Re: usb/hid: slab-out-of-bounds read in usbhid_parse

[Jaejoong Kim]

Hi Alan

2017-09-21 0:50 GMT+09:00 Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>:
> On Wed, 20 Sep 2017, Kim Jaejoong wrote:
>
>> To. usb & input guys.
>>
>> While dig this report, i was wondering about bNumDescriptors in HID descriptor.
>> HID document from usb.org said, 'this number must be at least one (1)
>> as a Report descriptor will always be present.'
>>
>> There is no mention of the order of class descriptors. Suppose you
>> have a HID device with a report descriptor and a physical descriptor.
>>
>> If you have the following hid descriptor in this case,
>> HID descriptor
>>    bLength: 12
>>    bDescriptor Type: HID
>>    .. skip
>>    bNumDescriptors: 2
>>    bDescriptorType: physical
>>    bDescriptorLength: any
>>    bDescriptorType: Report
>>    bDescriptorLength: any
>>
>> If the order of the report descriptor is the second as above,
>> usbhid_parse () will fail because my patch is only check the first
>> bDescriptor Type.
>> But If the order of the report descriptor is always first, there is no
>> problem. How do you think this?
>
> The descriptors can appear in any order.  You should not assume that
> the report descriptor will always come first.

Thanks for clarifying. I will resend patch with modification.

Jaejoong

>
> Alan Stern
>