From: "Matthieu Baerts (NGI0)" <matttbe@kernel.org>

mptcp_pm_parse_entry() will check if the given attribute is defined. If
not, it will return a generic error: "missing address info".

It might then not be clear for the userspace developer which attribute
is missing, especially when the command takes multiple addresses.

By using GENL_REQ_ATTR_CHECK(), the userspace will get a hint about
which attribute is missing, making thing clearer. Note that this is what
was already done for most of the other MPTCP NL commands, this patch
simply adds the missing ones.

Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/pm_netlink.c   | 18 +++++++++++++++---
 net/mptcp/pm_userspace.c |  6 +++++-
 2 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index 528718cb70ec..46852c479b43 100644
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -1393,11 +1393,15 @@ static bool mptcp_pm_has_addr_attr_id(const struct nlattr *attr,
 
 int mptcp_pm_nl_add_addr_doit(struct sk_buff *skb, struct genl_info *info)
 {
-	struct nlattr *attr = info->attrs[MPTCP_PM_ENDPOINT_ADDR];
 	struct pm_nl_pernet *pernet = genl_info_pm_nl(info);
 	struct mptcp_pm_addr_entry addr, *entry;
+	struct nlattr *attr;
 	int ret;
 
+	if (GENL_REQ_ATTR_CHECK(info, MPTCP_PM_ENDPOINT_ADDR))
+		return -EINVAL;
+
+	attr = info->attrs[MPTCP_PM_ENDPOINT_ADDR];
 	ret = mptcp_pm_parse_entry(attr, info, true, &addr);
 	if (ret < 0)
 		return ret;
@@ -1590,12 +1594,16 @@ static int mptcp_nl_remove_id_zero_address(struct net *net,
 
 int mptcp_pm_nl_del_addr_doit(struct sk_buff *skb, struct genl_info *info)
 {
-	struct nlattr *attr = info->attrs[MPTCP_PM_ENDPOINT_ADDR];
 	struct pm_nl_pernet *pernet = genl_info_pm_nl(info);
 	struct mptcp_pm_addr_entry addr, *entry;
 	unsigned int addr_max;
+	struct nlattr *attr;
 	int ret;
 
+	if (GENL_REQ_ATTR_CHECK(info, MPTCP_PM_ENDPOINT_ADDR))
+		return -EINVAL;
+
+	attr = info->attrs[MPTCP_PM_ENDPOINT_ADDR];
 	ret = mptcp_pm_parse_entry(attr, info, false, &addr);
 	if (ret < 0)
 		return ret;
@@ -1767,13 +1775,17 @@ int mptcp_nl_fill_addr(struct sk_buff *skb,
 
 int mptcp_pm_nl_get_addr(struct sk_buff *skb, struct genl_info *info)
 {
-	struct nlattr *attr = info->attrs[MPTCP_PM_ENDPOINT_ADDR];
 	struct pm_nl_pernet *pernet = genl_info_pm_nl(info);
 	struct mptcp_pm_addr_entry addr, *entry;
 	struct sk_buff *msg;
+	struct nlattr *attr;
 	void *reply;
 	int ret;
 
+	if (GENL_REQ_ATTR_CHECK(info, MPTCP_PM_ENDPOINT_ADDR))
+		return -EINVAL;
+
+	attr = info->attrs[MPTCP_PM_ENDPOINT_ADDR];
 	ret = mptcp_pm_parse_entry(attr, info, false, &addr);
 	if (ret < 0)
 		return ret;
diff --git a/net/mptcp/pm_userspace.c b/net/mptcp/pm_userspace.c
index dc9ebfb06d96..801b1280a1aa 100644
--- a/net/mptcp/pm_userspace.c
+++ b/net/mptcp/pm_userspace.c
@@ -663,20 +663,24 @@ int mptcp_userspace_pm_dump_addr(struct sk_buff *msg,
 int mptcp_userspace_pm_get_addr(struct sk_buff *skb,
 				struct genl_info *info)
 {
-	struct nlattr *attr = info->attrs[MPTCP_PM_ENDPOINT_ADDR];
 	struct mptcp_pm_addr_entry addr, *entry;
 	struct mptcp_sock *msk;
 	struct sk_buff *msg;
+	struct nlattr *attr;
 	int ret = -EINVAL;
 	struct sock *sk;
 	void *reply;
 
+	if (GENL_REQ_ATTR_CHECK(info, MPTCP_PM_ENDPOINT_ADDR))
+		return ret;
+
 	msk = mptcp_userspace_pm_get_sock(info);
 	if (!msk)
 		return ret;
 
 	sk = (struct sock *)msk;
 
+	attr = info->attrs[MPTCP_PM_ENDPOINT_ADDR];
 	ret = mptcp_pm_parse_entry(attr, info, false, &addr);
 	if (ret < 0)
 		goto out;
-- 
2.45.2