Hi Julian, Comments below.
On Sun, Oct 19, 2025 at 06:57:00PM +0300, Julian Anastasov wrote: > Some places walk the services under mutex but they can just use RCU: > > * ip_vs_dst_event() uses ip_vs_forget_dev() which uses its own lock > to modify dest > * ip_vs_genl_dump_services(): ip_vs_genl_fill_service() just fills skb > * ip_vs_genl_parse_service(): move RCU lock to callers > ip_vs_genl_set_cmd(), ip_vs_genl_dump_dests() and ip_vs_genl_get_cmd() > * ip_vs_genl_dump_dests(): just fill skb > > Signed-off-by: Julian Anastasov <[email protected]> > --- > net/netfilter/ipvs/ip_vs_ctl.c | 47 +++++++++++++++++----------------- > 1 file changed, 23 insertions(+), 24 deletions(-) > > diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c > index 2fb9034b4f53..b18d08d79bcb 100644 > --- a/net/netfilter/ipvs/ip_vs_ctl.c > +++ b/net/netfilter/ipvs/ip_vs_ctl.c > @@ -1759,23 +1759,21 @@ static int ip_vs_dst_event(struct notifier_block > *this, unsigned long event, > if (event != NETDEV_DOWN || !ipvs) > return NOTIFY_DONE; > IP_VS_DBG(3, "%s() dev=%s\n", __func__, dev->name); > - mutex_lock(&ipvs->service_mutex); > + rcu_read_lock(); Control plane can still add destinations to svc->destinations that can be skipped by the rcu walk. I think it should be possible to trigger leaks with a sufficiently large list, given concurrent updates can happen. ip_vs_forget_dev() has its own lock, but this is a per-dest lock which is taken during the list walk. > for (idx = 0; idx < IP_VS_SVC_TAB_SIZE; idx++) { > - hlist_for_each_entry(svc, &ipvs->svc_table[idx], s_list) { > - list_for_each_entry(dest, &svc->destinations, > - n_list) { > + hlist_for_each_entry_rcu(svc, &ipvs->svc_table[idx], s_list) > + list_for_each_entry_rcu(dest, &svc->destinations, > + n_list) > ip_vs_forget_dev(dest, dev); > - } > - } > > - hlist_for_each_entry(svc, &ipvs->svc_fwm_table[idx], f_list) { > - list_for_each_entry(dest, &svc->destinations, > - n_list) { > + hlist_for_each_entry_rcu(svc, &ipvs->svc_fwm_table[idx], f_list) > + list_for_each_entry_rcu(dest, &svc->destinations, > + n_list) > ip_vs_forget_dev(dest, dev); > - } > - } > } > + rcu_read_unlock(); > > + mutex_lock(&ipvs->service_mutex); > spin_lock_bh(&ipvs->dest_trash_lock); > list_for_each_entry(dest, &ipvs->dest_trash, t_list) { > ip_vs_forget_dev(dest, dev); > @@ -3318,9 +3316,9 @@ static int ip_vs_genl_fill_service(struct sk_buff *skb, > goto nla_put_failure; > } > > - sched = rcu_dereference_protected(svc->scheduler, 1); > + sched = rcu_dereference(svc->scheduler); > sched_name = sched ? sched->name : "none"; > - pe = rcu_dereference_protected(svc->pe, 1); > + pe = rcu_dereference(svc->pe); > if (nla_put_string(skb, IPVS_SVC_ATTR_SCHED_NAME, sched_name) || > (pe && nla_put_string(skb, IPVS_SVC_ATTR_PE_NAME, pe->name)) || > nla_put(skb, IPVS_SVC_ATTR_FLAGS, sizeof(flags), &flags) || > @@ -3374,9 +3372,9 @@ static int ip_vs_genl_dump_services(struct sk_buff *skb, > struct net *net = sock_net(skb->sk); > struct netns_ipvs *ipvs = net_ipvs(net); > > - mutex_lock(&ipvs->service_mutex); > + rcu_read_lock(); Here I can see this is safe, because this is netlink path. > for (i = 0; i < IP_VS_SVC_TAB_SIZE; i++) { > - hlist_for_each_entry(svc, &ipvs->svc_table[i], s_list) { > + hlist_for_each_entry_rcu(svc, &ipvs->svc_table[i], s_list) { > if (++idx <= start) > continue; > if (ip_vs_genl_dump_service(skb, svc, cb) < 0) { > @@ -3387,7 +3385,7 @@ static int ip_vs_genl_dump_services(struct sk_buff *skb, > } > > for (i = 0; i < IP_VS_SVC_TAB_SIZE; i++) { > - hlist_for_each_entry(svc, &ipvs->svc_fwm_table[i], f_list) { > + hlist_for_each_entry_rcu(svc, &ipvs->svc_fwm_table[i], f_list) { > if (++idx <= start) > continue; > if (ip_vs_genl_dump_service(skb, svc, cb) < 0) { > @@ -3398,7 +3396,7 @@ static int ip_vs_genl_dump_services(struct sk_buff *skb, > } > > nla_put_failure: > - mutex_unlock(&ipvs->service_mutex); > + rcu_read_unlock(); > cb->args[0] = idx; > > return skb->len; > @@ -3454,13 +3452,11 @@ static int ip_vs_genl_parse_service(struct netns_ipvs > *ipvs, > usvc->fwmark = 0; > } > > - rcu_read_lock(); > if (usvc->fwmark) > svc = __ip_vs_svc_fwm_find(ipvs, usvc->af, usvc->fwmark); > else > svc = __ip_vs_service_find(ipvs, usvc->af, usvc->protocol, > &usvc->addr, usvc->port); > - rcu_read_unlock(); > *ret_svc = svc; > > /* If a full entry was requested, check for the additional fields */ > @@ -3587,7 +3583,7 @@ static int ip_vs_genl_dump_dests(struct sk_buff *skb, > struct net *net = sock_net(skb->sk); > struct netns_ipvs *ipvs = net_ipvs(net); > > - mutex_lock(&ipvs->service_mutex); > + rcu_read_lock(); > > /* Try to find the service for which to dump destinations */ > if (nlmsg_parse_deprecated(cb->nlh, GENL_HDRLEN, attrs, > IPVS_CMD_ATTR_MAX, ip_vs_cmd_policy, cb->extack)) > @@ -3599,7 +3595,7 @@ static int ip_vs_genl_dump_dests(struct sk_buff *skb, > goto out_err; > > /* Dump the destinations */ > - list_for_each_entry(dest, &svc->destinations, n_list) { > + list_for_each_entry_rcu(dest, &svc->destinations, n_list) { > if (++idx <= start) > continue; > if (ip_vs_genl_dump_dest(skb, dest, cb) < 0) { > @@ -3612,7 +3608,7 @@ static int ip_vs_genl_dump_dests(struct sk_buff *skb, > cb->args[0] = idx; > > out_err: > - mutex_unlock(&ipvs->service_mutex); > + rcu_read_unlock(); > > return skb->len; > } > @@ -3915,9 +3911,12 @@ static int ip_vs_genl_set_cmd(struct sk_buff *skb, > struct genl_info *info) > if (cmd == IPVS_CMD_NEW_SERVICE || cmd == IPVS_CMD_SET_SERVICE) > need_full_svc = true; > > + /* We use function that requires RCU lock */ > + rcu_read_lock(); This is ip_vs_genl_set_cmd path and the new per-netns mutex is held. I think __ip_vs_service_find() can now just access this mutex to check if it is held, using fourth parameter: list_for_each_entry_rcu(..., lockdep_is_held(&ipvs->service_mutex)) Then this rcu_read_lock() after mutex_lock(&ipvs->service_mutex) can be removed. I suspect you added it to quiet a rcu debugging splat. > ret = ip_vs_genl_parse_service(ipvs, &usvc, > info->attrs[IPVS_CMD_ATTR_SERVICE], > need_full_svc, &svc); > + rcu_read_unlock(); > if (ret) > goto out; >
