net/sched: act_simple: fix parsing of TCA_DEF_DATA

use nla_strlcpy() to avoid copying data beyond the length of TCA_DEF_DATA
netlink attribute, in case it is less than SIMP_MAX_DATA and it does not
end with '\0' character.

v2: fix errors in the commit message, thanks Hangbin Liu

Fixes: fa1b1cff ("net_cls_act: Make act_simple use of netlink policy.")
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/act_simple.c

@@ -53,22 +53,22 @@ static void tcf_simp_release(struct tc_action *a)
 	kfree(d->tcfd_defdata);
 }
 
-static int alloc_defdata(struct tcf_defact *d, char *defdata)
+static int alloc_defdata(struct tcf_defact *d, const struct nlattr *defdata)
 {
 	d->tcfd_defdata = kzalloc(SIMP_MAX_DATA, GFP_KERNEL);
 	if (unlikely(!d->tcfd_defdata))
 		return -ENOMEM;
-	strlcpy(d->tcfd_defdata, defdata, SIMP_MAX_DATA);
+	nla_strlcpy(d->tcfd_defdata, defdata, SIMP_MAX_DATA);
 	return 0;
 }
 
-static void reset_policy(struct tcf_defact *d, char *defdata,
+static void reset_policy(struct tcf_defact *d, const struct nlattr *defdata,
 			 struct tc_defact *p)
 {
 	spin_lock_bh(&d->tcf_lock);
 	d->tcf_action = p->action;
 	memset(d->tcfd_defdata, 0, SIMP_MAX_DATA);
-	strlcpy(d->tcfd_defdata, defdata, SIMP_MAX_DATA);
+	nla_strlcpy(d->tcfd_defdata, defdata, SIMP_MAX_DATA);
 	spin_unlock_bh(&d->tcf_lock);
 }
 
@@ -87,7 +87,6 @@ static int tcf_simp_init(struct net *net, struct nlattr *nla,
 	struct tcf_defact *d;
 	bool exists = false;
 	int ret = 0, err;
-	char *defdata;
 
 	if (nla == NULL)
 		return -EINVAL;
@@ -110,8 +109,6 @@ static int tcf_simp_init(struct net *net, struct nlattr *nla,
 		return -EINVAL;
 	}
 
-	defdata = nla_data(tb[TCA_DEF_DATA]);
-
 	if (!exists) {
 		ret = tcf_idr_create(tn, parm->index, est, a,
 				     &act_simp_ops, bind, false);
@@ -119,7 +116,7 @@ static int tcf_simp_init(struct net *net, struct nlattr *nla,
 			return ret;
 
 		d = to_defact(*a);
-		ret = alloc_defdata(d, defdata);
+		ret = alloc_defdata(d, tb[TCA_DEF_DATA]);
 		if (ret < 0) {
 			tcf_idr_release(*a, bind);
 			return ret;
@@ -133,7 +130,7 @@ static int tcf_simp_init(struct net *net, struct nlattr *nla,
 		if (!ovr)
 			return -EEXIST;
 
-		reset_policy(d, defdata, parm);
+		reset_policy(d, tb[TCA_DEF_DATA], parm);
 	}
 
 	if (ret == ACT_P_CREATED)