linux-kernel - Re: 2.6.25.3: su gets stuck for root

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Message-ID: <4846FBF2.9010206@skyrush.com>
Date:	Wed, 04 Jun 2008 14:32:50 -0600
From:	Joe Peterson <joe@...rush.com>
To:	Alan Cox <alan@...hat.com>
CC:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	David Newall <davidn@...idnewall.com>,
	Willy Tarreau <w@....eu>,
	Harald Dunkel <harald.dunkel@...nline.de>,
	linux-kernel@...r.kernel.org
Subject: Re: 2.6.25.3: su gets stuck for root

Alan Cox wrote:
>> tty = current->signal->tty = -142080000 or 0xf7880800
>> task->pgrg                 = -142405824 or 0xf7830f40
> 
> task->pgrp is a struct pid - you need the value it holds

Yeah, I figured later that giving you the addresses was rather useless.  :)

Anyway, here is more info:

tty_check_change: current->signal->tty = f7880800
tty_check_change: tty = f7880800
tty_check_change: tty->pgrp = f7b99e40
  tty->pgrp->count = 5
  tty->pgrp->level = 0
  tty->pgrp->numbers[0].nr = 6951
tty_check_change: task_pgrp(current) = f7b99d40
  task_pgrp(current)->count = 1
  task_pgrp(current)->level = 0
  task_pgrp(current)->numbers[0].nr = 6952
tty_check_change: kill_pgrp called; returning -ERESTARTSYS
set_termios: error return value (-512) from tty_check_change
foo       6951  0.0  0.1   2332  1096 tty1     S+   14:18   0:00 su foo
foo       6952  0.0  0.1   2988  1464 tty1     S    14:18   0:00 bash


So, looks like the tty->pgrp's process is the "su" command itself, and
the task_pgrp(current)'s process is "bash" - the shell started by the su.

						-Joe
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