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ipv6: gre: correct calculation of max_headroom 

gre_hlen already accounts for sizeof(struct ipv6_hdr) + gre header,
so initialize max_headroom to zero. Otherwise the

	if (encap_limit >= 0) {
		max_headroom += 8;
		mtu -= 8;
	}

increments an uninitialized variable before max_headroom was reset.

Found with coverity: 728539

Cc: Dmitry Kozlov <xeb@mail.ru>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Hannes Frederic Sowa 2013-09-29 05:40:50 +02:00 committed by David S. Miller
parent e58f6f4fb4
commit 3da812d860
1 changed files with 2 additions and 2 deletions
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4
net/ipv6/ip6_gre.c
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@ -618,7 +618,7 @@ static netdev_tx_t ip6gre_xmit2(struct sk_buff *skb,
struct ip6_tnl *tunnel = netdev_priv(dev);
struct net_device *tdev; /* Device to other host */
struct ipv6hdr *ipv6h; /* Our new IP header */
unsigned int max_headroom; /* The extra header space needed */
unsigned int max_headroom = 0; /* The extra header space needed */
int gre_hlen;
struct ipv6_tel_txoption opt;
int mtu;
@ -693,7 +693,7 @@ static netdev_tx_t ip6gre_xmit2(struct sk_buff *skb,
skb_scrub_packet(skb, !net_eq(tunnel->net, dev_net(dev)));
max_headroom = LL_RESERVED_SPACE(tdev) + gre_hlen + dst->header_len;
max_headroom += LL_RESERVED_SPACE(tdev) + gre_hlen + dst->header_len;
if (skb_headroom(skb) < max_headroom || skb_shared(skb) ||
(skb_cloned(skb) && !skb_clone_writable(skb, 0))) {