From 3e08f4a72f689c6296d336c2aab4bddd60c93ae2 Mon Sep 17 00:00:00 2001 From: Steffen Klassert Date: Tue, 1 Oct 2013 11:33:59 +0200 Subject: [PATCH] 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 Signed-off-by: Steffen Klassert Signed-off-by: David S. Miller --- net/ipv4/ip_tunnel.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c index d3fbad422e0e..dfc6d8a3caa7 100644 --- a/net/ipv4/ip_tunnel.c +++ b/net/ipv4/ip_tunnel.c @@ -642,13 +642,13 @@ void ip_tunnel_xmit(struct sk_buff *skb, struct net_device *dev, 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,