[PATCH 4.9 140/172] netfilter: use skb_to_full_sk in ip_route_me_harder

Greg Kroah-Hartman
2017-07-03T13:45:29Z

From: Florian Westphal <fw@strlen.de>

commit 29e09229d9f26129a39462fae0ddabc4d9533989 upstream.

inet_sk(skb->sk) is illegal in case skb is attached to request socket.

Fixes: ca6fb0651883 ("tcp: attach SYNACK messages to request sockets instead of listener")
Reported by: Daniel J Blueman <daniel@quora.org>
Signed-off-by: Florian Westphal <fw@strlen.de>
Tested-by: Daniel J Blueman <daniel@quora.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
net/ipv4/netfilter.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

--- a/net/ipv4/netfilter.c
+++ b/net/ipv4/netfilter.c
@@ -23,7 +23,8 @@ int ip_route_me_harder(struct net *net,
struct rtable *rt;
struct flowi4 fl4 = {};
__be32 saddr = iph->saddr;
- __u8 flags = skb->sk ? inet_sk_flowi_flags(skb->sk) : 0;
+ const struct sock *sk = skb_to_full_sk(skb);
+ __u8 flags = sk ? inet_sk_flowi_flags(sk) : 0;
struct net_device *dev = skb_dst(skb)->dev;
unsigned int hh_len;

@@ -40,7 +41,7 @@ int ip_route_me_harder(struct net *net,
fl4.daddr = iph->daddr;
fl4.saddr = saddr;
fl4.flowi4_tos = RT_TOS(iph->tos);
- fl4.flowi4_oif = skb->sk ? skb->sk->sk_bound_dev_if : 0;
+ fl4.flowi4_oif = sk ? sk->sk_bound_dev_if : 0;
if (!fl4.flowi4_oif)
fl4.flowi4_oif = l3mdev_master_ifindex(dev);
fl4.flowi4_mark = skb->mark;
@@ -61,7 +62,7 @@ int ip_route_me_harder(struct net *net,
xfrm_decode_session(skb, flowi4_to_flowi(&fl4), AF_INET) == 0) {
struct dst_entry *dst = skb_dst(skb);
skb_dst_set(skb, NULL);
- dst = xfrm_lookup(net, dst, flowi4_to_flowi(&fl4), skb->sk, 0);
+ dst = xfrm_lookup(net, dst, flowi4_to_flowi(&fl4), sk, 0);
if (IS_ERR(dst))
return PTR_ERR(dst);
skb_dst_set(skb, dst);