From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 526EC30ACFD; Mon, 13 Oct 2025 15:36:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760369816; cv=none; b=Tld3Gqd48EnqvMuScY72UL3xP02jRfYGDvxcZlfK2LHUcR0lR81C5TDcFUlaMHf7W2hcf6PfBVukJe157hL4l5uYXNY8VgPWtX0whWWxmCNDxoRisuzYC8f6GS9eFacODbE2VPEW6WvFW33Pdn6+n495+FyK2NKlhgVfXu7aQPg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760369816; c=relaxed/simple; bh=QBKEraeMjiB/PX7FcWkbi9r/MRirL26PbSkFWViIN8M=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=WYgvUZeO+hbdFyprUYVC8liyV4wSyfdfjvM6m/elatekFLPuKJW0UHv8UdM39FOh3hM0PBpIHZspUm5FAmZ60/TvtU4LkjHamWgn1M1/NB9c18mwwgxojRch4sjGDQ+wGc291e+yf+TBEEfBnOfiWzwyx9XMVL6r4+Dd32pnFeM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=vi4r359o; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="vi4r359o" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CFA11C4CEFE; Mon, 13 Oct 2025 15:36:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1760369816; bh=QBKEraeMjiB/PX7FcWkbi9r/MRirL26PbSkFWViIN8M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=vi4r359okqmCk49MylcTBQS86ZN/nFb92sVKhnGp/qiuS74WCpRzvLDg4ioh9O2vi GT0hlaQdSM8F63TxBsAPngVhTInbhC2hFkvlmr/LnRH72zsvHN3v98gWVe6BeZQQsn AXimnc3/di5AfzMblH8oSS1z1mJh00xiEXloWqW0= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+1651b5234028c294c339@syzkaller.appspotmail.com, Julian Anastasov , Zhang Tengfei , Florian Westphal , Sasha Levin Subject: [PATCH 6.17 346/563] ipvs: Use READ_ONCE/WRITE_ONCE for ipvs->enable Date: Mon, 13 Oct 2025 16:43:27 +0200 Message-ID: <20251013144423.804986868@linuxfoundation.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251013144411.274874080@linuxfoundation.org> References: <20251013144411.274874080@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.17-stable review patch. If anyone has any objections, please let me know. ------------------ From: Zhang Tengfei [ Upstream commit 944b6b216c0387ac3050cd8b773819ae360bfb1c ] KCSAN reported a data-race on the `ipvs->enable` flag, which is written in the control path and read concurrently from many other contexts. Following a suggestion by Julian, this patch fixes the race by converting all accesses to use `WRITE_ONCE()/READ_ONCE()`. This lightweight approach ensures atomic access and acts as a compiler barrier, preventing unsafe optimizations where the flag is checked in loops (e.g., in ip_vs_est.c). Additionally, the `enable` checks in the fast-path hooks (`ip_vs_in_hook`, `ip_vs_out_hook`, `ip_vs_forward_icmp`) are removed. These are unnecessary since commit 857ca89711de ("ipvs: register hooks only with services"). The `enable=0` condition they check for can only occur in two rare and non-fatal scenarios: 1) after hooks are registered but before the flag is set, and 2) after hooks are unregistered on cleanup_net. In the worst case, a single packet might be mishandled (e.g., dropped), which does not lead to a system crash or data corruption. Adding a check in the performance-critical fast-path to handle this harmless condition is not a worthwhile trade-off. Fixes: 857ca89711de ("ipvs: register hooks only with services") Reported-by: syzbot+1651b5234028c294c339@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=1651b5234028c294c339 Suggested-by: Julian Anastasov Link: https://lore.kernel.org/lvs-devel/2189fc62-e51e-78c9-d1de-d35b8e3657e3@ssi.bg/ Signed-off-by: Zhang Tengfei Acked-by: Julian Anastasov Signed-off-by: Florian Westphal Signed-off-by: Sasha Levin --- net/netfilter/ipvs/ip_vs_conn.c | 4 ++-- net/netfilter/ipvs/ip_vs_core.c | 11 ++++------- net/netfilter/ipvs/ip_vs_ctl.c | 6 +++--- net/netfilter/ipvs/ip_vs_est.c | 16 ++++++++-------- 4 files changed, 17 insertions(+), 20 deletions(-) diff --git a/net/netfilter/ipvs/ip_vs_conn.c b/net/netfilter/ipvs/ip_vs_conn.c index 965f3c8e5089d..37ebb0cb62b8b 100644 --- a/net/netfilter/ipvs/ip_vs_conn.c +++ b/net/netfilter/ipvs/ip_vs_conn.c @@ -885,7 +885,7 @@ static void ip_vs_conn_expire(struct timer_list *t) * conntrack cleanup for the net. */ smp_rmb(); - if (ipvs->enable) + if (READ_ONCE(ipvs->enable)) ip_vs_conn_drop_conntrack(cp); } @@ -1439,7 +1439,7 @@ void ip_vs_expire_nodest_conn_flush(struct netns_ipvs *ipvs) cond_resched_rcu(); /* netns clean up started, abort delayed work */ - if (!ipvs->enable) + if (!READ_ONCE(ipvs->enable)) break; } rcu_read_unlock(); diff --git a/net/netfilter/ipvs/ip_vs_core.c b/net/netfilter/ipvs/ip_vs_core.c index c7a8a08b73089..5ea7ab8bf4dcc 100644 --- a/net/netfilter/ipvs/ip_vs_core.c +++ b/net/netfilter/ipvs/ip_vs_core.c @@ -1353,9 +1353,6 @@ ip_vs_out_hook(void *priv, struct sk_buff *skb, const struct nf_hook_state *stat if (unlikely(!skb_dst(skb))) return NF_ACCEPT; - if (!ipvs->enable) - return NF_ACCEPT; - ip_vs_fill_iph_skb(af, skb, false, &iph); #ifdef CONFIG_IP_VS_IPV6 if (af == AF_INET6) { @@ -1940,7 +1937,7 @@ ip_vs_in_hook(void *priv, struct sk_buff *skb, const struct nf_hook_state *state return NF_ACCEPT; } /* ipvs enabled in this netns ? */ - if (unlikely(sysctl_backup_only(ipvs) || !ipvs->enable)) + if (unlikely(sysctl_backup_only(ipvs))) return NF_ACCEPT; ip_vs_fill_iph_skb(af, skb, false, &iph); @@ -2108,7 +2105,7 @@ ip_vs_forward_icmp(void *priv, struct sk_buff *skb, int r; /* ipvs enabled in this netns ? */ - if (unlikely(sysctl_backup_only(ipvs) || !ipvs->enable)) + if (unlikely(sysctl_backup_only(ipvs))) return NF_ACCEPT; if (state->pf == NFPROTO_IPV4) { @@ -2295,7 +2292,7 @@ static int __net_init __ip_vs_init(struct net *net) return -ENOMEM; /* Hold the beast until a service is registered */ - ipvs->enable = 0; + WRITE_ONCE(ipvs->enable, 0); ipvs->net = net; /* Counters used for creating unique names */ ipvs->gen = atomic_read(&ipvs_netns_cnt); @@ -2367,7 +2364,7 @@ static void __net_exit __ip_vs_dev_cleanup_batch(struct list_head *net_list) ipvs = net_ipvs(net); ip_vs_unregister_hooks(ipvs, AF_INET); ip_vs_unregister_hooks(ipvs, AF_INET6); - ipvs->enable = 0; /* Disable packet reception */ + WRITE_ONCE(ipvs->enable, 0); /* Disable packet reception */ smp_wmb(); ip_vs_sync_net_cleanup(ipvs); } diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c index 6a6fc44785337..4c8fa22be88ad 100644 --- a/net/netfilter/ipvs/ip_vs_ctl.c +++ b/net/netfilter/ipvs/ip_vs_ctl.c @@ -256,7 +256,7 @@ static void est_reload_work_handler(struct work_struct *work) struct ip_vs_est_kt_data *kd = ipvs->est_kt_arr[id]; /* netns clean up started, abort delayed work */ - if (!ipvs->enable) + if (!READ_ONCE(ipvs->enable)) goto unlock; if (!kd) continue; @@ -1483,9 +1483,9 @@ ip_vs_add_service(struct netns_ipvs *ipvs, struct ip_vs_service_user_kern *u, *svc_p = svc; - if (!ipvs->enable) { + if (!READ_ONCE(ipvs->enable)) { /* Now there is a service - full throttle */ - ipvs->enable = 1; + WRITE_ONCE(ipvs->enable, 1); /* Start estimation for first time */ ip_vs_est_reload_start(ipvs); diff --git a/net/netfilter/ipvs/ip_vs_est.c b/net/netfilter/ipvs/ip_vs_est.c index 15049b8267327..93a925f1ed9b8 100644 --- a/net/netfilter/ipvs/ip_vs_est.c +++ b/net/netfilter/ipvs/ip_vs_est.c @@ -231,7 +231,7 @@ static int ip_vs_estimation_kthread(void *data) void ip_vs_est_reload_start(struct netns_ipvs *ipvs) { /* Ignore reloads before first service is added */ - if (!ipvs->enable) + if (!READ_ONCE(ipvs->enable)) return; ip_vs_est_stopped_recalc(ipvs); /* Bump the kthread configuration genid */ @@ -306,7 +306,7 @@ static int ip_vs_est_add_kthread(struct netns_ipvs *ipvs) int i; if ((unsigned long)ipvs->est_kt_count >= ipvs->est_max_threads && - ipvs->enable && ipvs->est_max_threads) + READ_ONCE(ipvs->enable) && ipvs->est_max_threads) return -EINVAL; mutex_lock(&ipvs->est_mutex); @@ -343,7 +343,7 @@ static int ip_vs_est_add_kthread(struct netns_ipvs *ipvs) } /* Start kthread tasks only when services are present */ - if (ipvs->enable && !ip_vs_est_stopped(ipvs)) { + if (READ_ONCE(ipvs->enable) && !ip_vs_est_stopped(ipvs)) { ret = ip_vs_est_kthread_start(ipvs, kd); if (ret < 0) goto out; @@ -486,7 +486,7 @@ int ip_vs_start_estimator(struct netns_ipvs *ipvs, struct ip_vs_stats *stats) struct ip_vs_estimator *est = &stats->est; int ret; - if (!ipvs->est_max_threads && ipvs->enable) + if (!ipvs->est_max_threads && READ_ONCE(ipvs->enable)) ipvs->est_max_threads = ip_vs_est_max_threads(ipvs); est->ktid = -1; @@ -663,7 +663,7 @@ static int ip_vs_est_calc_limits(struct netns_ipvs *ipvs, int *chain_max) /* Wait for cpufreq frequency transition */ wait_event_idle_timeout(wq, kthread_should_stop(), HZ / 50); - if (!ipvs->enable || kthread_should_stop()) + if (!READ_ONCE(ipvs->enable) || kthread_should_stop()) goto stop; } @@ -681,7 +681,7 @@ static int ip_vs_est_calc_limits(struct netns_ipvs *ipvs, int *chain_max) rcu_read_unlock(); local_bh_enable(); - if (!ipvs->enable || kthread_should_stop()) + if (!READ_ONCE(ipvs->enable) || kthread_should_stop()) goto stop; cond_resched(); @@ -757,7 +757,7 @@ static void ip_vs_est_calc_phase(struct netns_ipvs *ipvs) mutex_lock(&ipvs->est_mutex); for (id = 1; id < ipvs->est_kt_count; id++) { /* netns clean up started, abort */ - if (!ipvs->enable) + if (!READ_ONCE(ipvs->enable)) goto unlock2; kd = ipvs->est_kt_arr[id]; if (!kd) @@ -787,7 +787,7 @@ static void ip_vs_est_calc_phase(struct netns_ipvs *ipvs) id = ipvs->est_kt_count; next_kt: - if (!ipvs->enable || kthread_should_stop()) + if (!READ_ONCE(ipvs->enable) || kthread_should_stop()) goto unlock; id--; if (id < 0) -- 2.51.0