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

Some errors reported by the userspace PM were vague: "this or that is
invalid".

It is easier for the userspace to know which part is wrong, instead of
having to guess that.

By splitting some error messages, NL_SET_ERR_MSG_ATTR() can be used
instead of GENL_SET_ERR_MSG() in order to give an additional hint to the
userspace developers about which attribute is wrong.

While at it, in mptcp_userspace_pm_set_flags() move the parsing after
the check linked to the local attribute.

Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/pm_userspace.c | 33 ++++++++++++++++++++++++++-------
 1 file changed, 26 insertions(+), 7 deletions(-)

diff --git a/net/mptcp/pm_userspace.c b/net/mptcp/pm_userspace.c
index b6cf8ea1161d..2cb42091bd08 100644
--- a/net/mptcp/pm_userspace.c
+++ b/net/mptcp/pm_userspace.c
@@ -223,8 +223,14 @@ int mptcp_pm_nl_announce_doit(struct sk_buff *skb, struct genl_info *info)
 		goto announce_err;
 	}
 
-	if (addr_val.addr.id == 0 || !(addr_val.flags & MPTCP_PM_ADDR_FLAG_SIGNAL)) {
-		GENL_SET_ERR_MSG(info, "invalid addr id or flags");
+	if (addr_val.addr.id == 0) {
+		NL_SET_ERR_MSG_ATTR(info->extack, addr, "invalid addr id");
+		err = -EINVAL;
+		goto announce_err;
+	}
+
+	if (!(addr_val.flags & MPTCP_PM_ADDR_FLAG_SIGNAL)) {
+		NL_SET_ERR_MSG_ATTR(info->extack, addr, "invalid addr flags");
 		err = -EINVAL;
 		goto announce_err;
 	}
@@ -531,8 +537,14 @@ int mptcp_pm_nl_subflow_destroy_doit(struct sk_buff *skb, struct genl_info *info
 		goto destroy_err;
 	}
 
-	if (!addr_l.addr.port || !addr_r.port) {
-		GENL_SET_ERR_MSG(info, "missing local or remote port");
+	if (!addr_l.addr.port) {
+		NL_SET_ERR_MSG_ATTR(info->extack, laddr, "missing local port");
+		err = -EINVAL;
+		goto destroy_err;
+	}
+
+	if (!addr_r.port) {
+		NL_SET_ERR_MSG_ATTR(info->extack, raddr, "missing remote port");
 		err = -EINVAL;
 		goto destroy_err;
 	}
@@ -580,13 +592,20 @@ int mptcp_userspace_pm_set_flags(struct sk_buff *skb, struct genl_info *info)
 	if (ret < 0)
 		goto set_flags_err;
 
+	if (loc.addr.family == AF_UNSPEC) {
+		NL_SET_ERR_MSG_ATTR(info->extack, attr,
+				    "invalid local address family");
+		ret = -EINVAL;
+		goto set_flags_err;
+	}
+
 	ret = mptcp_pm_parse_entry(attr_rem, info, false, &rem);
 	if (ret < 0)
 		goto set_flags_err;
 
-	if (loc.addr.family == AF_UNSPEC ||
-	    rem.addr.family == AF_UNSPEC) {
-		GENL_SET_ERR_MSG(info, "invalid address families");
+	if (rem.addr.family == AF_UNSPEC) {
+		NL_SET_ERR_MSG_ATTR(info->extack, attr_rem,
+				    "invalid remote address family");
 		ret = -EINVAL;
 		goto set_flags_err;
 	}
-- 
2.45.2