netdev - [PATCH] ipv6: do not increment mac header when it's unset

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Message-Id: <20161021083954.20941-1-Jason@zx2c4.com>
Date:   Fri, 21 Oct 2016 17:39:54 +0900
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     davem@...emloft.net, kuznet@....inr.ac.ru, jmorris@...ei.org,
        yoshfuji@...ux-ipv6.org, kaber@...sh.net, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, pageexec@...il.com,
        re.emese@...il.com
Cc:     "Jason A. Donenfeld" <Jason@...c4.com>
Subject: [PATCH] ipv6: do not increment mac header when it's unset

Otherwise we'll overflow the integer. This occurs when layer 3 tunneled
packets are handed off to the IPv6 layer.

Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
---
 net/ipv6/reassembly.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/ipv6/reassembly.c b/net/ipv6/reassembly.c
index e2ea311..431d69d 100644
--- a/net/ipv6/reassembly.c
+++ b/net/ipv6/reassembly.c
@@ -456,7 +456,8 @@ static int ip6_frag_reasm(struct frag_queue *fq, struct sk_buff *prev,
 	skb_network_header(head)[nhoff] = skb_transport_header(head)[0];
 	memmove(head->head + sizeof(struct frag_hdr), head->head,
 		(head->data - head->head) - sizeof(struct frag_hdr));
-	head->mac_header += sizeof(struct frag_hdr);
+	if (skb_mac_header_was_set(skb))
+		head->mac_header += sizeof(struct frag_hdr);
 	head->network_header += sizeof(struct frag_hdr);
 
 	skb_reset_transport_header(head);
-- 
2.10.1