Bug 1876

Summary: high X nice value allows to crash the host
Product: xorg Reporter: Jérôme <jerome.bouat>
Component: Server/GeneralAssignee: Xorg Project Team <xorg-team>
Status: RESOLVED NOTABUG QA Contact:
Severity: normal    
Priority: high    
Version: 6.7.0   
Hardware: x86 (IA32)   
OS: Linux (All)   
Whiteboard:
i915 platform: i915 features:

Description Jérôme 2004-11-21 13:08:18 UTC 
On my Linux distribution, X nice value is 0. With such value, I already crashed
a host.

I got a program which made an eavy use of X by updating as quick as possible a
window (I did not designed it). X server spent all its time in managing the
memory instead of displaying. The more X server was loaded, the more it became
loaded up to the crash of the system.

Some malicious programs could exploit this feature in order to launch an attack
which causes a deny of service and then a system crash.

Choosing a -9 nice value fixes the problem in case where X client are on the
same host as X server. Indeed the X client waits for the load of the X server to
dicrease before it can get more resources.

For the case where the X client is not on the same host as the X server, I
assume the network link will limit the refresh rate.

Here is the bug report I posted on for my Linux distro:
http://qa.mandrakesoft.com/show_bug.cgi?id=8977
Comment 1 Adam Jackson 2005-12-25 18:10:50 UTC 
don't do that then.

more accurately, if you can locate exactly where this crash is occuring, and
have a fix, then please attach it.  otherwise don't misconfigure your X server.

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