On 29-05-2009 07:18, Minoru Usui wrote:
> Hi,
>
> On Thu, 21 May 2009 09:22:56 +0900
> Minoru Usui <usui@xxxxxxxxxxxxxxxxx> wrote:
>
>> Hi
Hi,
>>
>> Unfortunately this is only panic report.
>>
>> I used cgroup net_cls subsystem, then kernel panic occured.
>> I attach panic message and kernel config in this mail's last paragraph.
>> If my operation is wrong, could you tell me how to use net_cls and
>> where the documentation is.
>>
>> # But I think panic is very bad even if my operation is wrong.
>
> I investigated this problem, and I found a bug in tc_ctl_tfilter() in net/sched/cls_api.c.
>
> When 'tc filter add' command is executed and proto-tcf does not exist,
> tcf_ctl_tfilter() allocates, initializes and chanins proto-tcf(tp) to
> cops->tcf_chain()'s chain before calling tp->ops->change().
>
> If tp->ops->change() returns an error, tcf_ctl_tfilter() returns an error
> too, but proto-tcf(tp) is not unchained yet.
>
> I think tcf_ctl_tfilter() shouldn't chain proto-tcf to the chain before it returns
> an error.
I didn't verify this too much, so I might be wrong, but it looks like
cls_cgroup_classify() does things a bit different than others (doesn't
check the 'head' etc. for NULL), so maybe you should consider fixing
it instead? (Btw., the tc classifier maintainer added to Cc).
Cheers,
Jarek P.
>
> Signed-off-by: Minoru Usui <usui@xxxxxxxxxxxxxxxxx>
>
> diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
> index 0759f32..756148b 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;
>
> @@ -314,8 +309,17 @@ replay:
> }
>
> err = tp->ops->change(tp, cl, t->tcm_handle, tca, &fh);
> - if (err == 0)
> - tfilter_notify(skb, n, tp, fh, RTM_NEWTFILTER);
> + if (err) {
> + tcf_destroy(tp);
> + goto errout;
> + }
> +
> + spin_lock_bh(root_lock);
> + tp->next = *back;
> + *back = tp;
> + spin_unlock_bh(root_lock);
> +
> + tfilter_notify(skb, n, tp, fh, RTM_NEWTFILTER);
>
> errout:
> if (cl)
>
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