> plan to apply the following patch to the reboot(2) manual page. Does
> it look okay to you?

You have documented the behavior as of 3.4.

The change in 3.9 is to allow that same behavior in a pid_namespace
created with a user namespace.  Aka in 3.9 the permission
check changed from capable(CAP_SYS_BOOT)  to ns_capable(pid_ns->user_ns, CAP_SYS_BOOT);

Eric

> Thanks,
>
> Michael
>
> diff --git a/man2/reboot.2 b/man2/reboot.2
> index 8347870..1c17b85 100644
> --- a/man2/reboot.2
> +++ b/man2/reboot.2
> @@ -24,7 +24,7 @@
>  .\" Modified, 27 May 2004, Michael Kerrisk <mtk.manpages@...il.com>
>  .\"     Added notes on capability requirements
>  .\"
> -.TH REBOOT 2 2010-10-31 "Linux" "Linux Programmer's Manual"
> +.TH REBOOT 2 2013-03-12 "Linux" "Linux Programmer's Manual"
>  .SH NAME
>  reboot \- reboot or enable/disable Ctrl-Alt-Del
>  .SH SYNOPSIS
> @@ -147,6 +147,26 @@ For the i386 architecture, the additional
> argument does not do
>  anything at present (2.1.122), but the type of reboot can be
>  determined by kernel command-line arguments ("reboot=...") to be
>  either warm or cold, and either hard or through the BIOS.
> +.SS Behavior inside PID namespaces
> +.\" commit commit 923c7538236564c46ee80c253a416705321f13e3
> +Since Linux 3.9, when
               ^^^ 3.4
> +.BR reboot ()
> +is called from a PID namespace (see
> +.BR pid_namespaces (7))
> +other than the initial PID namespace,
> +the effect of the call is to send a signal to the namespace "init" process.
> +.BR LINUX_REBOOT_CMD_RESTART
> +and
> +.BR LINUX_REBOOT_CMD_RESTART2
> +cause a
> +.BR SIGHUP
> +signal to be sent.
> +.BR LINUX_REBOOT_CMD_POWER_OFF
> +and
> +.BR LINUX_REBOOT_CMD_HALT
> +cause a
> +.B SIGINT
> +signal to be sent.
>  .SH RETURN VALUE
>  For the values of
>  .I cmd
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