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, 7 insertions, 3 deletions

diff --git a/net/dccp/ipv6.c b/net/dccp/ipv6.c
index 6e3f32575df7..dca711df9b60 100644
--- a/net/dccp/ipv6.c
+++ b/net/dccp/ipv6.c
@@ -564,7 +564,7 @@ static struct sock *dccp_v6_request_recv_sock(struct sock *sk,
 
         newsk = dccp_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
@@ -632,18 +632,22 @@ static struct sock *dccp_v6_request_recv_sock(struct sock *sk,
         newinet->inet_daddr = newinet->inet_saddr = LOOPBACK4_IPV6;
         newinet->inet_rcv_saddr = LOOPBACK4_IPV6;
 
+        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_nonewsk:
+        dst_release(dst);
 out:
         NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_LISTENDROPS);
         if (opt != NULL && opt != np->opt)
                 sock_kfree_s(sk, opt, opt->tot_len);
-        dst_release(dst);
         return NULL;
 }