ip_tunnel: Fix a memory corruption in ip_tunnel_xmit
We might extend the used aera of a skb beyond the total
headroom when we install the ipip header. Fix this by
calling skb_cow_head() unconditionally.
Bug was introduced with commit c544193214
("GRE: Refactor GRE tunneling code.")
Cc: Pravin Shelar <pshelar@nicira.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
index d3fbad4..dfc6d8a 100644
--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c
@@ -642,13 +642,13 @@
max_headroom = LL_RESERVED_SPACE(rt->dst.dev) + sizeof(struct iphdr)
+ rt->dst.header_len;
- if (max_headroom > dev->needed_headroom) {
+ if (max_headroom > dev->needed_headroom)
dev->needed_headroom = max_headroom;
- if (skb_cow_head(skb, dev->needed_headroom)) {
- dev->stats.tx_dropped++;
- dev_kfree_skb(skb);
- return;
- }
+
+ if (skb_cow_head(skb, dev->needed_headroom)) {
+ dev->stats.tx_dropped++;
+ dev_kfree_skb(skb);
+ return;
}
err = iptunnel_xmit(rt, skb, fl4.saddr, fl4.daddr, protocol,