tproxy: fix hash locking issue when using port redirection in __inet_inherit_port()

When __inet_inherit_port() is called on a tproxy connection the wrong locks are
held for the inet_bind_bucket it is added to. __inet_inherit_port() made an
implicit assumption that the listener's port number (and thus its bind bucket).
Unfortunately, if you're using the TPROXY target to redirect skbs to a
transparent proxy that assumption is not true anymore and things break.

This patch adds code to __inet_inherit_port() so that it can handle this case
by looking up or creating a new bind bucket for the child socket and updates
callers of __inet_inherit_port() to gracefully handle __inet_inherit_port()
failing.

Reported by and original patch from Stephen Buck <stephen.buck@exinda.com>.
See http://marc.info/?t=128169268200001&r=1&w=2 for the original discussion.

Signed-off-by: KOVACS Krisztian <hidden@balabit.hu>
Signed-off-by: Patrick McHardy <kaber@trash.net>

1 files changed, 8 insertions, 4 deletions

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index fe6d40418c0b..ba5258ef1c57 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1409,7 +1409,7 @@ static struct sock * tcp_v6_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
 
         newsk = tcp_create_openreq_child(sk, req, skb);
         if (newsk == NULL)
-                goto out;
+                goto out_nonewsk;
 
         /*
          * No need to charge this sock to the relevant IPv6 refcnt debug socks
@@ -1497,18 +1497,22 @@ static struct sock * tcp_v6_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
         }
 #endif
 
+        if (__inet_inherit_port(sk, newsk) < 0) {
+                sock_put(newsk);
+                goto out;
+        }
         __inet6_hash(newsk, NULL);
-        __inet_inherit_port(sk, newsk);
 
         return newsk;
 
 out_overflow:
         NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS);
-out:
-        NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_LISTENDROPS);
+out_nonewsk:
         if (opt && opt != np->opt)
                 sock_kfree_s(sk, opt, opt->tot_len);
         dst_release(dst);
+out:
+        NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_LISTENDROPS);
         return NULL;
 }