Re: [Qemu-devel] [PATCH] usb-mtp: Assert on suspicious TYPE_DATA packet from initiator

[Bandan Das <bsd@redhat.com>]

Peter Maydell <peter.maydell@linaro.org> writes:

> On 18 May 2018 at 19:38, Bandan Das <bsd@redhat.com> wrote:
>> Peter Maydell <peter.maydell@linaro.org> writes:
>>
>>> On 18 May 2018 at 19:22, Bandan Das <bsd@redhat.com> wrote:
>>>>
>>>> CID 1390604
>>>> If the initiator sends a packet with TYPE_DATA set without
>>>> initiating a CMD_GET_OBJECT_INFO first, then usb_mtp_get_data
>>>> can trip on a null s->data_out.
>>>>
>>>> Signed-off-by: Bandan Das <bsd@redhat.com>
>>>
>>> I think you said this can be provoked by the guest?
>>
>> Yes, this can only be initated by the guest as far as I
>> understand.
>>
>>> Misbehaving or malicious guests should never be able
>>> to provoke assertions.
>>
>> I am not sure, I thought it's better to kill a misbehaving guest rather
>> than silently letting it run. Anyway, it's possible to send a
>> No_Valid_ObjectInfo as well and we wouldn't have to mark it as a
>> false positive either.
>
> Broadly speaking, where we're emulating hardware we should do
> what the hardware does when the guest does wrong things to it.
> A real server doesn't suddenly vanish leaving behind a
> message saying "assertion failed" :-)

Posted v2 and agree with you! Especially, since the protocol does specify
the case where something like this can happen.

Thanks for reviewing,
Bandan

> thanks
> -- PMM