struct b43_dmaring *parse_cookie(struct b43_wldev *dev, u16 cookie, int *slot)
{
	struct b43_dma *dma = &dev->dma;
	struct b43_dmaring *ring = NULL;

	switch (cookie & 0xF000) {
	case 0x1000:
		ring = dma->tx_ring_AC_BK;
		break;
	case 0x2000:
		ring = dma->tx_ring_AC_BE;
		break;
	case 0x3000:
		ring = dma->tx_ring_AC_VI;
		break;
	case 0x4000:
		ring = dma->tx_ring_AC_VO;
		break;
	case 0x5000:
		ring = dma->tx_ring_mcast;
		break;
	}
	*slot = (cookie & 0x0FFF);
	if (unlikely(!ring || *slot < 0 || *slot >= ring->nr_slots)) {
		b43dbg(dev->wl, "TX-status contains "
		       "invalid cookie: 0x%04X\n", cookie);
		return NULL;
	}

	return ring;
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.