int qeth_mdio_read(struct net_device *dev, int phy_id, int regnum)
{
	struct qeth_card *card = dev->ml_priv;
	int rc = 0;

	switch (regnum) {
	case MII_BMCR: /* Basic mode control register */
		rc = BMCR_FULLDPLX;
		if ((card->info.link_type != QETH_LINK_TYPE_GBIT_ETH) &&
		    (card->info.link_type != QETH_LINK_TYPE_OSN) &&
		    (card->info.link_type != QETH_LINK_TYPE_10GBIT_ETH))
			rc |= BMCR_SPEED100;
		break;
	case MII_BMSR: /* Basic mode status register */
		rc = BMSR_ERCAP | BMSR_ANEGCOMPLETE | BMSR_LSTATUS |
		     BMSR_10HALF | BMSR_10FULL | BMSR_100HALF | BMSR_100FULL |
		     BMSR_100BASE4;
		break;
	case MII_PHYSID1: /* PHYS ID 1 */
		rc = (dev->dev_addr[0] << 16) | (dev->dev_addr[1] << 8) |
		     dev->dev_addr[2];
		rc = (rc >> 5) & 0xFFFF;
		break;
	case MII_PHYSID2: /* PHYS ID 2 */
		rc = (dev->dev_addr[2] << 10) & 0xFFFF;
		break;
	case MII_ADVERTISE: /* Advertisement control reg */
		rc = ADVERTISE_ALL;
		break;
	case MII_LPA: /* Link partner ability reg */
		rc = LPA_10HALF | LPA_10FULL | LPA_100HALF | LPA_100FULL |
		     LPA_100BASE4 | LPA_LPACK;
		break;
	case MII_EXPANSION: /* Expansion register */
		break;
	case MII_DCOUNTER: /* disconnect counter */
		break;
	case MII_FCSCOUNTER: /* false carrier counter */
		break;
	case MII_NWAYTEST: /* N-way auto-neg test register */
		break;
	case MII_RERRCOUNTER: /* rx error counter */
		rc = card->stats.rx_errors;
		break;
	case MII_SREVISION: /* silicon revision */
		break;
	case MII_RESV1: /* reserved 1 */
		break;
	case MII_LBRERROR: /* loopback, rx, bypass error */
		break;
	case MII_PHYADDR: /* physical address */
		break;
	case MII_RESV2: /* reserved 2 */
		break;
	case MII_TPISTATUS: /* TPI status for 10mbps */
		break;
	case MII_NCONFIG: /* network interface config */
		break;
	default:
		break;
	}
	return rc;
}

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.