netdev - Re: [Patch net 1/2] net_sched: Prevent creation of classes with TC_H

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Message-ID: <17414eab-445d-4669-89a9-855a872f7c16@redhat.com>
Date: Tue, 11 Mar 2025 13:47:32 +0100
From: Paolo Abeni <pabeni@...hat.com>
To: Simon Horman <horms@...nel.org>, Cong Wang <xiyou.wangcong@...il.com>
Cc: netdev@...r.kernel.org, jhs@...atatu.com, jiri@...nulli.us,
 mincho@...ori.io
Subject: Re: [Patch net 1/2] net_sched: Prevent creation of classes with
 TC_H_ROOT



On 3/11/25 11:48 AM, Simon Horman wrote:
> On Thu, Mar 06, 2025 at 03:23:54PM -0800, Cong Wang wrote:
>> The function qdisc_tree_reduce_backlog() uses TC_H_ROOT as a termination
>> condition when traversing up the qdisc tree to update parent backlog
>> counters. However, if a class is created with classid TC_H_ROOT, the
>> traversal terminates prematurely at this class instead of reaching the
>> actual root qdisc, causing parent statistics to be incorrectly maintained.
>> In case of DRR, this could lead to a crash as reported by Mingi Cho.
>>
>> Prevent the creation of any Qdisc class with classid TC_H_ROOT
>> (0xFFFFFFFF) across all qdisc types, as suggested by Jamal.
>>
>> Reported-by: Mingi Cho <mincho@...ori.io>
>> Signed-off-by: Cong Wang <xiyou.wangcong@...il.com>
> 
> Hi Cong,
> 
> This change looks good to me.
> But could we get a fixes tag?`
> 
> ...

Should be:

Fixes: 066a3b5b2346 ("[NET_SCHED] sch_api: fix
qdisc_tree_decrease_qlen() loop")

right?

/P