Re: [PATCH V3 net-next] ixgbe: Avoid unaligned access in ixgbe_atr() for LLC packets

On Mon, 2016-03-14 at 15:47 -0400, Sowmini Varadhan wrote:

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 skb->protocol. The only Ethernet II protocols handled
are IPv4 and IPv6

Signed-off-by: Sowmini Varadhan <redacted>
---
v2: Alexander Duyck comments
v3: filter out all ethertypes  except for Ethernet II and (IPv4 or
IPv6)

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

This does not apply since Alex Duyck beat you to the fix.  Here is the
patch he submitted on 3/15 which corrects the issue.  So I am dropping
your patch from the queue.

commit 04b8b51c34837765cf6250f69d419c439dc393bf
Author: Alexander Duyck [off-list ref]
Date:   Tue Mar 15 15:10:22 2016 -0700

    ixgbe: Fix ATR so that it correctly handles IPv6 extension headers
    
    The ATR code was assuming that it would be able to use tcp_hdr for
    every TCP frame that came through.  However this isn't the case as
it
    is possible for a frame to arrive that is TCP but sent through
something
    like a raw socket.  As a result the driver was setting up bad
filters in
    which tcp_hdr was really pointing to the network header so the data
was
    all invalid.
    
    In order to correct this I have added a bit of parsing logic that
will
    determine the TCP header location based off of the network header
and
    either the offset in the case of the IPv4 header, or a walk through
the
    IPv6 extension headers until it encounters the header that
indicates
    IPPROTO_TCP.  In addition I have added checks to verify that the
lowest
    protocol provided is recognized as IPv4 or IPv6 to help mitigate
raw
    sockets using ETH_P_ALL from having ATR applied to them.
    
    Signed-off-by: Alexander Duyck [off-list ref]