net: sched: don't release reference on action overwrite

Return from action init function with reference to action taken,
even when overwriting existing action.

Action init API initializes its fourth argument (pointer to pointer to tc
action) to either existing action with same index or newly created action.
In case of existing index(and bind argument is zero), init function returns
without incrementing action reference counter. Caller of action init then
proceeds working with action, without actually holding reference to it.
This means that action could be deleted concurrently.

Change action init behavior to always take reference to action before
returning successfully, in order to protect from concurrent deletion.

Reviewed-by: Marcelo Ricardo Leitner <[email protected]>
Signed-off-by: Vlad Buslov <[email protected]>
Signed-off-by: Jiri Pirko <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

Author: w1ldptr

net/sched/act_api.c

@@ -870,8 +870,6 @@ int tcf_action_init(struct net *net, struct tcf_proto *tp, struct nlattr *nla,
 		}
 		act->order = i;
 		sz += tcf_action_fill_size(act);
-		if (ovr)
-			refcount_inc(&act->tcfa_refcnt);
 		list_add_tail(&act->list, actions);
 	}
 

net/sched/act_bpf.c

@@ -311,9 +311,10 @@ static int tcf_bpf_init(struct net *net, struct nlattr *nla,
 		if (bind)
 			return 0;
 
-		tcf_idr_release(*act, bind);
-		if (!replace)
+		if (!replace) {
+			tcf_idr_release(*act, bind);
 			return -EEXIST;
+		}
 	}
 
 	is_bpf = tb[TCA_ACT_BPF_OPS_LEN] && tb[TCA_ACT_BPF_OPS];
@@ -356,8 +357,7 @@ static int tcf_bpf_init(struct net *net, struct nlattr *nla,
 
 	return res;
 out:
-	if (res == ACT_P_CREATED)
-		tcf_idr_release(*act, bind);
+	tcf_idr_release(*act, bind);
 
 	return ret;
 }

net/sched/act_connmark.c

@@ -135,9 +135,10 @@ static int tcf_connmark_init(struct net *net, struct nlattr *nla,
 		ci = to_connmark(*a);
 		if (bind)
 			return 0;
-		tcf_idr_release(*a, bind);
-		if (!ovr)
+		if (!ovr) {
+			tcf_idr_release(*a, bind);
 			return -EEXIST;
+		}
 		/* replacing action and zone */
 		ci->tcf_action = parm->action;
 		ci->zone = parm->zone;

net/sched/act_csum.c

@@ -76,18 +76,18 @@ static int tcf_csum_init(struct net *net, struct nlattr *nla,
 	} else {
 		if (bind)/* dont override defaults */
 			return 0;
-		tcf_idr_release(*a, bind);
-		if (!ovr)
+		if (!ovr) {
+			tcf_idr_release(*a, bind);
 			return -EEXIST;
+		}
 	}
 
 	p = to_tcf_csum(*a);
 	ASSERT_RTNL();
 
 	params_new = kzalloc(sizeof(*params_new), GFP_KERNEL);
 	if (unlikely(!params_new)) {
-		if (ret == ACT_P_CREATED)
-			tcf_idr_release(*a, bind);
+		tcf_idr_release(*a, bind);
 		return -ENOMEM;
 	}
 	params_old = rtnl_dereference(p->params);

net/sched/act_gact.c

@@ -100,9 +100,10 @@ static int tcf_gact_init(struct net *net, struct nlattr *nla,
 	} else {
 		if (bind)/* dont override defaults */
 			return 0;
-		tcf_idr_release(*a, bind);
-		if (!ovr)
+		if (!ovr) {
+			tcf_idr_release(*a, bind);
 			return -EEXIST;
+		}
 	}
 
 	gact = to_gact(*a);

net/sched/act_ife.c

@@ -498,12 +498,10 @@ static int tcf_ife_init(struct net *net, struct nlattr *nla,
 			return ret;
 		}
 		ret = ACT_P_CREATED;
-	} else {
+	} else if (!ovr) {
 		tcf_idr_release(*a, bind);
-		if (!ovr) {
-			kfree(p);
-			return -EEXIST;
-		}
+		kfree(p);
+		return -EEXIST;
 	}
 
 	ife = to_ife(*a);
@@ -548,6 +546,8 @@ static int tcf_ife_init(struct net *net, struct nlattr *nla,
 
 			if (exists)
 				spin_unlock_bh(&ife->tcf_lock);
+			tcf_idr_release(*a, bind);
+
 			kfree(p);
 			return err;
 		}

net/sched/act_ipt.c

@@ -145,10 +145,11 @@ static int __tcf_ipt_init(struct net *net, unsigned int id, struct nlattr *nla,
 	} else {
 		if (bind)/* dont override defaults */
 			return 0;
-		tcf_idr_release(*a, bind);
 
-		if (!ovr)
+		if (!ovr) {
+			tcf_idr_release(*a, bind);
 			return -EEXIST;
+		}
 	}
 	hook = nla_get_u32(tb[TCA_IPT_HOOK]);
 

net/sched/act_mirred.c

@@ -132,10 +132,9 @@ static int tcf_mirred_init(struct net *net, struct nlattr *nla,
 		if (ret)
 			return ret;
 		ret = ACT_P_CREATED;
-	} else {
+	} else if (!ovr) {
 		tcf_idr_release(*a, bind);
-		if (!ovr)
-			return -EEXIST;
+		return -EEXIST;
 	}
 	m = to_mirred(*a);
 

net/sched/act_nat.c

@@ -66,9 +66,10 @@ static int tcf_nat_init(struct net *net, struct nlattr *nla, struct nlattr *est,
 	} else {
 		if (bind)
 			return 0;
-		tcf_idr_release(*a, bind);
-		if (!ovr)
+		if (!ovr) {
+			tcf_idr_release(*a, bind);
 			return -EEXIST;
+		}
 	}
 	p = to_tcf_nat(*a);
 

net/sched/act_pedit.c

@@ -194,8 +194,8 @@ static int tcf_pedit_init(struct net *net, struct nlattr *nla,
 	} else {
 		if (bind)
 			goto out_free;
-		tcf_idr_release(*a, bind);
 		if (!ovr) {
+			tcf_idr_release(*a, bind);
 			ret = -EEXIST;
 			goto out_free;
 		}