[4.2.y-ckt stable] Patch "flow_dissector: Fix unaligned access in __skb_flow_dissector when used by eth_get_headlen" has been added to the 4.2.y-ckt tree

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    flow_dissector: Fix unaligned access in __skb_flow_dissector when used by eth_get_headlen

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt5.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

---8<------------------------------------------------------------

>From a95c6ae1faa9b7990b101f6876e4cb80306dc940 Mon Sep 17 00:00:00 2001
From: Alexander Duyck <aduyck at mirantis.com>
Date: Tue, 9 Feb 2016 02:49:54 -0800
Subject: flow_dissector: Fix unaligned access in __skb_flow_dissector when
 used by eth_get_headlen

[ Upstream commit 461547f3158978c180d74484d58e82be9b8e7357, since
  we lack the flow dissector flags in this release we guard the
  flow label access using a test on 'skb' being NULL ]

This patch fixes an issue with unaligned accesses when using
eth_get_headlen on a page that was DMA aligned instead of being IP aligned.
The fact is when trying to check the length we don't need to be looking at
the flow label so we can reorder the checks to first check if we are
supposed to gather the flow label and then make the call to actually get
it.

v2:  Updated path so that either STOP_AT_FLOW_LABEL or KEY_FLOW_LABEL can
     cause us to check for the flow label.

Reported-by: Sowmini Varadhan <sowmini.varadhan at oracle.com>
Signed-off-by: Alexander Duyck <aduyck at mirantis.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 net/core/flow_dissector.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index 2a834c6..bb98f8b 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -192,7 +192,6 @@ ip:
 	case htons(ETH_P_IPV6): {
 		const struct ipv6hdr *iph;
 		struct ipv6hdr _iph;
-		__be32 flow_label;

 ipv6:
 		iph = __skb_header_pointer(skb, nhoff, sizeof(_iph), data, hlen, &_iph);
@@ -214,8 +213,9 @@ ipv6:
 			key_control->addr_type = FLOW_DISSECTOR_KEY_IPV6_ADDRS;
 		}

-		flow_label = ip6_flowlabel(iph);
-		if (flow_label) {
+		if (skb && ip6_flowlabel(iph)) {
+			__be32 flow_label = ip6_flowlabel(iph);
+
 			if (skb_flow_dissector_uses_key(flow_dissector,
 				FLOW_DISSECTOR_KEY_FLOW_LABEL)) {
 				key_tags = skb_flow_dissector_target(flow_dissector,
--
2.7.0