linux-kernel - Re: [PATCH net] net/sched: cls_api: Initialize miss_cookie

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Date:   Thu, 20 Apr 2023 20:35:05 +0200
From:   Ivan Vecera <ivecera@...hat.com>
To:     Pedro Tammela <pctammela@...atatu.com>, netdev@...r.kernel.org
Cc:     Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Paul Blakey <paulb@...dia.com>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net] net/sched: cls_api: Initialize miss_cookie_node when
 action miss is not used



On 20. 04. 23 20:21, Pedro Tammela wrote:
> On 20/04/2023 14:59, Ivan Vecera wrote:
>> Function tcf_exts_init_ex() sets exts->miss_cookie_node ptr only
>> when use_action_miss is true so it assumes in other case that
>> the field is set to NULL by the caller. If not then the field
>> contains garbage and subsequent tcf_exts_destroy() call results
>> in a crash.
>> Initialize .miss_cookie_node pointer to NULL when use_action_miss
>> parameter is false to avoid this potential scenario.
>>
>> Fixes: 80cd22c35c90 ("net/sched: cls_api: Support hardware miss to tc 
>> action")
>> Signed-off-by: Ivan Vecera <ivecera@...hat.com>
>> ---
>>   net/sched/cls_api.c | 6 +++++-
>>   1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
>> index 35785a36c80298..8bc5b9d6a2916e 100644
>> --- a/net/sched/cls_api.c
>> +++ b/net/sched/cls_api.c
>> @@ -3224,8 +3224,12 @@ int tcf_exts_init_ex(struct tcf_exts *exts, 
>> struct net *net, int action,
>>       exts->action = action;
>>       exts->police = police;
>> -    if (!use_action_miss)
>> +    if (!use_action_miss) {
>> +#ifdef CONFIG_NET_CLS_ACT
>> +        exts->miss_cookie_node = NULL;
>> +#endif
>>           return 0;
>> +    }
>>       err = tcf_exts_miss_cookie_base_alloc(exts, tp, handle);
>>       if (err)
> 
> The problem described here also happens in the case some error happens 
> if the action array allocation fails and before the 'miss_cookie_node' 
> assignment inside 'tcf_exts_miss_cookie_base_alloc()'.
> 
> Seems like a better way to solve this issue is to just:
> diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
> index 35785a36c802..3c3629c9e7b6 100644
> --- a/net/sched/cls_api.c
> +++ b/net/sched/cls_api.c
> @@ -3211,6 +3211,7 @@ int tcf_exts_init_ex(struct tcf_exts *exts, struct 
> net *net, int action,
>   #ifdef CONFIG_NET_CLS_ACT
>          exts->type = 0;
>          exts->nr_actions = 0;
> +       exts->miss_cookie_node = NULL;
>          /* Note: we do not own yet a reference on net.
>           * This reference might be taken later from tcf_exts_get_net().
>           */

Looks better, will repost...

Thanks

Ivan