linux-kernel - Re: [usb-gadget-udc] question about null check after calling phys_to

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Message-ID: <20170516112837.Horde.ri3T1l55zoI08Pf29kOpXn4@gator4166.hostgator.com>
Date:   Tue, 16 May 2017 11:28:37 -0500
From:   "Gustavo A. R. Silva" <garsilva@...eddedor.com>
To:     Felipe Balbi <balbi@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Michal Nazarewicz <mina86@...a86.com>,
        linux-geode@...ts.infradead.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Peter Senna Tschudin <peter.senna@...il.com>
Subject: Re: [usb-gadget-udc] question about null check after calling
 phys_to_virt() function

Hi Felipe,

Quoting Felipe Balbi <balbi@...nel.org>:

> Hi,
>
> "Gustavo A. R. Silva" <garsilva@...eddedor.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