From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-188.mta1.migadu.com (out-188.mta1.migadu.com [95.215.58.188]) (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 92E2D2874FC for ; Fri, 26 Sep 2025 07:41:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.188 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758872502; cv=none; b=Ps5Q6rl4qD9ljycTtMW2mZi6O+jGmZ8nFINj2zgKmLrT+Bg+eBHPlXpHryJ/UfykYGdL3OOcC0qZ3hQfI5A09AA/RRv4YaOy9Ag5ydz+iinWRDQvgdVPgLhVanfCRv6kxSAxdrqYk9PBYdYiwo7LKLKQQWhUGWiiaYaz3RpPuik= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758872502; c=relaxed/simple; bh=PfeFydI8sqj1s29pMYCUGv6K1VfSyY9gTP2CDLFhZUc=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=oNuvCNjKcMZ4NRieLN5jgFmAlGUfhLZZziW/ZBjOy7cuUw4Mf/A3a+aHJ9jBmmtxYWQurRqbO5zdpsWvyk9UZug3zQByi/EsJfy019w99tZQgjmg672kaQE1Fg2aTOG4MoquTBEu5gpB9l5hTQmgKGaCet+3v4Dks06H37928vk= 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=Fat83D9l; arc=none smtp.client-ip=95.215.58.188 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="Fat83D9l" 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=1758872498; 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: in-reply-to:in-reply-to:references:references; bh=mF1yGTZwcqF8A3rdntQTIFfmsVzWfGaD0gESIg8hgBI=; b=Fat83D9lqiip9vx63xjOxeAVmsbwt+Nj/LquH/3OvgeQNYBV6FuxpK+SyIaAtL+Ag+enR3 JEJdKtoEhs5DgQIbPT9ReODqBXMGJh7U29Plac4OaKzhWZk/tUKBG6zhl/4IXlNU0O8kWx DIP11Ko4hMozWxOqyqQpkDySnVAClPk= From: xuanqiang.luo@linux.dev To: edumazet@google.com, kuniyu@google.com Cc: kerneljasonxing@gmail.com, davem@davemloft.net, kuba@kernel.org, netdev@vger.kernel.org, Xuanqiang Luo Subject: [PATCH net-next v7 2/3] inet: Avoid ehash lookup race in inet_ehash_insert() Date: Fri, 26 Sep 2025 15:40:32 +0800 Message-Id: <20250926074033.1548675-3-xuanqiang.luo@linux.dev> In-Reply-To: <20250926074033.1548675-1-xuanqiang.luo@linux.dev> References: <20250926074033.1548675-1-xuanqiang.luo@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: Xuanqiang Luo Since ehash lookups are lockless, if one CPU performs a lookup while another concurrently deletes and inserts (removing reqsk and inserting sk), the lookup may fail to find the socket, an RST may be sent. The call trace map is drawn as follows: CPU 0 CPU 1 ----- ----- inet_ehash_insert() spin_lock() sk_nulls_del_node_init_rcu(osk) __inet_lookup_established() (lookup failed) __sk_nulls_add_node_rcu(sk, list) spin_unlock() As both deletion and insertion operate on the same ehash chain, this patch introduces a new sk_nulls_replace_node_init_rcu() helper functions to implement atomic replacement. Fixes: 5e0724d027f0 ("tcp/dccp: fix hashdance race for passive sessions") Reviewed-by: Kuniyuki Iwashima Signed-off-by: Xuanqiang Luo --- include/net/sock.h | 14 ++++++++++++++ net/ipv4/inet_hashtables.c | 8 ++++++-- 2 files changed, 20 insertions(+), 2 deletions(-) diff --git a/include/net/sock.h b/include/net/sock.h index 0fd465935334..5d67f5cbae52 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -854,6 +854,20 @@ static inline bool sk_nulls_del_node_init_rcu(struct sock *sk) return rc; } +static inline bool sk_nulls_replace_node_init_rcu(struct sock *old, + struct sock *new) +{ + if (sk_hashed(old)) { + hlist_nulls_replace_init_rcu(&old->sk_nulls_node, + &new->sk_nulls_node); + DEBUG_NET_WARN_ON_ONCE(refcount_read(&old->sk_refcnt) == 1); + __sock_put(old); + return true; + } + + return false; +} + static inline void __sk_add_node(struct sock *sk, struct hlist_head *list) { hlist_add_head(&sk->sk_node, list); diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c index ef4ccfd46ff6..1ec224562494 100644 --- a/net/ipv4/inet_hashtables.c +++ b/net/ipv4/inet_hashtables.c @@ -685,8 +685,11 @@ bool inet_ehash_insert(struct sock *sk, struct sock *osk, bool *found_dup_sk) spin_lock(lock); if (osk) { WARN_ON_ONCE(sk->sk_hash != osk->sk_hash); - ret = sk_nulls_del_node_init_rcu(osk); - } else if (found_dup_sk) { + ret = sk_nulls_replace_node_init_rcu(osk, sk); + goto unlock; + } + + if (found_dup_sk) { *found_dup_sk = inet_ehash_lookup_by_sk(sk, list); if (*found_dup_sk) ret = false; @@ -695,6 +698,7 @@ bool inet_ehash_insert(struct sock *sk, struct sock *osk, bool *found_dup_sk) if (ret) __sk_nulls_add_node_rcu(sk, list); +unlock: spin_unlock(lock); return ret; -- 2.25.1