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

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Date:	Sun, 01 Jun 2008 23:55:06 -0600
From:	Joe Peterson <joe@...rush.com>
To:	Willy Tarreau <w@....eu>
CC:	Harald Dunkel <harald.dunkel@...nline.de>,
	linux-kernel@...r.kernel.org, Alan Cox <alan@...hat.com>
Subject: Re: 2.6.25.3: su gets stuck for root

Willy Tarreau wrote:
> Guys, you should test if "kill -CONT $pid" wakes the process up.
> It might be possible that some obscure bug appeared in the tty
> code resulting in SIGTTOU sometimes being sent to the caller,
> although that seems rather strange :-/

Just tried this ("kill -CONT <pid>") - no luck.

BTW, it should be possible, I would think, for others to duplicate this
fairly easily.  Just:

1) make a user, "foo", with login shell set to /bin/bash
2) create a .bashrc in foo's home dir with contents:

sleep 2
stty -ixany

3) cp .bashrc .bash_profile  (only needed to test "su - foo" too)
4) become root
5) type "su foo" (or "su - foo")

Sometimes it takes a second try to get it to happen.  If the su hangs,
check to see if the stty process is in state "T".  Also, it may make a
difference if you are logged in already as foo or are using X.  I first
noticed this with no users logged in (except root) and no X running (but
I can reproduce with X/xterm as well using this simple test case).  It
seems timing is a factor, so it's worth trying various things.

					-Joe
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