Subject: [PATCH 2/7] mark root hnode explicitly

From: Al Viro <[email-masked]>
Date: Wed, 5 Sep 2018 20:04:09 +0100

From: Al Viro <[email-masked]>

... and disallow deleting or linking to such

Signed-off-by: Al Viro <[email-masked]>
---
 net/sched/cls_u32.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c
index 3f985f29ef30..9ea5f2be907b 100644
--- a/net/sched/cls_u32.c
+++ b/net/sched/cls_u32.c
@@ -91,6 +91,7 @@ struct tc_u_hnode {
 	 */
 	struct tc_u_knode __rcu	*ht[1];
 };
+#define TCA_CLS_FLAGS_U32_ROOT (1<<8)
 
 struct tc_u_common {
 	struct tc_u_hnode __rcu	*hlist;
@@ -377,6 +378,7 @@ static int u32_init(struct tcf_proto *tp)
 	root_ht->refcnt++;
 	root_ht->handle = tp_c ? gen_new_htid(tp_c, root_ht) : 0x80000000;
 	root_ht->prio = tp->prio;
+	root_ht->flags = TCA_CLS_FLAGS_U32_ROOT;
 	idr_init(&root_ht->handle_idr);
 
 	if (tp_c == NULL) {
@@ -491,7 +493,8 @@ static void u32_clear_hw_hnode(struct tcf_proto *tp, struct tc_u_hnode *h,
 	struct tcf_block *block = tp->chain->block;
 	struct tc_cls_u32_offload cls_u32 = {};
 
-	tc_cls_common_offload_init(&cls_u32.common, tp, h->flags, extack);
+	tc_cls_common_offload_init(&cls_u32.common, tp,
+		h->flags & ~TCA_CLS_FLAGS_U32_ROOT, extack);
 	cls_u32.command = TC_CLSU32_DELETE_HNODE;
 	cls_u32.hnode.divisor = h->divisor;
 	cls_u32.hnode.handle = h->handle;
@@ -693,7 +696,7 @@ static int u32_delete(struct tcf_proto *tp, void *arg, bool *last,
 		goto out;
 	}
 
-	if (root_ht == ht) {
+	if (ht->flags & TCA_CLS_FLAGS_U32_ROOT) {
 		NL_SET_ERR_MSG_MOD(extack, "Not allowed to delete root node");
 		return -EINVAL;
 	}
@@ -795,6 +798,10 @@ static int u32_set_parms(struct net *net, struct tcf_proto *tp,
 				NL_SET_ERR_MSG_MOD(extack, "Link hash table not found");
 				return -EINVAL;
 			}
+			if (ht_down->flags & TCA_CLS_FLAGS_U32_ROOT) {
+				NL_SET_ERR_MSG_MOD(extack, "Not linke to root node");
+				return -EINVAL;
+			}
 			ht_down->refcnt++;
 		}
 
@@ -1214,7 +1221,8 @@ static int u32_reoffload_hnode(struct tcf_proto *tp, struct tc_u_hnode *ht,
 	struct tc_cls_u32_offload cls_u32 = {};
 	int err;
 
-	tc_cls_common_offload_init(&cls_u32.common, tp, ht->flags, extack);
+	tc_cls_common_offload_init(&cls_u32.common, tp,
+		ht->flags & ~TCA_CLS_FLAGS_U32_ROOT, extack);
 	cls_u32.command = add ? TC_CLSU32_NEW_HNODE : TC_CLSU32_DELETE_HNODE;
 	cls_u32.hnode.divisor = ht->divisor;
 	cls_u32.hnode.handle = ht->handle;
-- 
2.11.0