static int tg3_phy_lpbk_set(struct tg3 *tp, u32 speed, bool extlpbk)
{
	u32 val, bmcr, mac_mode, ptest = 0;

	tg3_phy_toggle_apd(tp, false);
	tg3_phy_toggle_automdix(tp, 0);

	if (extlpbk && tg3_phy_set_extloopbk(tp))
		return -EIO;

	bmcr = BMCR_FULLDPLX;
	switch (speed) {
	case SPEED_10:
		break;
	case SPEED_100:
		bmcr |= BMCR_SPEED100;
		break;
	case SPEED_1000:
	default:
		if (tp->phy_flags & TG3_PHYFLG_IS_FET) {
			speed = SPEED_100;
			bmcr |= BMCR_SPEED100;
		} else {
			speed = SPEED_1000;
			bmcr |= BMCR_SPEED1000;
		}
	}

	if (extlpbk) {
		if (!(tp->phy_flags & TG3_PHYFLG_IS_FET)) {
			tg3_readphy(tp, MII_CTRL1000, &val);
			val |= CTL1000_AS_MASTER |
			       CTL1000_ENABLE_MASTER;
			tg3_writephy(tp, MII_CTRL1000, val);
		} else {
			ptest = MII_TG3_FET_PTEST_TRIM_SEL |
				MII_TG3_FET_PTEST_TRIM_2;
			tg3_writephy(tp, MII_TG3_FET_PTEST, ptest);
		}
	} else
		bmcr |= BMCR_LOOPBACK;

	tg3_writephy(tp, MII_BMCR, bmcr);

	/* The write needs to be flushed for the FETs */
	if (tp->phy_flags & TG3_PHYFLG_IS_FET)
		tg3_readphy(tp, MII_BMCR, &bmcr);

	udelay(40);

	if ((tp->phy_flags & TG3_PHYFLG_IS_FET) &&
	    tg3_asic_rev(tp) == ASIC_REV_5785) {
		tg3_writephy(tp, MII_TG3_FET_PTEST, ptest |
			     MII_TG3_FET_PTEST_FRC_TX_LINK |
			     MII_TG3_FET_PTEST_FRC_TX_LOCK);

		/* The write needs to be flushed for the AC131 */
		tg3_readphy(tp, MII_TG3_FET_PTEST, &val);
	}

	/* Reset to prevent losing 1st rx packet intermittently */
	if ((tp->phy_flags & TG3_PHYFLG_MII_SERDES) &&
	    tg3_flag(tp, 5780_CLASS)) {
		tw32_f(MAC_RX_MODE, RX_MODE_RESET);
		udelay(10);
		tw32_f(MAC_RX_MODE, tp->rx_mode);
	}

	mac_mode = tp->mac_mode &
		   ~(MAC_MODE_PORT_MODE_MASK | MAC_MODE_HALF_DUPLEX);
	if (speed == SPEED_1000)
		mac_mode |= MAC_MODE_PORT_MODE_GMII;
	else
		mac_mode |= MAC_MODE_PORT_MODE_MII;

	if (tg3_asic_rev(tp) == ASIC_REV_5700) {
		u32 masked_phy_id = tp->phy_id & TG3_PHY_ID_MASK;

		if (masked_phy_id == TG3_PHY_ID_BCM5401)
			mac_mode &= ~MAC_MODE_LINK_POLARITY;
		else if (masked_phy_id == TG3_PHY_ID_BCM5411)
			mac_mode |= MAC_MODE_LINK_POLARITY;

		tg3_writephy(tp, MII_TG3_EXT_CTRL,
			     MII_TG3_EXT_CTRL_LNK3_LED_MODE);
	}

	tw32(MAC_MODE, mac_mode);
	udelay(40);

	return 0;
}

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.