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

From: Gustavo A. R. Silva
Date: Tue May 16 2017 - 12:29:14 EST

Hi Felipe,

Quoting Felipe Balbi <balbi@xxxxxxxxxx>:


"Gustavo A. R. Silva" <garsilva@xxxxxxxxxxxxxx> 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(
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 */

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.

Gustavo A. R. Silva