[PATCH] inet: fix fast path in __inet_hash_connect()

From: Pietro Borrello <borrello@diag.uniroma1.it>
To: "David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
	David Ahern <dsahern@kernel.org>
Cc: Cristiano Giuffrida <c.giuffrida@vu.nl>,
	"Bos, H.J." <h.j.bos@vu.nl>, Jakob Koschel <jkl820.git@gmail.com>,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	Pietro Borrello <borrello@diag.uniroma1.it>
Subject: [PATCH] inet: fix fast path in __inet_hash_connect()
Date: Thu, 12 Jan 2023 15:39:23 +0000	[thread overview]
Message-ID: <20230112-inet_hash_connect_bind_head-v1-1-7e3c770157c8@diag.uniroma1.it> (raw)

__inet_hash_connect() has a fast path taken if sk_head(&tb->owners) is
equal to the sk parameter.
sk_head() returns the list_entry() with respect to the sk_node field.
However entries in the tb->owners list are inserted with respect to the
sk_bind_node field with sk_add_bind_node().
Thus the check would never pass and the fast path never execute.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Pietro Borrello <borrello@diag.uniroma1.it>
---
 include/net/sock.h         | 10 ++++++++++
 net/ipv4/inet_hashtables.c |  2 +-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/include/net/sock.h b/include/net/sock.h
index dcd72e6285b2..23fc403284db 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -860,6 +860,16 @@ static inline void sk_nulls_add_node_rcu(struct sock *sk, struct hlist_nulls_hea
 	__sk_nulls_add_node_rcu(sk, list);
 }
 
+static inline struct sock *__sk_bind_head(const struct hlist_head *head)
+{
+	return hlist_entry(head->first, struct sock, sk_bind_node);
+}
+
+static inline struct sock *sk_bind_head(const struct hlist_head *head)
+{
+	return hlist_empty(head) ? NULL : __sk_bind_head(head);
+}
+
 static inline void __sk_del_bind_node(struct sock *sk)
 {
 	__hlist_del(&sk->sk_bind_node);
diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index d039b4e732a3..a805e086fb48 100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -998,7 +998,7 @@ int __inet_hash_connect(struct inet_timewait_death_row *death_row,
 						  hinfo->bhash_size)];
 		tb = inet_csk(sk)->icsk_bind_hash;
 		spin_lock_bh(&head->lock);
-		if (sk_head(&tb->owners) == sk && !sk->sk_bind_node.next) {
+		if (sk_bind_head(&tb->owners) == sk && !sk->sk_bind_node.next) {
 			inet_ehash_nolisten(sk, NULL, NULL);
 			spin_unlock_bh(&head->lock);
 			return 0;

---
base-commit: 1b929c02afd37871d5afb9d498426f83432e71c2
change-id: 20230112-inet_hash_connect_bind_head-8f2dc98f08b1

Best regards,
-- 
Pietro Borrello <borrello@diag.uniroma1.it>
