[PATCH] fpga zynq: Check the bitstream for validity

[Matthias Brugger]

On 10/27/2016 04:39 PM, Jason Gunthorpe wrote:
> On Thu, Oct 27, 2016 at 10:50:48AM +0200, Matthias Brugger wrote:
>>> +		/* Sanity check the proposed bitstream. It must start with the
>>> +		 * sync word in the correct byte order and be a multiple of 4
>>> +		 * bytes.
>>> +		 */
>>> +		if (count <= 4 || buf[0] != 0x66 || buf[1] != 0x55 ||
>>> +		    buf[2] != 0x99 || buf[3] != 0xaa) {
>>
>> This checks if the bit stream is bigger then 4 bytes. We error out before,
>> if it is smaller.
>
> We do? Where?
>

Just a few lines before:

+	/* All valid bitstreams are multiples of 32 bits */
+	if ((count % 4) != 0)
+		return -EINVAL;
+

The only case we don't check is, if count == 0. If we check that here, 
we can get rid of the count <= 4 check.

>> So you should fix the wording in the comment and check for count ==
>> 4.
>
> Ah right, the comment reflected an earlier revision that had the
> length check here.
>
> The count <= 4 should stay here since it is primarily guarding against
> read past the buffer in the if.

If you insist in doing this check, it should be count < 4, because we 
check the first four elements of buf, or do I miss something?

Cheers,
Matthias

>
> Jason
>
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