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Re: [usb-gadget-udc] question about null check after calling phys_to_virt() function

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  Re: [usb-gadget-udc] question about null check after calling phys_to_virt() function Felipe Balbi <balbi@kernel.org> - 2017-05-16 10:20 +0200
    Re: [usb-gadget-udc] question about null check after calling  phys_to_virt() function "Gustavo A. R. Silva" <garsilva@embeddedor.com> - 2017-05-16 18:30 +0200

#1642298 — Re: [usb-gadget-udc] question about null check after calling phys_to_virt() function

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Hi,

"Gustavo A. R. Silva" <garsilva@embeddedor.com> writes:
> Hello everybody,
>
> While looking into Coverity ID 145958 I ran into the following piece  
> of code at drivers/usb/gadget/udc/amd5536udc.c:852:
>
> } else if (i == buf_len) {
>          /* first td */
>          td = (struct udc_data_dma *)phys_to_virt(
>                                  req->td_data->next);
>          td->status = 0;
> } else {
>          td = (struct udc_data_dma *)phys_to_virt(last->next);
>          td->status = 0;
> }
>
> if (td)
>          td->bufptr = req->req.dma + i; /* assign buffer */
> else
>          break;
>
> The issue here is that _td_ pointer is being dereferenced before null check.
>
> After searching for calls to phys_to_virt() function, I've noticed  
> that is not common at all to test the returned address value.
>
> So either the null check at line 862 is not needed or a null check  
> before each td->status = 0; needs to be added.

just remove the previous null check

-- 
balbi

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#1642660 — Re: [usb-gadget-udc] question about null check after calling phys_to_virt() function

Hi Felipe,

Quoting Felipe Balbi <balbi@kernel.org>:

> Hi,
>
> "Gustavo A. R. Silva" <garsilva@embeddedor.com> writes:
>> Hello everybody,
>>
>> While looking into Coverity ID 145958 I ran into the following piece
>> of code at drivers/usb/gadget/udc/amd5536udc.c:852:
>>
>> } else if (i == buf_len) {
>>          /* first td */
>>          td = (struct udc_data_dma *)phys_to_virt(
>>                                  req->td_data->next);
>>          td->status = 0;
>> } else {
>>          td = (struct udc_data_dma *)phys_to_virt(last->next);
>>          td->status = 0;
>> }
>>
>> if (td)
>>          td->bufptr = req->req.dma + i; /* assign buffer */
>> else
>>          break;
>>
>> The issue here is that _td_ pointer is being dereferenced before null check.
>>
>> After searching for calls to phys_to_virt() function, I've noticed
>> that is not common at all to test the returned address value.
>>
>> So either the null check at line 862 is not needed or a null check
>> before each td->status = 0; needs to be added.
>
> just remove the previous null check
>

I get it.

Thanks!
--
Gustavo A. R. Silva

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