netdev - SELinux/IP_PASSSEC regression in 4.13-rcX

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Date:   Fri, 21 Jul 2017 18:19:06 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org
Cc:     selinux@...ho.nsa.gov
Subject: SELinux/IP_PASSSEC regression in 4.13-rcX

Hello,

I've been seeing a SELinux regression with IP_PASSSEC on the v4.13-rcX
kernels and finally tracked the problem down to the
skb_release_head_state() call in __udp_queue_rcv_skb().  Looking at
the code and the git log it would appear that the likely culprit is
0a463c78d25b ("udp: avoid a cache miss on dequeue
"); it looks similar to IP option problem fixed in 0ddf3fb2c43d2.

>From a SELinux/IP_PASSSEC point of view we need access to the skb->sp
pointer to examine the SAs.  I'm posting this here without a patch
because it isn't clear to me how you would like to fix the problem; my
initial thought would be to simply make the skb_release_head_state()
conditional on the skb->sp pointer, much like the IP options fix, but
I'm not sure if you have a more clever idea.

-- 
paul moore
www.paul-moore.com