From: Pavel Skripkin <paskripkin@gmail.com>
To: Eric Dumazet <eric.dumazet@gmail.com>,
tcs.kernel@gmail.com, vinicius.gomes@intel.com, jhs@mojatatu.com,
xiyou.wangcong@gmail.com, jiri@resnulli.us, davem@davemloft.net,
kuba@kernel.org, netdev@vger.kernel.org
Cc: Haimin Zhang <tcs_kernel@tencent.com>
Subject: Re: [PATCH] net:sched fix array-index-out-of-bounds in taprio_change
Date: Wed, 11 Aug 2021 11:35:38 +0300 [thread overview]
Message-ID: <9c3e8561-bced-fe61-e7ac-e7635a3f9a7c@gmail.com> (raw)
In-Reply-To: <1852afdd-7c93-fdbc-404f-a5c76b9bc5d7@gmail.com>
On 8/11/21 11:30 AM, Pavel Skripkin wrote:
> On 8/11/21 10:44 AM, Eric Dumazet wrote:
>>
>>
>> On 8/11/21 7:10 AM, tcs.kernel@gmail.com wrote:
>>> From: Haimin Zhang <tcs_kernel@tencent.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@syzkaller.appspotmail.com
>>> Signed-off-by: Haimin Zhang <tcs_kernel@tencent.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 ?
>>
>>
>
> Hi, Eric!
>
> I've looked into this bug, but I decided to write a reproducer for it
> first. Unfortunately, I didn't finish it yesterday, but I have an idea
> about what happened:
>
> taprio_parse_mqprio_opt() may return 0 before qopt->num_tc check:
>
> /* If num_tc is already set, it means that the user already
> * configured the mqprio part
> */
> if (dev->num_tc)
> return 0;
>
> Then taprio_mqprio_cmp() fails here:
>
> if (!mqprio || mqprio->num_tc != dev->num_tc)
> return -1;
>
> That's why we won't get shift-out-of-bound in taprio_mqprio_cmp().
^^^^^^^^^^^^^^^^^
array-index-out-of-bounds
Sorry for confusion
With regards,
Pavel Skripkin
next prev parent reply other threads:[~2021-08-11 8:35 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-11 5:10 [PATCH] net:sched fix array-index-out-of-bounds in taprio_change tcs.kernel
2021-08-11 7:44 ` Eric Dumazet
2021-08-11 8:30 ` Pavel Skripkin
2021-08-11 8:35 ` Pavel Skripkin [this message]
2021-08-11 8:36 ` Haimin Zhang
2021-08-30 2:09 ` Haimin Zhang
2021-08-30 16:10 ` Jakub Kicinski
2021-08-12 17:53 ` Jakub Kicinski
-- strict thread matches above, loose matches on Subject: below --
2021-08-11 4:09 tcs.kernel
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