netfilter: tproxy: do not assign timewait sockets to skb->sk

Assigning a socket in timewait state to skb->sk can trigger
kernel oops, e.g. in nfnetlink_log, which does:

if (skb->sk) {
        read_lock_bh(&skb->sk->sk_callback_lock);
        if (skb->sk->sk_socket && skb->sk->sk_socket->file) ...

in the timewait case, accessing sk->sk_callback_lock and sk->sk_socket
is invalid.

Either all of these spots will need to add a test for sk->sk_state != TCP_TIME_WAIT,
or xt_TPROXY must not assign a timewait socket to skb->sk.

This does the latter.

If a TW socket is found, assign the tproxy nfmark, but skip the skb->sk assignment,
thus mimicking behaviour of a '-m socket .. -j MARK/ACCEPT' re-routing rule.

The 'SYN to TW socket' case is left unchanged -- we try to redirect to the
listener socket.

Cc: Balazs Scheidler <bazsi@balabit.hu>
Cc: KOVACS Krisztian <hidden@balabit.hu>
Signed-off-by: Florian Westphal <fwestphal@astaro.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>

1 files changed, 1 insertions, 11 deletions

diff --git a/include/net/netfilter/nf_tproxy_core.h b/include/net/netfilter/nf_tproxy_core.h
index cd85b3bc8327..e505358d8999 100644
--- a/include/net/netfilter/nf_tproxy_core.h
+++ b/include/net/netfilter/nf_tproxy_core.h
@@ -201,18 +201,8 @@ nf_tproxy_get_sock_v6(struct net *net, const u8 protocol,
 }
 #endif
 
-static inline void
-nf_tproxy_put_sock(struct sock *sk)
-{
-        /* TIME_WAIT inet sockets have to be handled differently */
-        if ((sk->sk_protocol == IPPROTO_TCP) && (sk->sk_state == TCP_TIME_WAIT))
-                inet_twsk_put(inet_twsk(sk));
-        else
-                sock_put(sk);
-}
-
 /* assign a socket to the skb -- consumes sk */
-int
+void
 nf_tproxy_assign_sock(struct sk_buff *skb, struct sock *sk);
 
 #endif