Merge branch 'net-sched-race-fix'

Cong Wang says:

====================
net_sched: close the race between call_rcu() and cleanup_net()

This patchset tries to fix the race between call_rcu() and
cleanup_net() again. Without holding the netns refcnt the
tc_action_net_exit() in netns workqueue could be called before
filter destroy works in tc filter workqueue. This patchset
moves the netns refcnt from tc actions to tcf_exts, without
breaking per-netns tc actions.

Patch 1 reverts the previous fix, patch 2 introduces two new
API's to help to address the bug and the rest patches switch
to the new API's. Please see each patch for details.

I was not able to reproduce this bug, but now after adding
some delay in filter destroy work I manage to trigger the
crash. After this patchset, the crash is not reproducible
any more and the debugging printk's show the order is expected
too.
====================

Fixes: ddf97cc ("net_sched: add network namespace support for tc actions")
Reported-by: Lucas Bates <lucasb@mojatatu.com>
Cc: Lucas Bates <lucasb@mojatatu.com>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/act_api.h

@@ -14,7 +14,6 @@
 struct tcf_idrinfo {
 	spinlock_t	lock;
 	struct idr	action_idr;
-	struct net	*net;
 };
 
 struct tc_action_ops;
@@ -106,15 +105,14 @@ struct tc_action_net {
 
 static inline
 int tc_action_net_init(struct tc_action_net *tn,
-		       const struct tc_action_ops *ops, struct net *net)
+		       const struct tc_action_ops *ops)
 {
 	int err = 0;
 
 	tn->idrinfo = kmalloc(sizeof(*tn->idrinfo), GFP_KERNEL);
 	if (!tn->idrinfo)
 		return -ENOMEM;
 	tn->ops = ops;
-	tn->idrinfo->net = net;
 	spin_lock_init(&tn->idrinfo->lock);
 	idr_init(&tn->idrinfo->action_idr);
 	return err;

include/net/pkt_cls.h

@@ -94,6 +94,7 @@ struct tcf_exts {
 	__u32	type; /* for backward compat(TCA_OLD_COMPAT) */
 	int nr_actions;
 	struct tc_action **actions;
+	struct net *net;
 #endif
 	/* Map to export classifier specific extension TLV types to the
 	 * generic extensions API. Unsupported extensions must be set to 0.
@@ -107,6 +108,7 @@ static inline int tcf_exts_init(struct tcf_exts *exts, int action, int police)
 #ifdef CONFIG_NET_CLS_ACT
 	exts->type = 0;
 	exts->nr_actions = 0;
+	exts->net = NULL;
 	exts->actions = kcalloc(TCA_ACT_MAX_PRIO, sizeof(struct tc_action *),
 				GFP_KERNEL);
 	if (!exts->actions)
@@ -117,6 +119,28 @@ static inline int tcf_exts_init(struct tcf_exts *exts, int action, int police)
 	return 0;
 }
 
+/* Return false if the netns is being destroyed in cleanup_net(). Callers
+ * need to do cleanup synchronously in this case, otherwise may race with
+ * tc_action_net_exit(). Return true for other cases.
+ */
+static inline bool tcf_exts_get_net(struct tcf_exts *exts)
+{
+#ifdef CONFIG_NET_CLS_ACT
+	exts->net = maybe_get_net(exts->net);
+	return exts->net != NULL;
+#else
+	return true;
+#endif
+}
+
+static inline void tcf_exts_put_net(struct tcf_exts *exts)
+{
+#ifdef CONFIG_NET_CLS_ACT
+	if (exts->net)
+		put_net(exts->net);
+#endif
+}
+
 static inline void tcf_exts_to_list(const struct tcf_exts *exts,
 				    struct list_head *actions)
 {

net/sched/act_api.c

@@ -78,7 +78,6 @@ static void tcf_idr_remove(struct tcf_idrinfo *idrinfo, struct tc_action *p)
 	spin_lock_bh(&idrinfo->lock);
 	idr_remove_ext(&idrinfo->action_idr, p->tcfa_index);
 	spin_unlock_bh(&idrinfo->lock);
-	put_net(idrinfo->net);
 	gen_kill_estimator(&p->tcfa_rate_est);
 	free_tcf(p);
 }
@@ -337,7 +336,6 @@ int tcf_idr_create(struct tc_action_net *tn, u32 index, struct nlattr *est,
 	p->idrinfo = idrinfo;
 	p->ops = ops;
 	INIT_LIST_HEAD(&p->list);
-	get_net(idrinfo->net);
 	*a = p;
 	return 0;
 }

net/sched/act_bpf.c

@@ -398,7 +398,7 @@ static __net_init int bpf_init_net(struct net *net)
 {
 	struct tc_action_net *tn = net_generic(net, bpf_net_id);
 
-	return tc_action_net_init(tn, &act_bpf_ops, net);
+	return tc_action_net_init(tn, &act_bpf_ops);
 }
 
 static void __net_exit bpf_exit_net(struct net *net)

net/sched/act_connmark.c

@@ -206,7 +206,7 @@ static __net_init int connmark_init_net(struct net *net)
 {
 	struct tc_action_net *tn = net_generic(net, connmark_net_id);
 
-	return tc_action_net_init(tn, &act_connmark_ops, net);
+	return tc_action_net_init(tn, &act_connmark_ops);
 }
 
 static void __net_exit connmark_exit_net(struct net *net)

net/sched/act_csum.c

@@ -626,7 +626,7 @@ static __net_init int csum_init_net(struct net *net)
 {
 	struct tc_action_net *tn = net_generic(net, csum_net_id);
 
-	return tc_action_net_init(tn, &act_csum_ops, net);
+	return tc_action_net_init(tn, &act_csum_ops);
 }
 
 static void __net_exit csum_exit_net(struct net *net)

net/sched/act_gact.c

@@ -232,7 +232,7 @@ static __net_init int gact_init_net(struct net *net)
 {
 	struct tc_action_net *tn = net_generic(net, gact_net_id);
 
-	return tc_action_net_init(tn, &act_gact_ops, net);
+	return tc_action_net_init(tn, &act_gact_ops);
 }
 
 static void __net_exit gact_exit_net(struct net *net)

net/sched/act_ife.c

@@ -818,7 +818,7 @@ static __net_init int ife_init_net(struct net *net)
 {
 	struct tc_action_net *tn = net_generic(net, ife_net_id);
 
-	return tc_action_net_init(tn, &act_ife_ops, net);
+	return tc_action_net_init(tn, &act_ife_ops);
 }
 
 static void __net_exit ife_exit_net(struct net *net)

net/sched/act_ipt.c

@@ -334,7 +334,7 @@ static __net_init int ipt_init_net(struct net *net)
 {
 	struct tc_action_net *tn = net_generic(net, ipt_net_id);
 
-	return tc_action_net_init(tn, &act_ipt_ops, net);
+	return tc_action_net_init(tn, &act_ipt_ops);
 }
 
 static void __net_exit ipt_exit_net(struct net *net)
@@ -384,7 +384,7 @@ static __net_init int xt_init_net(struct net *net)
 {
 	struct tc_action_net *tn = net_generic(net, xt_net_id);
 
-	return tc_action_net_init(tn, &act_xt_ops, net);
+	return tc_action_net_init(tn, &act_xt_ops);
 }
 
 static void __net_exit xt_exit_net(struct net *net)

net/sched/act_mirred.c

@@ -343,7 +343,7 @@ static __net_init int mirred_init_net(struct net *net)
 {
 	struct tc_action_net *tn = net_generic(net, mirred_net_id);
 
-	return tc_action_net_init(tn, &act_mirred_ops, net);
+	return tc_action_net_init(tn, &act_mirred_ops);
 }
 
 static void __net_exit mirred_exit_net(struct net *net)

net/sched/act_nat.c

@@ -307,7 +307,7 @@ static __net_init int nat_init_net(struct net *net)
 {
 	struct tc_action_net *tn = net_generic(net, nat_net_id);
 
-	return tc_action_net_init(tn, &act_nat_ops, net);
+	return tc_action_net_init(tn, &act_nat_ops);
 }
 
 static void __net_exit nat_exit_net(struct net *net)

net/sched/act_pedit.c

@@ -450,7 +450,7 @@ static __net_init int pedit_init_net(struct net *net)
 {
 	struct tc_action_net *tn = net_generic(net, pedit_net_id);
 
-	return tc_action_net_init(tn, &act_pedit_ops, net);
+	return tc_action_net_init(tn, &act_pedit_ops);
 }
 
 static void __net_exit pedit_exit_net(struct net *net)

net/sched/act_police.c

@@ -331,7 +331,7 @@ static __net_init int police_init_net(struct net *net)
 {
 	struct tc_action_net *tn = net_generic(net, police_net_id);
 
-	return tc_action_net_init(tn, &act_police_ops, net);
+	return tc_action_net_init(tn, &act_police_ops);
 }
 
 static void __net_exit police_exit_net(struct net *net)

net/sched/act_sample.c

@@ -240,7 +240,7 @@ static __net_init int sample_init_net(struct net *net)
 {
 	struct tc_action_net *tn = net_generic(net, sample_net_id);
 
-	return tc_action_net_init(tn, &act_sample_ops, net);
+	return tc_action_net_init(tn, &act_sample_ops);
 }
 
 static void __net_exit sample_exit_net(struct net *net)

net/sched/act_simple.c

@@ -201,7 +201,7 @@ static __net_init int simp_init_net(struct net *net)
 {
 	struct tc_action_net *tn = net_generic(net, simp_net_id);
 
-	return tc_action_net_init(tn, &act_simp_ops, net);
+	return tc_action_net_init(tn, &act_simp_ops);
 }
 
 static void __net_exit simp_exit_net(struct net *net)

net/sched/act_skbedit.c

@@ -238,7 +238,7 @@ static __net_init int skbedit_init_net(struct net *net)
 {
 	struct tc_action_net *tn = net_generic(net, skbedit_net_id);
 
-	return tc_action_net_init(tn, &act_skbedit_ops, net);
+	return tc_action_net_init(tn, &act_skbedit_ops);
 }
 
 static void __net_exit skbedit_exit_net(struct net *net)

net/sched/act_skbmod.c

@@ -263,7 +263,7 @@ static __net_init int skbmod_init_net(struct net *net)
 {
 	struct tc_action_net *tn = net_generic(net, skbmod_net_id);
 
-	return tc_action_net_init(tn, &act_skbmod_ops, net);
+	return tc_action_net_init(tn, &act_skbmod_ops);
 }
 
 static void __net_exit skbmod_exit_net(struct net *net)

net/sched/act_tunnel_key.c

@@ -322,7 +322,7 @@ static __net_init int tunnel_key_init_net(struct net *net)
 {
 	struct tc_action_net *tn = net_generic(net, tunnel_key_net_id);
 
-	return tc_action_net_init(tn, &act_tunnel_key_ops, net);
+	return tc_action_net_init(tn, &act_tunnel_key_ops);
 }
 
 static void __net_exit tunnel_key_exit_net(struct net *net)

net/sched/act_vlan.c

@@ -269,7 +269,7 @@ static __net_init int vlan_init_net(struct net *net)
 {
 	struct tc_action_net *tn = net_generic(net, vlan_net_id);
 
-	return tc_action_net_init(tn, &act_vlan_ops, net);
+	return tc_action_net_init(tn, &act_vlan_ops);
 }
 
 static void __net_exit vlan_exit_net(struct net *net)

net/sched/cls_api.c

@@ -927,6 +927,7 @@ int tcf_exts_validate(struct net *net, struct tcf_proto *tp, struct nlattr **tb,
 				exts->actions[i++] = act;
 			exts->nr_actions = i;
 		}
+		exts->net = net;
 	}
 #else
 	if ((exts->action && tb[exts->action]) ||

net/sched/cls_basic.c

@@ -85,16 +85,21 @@ static int basic_init(struct tcf_proto *tp)
 	return 0;
 }
 
+static void __basic_delete_filter(struct basic_filter *f)
+{
+	tcf_exts_destroy(&f->exts);
+	tcf_em_tree_destroy(&f->ematches);
+	tcf_exts_put_net(&f->exts);
+	kfree(f);
+}
+
 static void basic_delete_filter_work(struct work_struct *work)
 {
 	struct basic_filter *f = container_of(work, struct basic_filter, work);
 
 	rtnl_lock();
-	tcf_exts_destroy(&f->exts);
-	tcf_em_tree_destroy(&f->ematches);
+	__basic_delete_filter(f);
 	rtnl_unlock();
-
-	kfree(f);
 }
 
 static void basic_delete_filter(struct rcu_head *head)
@@ -113,7 +118,10 @@ static void basic_destroy(struct tcf_proto *tp)
 	list_for_each_entry_safe(f, n, &head->flist, link) {
 		list_del_rcu(&f->link);
 		tcf_unbind_filter(tp, &f->res);
-		call_rcu(&f->rcu, basic_delete_filter);
+		if (tcf_exts_get_net(&f->exts))
+			call_rcu(&f->rcu, basic_delete_filter);
+		else
+			__basic_delete_filter(f);
 	}
 	kfree_rcu(head, rcu);
 }
@@ -125,6 +133,7 @@ static int basic_delete(struct tcf_proto *tp, void *arg, bool *last)
 
 	list_del_rcu(&f->link);
 	tcf_unbind_filter(tp, &f->res);
+	tcf_exts_get_net(&f->exts);
 	call_rcu(&f->rcu, basic_delete_filter);
 	*last = list_empty(&head->flist);
 	return 0;
@@ -219,6 +228,7 @@ static int basic_change(struct net *net, struct sk_buff *in_skb,
 	if (fold) {
 		list_replace_rcu(&fold->link, &fnew->link);
 		tcf_unbind_filter(tp, &fold->res);
+		tcf_exts_get_net(&fold->exts);
 		call_rcu(&fold->rcu, basic_delete_filter);
 	} else {
 		list_add_rcu(&fnew->link, &head->flist);

net/sched/cls_bpf.c

@@ -249,6 +249,7 @@ static int cls_bpf_init(struct tcf_proto *tp)
 static void __cls_bpf_delete_prog(struct cls_bpf_prog *prog)
 {
 	tcf_exts_destroy(&prog->exts);
+	tcf_exts_put_net(&prog->exts);
 
 	if (cls_bpf_is_ebpf(prog))
 		bpf_prog_put(prog->filter);
@@ -282,7 +283,10 @@ static void __cls_bpf_delete(struct tcf_proto *tp, struct cls_bpf_prog *prog)
 	cls_bpf_stop_offload(tp, prog);
 	list_del_rcu(&prog->link);
 	tcf_unbind_filter(tp, &prog->res);
-	call_rcu(&prog->rcu, cls_bpf_delete_prog_rcu);
+	if (tcf_exts_get_net(&prog->exts))
+		call_rcu(&prog->rcu, cls_bpf_delete_prog_rcu);
+	else
+		__cls_bpf_delete_prog(prog);
 }
 
 static int cls_bpf_delete(struct tcf_proto *tp, void *arg, bool *last)
@@ -516,6 +520,7 @@ static int cls_bpf_change(struct net *net, struct sk_buff *in_skb,
 	if (oldprog) {
 		list_replace_rcu(&oldprog->link, &prog->link);
 		tcf_unbind_filter(tp, &oldprog->res);
+		tcf_exts_get_net(&oldprog->exts);
 		call_rcu(&oldprog->rcu, cls_bpf_delete_prog_rcu);
 	} else {
 		list_add_rcu(&prog->link, &head->plist);

net/sched/cls_cgroup.c

@@ -60,15 +60,21 @@ static const struct nla_policy cgroup_policy[TCA_CGROUP_MAX + 1] = {
 	[TCA_CGROUP_EMATCHES]	= { .type = NLA_NESTED },
 };
 
+static void __cls_cgroup_destroy(struct cls_cgroup_head *head)
+{
+	tcf_exts_destroy(&head->exts);
+	tcf_em_tree_destroy(&head->ematches);
+	tcf_exts_put_net(&head->exts);
+	kfree(head);
+}
+
 static void cls_cgroup_destroy_work(struct work_struct *work)
 {
 	struct cls_cgroup_head *head = container_of(work,
 						    struct cls_cgroup_head,
 						    work);
 	rtnl_lock();
-	tcf_exts_destroy(&head->exts);
-	tcf_em_tree_destroy(&head->ematches);
-	kfree(head);
+	__cls_cgroup_destroy(head);
 	rtnl_unlock();
 }
 
@@ -124,8 +130,10 @@ static int cls_cgroup_change(struct net *net, struct sk_buff *in_skb,
 		goto errout;
 
 	rcu_assign_pointer(tp->root, new);
-	if (head)
+	if (head) {
+		tcf_exts_get_net(&head->exts);
 		call_rcu(&head->rcu, cls_cgroup_destroy_rcu);
+	}
 	return 0;
 errout:
 	tcf_exts_destroy(&new->exts);
@@ -138,8 +146,12 @@ static void cls_cgroup_destroy(struct tcf_proto *tp)
 	struct cls_cgroup_head *head = rtnl_dereference(tp->root);
 
 	/* Head can still be NULL due to cls_cgroup_init(). */
-	if (head)
-		call_rcu(&head->rcu, cls_cgroup_destroy_rcu);
+	if (head) {
+		if (tcf_exts_get_net(&head->exts))
+			call_rcu(&head->rcu, cls_cgroup_destroy_rcu);
+		else
+			__cls_cgroup_destroy(head);
+	}
 }
 
 static int cls_cgroup_delete(struct tcf_proto *tp, void *arg, bool *last)