netdev - Re: Network hang after c3f1010b30f7fc611139cfb702a8685741aa6827 with CIPSO & Smack

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Message-ID: <CAHC9VhQsJoA3856MZgaJaHwGAcnXCoe0hn2AtEikcCTZx46Jsg@mail.gmail.com>
Date:	Wed, 6 Jul 2016 08:50:47 -0400
From:	Paul Moore <paul@...l-moore.com>
To:	Casey Schaufler <casey@...aufler-ca.com>
Cc:	David Miller <davem@...emloft.net>, dsa@...ulusnetworks.com,
	Linux-Netdev <netdev@...r.kernel.org>
Subject: Re: Network hang after c3f1010b30f7fc611139cfb702a8685741aa6827 with
 CIPSO & Smack

On Tue, Jul 5, 2016 at 8:38 PM, Casey Schaufler <casey@...aufler-ca.com> wrote:
> I have encountered a system hang with my Smack
> networking tests that bisects to the change below.
> I can't say that I have any idea why the change
> would impact the Smack processing, but there appears
> to be some serious packet processing going on. The
> Smack code is using CIPSO on the loopback interface.
> The test is supposed to verify that labels can be
> set on the packets using CIPSO. Unlabeled packets
> do not appear to be impacted. I do not know if SELinux
> is affected, and if not, why not. Smack and SELinux
> use CIPSO differently.

For the past several months I've been running the SELinux testsuite on
a weekly basis against Linus' kernel plus the SELinux and audit
development trees and I haven't noticed any problems that haven't
already been reported.  While not exhaustive, the testsuite does
exercise the NetLabel/CIPSO code.  I'll see if I can take a closer
look at the Smack code, but do you rely on the inet_skb_param values
in Smack?  We did have a similar problem in the NetLabel core code
that we fixed with 04f81f0154e4bf002be6f4d85668ce1257efa4d9; it's
possible there is a similar problem in code that we just aren't
exercising with SELinux at the moment.

* https://github.com/SELinuxProject/selinux-testsuite
* https://copr.fedorainfracloud.org/coprs/pcmoore/kernel-secnext

> commit c3f1010b30f7fc611139cfb702a8685741aa6827
> Merge: ca4aa97 0b922b7
> Author: David S. Miller <davem@...emloft.net>
> Date:   Wed May 11 19:31:40 2016 -0400
>
>     Merge branch 'vrf-pktinfo'
>
>     David Ahern says:
>
>     ====================
>     net: vrf: Fixup PKTINFO to return enslaved device index
>
>     Applications such as OSPF and BFD need the original ingress device not
>     the VRF device; the latter can be derived from the former. To that end
>     move the packet intercept from an rx handler that is invoked by
>     __netif_receive_skb_core to the ipv4 and ipv6 receive processing.
>
>     IPv6 already saves the skb_iif to the control buffer in ipv6_rcv. Since
>     the skb->dev has not been switched the cb has the enslaved device. Make
>     the same happen for IPv4 by adding the skb_iif to inet_skb_parm and set
>     it in ipv4 code after clearing the skb control buffer similar to IPv6.
>     From there the pktinfo can just pull it from cb with the PKTINFO_SKB_CB
>     cast.
>     ====================
>
>     Signed-off-by: David S. Miller <davem@...emloft.net>

-- 
paul moore
www.paul-moore.com