net: genetlink: push attrbuf allocation and parsing to a separate function

To be re-usable by dumpit as well, push the code that is taking care of
attrbuf allocation and parting from doit into separate function.
Introduce a helper to free the buffer too.

Check family->maxattr too before calling kfree() to be symmetrical with
the allocation check.
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/netlink/genetlink.c

@@ -468,6 +468,45 @@ static void genl_dumpit_info_free(const struct genl_dumpit_info *info)
 	kfree(info);
 }
 
+static struct nlattr **
+genl_family_rcv_msg_attrs_parse(const struct genl_family *family,
+				struct nlmsghdr *nlh,
+				struct netlink_ext_ack *extack,
+				const struct genl_ops *ops,
+				int hdrlen,
+				enum genl_validate_flags no_strict_flag)
+{
+	enum netlink_validation validate = ops->validate & no_strict_flag ?
+					   NL_VALIDATE_LIBERAL :
+					   NL_VALIDATE_STRICT;
+	struct nlattr **attrbuf;
+	int err;
+
+	if (family->maxattr && family->parallel_ops) {
+		attrbuf = kmalloc_array(family->maxattr + 1,
+					sizeof(struct nlattr *), GFP_KERNEL);
+		if (!attrbuf)
+			return ERR_PTR(-ENOMEM);
+	} else {
+		attrbuf = family->attrbuf;
+	}
+
+	err = __nlmsg_parse(nlh, hdrlen, attrbuf, family->maxattr,
+			    family->policy, validate, extack);
+	if (err && family->maxattr && family->parallel_ops) {
+		kfree(attrbuf);
+		return ERR_PTR(err);
+	}
+	return attrbuf;
+}
+
+static void genl_family_rcv_msg_attrs_free(const struct genl_family *family,
+					   struct nlattr **attrbuf)
+{
+	if (family->maxattr && family->parallel_ops)
+		kfree(attrbuf);
+}
+
 static int genl_lock_start(struct netlink_callback *cb)
 {
 	const struct genl_ops *ops = genl_dumpit_info(cb)->ops;
@@ -599,26 +638,11 @@ static int genl_family_rcv_msg_doit(const struct genl_family *family,
 	if (!ops->doit)
 		return -EOPNOTSUPP;
 
-	if (family->maxattr && family->parallel_ops) {
-		attrbuf = kmalloc_array(family->maxattr + 1,
-					sizeof(struct nlattr *),
-					GFP_KERNEL);
-		if (attrbuf == NULL)
-			return -ENOMEM;
-	} else
-		attrbuf = family->attrbuf;
-
-	if (attrbuf) {
-		enum netlink_validation validate = NL_VALIDATE_STRICT;
-
-		if (ops->validate & GENL_DONT_VALIDATE_STRICT)
-			validate = NL_VALIDATE_LIBERAL;
-
-		err = __nlmsg_parse(nlh, hdrlen, attrbuf, family->maxattr,
-				    family->policy, validate, extack);
-		if (err < 0)
-			goto out;
-	}
+	attrbuf = genl_family_rcv_msg_attrs_parse(family, nlh, extack,
+						  ops, hdrlen,
+						  GENL_DONT_VALIDATE_STRICT);
+	if (IS_ERR(attrbuf))
+		return PTR_ERR(attrbuf);
 
 	info.snd_seq = nlh->nlmsg_seq;
 	info.snd_portid = NETLINK_CB(skb).portid;
@@ -642,8 +666,7 @@ static int genl_family_rcv_msg_doit(const struct genl_family *family,
 		family->post_doit(ops, skb, &info);
 
 out:
-	if (family->parallel_ops)
-		kfree(attrbuf);
+	genl_family_rcv_msg_attrs_free(family, attrbuf);
 
 	return err;
 }