On Thu, Jan 10, 2002 at 04:12:11PM +0100, David Balazic wrote:
>the console ( keyboard+mouse+screen ) of a linux system can be locked up
>by a non-root user with the "help" of an xfree86 server.
>
>I first reported it to the linux kernel mailing list, but they pointed me here.
>Here are the relevant messages :
>
>My first mail :
>---begin---
>Subject: Simple local DOS
>   Date: Wed, 09 Jan 2002 17:51:03 +0100
>   From: David Balazic <[EMAIL PROTECTED]>
>     To: "[EMAIL PROTECTED]" <[EMAIL PROTECTED]>
>
>log in on some virtual terminal, then run the following line
>in a bourne type shell, like bash :
>
>X 2>&1 | less
>
>A reboot "fixes" it. We want to reach windows level quality on desktop
>after all, don't we ?
>
>---end--- 
>
>Message from David S. Miller suggesting to take it to xfree86 people :
>
>---begin---
>Subject: Re: Simple local DOS
>       Date: Thu, 10 Jan 2002 05:56:51 -0800 (PST)
>      From: "David S. Miller" <[EMAIL PROTECTED]>
>        To: [EMAIL PROTECTED]
>        CC: [EMAIL PROTECTED], [EMAIL PROTECTED]
>
>   From: David Balazic <[EMAIL PROTECTED]>
>   Date: Thu, 10 Jan 2002 14:46:19 +0100
>   
>   > all this is off-topic on linux-kernel,
>   
>   non-root user locked up the console code. console code is part of kernel.
>   it is a kernel topic.
>
>The real issue is that X has the console in an indeterminate state (it
>probably just saved the VGA state and is outputting probing
>information) but now it is blocked on terminal output due to the
>"less".
>
>There is nothing the kernel can do about what X is up to.  The suid
>wrapper for X can check if stdout/stderr is a pipe and refuse to run
>if it is.
>
>So really, it is in fact off topic for linux-kernel.  Please take this
>to the xfree86 lists, I'm sure they'll be more than happy to fix it.
>
>Franks a lot,
>David S. Miller
>[EMAIL PROTECTED]
>---end---

I guess a quick workaround would be to make the X server do that check
(when started by a non-root user).

Would another solution be to not block on stdout/stderr?

David
-- 
David Dawes                                  Email: [EMAIL PROTECTED]
Tungsten Graphics, Inc                       http://www.tungstengraphics.com
Founder/President, Release Engineer          Phone: +1 570 764 0288
The XFree86 Project, Inc                     http://www.xfree86.org/~dawes
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