linux-kernel - Re: NULL pointer dereference in selinux_ip_postroute

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Date:	Tue, 07 Aug 2012 15:31:21 -0700
From:	John Stultz <johnstul@...ibm.com>
To:	Paul Moore <paul@...l-moore.com>
CC:	lkml <linux-kernel@...r.kernel.org>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	James Morris <james.l.morris@...cle.com>, selinux@...ho.nsa.gov
Subject: Re: NULL pointer dereference in selinux_ip_postroute_compat

On 08/07/2012 03:26 PM, John Stultz wrote:
> On 08/07/2012 03:01 PM, Paul Moore wrote:
>> On Tue, Aug 7, 2012 at 5:58 PM, John Stultz <john.stultz@...aro.org> 
>> wrote:
>>> On 08/07/2012 02:50 PM, Paul Moore wrote:
>>>> On Tue, Aug 7, 2012 at 2:12 PM, John Stultz <john.stultz@...aro.org>
>>>> wrote:
>>>>> Hi,
>>>>>       With my kvm environment using 3.6-rc1+, I'm seeing NULL pointer
>>>>> dereferences in selinux_ip_postroute_compat(). It looks like the 
>>>>> sksec
>>>>> value
>>>>> is null and we die in the following line:
>>>>>
>>>>>       if (selinux_xfrm_postroute_last(sksec->sid, skb, &ad, proto))
>>>>>
>>>>> This triggers every time I shutdown the machine, but has also 
>>>>> triggered
>>>>> randomly after a few hours.
>>>>>
>>>>> This is on an ubuntu 12.04 image, not using selinux.
>>>> NOTE: Adding the SELinux list to the CC line
>>> Thanks!
>>>
>>>> Hi,
>>>>
>>>> I'm trying to understand this and I was hoping you could you clarify a
>>>> few things for me:
>>>>
>>>> * Is the panic in the Ubuntu 12.04 guest, or the host?  If the host,
>>>> could you share what distribution you are using?
>>> Sorry, its a 12.04 guest.  I think the host is Ubuntu 12.04 as well.
>>>
>>>
>>>> * When you say you are not using SELinux, could you be more specific?
>>>> It seems odd that you are not using SELinux but the panic is happening
>>>> in a SELinux hook.
>>> I just mean that, being Ubuntu,  the system (userland) isn't 
>>> configured to
>>> use selinux.  SELinux is just enabled in the kernel config.
>> Thanks for the quick response, I'll setup an Ubuntu guest and see if I
>> can reproduce this ... something is odd.  Anything non-standard about
>> your guest install or anything else you think might be helpful?
> Don't think so.  Just a standard 64bit ubuntu 12.04 install.
>
> Since I'm booting kernel/initrd from the commandline, the initrd *may* 
> be older then 12.04, I can't quite remember when I copied that out of 
> the image. I'll see if it still triggers if I copy the current initrd 
> out.

Nope, that's not it, I just triggered the same thing w/ the Ubuntu 12.04 
initrd on the image.

thanks
-john

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