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

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Date:	Wed, 14 May 2008 19:17:53 +0200
From:	"Vegard Nossum" <vegard.nossum@...il.com>
To:	"Harald Dunkel" <harald.dunkel@...nline.de>,
	"Alan Cox" <alan@...rguk.ukuu.org.uk>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: 2.6.25.3: su gets stuck for root

On Wed, May 14, 2008 at 7:05 PM, Harald Dunkel
<harald.dunkel@...nline.de> wrote:
> Vegard Nossum wrote:
>>
>> Ah, tough luck. What if you attach an strace to the already stuck
>> process? Like strace -p pid. It's a long shot, but worth a try, I
>> suppose.
>>
>
> As suggested I attached strace to the blocking stty. I got a
> continuous flow of
>
> :
> :
> ioctl(0, SNDCTL_TMR_STOP or TCSETSW, {B38400 opost isig icanon echo ...}) =
> ? ERESTARTSYS (To be restarted)
> --- SIGTTOU (Stopped (tty output)) @ 0 (0) ---
> --- SIGTTOU (Stopped (tty output)) @ 0 (0) ---
> :
> :
>
> I also moved back to an old version of coreutils from about
> 4 months ago. Same result.

Looks good. Adding Alan Cox to conversation. Original report:

--------
If I run "su someuser" as root, then it gets stuck. No prompt. I cannot
interrupt it with ^C or ^Z either. /var/log/auth.log says:

May 13 08:06:41 pluto su[4193]: Successful su for root by harri
May 13 08:06:41 pluto su[4193]: + pts/3 harri:root
May 13 08:06:41 pluto su[4193]: pam_unix(su:session): session opened
for user root by harri(uid=1000)

ps shows:

% ps -ef | grep pts/3
harri     4007  4006  0 07:58 pts/3    00:00:00 bash
root      4193  4007  0 08:06 pts/3    00:00:00 su
root      4194  4193  0 08:06 pts/3    00:00:00 bash
root      4209  4194  0 08:08 pts/3    00:00:00 su
root      4210  4209  0 08:08 pts/3    00:00:00 bash
root      4217  4210  0 08:08 pts/3    00:00:00 stty intr ^C

So obviously 'stty' is to blame here (called from root's .bashrc, as
it seems). But for 2.6.24.4 there is no such problem.
--------


Vegard

-- 
"The animistic metaphor of the bug that maliciously sneaked in while
the programmer was not looking is intellectually dishonest as it
disguises that the error is the programmer's own creation."
	-- E. W. Dijkstra, EWD1036
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