Patch "vlan: Fix untag operations of stacked vlans with REORDER_HEADER off" has been added to the 4.3-stable tree

Patch "vlan: Fix untag operations of stacked vlans with REORDER_HEADER off" has been added to the 4.3-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    vlan: Fix untag operations of stacked vlans with REORDER_HEADER off

to the 4.3-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     vlan-fix-untag-operations-of-stacked-vlans-with-reorder_header-off.patch
and it can be found in the queue-4.3 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Wed Dec 30 19:48:47 PST 2015
From: Vlad Yasevich <vyasevich@gmail.com>
Date: Mon, 16 Nov 2015 15:43:44 -0500
Subject: vlan: Fix untag operations of stacked vlans with REORDER_HEADER off

From: Vlad Yasevich <vyasevich@gmail.com>

[ Upstream commit a6e18ff111701b4ff6947605bfbe9594ec42a6e8 ]

When we have multiple stacked vlan devices all of which have
turned off REORDER_HEADER flag, the untag operation does not
locate the ethernet addresses correctly for nested vlans.
The reason is that in case of REORDER_HEADER flag being off,
the outer vlan headers are put back and the mac_len is adjusted
to account for the presense of the header.  Then, the subsequent
untag operation, for the next level vlan, always use VLAN_ETH_HLEN
to locate the begining of the ethernet header and that ends up
being a multiple of 4 bytes short of the actuall beginning
of the mac header (the multiple depending on the how many vlan
encapsulations ethere are).

As a reslult, if there are multiple levles of vlan devices
with REODER_HEADER being off, the recevied packets end up
being dropped.

To solve this, we use skb->mac_len as the offset.  The value
is always set on receive path and starts out as a ETH_HLEN.
The value is also updated when the vlan header manupations occur
so we know it will be correct.

Signed-off-by: Vladislav Yasevich <vyasevic@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/core/skbuff.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -4268,7 +4268,8 @@ static struct sk_buff *skb_reorder_vlan_
 		return NULL;
 	}
 
-	memmove(skb->data - ETH_HLEN, skb->data - VLAN_ETH_HLEN, 2 * ETH_ALEN);
+	memmove(skb->data - ETH_HLEN, skb->data - skb->mac_len,
+		2 * ETH_ALEN);
 	skb->mac_header += VLAN_HLEN;
 	return skb;
 }


Patches currently in stable-queue which might be from vyasevich@gmail.com are

queue-4.3/ipv6-sctp-clone-options-to-avoid-use-after-free.patch
queue-4.3/skbuff-fix-offset-error-in-skb_reorder_vlan_header.patch
queue-4.3/sctp-update-the-netstamp_needed-counter-when-copying-sockets.patch
queue-4.3/sctp-also-copy-sk_tsflags-when-copying-the-socket.patch
queue-4.3/sctp-use-the-same-clock-as-if-sock-source-timestamps-were-on.patch
queue-4.3/vlan-fix-untag-operations-of-stacked-vlans-with-reorder_header-off.patch