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

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.

I think it would be good to apply a patch like the following one:

- td->status = 0;
+
+ if (td)
+ td->status = 0;
+ else
+ break;
} else {
td = (struct udc_data_dma *)phys_to_virt(last->next);
- td->status = 0;
+
+ if (td)
+ td->status = 0;
+ else
+ break;
}

- if (td)
- td->bufptr = req->req.dma + i; /* assign buffer */
- else
- break;
+ td->bufptr = req->req.dma + i; /* assign buffer */


What do you think?

Thanks in advance for your comments
--
Gustavo A. R. Silva




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