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Subject: Re: [PATCH v3 3/3] uio: fix crash after the device is unregistered
To:     Mike Christie <mchristi@redhat.com>, gregkh@linuxfoundation.org,
        linux-kernel@vger.kernel.org
Cc:     hamish.martin@alliedtelesis.co.nz, jannh@google.com,
        pkalever@redhat.com, pkarampu@redhat.com, atumball@redhat.com,
        sabose@redhat.com
References: <1530845836-49101-1-git-send-email-xiubli@redhat.com>
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 <5B3FBBF1.9080902@redhat.com>
From:   Xiubo Li <xiubli@redhat.com>
Message-ID: <434b1b7c-604d-a446-b73a-8de7a50817c5@redhat.com>
Date:   Sat, 7 Jul 2018 09:47:11 +0800
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On 2018/7/7 2:58, Mike Christie wrote:
> On 07/05/2018 09:57 PM, xiubli@redhat.com wrote:
>>   void uio_event_notify(struct uio_info *info)
>>   {
>> -	struct uio_device *idev = info->uio_dev;
>> +	struct uio_device *idev;
>> +
>> +	if (!info)
>> +		return;
>> +
>> +	idev = info->uio_dev;
>>   
> For this one too, I am not sure if it is needed.
>
> uio_interrupt -> uio_event_notify. See other mail.
>
> driver XYZ -> uio_event_notify. I think drivers need to handle this and
> set some bits and/or perform some cleanup to make sure they are not
> calling uio_event_notify after it has called uio_unregister_device. The
> problem with the above test is if they do not they could have called
> uio_unregister_device right after the info test so you could still hit
> the problem.

When we are tcmu_destroy_device(), if the netlink notify event to 
userspace is not successful then the TCMU will call the uio unregister, 
which will set the idev->info = NULL, without close and deleting the 
device in userspace. But the TCMU could still queue cmds to the ring 
buffer, then the uio_event_notify will be called.

For this case only when using idev->info it would happen. And currently 
there is no need to check this, I will remove it for now.

Thanks,

BRs