Re: [PATCH] usb: usbip: fix null pointer dereference

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From	Krzysztof Opasiak <k.opasiak@samsung.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH] usb: usbip: fix null pointer dereference
Date	Mon, 06 Jun 2016 10:30:01 +0200
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On 06/05/2016 07:54 PM, Sudip Mukherjee wrote:
> On Friday 03 June 2016 09:29 AM, Krzysztof Opasiak wrote:
>>
>>
>> On 06/02/2016 03:22 PM, Sudip Mukherjee wrote:
>>> We have been dereferencing udc before checking it. Lets use it after it
>>> has been checked.
>>>
>>
>> To be honest I have mixed feelings about this patch.
>>
>> On one hand it prevents us from dereferencing potential NULL ptr what is
>> generally good. But on the other hand it seems to be a little bit
>> pointless overhead. This function is called only in one place, it's
>> internal function of vudc driver and in addition generally it is
>> currently impossible that this function will get NULL ptr as parameter
>> as it's value is taken from container_of(). Not to mention that if this
>> is NULL or garbage we will end up in NULL ptr dereference much earlier
>> before calling this function.
>>
>> So if there is something that you would like to fix with this patch and
>> you have a real problem with this function could you please provide us
>> some more details (for example stack trace)? If this patch is just to
>> prevent us from something that will never happen then I would rather to
>> not submit this. In my opinion if we get a NULL in this function this
>> means that we have some serious problem in UDC core and this check will
>> just mask this error.
> 
> Yes, I should have seen earlier that the only caller has already
> dereferenced udc. So maybe the following will be appropriate in this
> situation.
>

Your patch does exactly what Alan suggested and I agree with it;)

Could you please resend this properly so Greg can easily pick it up?

Best regards,
-- 
Krzysztof Opasiak
Samsung R&D Institute Poland
Samsung Electronics

Thread

[PATCH] usb: usbip: fix null pointer dereference Sudip Mukherjee <sudipm.mukherjee@gmail.com> - 2016-06-02 20:00 +0200
  Re: [PATCH] usb: usbip: fix null pointer dereference Krzysztof Opasiak <k.opasiak@samsung.com> - 2016-06-03 10:30 +0200
    Re: [PATCH] usb: usbip: fix null pointer dereference Alan Stern <stern@rowland.harvard.edu> - 2016-06-03 16:30 +0200
    Re: [PATCH] usb: usbip: fix null pointer dereference Sudip Mukherjee <sudipm.mukherjee@gmail.com> - 2016-06-05 20:00 +0200
      Re: [PATCH] usb: usbip: fix null pointer dereference Krzysztof Opasiak <k.opasiak@samsung.com> - 2016-06-06 10:30 +0200
        Re: [PATCH] usb: usbip: fix null pointer dereference Sudip Mukherjee <sudipm.mukherjee@gmail.com> - 2016-06-06 10:50 +0200

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