netdev - Re: [PATCH net 1/1] cls_api.c: Fix dumping of non-existing actions' stats.

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Date:	Tue, 3 Feb 2015 09:39:39 -0800
From:	Cong Wang <cwang@...pensource.com>
To:	Ignacy Gawędzki 
	<ignacy.gawedzki@...en-communications.fr>,
	netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net 1/1] cls_api.c: Fix dumping of non-existing actions' stats.

On Tue, Feb 3, 2015 at 9:32 AM, Ignacy Gawędzki
<ignacy.gawedzki@...en-communications.fr> wrote:
> In tcf_exts_dump_stats(), ensure that exts->actions is not empty before
> accessing the first element of that list and calling tcf_action_copy_stats()
> on it.  This fixes some random segvs when adding filters of type "basic" with
> no particular action.
>
> This also fixes the dumping of those "no-action" filters, which more often
> than not made calls to tcf_action_copy_stats() fail and consequently netlink
> attributes added by the caller to be removed by a call to nla_nest_cancel().
>
> Signed-off-by: Ignacy Gawędzki <ignacy.gawedzki@...en-communications.fr>
> ---
>  net/sched/cls_api.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
> index aad6a67..30e6967 100644
> --- a/net/sched/cls_api.c
> +++ b/net/sched/cls_api.c
> @@ -602,9 +602,12 @@ EXPORT_SYMBOL(tcf_exts_dump);
>  int tcf_exts_dump_stats(struct sk_buff *skb, struct tcf_exts *exts)
>  {
>  #ifdef CONFIG_NET_CLS_ACT
> -       struct tc_action *a = tcf_exts_first_act(exts);
> -       if (tcf_action_copy_stats(skb, a, 1) < 0)
> -               return -1;
> +       struct tc_action *a;
> +       if (!list_empty(&exts->actions)) {
> +               a = tcf_exts_first_act(exts);
> +               if (tcf_action_copy_stats(skb, a, 1) < 0)
> +                       return -1;
> +       }

Hmm, or just fix tcf_exts_first_act()? Let it call list_first_entry_or_null().

Also, please add Fixes: tag.

Fixes: commit 33be627159913b094bb578e83e9a7fdc66c10208
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