[PATCH] hidclass.sys: fixed size passed IOCTL_HID_GET_INPUT_REPORT (Coverity)

[Sebastian Lackner]

On 19.10.2015 15:04, Aric Stewart wrote:
> On 10/17/15 8:34 AM, Marcus Meissner wrote:
>> On Sat, Oct 17, 2015 at 03:31:24PM +0200, Sebastian Lackner wrote:
>>> On 17.10.2015 14:52, Marcus Meissner wrote:
>>>> 1327477 Wrong sizeof argument
>>>>
>>>> Signed-off-by: Marcus Meissner <marcus at jet.franken.de>
>>>> ---
>>>>   dlls/hidclass.sys/device.c | 2 +-
>>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/dlls/hidclass.sys/device.c b/dlls/hidclass.sys/device.c
>>>> index e7e7e11..dcc7d3c 100644
>>>> --- a/dlls/hidclass.sys/device.c
>>>> +++ b/dlls/hidclass.sys/device.c
>>>> @@ -277,7 +277,7 @@ static DWORD CALLBACK hid_device_thread(void *args)
>>>>               packet->reportId = 0;
>>>>   
>>>>               irp = IoBuildDeviceIoControlRequest(IOCTL_HID_GET_INPUT_REPORT,
>>>> -                device, NULL, 0, packet, sizeof(packet), TRUE, events[0],
>>>> +                device, NULL, 0, packet, sizeof(*packet)+ext->preparseData->caps.InputReportByteLength, TRUE, events[0],
>>>>                   &irp_status);
>>>>   
>>>>               irpsp = IoGetNextIrpStackLocation(irp);
>>>>
>>>
>>> This looks wrong, you have to allocate a separate buffer, and then copy it (like in the code below).
>>> I don't know why some of these buffers are HEAP_ZERO_MEMORY though, and others not? Adding Aric, he
>>> might want to review this part again, especially since Coverity detected more issues in this code
>>> (unnecessary assignment of "rc" for example).
>>
>> something seems wrong though here, yes.
>>
>> rc issue is "CID 1327478 Unused value"
>>
>> Ciao, Marcus
>>
> 
> What is happening here is that the HID_XFER_PACKET is not a variable length structure, it takes a pointer to the buffer.  I am taking a bit of a shortcut and instead of allocating the HID_XFER_PACKET structure and a separate buffer, I am allocating 1 block of memory that is both, the buffer just comes after the HID_XFER_PACKET structure. 
> 
> I am pretty sure Marcus' original patch is unnecessary.  I am not surprised that there are issues in this code area though. It when through a lot of revision and tweaking as I was getting things working and that often results in cruft. 
> 
> -aric
> 

I still don't think its correct. The IOCTL_HID_GET_INPUT_REPORT expects a raw data buffer,
without any header in front of it, right? Then you would have to pass packet->reportBuffer
(and the correct size) to IoBuildDeviceIoControlRequest, but that doesn't work because
the buffer will be deallocated automatically after the request is done.