From 3da812d860755925da890e8c713f2d2e2d7b1bae Mon Sep 17 00:00:00 2001 From: Hannes Frederic Sowa Date: Sun, 29 Sep 2013 05:40:50 +0200 Subject: [PATCH] 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 Signed-off-by: Hannes Frederic Sowa Acked-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv6/ip6_gre.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c index 6b26e9feafb9..7bb5446b9d73 100644 --- a/net/ipv6/ip6_gre.c +++ b/net/ipv6/ip6_gre.c @@ -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))) {