netlink: Add nla_memdup() to wrap kmemdup() use on nlattr

Wrap several common instances of:
	kmemdup(nla_data(attr), nla_len(attr), GFP_KERNEL);

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Acked-by: Johannes Berg <johannes@sipsolutions.net>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sched/act_bpf.c b/net/sched/act_bpf.c
index 1d39600..9ff06cf 100644
--- a/net/sched/act_bpf.c
+++ b/net/sched/act_bpf.c
@@ -226,9 +226,7 @@ static int tcf_bpf_init_from_efd(struct nlattr **tb, struct tcf_bpf_cfg *cfg)
 		return PTR_ERR(fp);
 
 	if (tb[TCA_ACT_BPF_NAME]) {
-		name = kmemdup(nla_data(tb[TCA_ACT_BPF_NAME]),
-			       nla_len(tb[TCA_ACT_BPF_NAME]),
-			       GFP_KERNEL);
+		name = nla_memdup(tb[TCA_ACT_BPF_NAME], GFP_KERNEL);
 		if (!name) {
 			bpf_prog_put(fp);
 			return -ENOMEM;
diff --git a/net/sched/cls_bpf.c b/net/sched/cls_bpf.c
index bb1d5a4..52dc85a 100644
--- a/net/sched/cls_bpf.c
+++ b/net/sched/cls_bpf.c
@@ -369,9 +369,7 @@ static int cls_bpf_prog_from_efd(struct nlattr **tb, struct cls_bpf_prog *prog,
 		return PTR_ERR(fp);
 
 	if (tb[TCA_BPF_NAME]) {
-		name = kmemdup(nla_data(tb[TCA_BPF_NAME]),
-			       nla_len(tb[TCA_BPF_NAME]),
-			       GFP_KERNEL);
+		name = nla_memdup(tb[TCA_BPF_NAME], GFP_KERNEL);
 		if (!name) {
 			bpf_prog_put(fp);
 			return -ENOMEM;
diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index 271707d..0d3ab4b 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -10625,8 +10625,7 @@ static int handle_nan_filter(struct nlattr *attr_filter,
 
 	i = 0;
 	nla_for_each_nested(attr, attr_filter, rem) {
-		filter[i].filter = kmemdup(nla_data(attr), nla_len(attr),
-					   GFP_KERNEL);
+		filter[i].filter = nla_memdup(attr, GFP_KERNEL);
 		filter[i].len = nla_len(attr);
 		i++;
 	}