[PATCH net-2.6] gre: fix improper error handling
From: Dmitry Kozlov <hidden>
Date: 2011-07-22 09:35:35
Fix improper protocol err_handler, current implementation is fully unapplicable and may cause kernel crash due to double kfree_skb. Signed-off-by: Dmitry Kozlov <redacted> -- net/ipv4/gre.c | 23 +++++++---------------- 1 files changed, 7 insertions(+), 16 deletions(-)
diff --git a/net/ipv4/gre.c b/net/ipv4/gre.c
index c6933f2..a8126fe 100644
--- a/net/ipv4/gre.c
+++ b/net/ipv4/gre.c@@ -15,6 +15,7 @@ #include <linux/kmod.h> #include <linux/skbuff.h> #include <linux/in.h> +#include <linux/ip.h> #include <linux/netdevice.h> #include <linux/version.h> #include <linux/spinlock.h>
@@ -97,27 +98,17 @@ drop: static void gre_err(struct sk_buff *skb, u32 info) { const struct gre_protocol *proto; - u8 ver; - - if (!pskb_may_pull(skb, 12)) - goto drop; - - ver = skb->data[1]&0x7f; + const struct iphdr *iph = (const struct iphdr *)skb->data; + u8 ver = skb->data[(iph->ihl<<2) + 1]&0x7f; + if (ver >= GREPROTO_MAX) - goto drop; + return; rcu_read_lock(); proto = rcu_dereference(gre_proto[ver]); - if (!proto || !proto->err_handler) - goto drop_unlock; - proto->err_handler(skb, info); - rcu_read_unlock(); - return; - -drop_unlock: + if (proto && proto->err_handler) + proto->err_handler(skb, info); rcu_read_unlock(); -drop: - kfree_skb(skb); } static const struct net_protocol net_gre_protocol = {