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>

include/net/netlink.h

@@ -1190,6 +1190,16 @@ static inline struct in6_addr nla_get_in6_addr(const struct nlattr *nla)
 	return tmp;
 }
 
+/**
+ * nla_memdup - duplicate attribute memory (kmemdup)
+ * @src: netlink attribute to duplicate from
+ * @gfp: GFP mask
+ */
+static inline void *nla_memdup(const struct nlattr *src, gfp_t gfp)
+{
+	return kmemdup(nla_data(src), nla_len(src), gfp);
+}
+
 /**
  * nla_nest_start - Start a new level of nested attributes
  * @skb: socket buffer to add attributes to

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;

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;

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++;
 	}