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

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Message-ID: <CANn89iKiEe4rwq0uPKBqWdQvM6RvRmw=zfMXhzXN9t7iGVgy-A@mail.gmail.com>
Date: Mon, 4 Nov 2024 11:11:03 +0100
From: Eric Dumazet <edumazet@...gle.com>
To: Alexandre Ferrieux <alexandre.ferrieux@...il.com>
Cc: alexandre.ferrieux@...nge.com, netdev@...r.kernel.org
Subject: Re: [PATCH net] Fix u32's systematic failure to free IDR entries for hnodes.

On Fri, Nov 1, 2024 at 7:43 PM Alexandre Ferrieux
<alexandre.ferrieux@...il.com> wrote:
>
> To generate hnode handles (in gen_new_htid()), u32 uses IDR and
> encodes the returned small integer into a strucured 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>
> ---


$ scripts/get_maintainer.pl net/sched/cls_u32.c

->

Jamal Hadi Salim <jhs@...atatu.com> (maintainer:TC subsystem)
Cong Wang <xiyou.wangcong@...il.com> (maintainer:TC subsystem)
Jiri Pirko <jiri@...nulli.us> (maintainer:TC subsystem)

Please resend adding them to get their feedback ?

Thank you.

>  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
>