netdev - [PATCH net] Fix u32's systematic failure to free IDR entries for hnodes.

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Message-Id: <20241104102615.257784-1-alexandre.ferrieux@orange.com>
Date: Mon,  4 Nov 2024 11:26:15 +0100
From: Alexandre Ferrieux <alexandre.ferrieux@...il.com>
To: edumazet@...gle.com
Cc: jhs@...atatu.com,
	xiyou.wangcong@...il.com,
	jiri@...nulli.us,
	alexandre.ferrieux@...nge.com,
	netdev@...r.kernel.org
Subject: [PATCH net] Fix u32's systematic failure to free IDR entries for hnodes.

To generate hnode handles (in gen_new_htid()), u32 uses IDR and
encodes the returned small integer into a structured 32-bit
word. Unfortunately, at disposal time, the needed decoding
is not done. As a result, idr_remove() fails, and the IDR
fills up. Since its size is 2048, the following script ends up
with "Filter already exists":

  tc filter add dev myve $FILTER1
  tc filter add dev myve $FILTER2
  for i in {1..2048}
  do
    echo $i
    tc filter del dev myve $FILTER2
    tc filter add dev myve $FILTER2
  done

This patch adds the missing decoding logic for handles that
deserve it.

Signed-off-by: Alexandre Ferrieux <alexandre.ferrieux@...nge.com>
---
 net/sched/cls_u32.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c
index 9412d88a99bc..54b5fca623da 100644
--- a/net/sched/cls_u32.c
+++ b/net/sched/cls_u32.c
@@ -41,6 +41,16 @@
 #include <linux/idr.h>
 #include <net/tc_wrapper.h>
 
+static inline unsigned int handle2id(unsigned int h)
+{
+	return ((h & 0x80000000) ? ((h >> 20) & 0x7FF) : h);
+}
+
+static inline unsigned int id2handle(unsigned int id)
+{
+	return (id | 0x800U) << 20;
+}
+
 struct tc_u_knode {
 	struct tc_u_knode __rcu	*next;
 	u32			handle;
@@ -310,7 +320,7 @@ static u32 gen_new_htid(struct tc_u_common *tp_c, struct tc_u_hnode *ptr)
 	int id = idr_alloc_cyclic(&tp_c->handle_idr, ptr, 1, 0x7FF, GFP_KERNEL);
 	if (id < 0)
 		return 0;
-	return (id | 0x800U) << 20;
+	return id2handle(id);
 }
 
 static struct hlist_head *tc_u_common_hash;
@@ -360,7 +370,7 @@ static int u32_init(struct tcf_proto *tp)
 		return -ENOBUFS;
 
 	refcount_set(&root_ht->refcnt, 1);
-	root_ht->handle = tp_c ? gen_new_htid(tp_c, root_ht) : 0x80000000;
+	root_ht->handle = tp_c ? gen_new_htid(tp_c, root_ht) : id2handle(0);
 	root_ht->prio = tp->prio;
 	root_ht->is_root = true;
 	idr_init(&root_ht->handle_idr);
@@ -612,7 +622,7 @@ static int u32_destroy_hnode(struct tcf_proto *tp, struct tc_u_hnode *ht,
 		if (phn == ht) {
 			u32_clear_hw_hnode(tp, ht, extack);
 			idr_destroy(&ht->handle_idr);
-			idr_remove(&tp_c->handle_idr, ht->handle);
+			idr_remove(&tp_c->handle_idr, handle2id(ht->handle));
 			RCU_INIT_POINTER(*hn, ht->next);
 			kfree_rcu(ht, rcu);
 			return 0;
@@ -989,7 +999,7 @@ static int u32_change(struct net *net, struct sk_buff *in_skb,
 
 		err = u32_replace_hw_hnode(tp, ht, userflags, extack);
 		if (err) {
-			idr_remove(&tp_c->handle_idr, handle);
+			idr_remove(&tp_c->handle_idr, handle2id(handle));
 			kfree(ht);
 			return err;
 		}
-- 
2.30.2