netdev - [PATCH] tcp: disallow bind() to reuse addr/port

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Date:	Tue, 11 Jan 2011 12:14:22 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Daniel Baluta <daniel.baluta@...il.com>,
	David Miller <davem@...emloft.net>
Cc:	Gaspar Chilingarov <gasparch@...il.com>,
	netdev <netdev@...r.kernel.org>
Subject: [PATCH] tcp: disallow bind() to reuse addr/port

Le mercredi 05 janvier 2011 à 11:00 +0200, Daniel Baluta a écrit :

> Going back to my first email, are there any follow ups on your
> "tcp: bind() fix when many ports are bound" patch. I've searched
> netdev archives but no luck. I might have missed something.
> 
> I really appreciate your help.
> 

I believe following patch should solve the problem.

Thanks for reminding us this issue !

I checked FreeBSD : It doesnt allow two sockets (in CLOSE state) bound
on same addr/port, even if both have REUSEADDR set



[PATCH] tcp: disallow bind() to reuse addr/port

inet_csk_bind_conflict() logic currently disallows a bind() if
it finds a friend socket (a socket bound on same address/port)
satisfying a set of conditions :

1) Current (to be bound) socket doesnt have sk_reuse set
OR
2) other socket doesnt have sk_reuse set
OR
3) other socket is in LISTEN state

We should add the CLOSE state in the 3) condition, in order to avoid two
REUSEADDR sockets in CLOSE state with same local address/port, since
this can deny further operations.

Note : a prior patch tried to address the problem in a different (and
buggy) way. (commit fda48a0d7a8412ced tcp: bind() fix when many ports
are bound).

Reported-by: Gaspar Chilingarov <gasparch@...il.com>
Reported-by: Daniel Baluta <daniel.baluta@...il.com>
Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
---
 net/ipv4/inet_connection_sock.c  |    5 +++--
 net/ipv6/inet6_connection_sock.c |    2 +-
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 25e3181..9f6d585 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -73,7 +73,7 @@ int inet_csk_bind_conflict(const struct sock *sk,
 		     !sk2->sk_bound_dev_if ||
 		     sk->sk_bound_dev_if == sk2->sk_bound_dev_if)) {
 			if (!reuse || !sk2->sk_reuse ||
-			    sk2->sk_state == TCP_LISTEN) {
+			    ((1 << sk2->sk_state) & (TCPF_LISTEN | TCPF_CLOSE))) {
 				const __be32 sk2_rcv_saddr = sk_rcv_saddr(sk2);
 				if (!sk2_rcv_saddr || !sk_rcv_saddr(sk) ||
 				    sk2_rcv_saddr == sk_rcv_saddr(sk))
@@ -122,7 +122,8 @@ again:
 					    (tb->num_owners < smallest_size || smallest_size == -1)) {
 						smallest_size = tb->num_owners;
 						smallest_rover = rover;
-						if (atomic_read(&hashinfo->bsockets) > (high - low) + 1) {
+						if (atomic_read(&hashinfo->bsockets) > (high - low) + 1 && 
+						    !inet_csk(sk)->icsk_af_ops->bind_conflict(sk, tb)) {
 							spin_unlock(&head->lock);
 							snum = smallest_rover;
 							goto have_snum;
diff --git a/net/ipv6/inet6_connection_sock.c b/net/ipv6/inet6_connection_sock.c
index e46305d..d144e62 100644
--- a/net/ipv6/inet6_connection_sock.c
+++ b/net/ipv6/inet6_connection_sock.c
@@ -44,7 +44,7 @@ int inet6_csk_bind_conflict(const struct sock *sk,
 		     !sk2->sk_bound_dev_if ||
 		     sk->sk_bound_dev_if == sk2->sk_bound_dev_if) &&
 		    (!sk->sk_reuse || !sk2->sk_reuse ||
-		     sk2->sk_state == TCP_LISTEN) &&
+		     ((1 << sk2->sk_state) & (TCPF_LISTEN | TCPF_CLOSE))) &&
 		     ipv6_rcv_saddr_equal(sk, sk2))
 			break;
 	}


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