netfilter: use skb_to_full_sk in ip_route_me_harder

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>

diff --git a/net/ipv4/netfilter.c b/net/ipv4/netfilter.c
index c3776ff6749f18d1bf3c5c5084d3e7656291539d..699f8a5457a37cd7d80d9532e287fd894446172d 100644 (file)
--- a/net/ipv4/netfilter.c
+++ b/net/ipv4/netfilter.c
@@ -23,7 +23,8 @@ int ip_route_me_harder(struct net *net, struct sk_buff *skb, unsigned int addr_t
        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;
        unsigned int hh_len;
 
        if (addr_type == RTN_UNSPEC)
@@ -39,7 +40,7 @@ int ip_route_me_harder(struct net *net, struct sk_buff *skb, unsigned int addr_t
        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;
        fl4.flowi4_mark = skb->mark;
        fl4.flowi4_flags = flags;
        rt = ip_route_output_key(net, &fl4);
@@ -58,7 +59,7 @@ int ip_route_me_harder(struct net *net, struct sk_buff *skb, unsigned int addr_t
            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);