Re: Patched base.c file for the CVE-2012-0056 root privilege escalation exploit for the 3.0.17 VServer kernel

On Mon January 23 2012, Jean Weisbuch wrote:
> Hello everyone,
> 
> The kernel >=2.6.39 are vulnerable to a privilege escalation exploit 
> related to /proc/<pid>/mem, i tested one of the available exploit on a 
> 3.0.9 VServer kernel and it allow any unprivileged user on the host 
> system but also on guests to gain root privilege ; for more infos about 
> it : http://blog.zx2c4.com/749
>

My reading of that description shows that one of the steps required
is to determine a matching self_exec_id -

Which is trivial to do, since the id is evidently initialized to a
fixed value when it is created.

It would be better to also initialize the self_exec_id to a random
number when it is created.
That is, the same handling of an IV when creating a encrypted block.
 
> I patched a VServer patched base.c with the Linus patch 
> (http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=e268337dfe26dfc7efd422a804dbb27977a3cccc#patch1) 
> from the 3.0.17 sources (from the linux-source-3.0.17-vs2.3.2.1-beng 
> package), i had to manually patch the chunck #1 which was rejected at 
> first but the others didnt make any complaint.
> 

It does not appear to my from reading that, that self_exec_id is being
randomized when created.

> Here is the patched base.c file : http://jbboin.phpnet.org/base.c
> 
> I am now compiling a kernel package with this patch, will share the 
> package as soon as it finished compiling (and if it seems to work).
> 

Sorry, I don't have the skills to test my own suggestion;
so it needs to only remain as a suggestion at this point.

Mike
> 
> Regards.
> 
>