6.12-stable review patch. If anyone has any objections, please let me know.
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From: Zhang Tengfei zhtfdev@gmail.com
[ 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 ja@ssi.bg Link: https://lore.kernel.org/lvs-devel/2189fc62-e51e-78c9-d1de-d35b8e3657e3@ssi.b... Signed-off-by: Zhang Tengfei zhtfdev@gmail.com Acked-by: Julian Anastasov ja@ssi.bg Signed-off-by: Florian Westphal fw@strlen.de Signed-off-by: Sasha Levin sashal@kernel.org --- 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 c0289f83f96df..327baa17882a8 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); }
@@ -1433,7 +1433,7 @@ 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 3224f6e17e736..3219338feca4d 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; @@ -1482,9 +1482,9 @@ 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 f821ad2e19b35..3492108bb3b97 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 */ @@ -305,7 +305,7 @@ 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); @@ -342,7 +342,7 @@ 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; @@ -485,7 +485,7 @@ 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; @@ -662,7 +662,7 @@ 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; }
@@ -680,7 +680,7 @@ 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();
@@ -756,7 +756,7 @@ 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) @@ -786,7 +786,7 @@ 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)