netdev - Re: [PATCH] net:sched fix array-index-out-of-bounds in taprio

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Date:   Mon, 30 Aug 2021 10:09:38 +0800
From:   Haimin Zhang <tcs.kernel@...il.com>
To:     Eric Dumazet <eric.dumazet@...il.com>, vinicius.gomes@...el.com,
        jhs@...atatu.com, xiyou.wangcong@...il.com, jiri@...nulli.us,
        davem@...emloft.net, kuba@...nel.org, netdev@...r.kernel.org
Cc:     Haimin Zhang <tcs_kernel@...cent.com>
Subject: Re: [PATCH] net:sched fix array-index-out-of-bounds in taprio_change

hi，i wonder to know what‘s going on with this patch ?
are you plannig to merge it ?


在 2021/8/11 16:36, Haimin Zhang 写道:
> 
> 
> 在 2021/8/11 15:44, Eric Dumazet 写道:
>>
>>
>> On 8/11/21 7:10 AM, tcs.kernel@...il.com wrote:
>>> From: Haimin Zhang <tcs_kernel@...cent.com>
>>>
>>> syzbot report an array-index-out-of-bounds in taprio_change
>>> index 16 is out of range for type '__u16 [16]'
>>> that's because mqprio->num_tc is lager than TC_MAX_QUEUE,so we check
>>> the return value of netdev_set_num_tc.
>>>
>>> Reported-by: syzbot+2b3e5fb6c7ef285a94f6@...kaller.appspotmail.com
>>> Signed-off-by: Haimin Zhang <tcs_kernel@...cent.com>
>>> ---
>>>   net/sched/sch_taprio.c | 4 +++-
>>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
>>> index 9c79374..1ab2fc9 100644
>>> --- a/net/sched/sch_taprio.c
>>> +++ b/net/sched/sch_taprio.c
>>> @@ -1513,7 +1513,9 @@ static int taprio_change(struct Qdisc *sch, 
>>> struct nlattr *opt,
>>>       taprio_set_picos_per_byte(dev, q);
>>>       if (mqprio) {
>>> -        netdev_set_num_tc(dev, mqprio->num_tc);
>>> +        err = netdev_set_num_tc(dev, mqprio->num_tc);
>>> +        if (err)
>>> +            goto free_sched;
>>>           for (i = 0; i < mqprio->num_tc; i++)
>>>               netdev_set_tc_queue(dev, i,
>>>                           mqprio->count[i],
>>>
>>
>> When was the bug added ?
>>
>> Hint: Please provide a Fixes: tag
>>
>> taprio_parse_mqprio_opt() already checks :
>>
>> /* Verify num_tc is not out of max range */
>> if (qopt->num_tc > TC_MAX_QUEUE) {
>>      NL_SET_ERR_MSG(extack, "Number of traffic classes is outside 
>> valid range");
>>      return -EINVAL;
>> }
>>
>> So what is happening exactly ?
>>
>>
>>
>>
> syzkaller reported this problem,the log shows mqprio->count[16] is 
> accessed.
> here is the log
> https://syzkaller.appspot.com/bug?id=3a3677d4e7539ec5e671a81e32882ad40b5f7b64 
> 
> 
> the added check logic is hurtlessness,and netdev_set_num_tc does have a 
> return value.