linux-kernel - Re: NULL pointer dereference in selinux_ip_postroute

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Date:	Tue, 07 Aug 2012 15:26:48 -0700
From:	John Stultz <john.stultz@...aro.org>
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 03:01 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.

thanks
-john

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