tcp: Add TIME_WAIT sockets in bhash2.

Jiri Slaby reported regression of bind() with a simple repro. [0]

The repro creates a TIME_WAIT socket and tries to bind() a new socket
with the same local address and port.  Before commit 28044fc1d495 ("net:
Add a bhash2 table hashed by port and address"), the bind() failed with
-EADDRINUSE, but now it succeeds.

The cited commit should have put TIME_WAIT sockets into bhash2; otherwise,
inet_bhash2_conflict() misses TIME_WAIT sockets when validating bind()
requests if the address is not a wildcard one.

The straight option is to move sk_bind2_node from struct sock to struct
sock_common to add twsk to bhash2 as implemented as RFC. [1]  However, the
binary layout change in the struct sock could affect performances moving
hot fields on different cachelines.

To avoid that, we add another TIME_WAIT list in inet_bind2_bucket and check
it while validating bind().

[0]: https://lore.kernel.org/netdev/6b971a4e-c7d8-411e-1f92-fda29b5b2fb9@kernel.org/
[1]: https://lore.kernel.org/netdev/20221221151258.25748-2-kuniyu@amazon.com/

Fixes: 28044fc1d495 ("net: Add a bhash2 table hashed by port and address")
Reported-by: Jiri Slaby <jirislaby@kernel.org>
Suggested-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Acked-by: Joanne Koong <joannelkoong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 3 deletions

diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index d039b4e732a3..24a38b56fab9 100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -116,6 +116,7 @@ static void inet_bind2_bucket_init(struct inet_bind2_bucket *tb,
 #endif
 		tb->rcv_saddr = sk->sk_rcv_saddr;
 	INIT_HLIST_HEAD(&tb->owners);
+	INIT_HLIST_HEAD(&tb->deathrow);
 	hlist_add_head(&tb->node, &head->chain);
 }
 
@@ -137,7 +138,7 @@ struct inet_bind2_bucket *inet_bind2_bucket_create(struct kmem_cache *cachep,
 /* Caller must hold hashbucket lock for this tb with local BH disabled */
 void inet_bind2_bucket_destroy(struct kmem_cache *cachep, struct inet_bind2_bucket *tb)
 {
-	if (hlist_empty(&tb->owners)) {
+	if (hlist_empty(&tb->owners) && hlist_empty(&tb->deathrow)) {
 		__hlist_del(&tb->node);
 		kmem_cache_free(cachep, tb);
 	}
@@ -1103,15 +1104,16 @@ ok:
 	/* Head lock still held and bh's disabled */
 	inet_bind_hash(sk, tb, tb2, port);
 
-	spin_unlock(&head2->lock);
-
 	if (sk_unhashed(sk)) {
 		inet_sk(sk)->inet_sport = htons(port);
 		inet_ehash_nolisten(sk, (struct sock *)tw, NULL);
 	}
 	if (tw)
 		inet_twsk_bind_unhash(tw, hinfo);
+
+	spin_unlock(&head2->lock);
 	spin_unlock(&head->lock);
+
 	if (tw)
 		inet_twsk_deschedule_put(tw);
 	local_bh_enable();