Re: [PATCH] nfc: virtual_ncidev: Add variable to check if ndev is running

Krzysztof Kozlowski
2023-11-20T10:45:55Z

On 20/11/2023 11:39, Nguyen Dinh Phi wrote:
>>>> mutex_lock(&vdev->mtx);
>>>> kfree_skb(vdev->send_buff);
>>>> vdev->send_buff = NULL;
>>>> + vdev->running = false;
>>>> mutex_unlock(&vdev->mtx);
>>>>
>>>> return 0;
>>>> @@ -50,7 +55,7 @@ static int virtual_nci_send(struct nci_dev *ndev, struct sk_buff *skb)
>>>> struct virtual_nci_dev *vdev = nci_get_drvdata(ndev);
>>>>
>>>> mutex_lock(&vdev->mtx);
>>>> - if (vdev->send_buff) {
>>>> + if (vdev->send_buff || !vdev->running) {
>>>
>>> Dear Krzysztof,
>>>
>>> I agree this defensive code.
>>> But i think NFC submodule has to avoid this situation.(calling send function of closed nci_dev)
>>> Could you check this?
>>
>> This code looks not effective. At this point vdev->send_buff is always
>> false, so the additional check would not bring any value.
>>
>> I don't see this fixing anything. Syzbot also does not seem to agree.
>>
>> Nguyen, please test your patches against syzbot *before* sending them.
>> If you claim this fixes the report, please provide me the link to syzbot
>> test results confirming it is fixed.
>>
>> I looked at syzbot dashboard and do not see this issue fixed with this
>> patch.
>>
>> Best regards,
>> Krzysztof
>>
>
> Hi Krzysztof,
>
> I've submitted it to syzbot, it is the test request that created at
> [2023/11/20 09:39] in dashboard link
> https://syzkaller.appspot.com/bug?extid=6eb09d75211863f15e3e

...and I see there two errors.

I don't know, maybe I miss something obvious (our brains like to do it
sometimes), but please explain me how this could fix anything?

Best regards,
Krzysztof