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>
diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
index 6b26e9f..7bb5446 100644
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -618,7 +618,7 @@
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 @@
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))) {