Subject: Re: [BUG] net_cls: Panic occured when net_cls subsystem use

From: Jarek Poplawski <[email-masked]>
Date: Sat, 30 May 2009 00:59:29 +0200

On Fri, May 29, 2009 at 09:54:29AM -0400, jamal wrote:
> Hi Minoru,
> 
> I hate to do this to you after i made suggestions on how to
> make the changes.... (as an adult i hate it when people do it to
> me;->)
> But sometimes code helps. So what i meant is the attached patch.
> I havent even compiled it yet.
> If it works, please submit it and add yourself as the author
> (and a signed-off from me). Then we can revisit the init()
> issue in cls_group..
> You should also cc tgraf in your cls_grp config questions.
> 
> cheers,
> jamal
> 
> On Fri, 2009-05-29 at 09:46 -0400, jamal wrote:
> > 
> > This is incorrect. tp may already exist and you dont want to destroy
> > for failure to change its parameters. You also dont want to reattach
> > an existing tp because it succeeded in parameter change. 
> > So the soln is to check if this is a new tp and then do what you did
> > above...
> > Did that make sense?
> > 
> > cheers,
> > jamal

> diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
> index 0759f32..8760a48 100644
> --- a/net/sched/cls_api.c
> +++ b/net/sched/cls_api.c
> @@ -266,11 +266,6 @@ replay:
>  			goto errout;
>  		}
>  
> -		spin_lock_bh(root_lock);
> -		tp->next = *back;
> -		*back = tp;
> -		spin_unlock_bh(root_lock);
> -
>  	} else if (tca[TCA_KIND] && nla_strcmp(tca[TCA_KIND], tp->ops->kind))
>  		goto errout;
>  
...
        } else {
                switch (n->nlmsg_type) {
                case RTM_NEWTFILTER:
                        err = -EEXIST;
                        if (n->nlmsg_flags & NLM_F_EXCL)
                                goto errout;
                        break;

Probably this case needs tcf_destroy() too.

Cheers,
Jarek P.

> @@ -314,8 +309,21 @@ replay:
>  	}
>  
>  	err = tp->ops->change(tp, cl, t->tcm_handle, tca, &fh);
> -	if (err == 0)
> +	if (err == 0) {
> +		if (n->nlmsg_type == RTM_NEWTFILTER &&
> +		    (n->nlmsg_flags&NLM_F_CREATE)) {
> +			spin_lock_bh(root_lock);
> +			tp->next = *back;
> +			*back = tp;
> +			spin_unlock_bh(root_lock);
> +		}
>  		tfilter_notify(skb, n, tp, fh, RTM_NEWTFILTER);
> +	} else {
> +		if (n->nlmsg_type == RTM_NEWTFILTER &&
> +		    (n->nlmsg_flags&NLM_F_CREATE)) {
> +			tcf_destroy(tp);
> +		}
> +	}
>  
>  errout:
>  	if (cl)