A data-race was detected by KCSAN between ip_vs_add_service() which acts as a writer, and ip_vs_out_hook() which acts as a reader. This can lead to unpredictable behavior and crashes. One observed symptom is the "no destination available" error when processing packets.
The race occurs on the `enable` flag within the `netns_ipvs` struct. This flag was being written in the configuration path without any protection, while concurrently being read in the packet processing path. This lack of synchronization means a reader on one CPU could see a partially initialized service, leading to incorrect behavior. To fix this, convert the `enable` flag from a plain integer to an atomic_t. This ensures that all reads and writes to the flag are atomic. More importantly, using atomic_set() and atomic_read() provides the necessary memory barriers to guarantee that changes to other fields of the service are visible to the reader CPU before the service is marked as enabled. Reported-by: syzbot+1651b5234028c294c...@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=1651b5234028c294c339 Signed-off-by: Zhang Tengfei <zhtf...@gmail.com> --- include/net/ip_vs.h | 2 +- net/netfilter/ipvs/ip_vs_conn.c | 4 ++-- net/netfilter/ipvs/ip_vs_core.c | 10 +++++----- net/netfilter/ipvs/ip_vs_ctl.c | 6 +++--- net/netfilter/ipvs/ip_vs_est.c | 16 ++++++++-------- 5 files changed, 19 insertions(+), 19 deletions(-) diff --git a/include/net/ip_vs.h b/include/net/ip_vs.h index 29a36709e7f3..58b2ad7906e8 100644 --- a/include/net/ip_vs.h +++ b/include/net/ip_vs.h @@ -895,7 +895,7 @@ struct ipvs_sync_daemon_cfg { /* IPVS in network namespace */ struct netns_ipvs { int gen; /* Generation */ - int enable; /* enable like nf_hooks do */ + atomic_t enable; /* enable like nf_hooks do */ /* Hash table: for real service lookups */ #define IP_VS_RTAB_BITS 4 #define IP_VS_RTAB_SIZE (1 << IP_VS_RTAB_BITS) diff --git a/net/netfilter/ipvs/ip_vs_conn.c b/net/netfilter/ipvs/ip_vs_conn.c index 965f3c8e5089..5c97f85929b4 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 (atomic_read(&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 (!atomic_read(&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 c7a8a08b7308..84eed2e45927 100644 --- a/net/netfilter/ipvs/ip_vs_core.c +++ b/net/netfilter/ipvs/ip_vs_core.c @@ -1353,7 +1353,7 @@ 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) + if (!atomic_read(&ipvs->enable)) return NF_ACCEPT; ip_vs_fill_iph_skb(af, skb, false, &iph); @@ -1940,7 +1940,7 @@ 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) || !atomic_read(&ipvs->enable))) return NF_ACCEPT; ip_vs_fill_iph_skb(af, skb, false, &iph); @@ -2108,7 +2108,7 @@ 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) || !atomic_read(&ipvs->enable))) return NF_ACCEPT; if (state->pf == NFPROTO_IPV4) { @@ -2295,7 +2295,7 @@ static int __net_init __ip_vs_init(struct net *net) return -ENOMEM; /* Hold the beast until a service is registered */ - ipvs->enable = 0; + atomic_set(&ipvs->enable, 0); ipvs->net = net; /* Counters used for creating unique names */ ipvs->gen = atomic_read(&ipvs_netns_cnt); @@ -2367,7 +2367,7 @@ 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 */ + atomic_set(&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 6a6fc4478533..ad7e1c387c1f 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 (!atomic_read(&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 (!atomic_read(&ipvs->enable)) { /* Now there is a service - full throttle */ - ipvs->enable = 1; + atomic_set(&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 15049b826732..c5aa2660de92 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 (!atomic_read(&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) + atomic_read(&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 (atomic_read(&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 && atomic_read(&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 (!atomic_read(&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 (!atomic_read(&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 (!atomic_read(&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 (!atomic_read(&ipvs->enable) || kthread_should_stop()) goto unlock; id--; if (id < 0) -- 2.47.3
