[3.13.y-ckt stable] Patch "macvtap: make sure neighbour code can push ethernet header" has been added to staging queue

[Kamal Mostafa]

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

    macvtap: make sure neighbour code can push ethernet header

to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11-ckt19.

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

For more information about the 3.13.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 295817aab8a5e724840822f72b3dce365caeca08 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet at google.com>
Date: Fri, 27 Feb 2015 18:35:35 -0800
Subject: macvtap: make sure neighbour code can push ethernet header

[ Upstream commit 2f1d8b9e8afa5a833d96afcd23abcb8cdf8d83ab ]

Brian reported crashes using IPv6 traffic with macvtap/veth combo.

I tracked the crashes in neigh_hh_output()

-> memcpy(skb->data - HH_DATA_MOD, hh->hh_data, HH_DATA_MOD);

Neighbour code assumes headroom to push Ethernet header is
at least 16 bytes.

It appears macvtap has only 14 bytes available on arches
where NET_IP_ALIGN is 0 (like x86)

Effect is a corruption of 2 bytes right before skb->head,
and possible crashes if accessing non existing memory.

This fix should also increase IPv4 performance, as paranoid code
in ip_finish_output2() wont have to call skb_realloc_headroom()

Reported-by: Brian Rak <brak at vultr.com>
Tested-by: Brian Rak <brak at vultr.com>
Signed-off-by: Eric Dumazet <edumazet at google.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/net/macvtap.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 5aead8c..d1c23e6 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -635,12 +635,15 @@ static int macvtap_skb_to_vnet_hdr(const struct sk_buff *skb,
 	return 0;
 }

+/* Neighbour code has some assumptions on HH_DATA_MOD alignment */
+#define MACVTAP_RESERVE HH_DATA_OFF(ETH_HLEN)
+
 /* Get packet from user space buffer */
 static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *m,
 				const struct iovec *iv, unsigned long total_len,
 				size_t count, int noblock)
 {
-	int good_linear = SKB_MAX_HEAD(NET_IP_ALIGN);
+	int good_linear = SKB_MAX_HEAD(MACVTAP_RESERVE);
 	struct sk_buff *skb;
 	struct macvlan_dev *vlan;
 	unsigned long len = total_len;
@@ -699,7 +702,7 @@ static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *m,
 			linear = vnet_hdr.hdr_len;
 	}

-	skb = macvtap_alloc_skb(&q->sk, NET_IP_ALIGN, copylen,
+	skb = macvtap_alloc_skb(&q->sk, MACVTAP_RESERVE, copylen,
 				linear, noblock, &err);
 	if (!skb)
 		goto err;
--
1.9.1