netdev - [PATCH v2 net-next] ixgbe: Avoid unaligned access in ixgbe

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Message-ID: <20160314174624.GG5084@oracle.com>
Date:	Mon, 14 Mar 2016 13:46:24 -0400
From:	Sowmini Varadhan <sowmini.varadhan@...cle.com>
To:	intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org
Cc:	sowmini.varadhan@...cle.com, alexander.duyck@...il.com,
	jeffrey.t.kirsher@...el.com, jesse.brandeburg@...el.com,
	shannon.nelson@...el.com, carolyn.wyborny@...el.com,
	donald.c.skidmore@...el.com, bruce.w.allan@...el.com,
	john.ronciak@...el.com, mitch.a.williams@...el.com
Subject: [PATCH v2 net-next] ixgbe: Avoid unaligned access in ixgbe_atr() for
 LLC packets


For LLC based protocols like lldp, stp etc., the ethernet header
is an 802.3 header with a h_proto that is not 0x800, 0x86dd, or
even 0x806.  In this world, the skb_network_header() points at
the DSAP/SSAP/..  and is not likely to be NET_IP_ALIGNed in
ixgbe_atr().

With LLC, drivers are not likely to correctly find IPVERSION,
or "6", at hdr.ipv4->version, but will instead just needlessly
trigger an unaligned access. (IPv4/IPv6 over LLC is almost never
implemented).

The unaligned access is thus avoidable: bail out quickly after
examining first->protocol.

Signed-off-by: Sowmini Varadhan <sowmini.varadhan@...cle.com>
---
v2: Alexander Duyck comments.

 drivers/net/ethernet/intel/ixgbe/ixgbe_main.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
index 4d6223d..b25e603 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
@@ -7574,6 +7574,11 @@ static void ixgbe_atr(struct ixgbe_ring *ring,
 	if (!ring->atr_sample_rate)
 		return;
 
+	if (first->protocol != htons(ETH_P_IP) &&
+	    first->protocol != htons(ETH_P_IPV6) &&
+	    first->protocol != htons(ETH_P_ARP))
+		return;
+
 	ring->atr_count++;
 
 	/* snag network header to get L4 type and address */
-- 
1.7.1