dcd_pic32: Fix memory overwrite in incoming data

When transfer was finished rx_fifo_read() read all that
was to read RXPKTRDY was cleared allowing next packet to
be received.
Then xfer_complete was called.
Interrupt for OUT endpoint was left enable, that would not
be a problem if data was handled fast and new transfer was
scheduled.
For MSC when host sends a lot of data this interrupt that was
enabled could cause epn_handle_rx_int() to be called after
transfer was completed and next was not scheduled yet.
Without TU_ASSERT that was added to detect this, incoming
data was written past buffer provided by user code resulting
in random memory corruption.

This just blocks RX interrupt when transfer is finished,
and also only unmasked rx interrupts are handled.

Author: kasjer

src/portable/microchip/pic32mz/dcd_pic32mz.c

@@ -564,6 +564,7 @@ static void epn_handle_rx_int(uint8_t epnum)
     TU_ASSERT(xfer->transferred <= xfer->total_len,);
     if (transferred < xfer->max_packet_size || xfer->transferred == xfer->total_len)
     {
+      USB_REGS->INTRRXEbits.w &= ~(1u << epnum);
       xfer_complete(xfer, XFER_RESULT_SUCCESS, true);
     }
   }
@@ -692,7 +693,7 @@ void dcd_int_handler(uint8_t rhport)
   int i;
   uint8_t mask;
   __USBCSR2bits_t csr2_bits;
-  uint16_t rxints = USB_REGS->INTRRX;
+  uint16_t rxints = USB_REGS->INTRRX & USB_REGS->INTRRXEbits.w;
   uint16_t txints = USB_REGS->INTRTX;
   csr2_bits = USBCSR2bits;
   (void) rhport;