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

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Message-ID: <433f99bd-5f68-4f4a-87c4-f8fd22bea95f@mojatatu.com>
Date: Mon, 4 Nov 2024 14:00:15 -0300
From: Pedro Tammela <pctammela@...atatu.com>
To: Alexandre Ferrieux <alexandre.ferrieux@...il.com>, edumazet@...gle.com
Cc: jhs@...atatu.com, xiyou.wangcong@...il.com, jiri@...nulli.us,
 alexandre.ferrieux@...nge.com, netdev@...r.kernel.org
Subject: Re: [PATCH net] Fix u32's systematic failure to free IDR entries for
 hnodes.

On 04/11/2024 07:26, Alexandre Ferrieux wrote:
> 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>

SoB does not match sender, probably missing 'From:' tag
Also, this seems to deserve a 'Fixes:' tag as well

> ---
>   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;
> +}
> +

'static inline' is discouraged in .c files

>   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;
>   		}