[U-Boot] [PATCH] usb: check udev before dereferencing

[Marek Vasut]

On 11/12/2016 07:10 PM, Anatolij Gustschin wrote:
> On Sat, 12 Nov 2016 10:36:42 +0100
> Marek Vasut marex at denx.de wrote:
> ...
>>>  		udev = dev_get_parent_priv(child);
>>> +		if (!udev)
>>> +			continue;  
>>
>> I don't quite understand the problem from the patch description, but
>> shouldn't all the return values from dev_get_parent_priv() be checked
>> this way , not just these two ?
> 
> The problem is that when dereferencing NULL udev we later access
> some random address (e.g. when accessing dev->dev->parent in
> usb_show_tree_graph()). dev->dev pointer is random DRAM data there,
> when dereferencing it, data abort happens when random address
> is outside of valid address range.

I mean, I understand that udev can be NULL and we don't check it. But is
udev == NULL an expected possibility ? And if so, when does such thing
happen ?

> Probably we should check elsewhere, at least where it might
> return NULL.

OK

>>
>> Why does dev_get_parent_priv() return NULL here ?
> 
> it returns NULL because the dev->parent_priv is not allocated for
> usb_mass_storage.lun0 device. I do not know the reason why.

That's probably what needs to be fixed , no ?

Also, we should most likely check all the return values of
dev_get_parent_priv() in cmd/usb.c, not just these two.

-- 
Best regards,
Marek Vasut