From: hannes@stressinduktion.org <hannes@stressinduktion.org>
Date: Wed, 1 Apr 2015 15:07:44 +0000 (+0200)
Subject: ipv6: protect skb->sk accesses from recursive dereference inside the stack
X-Git-Tag: omap-for-v4.1/fixes-rc1~225^2~4
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f60e5990d9c1424af9dbca60a23ba2a1c7c1ce90;p=pandora-kernel.git

ipv6: protect skb->sk accesses from recursive dereference inside the stack

We should not consult skb->sk for output decisions in xmit recursion
levels > 0 in the stack. Otherwise local socket settings could influence
the result of e.g. tunnel encapsulation process.

ipv6 does not conform with this in three places:

1) ip6_fragment: we do consult ipv6_npinfo for frag_size

2) sk_mc_loop in ipv6 uses skb->sk and checks if we should
   loop the packet back to the local socket

3) ip6_skb_dst_mtu could query the settings from the user socket and
   force a wrong MTU

Furthermore:
In sk_mc_loop we could potentially land in WARN_ON(1) if we use a
PF_PACKET socket ontop of an IPv6-backed vxlan device.

Reuse xmit_recursion as we are currently only interested in protecting
tunnel devices.

Cc: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

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