netdev - [PATCH 4.4 stable 03/10] ipv6: do not increment mac header when it's unset

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Message-Id: <20191008112309.9571-4-geokohma@cisco.com>
Date:   Tue,  8 Oct 2019 13:23:02 +0200
From:   Georg Kohmann <geokohma@...co.com>
To:     netdev@...r.kernel.org
Cc:     Georg Kohmann <geokohma@...co.com>,
        "Jason A . Donenfeld" <Jason@...c4.com>,
        "David S . Miller" <davem@...emloft.net>
Subject: [PATCH 4.4 stable 03/10] ipv6: do not increment mac header when it's unset

commit b678aa578c9e ("ipv6: do not increment mac header when it's unset")
Author: Jason A. Donenfeld <Jason@...c4.com>
Date:   Fri Oct 21 18:28:25 2016 +0900

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>
Signed-off-by: David S. Miller <davem@...emloft.net>
---
 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 ec917f5..2842ccf 100644
--- a/net/ipv6/reassembly.c
+++ b/net/ipv6/reassembly.c
@@ -418,7 +418,8 @@ 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(head))
+		head->mac_header += sizeof(struct frag_hdr);
 	head->network_header += sizeof(struct frag_hdr);
 
 	skb_reset_transport_header(head);
-- 
2.10.2