bugtraq - Re: Linux kernel ELF core dump privilege elevation (kernel module workaround)

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Date: Thu, 12 May 2005 17:31:58 -0500
From: chris <fool@....net>
To: Andrew Griffiths <andrewg@...inemenace.org>
Cc: full-disclosure@...ts.netsys.com, bugtraq@...urityfocus.com,
	vulnwatch@...nwatch.org
Subject: Re: Linux kernel ELF core dump privilege elevation (kernel module workaround)

On Thu, May 12, 2005 at 12:29:02AM +0000, Andrew Griffiths wrote:

> It loops over all processes and sets the soft limit and hard limit for
> processes to 0. The limits.conf measure isn't entirely enough if people
> have screen sessions, or you have various daemons running etc. 

We've used "echo / > /proc/sys/kernel/core_pattern" to disable coredumps
by all processes (using kernel 2.4.29).  This seems to affect all
running processes without doing anything drastic or dangerous (except
disabling coredumps =)).  To disable all for all but root processes you
can use something like " /core " instead of " / " in the above example,
but then you may still be vulnerable as Andrew points out to pre-existing
screen or Xwin sessions running as root--not sure about that but better
safe than sorry.

I haven't read the code to see if this is an unintentional effect, but
it sure seems to work under 2.4.29 at least.  I got the idea from this
page:

	http://www.aplawrence.com/Forum/TonyLawrence9.html