Merge branch 'net_sched-prevent-creation-of-classes-with-tc_h_root'

Cong Wang says:

====================
net_sched: Prevent creation of classes with TC_H_ROOT

This patchset contains a bug fix and its TDC test case.
====================

Link: https://patch.msgid.link/20250306232355.93864-1-xiyou.wangcong@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: kuba-moo

net/sched/sch_api.c

@@ -2254,6 +2254,12 @@ static int tc_ctl_tclass(struct sk_buff *skb, struct nlmsghdr *n,
 		return -EOPNOTSUPP;
 	}
 
+	/* Prevent creation of traffic classes with classid TC_H_ROOT */
+	if (clid == TC_H_ROOT) {
+		NL_SET_ERR_MSG(extack, "Cannot create traffic class with classid TC_H_ROOT");
+		return -EINVAL;
+	}
+
 	new_cl = cl;
 	err = -EOPNOTSUPP;
 	if (cops->change)

tools/testing/selftests/tc-testing/tc-tests/qdiscs/drr.json

@@ -61,5 +61,30 @@
         "teardown": [
             "$TC qdisc del dev $DUMMY handle 1: root"
         ]
+    },
+    {
+        "id": "4009",
+        "name": "Reject creation of DRR class with classid TC_H_ROOT",
+        "category": [
+            "qdisc",
+            "drr"
+        ],
+        "plugins": {
+            "requires": "nsPlugin"
+        },
+        "setup": [
+            "$TC qdisc add dev $DUMMY root handle ffff: drr",
+            "$TC filter add dev $DUMMY parent ffff: basic classid ffff:1",
+            "$TC class add dev $DUMMY parent ffff: classid ffff:1 drr",
+            "$TC filter add dev $DUMMY parent ffff: prio 1 u32 match u16 0x0000 0xfe00 at 2 flowid ffff:ffff"
+        ],
+        "cmdUnderTest": "$TC class add dev $DUMMY parent ffff: classid ffff:ffff drr",
+        "expExitCode": "2",
+        "verifyCmd": "$TC class show dev $DUMMY",
+        "matchPattern": "class drr ffff:ffff",
+        "matchCount": "0",
+        "teardown": [
+            "$TC qdisc del dev $DUMMY root"
+        ]
     }
 ]