From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-177.mta1.migadu.com (out-177.mta1.migadu.com [95.215.58.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 025803F65FD for ; Thu, 19 Mar 2026 18:18:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.177 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773944309; cv=none; b=gEv1k/f8dnx5O8zWZ0VV9Pjn6xf5RdPPbDEK7lomkjKwuEHylprvBtKe9eArmFApiCDKJzRzTA/nM7D5yHXSDr2+iT/iGChWIf35UwxcNWfCwuuGvEYN1O57IWYmgUJDM4+luB0Y9SFoVay7ybOYkD1WrfYvNu+S4qScidPwfuI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773944309; c=relaxed/simple; bh=D04F0zImx7hACstAggIXl/06ZXOel3GSj+gbpGmZfDQ=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=K/7jGxTQgAH1Xa+KxbEU6qz7PoYuAwztclTK16TPhrSOUPTNG01fL8UPJ5HnGDnsW0fK6ucsjBWoWHoNMPDpFjQx76aElClZhzv4mHcy9MWyanI07FBJg3T4JbDZcbiljQ2k17UVHr5NzBJWhoDRr2qAqO8zOXN4fz91OMnk89I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=lr035Gvk; arc=none smtp.client-ip=95.215.58.177 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="lr035Gvk" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1773944306; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=0D5Llu4ZQ3owDkePI5Vqs7Ijz0RVARo9vrMsWRlAzew=; b=lr035Gvk0QmuAGxfcH2zY20hqbmuaAnk1JBU4UgLgvEmhiwJtnqiP6t+2OwQwdq8TR5WKG b76HnT+6b6KeU0TpBWbwT5QmHnv2mTuD6D7lQ9/1vzj4xjQr8YfKqbDvqlDlfllQM0eHzx mkJrXwoO7j9xZFd20pXsL3ewoDKHCCQ= From: Martin KaFai Lau To: netdev@vger.kernel.org Cc: 'David Miller ' , 'Jakub Kicinski ' , 'Eric Dumazet ' , 'Paolo Abeni ' , 'Kuniyuki Iwashima ' , Andrew Onyshchuk Subject: [PATCH net] udp: Fix wildcard bind conflict check when using hash2 Date: Thu, 19 Mar 2026 11:18:17 -0700 Message-ID: <20260319181817.1901357-1-martin.lau@linux.dev> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT From: Martin KaFai Lau When binding a udp_sock to a local address and port, UDP uses two hashes (udptable->hash and udptable->hash2) for collision detection. The current code switches to "hash2" when hslot->count > 10. "hash2" is keyed by local address and local port. "hash" is keyed by local port only. The issue can be shown in the following bind sequence (pseudo code): bind(fd1, "[fd00::1]:8888") bind(fd2, "[fd00::2]:8888") bind(fd3, "[fd00::3]:8888") bind(fd4, "[fd00::4]:8888") bind(fd5, "[fd00::5]:8888") bind(fd6, "[fd00::6]:8888") bind(fd7, "[fd00::7]:8888") bind(fd8, "[fd00::8]:8888") bind(fd9, "[fd00::9]:8888") bind(fd10, "[fd00::10]:8888") /* Correctly return -EADDRINUSE because "hash" is used * instead of "hash2". udp_lib_lport_inuse() detects the * conflict. */ bind(fail_fd, "[::]:8888") /* After one more socket is bound to "[fd00::11]:8888", * hslot->count exceeds 10 and "hash2" is used instead. */ bind(fd11, "[fd00::11]:8888") bind(fail_fd, "[::]:8888") /* succeeds unexpectedly */ The same issue applies to the IPv4 wildcard address "0.0.0.0" and the IPv4-mapped wildcard address "::ffff:0.0.0.0". For example, if there are existing sockets bound to "192.168.1.[1-11]:8888", then binding "0.0.0.0:8888" or "[::ffff:0.0.0.0]:8888" can also miss the conflict when hslot->count > 10. TCP inet_csk_get_port() already has the correct check in inet_use_bhash2_on_bind(). Rename it to inet_use_hash2_on_bind() and move it to inet_hashtables.h so udp.c can reuse it in this fix. Fixes: 30fff9231fad ("udp: bind() optimisation") Reported-by: Andrew Onyshchuk Signed-off-by: Martin KaFai Lau --- include/net/inet_hashtables.h | 14 ++++++++++++++ net/ipv4/inet_connection_sock.c | 20 +++----------------- net/ipv4/udp.c | 2 +- 3 files changed, 18 insertions(+), 18 deletions(-) diff --git a/include/net/inet_hashtables.h b/include/net/inet_hashtables.h index 5a979dcab538..6d936e9f2fd3 100644 --- a/include/net/inet_hashtables.h +++ b/include/net/inet_hashtables.h @@ -264,6 +264,20 @@ inet_bhashfn_portaddr(const struct inet_hashinfo *hinfo, const struct sock *sk, return &hinfo->bhash2[hash & (hinfo->bhash_size - 1)]; } +static inline bool inet_use_hash2_on_bind(const struct sock *sk) +{ +#if IS_ENABLED(CONFIG_IPV6) + if (sk->sk_family == AF_INET6) { + if (ipv6_addr_any(&sk->sk_v6_rcv_saddr)) + return false; + + if (!ipv6_addr_v4mapped(&sk->sk_v6_rcv_saddr)) + return true; + } +#endif + return sk->sk_rcv_saddr != htonl(INADDR_ANY); +} + struct inet_bind_hashbucket * inet_bhash2_addr_any_hashbucket(const struct sock *sk, const struct net *net, int port); diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c index 5dfac6ce1110..e961936b6be7 100644 --- a/net/ipv4/inet_connection_sock.c +++ b/net/ipv4/inet_connection_sock.c @@ -154,20 +154,6 @@ bool inet_sk_get_local_port_range(const struct sock *sk, int *low, int *high) } EXPORT_SYMBOL(inet_sk_get_local_port_range); -static bool inet_use_bhash2_on_bind(const struct sock *sk) -{ -#if IS_ENABLED(CONFIG_IPV6) - if (sk->sk_family == AF_INET6) { - if (ipv6_addr_any(&sk->sk_v6_rcv_saddr)) - return false; - - if (!ipv6_addr_v4mapped(&sk->sk_v6_rcv_saddr)) - return true; - } -#endif - return sk->sk_rcv_saddr != htonl(INADDR_ANY); -} - static bool inet_bind_conflict(const struct sock *sk, struct sock *sk2, kuid_t uid, bool relax, bool reuseport_cb_ok, bool reuseport_ok) @@ -259,7 +245,7 @@ static int inet_csk_bind_conflict(const struct sock *sk, * checks separately because their spinlocks have to be acquired/released * independently of each other, to prevent possible deadlocks */ - if (inet_use_bhash2_on_bind(sk)) + if (inet_use_hash2_on_bind(sk)) return tb2 && inet_bhash2_conflict(sk, tb2, uid, relax, reuseport_cb_ok, reuseport_ok); @@ -376,7 +362,7 @@ inet_csk_find_open_port(const struct sock *sk, struct inet_bind_bucket **tb_ret, head = &hinfo->bhash[inet_bhashfn(net, port, hinfo->bhash_size)]; spin_lock_bh(&head->lock); - if (inet_use_bhash2_on_bind(sk)) { + if (inet_use_hash2_on_bind(sk)) { if (inet_bhash2_addr_any_conflict(sk, port, l3mdev, relax, false)) goto next_port; } @@ -562,7 +548,7 @@ int inet_csk_get_port(struct sock *sk, unsigned short snum) check_bind_conflict = false; } - if (check_bind_conflict && inet_use_bhash2_on_bind(sk)) { + if (check_bind_conflict && inet_use_hash2_on_bind(sk)) { if (inet_bhash2_addr_any_conflict(sk, port, l3mdev, true, true)) goto fail_unlock; } diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c index b60fad393e18..cb99a3c27053 100644 --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -287,7 +287,7 @@ int udp_lib_get_port(struct sock *sk, unsigned short snum, } else { hslot = udp_hashslot(udptable, net, snum); spin_lock_bh(&hslot->lock); - if (hslot->count > 10) { + if (inet_use_hash2_on_bind(sk) && hslot->count > 10) { int exist; unsigned int slot2 = udp_sk(sk)->udp_portaddr_hash ^ snum; -- 2.52.0