drivers/net/phy/phy_device.c:1772 phy_detach() error: we previously assumed 'dev' could be null (see line 1752)

From: Dan Carpenter
Date: Wed Jul 20 2022 - 05:46:09 EST

tree: https://github.com/tobetter/linux odroid-5.19.y
head: 0569e1291a824471ea27c9e90132881c0232a3a0
commit: 898624b63a33622330468fd8007048dc1981492d ODROID-COMMON: phy/realtek: add Wake-on-Lan to Realtek PHY
config: i386-randconfig-m021-20220718 (https://download.01.org/0day-ci/archive/20220720/202207200005.1kAdinkP-lkp@xxxxxxxxx/config)
compiler: gcc-11 (Debian 11.3.0-3) 11.3.0

If you fix the issue, kindly add following tag where applicable
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>

smatch warnings:
drivers/net/phy/phy_device.c:1772 phy_detach() error: we previously assumed 'dev' could be null (see line 1752)
drivers/net/phy/phy_device.c:1784 phy_detach() warn: variable dereferenced before check 'dev' (see line 1772)

vim +/dev +1772 drivers/net/phy/phy_device.c

6349084746ff4f Michael Walle 2020-05-06 1727
b3df0da886ffdb Randy Dunlap 2007-03-06 1728 /**
b3df0da886ffdb Randy Dunlap 2007-03-06 1729 * phy_detach - detach a PHY device from its network device
b3df0da886ffdb Randy Dunlap 2007-03-06 1730 * @phydev: target phy_device struct
7322967bc1bd97 Russell King 2015-09-24 1731 *
7322967bc1bd97 Russell King 2015-09-24 1732 * This detaches the phy device from its network device and the phy
7322967bc1bd97 Russell King 2015-09-24 1733 * driver, and drops the reference count taken in phy_attach_direct().
b3df0da886ffdb Randy Dunlap 2007-03-06 1734 */
e13934563db047 Andy Fleming 2005-08-24 1735 void phy_detach(struct phy_device *phydev)
e13934563db047 Andy Fleming 2005-08-24 1736 {
ec988ad78ed6d1 Florian Fainelli 2016-12-06 1737 struct net_device *dev = phydev->attached_dev;
2db2d9d1ac3722 Ioana Ciornei 2019-05-28 1738 struct module *ndev_owner = NULL;
3e3aaf64941698 Russell King 2015-09-24 1739 struct mii_bus *bus;
b3565f278a9bab Ezequiel Garcia 2014-07-23 1740
a3995460491d45 Florian Fainelli 2017-05-27 1741 if (phydev->sysfs_links) {
2db2d9d1ac3722 Ioana Ciornei 2019-05-28 1742 if (dev)

Check for NULL

5568363f0cb358 Florian Fainelli 2017-05-25 1743 sysfs_remove_link(&dev->dev.kobj, "phydev");
5568363f0cb358 Florian Fainelli 2017-05-25 1744 sysfs_remove_link(&phydev->mdio.dev.kobj, "attached_dev");
a3995460491d45 Florian Fainelli 2017-05-27 1745 }
c920f745f45d46 Ioana Ciornei 2019-05-28 1746
c920f745f45d46 Ioana Ciornei 2019-05-28 1747 if (!phydev->attached_dev)
c920f745f45d46 Ioana Ciornei 2019-05-28 1748 sysfs_remove_file(&phydev->mdio.dev.kobj,
c920f745f45d46 Ioana Ciornei 2019-05-28 1749 &dev_attr_phy_standalone.attr);
c920f745f45d46 Ioana Ciornei 2019-05-28 1750
93f41e67dc8ff0 Heiner Kallweit 2018-09-24 1751 phy_suspend(phydev);
2db2d9d1ac3722 Ioana Ciornei 2019-05-28 @1752 if (dev) {

Another check

c1f19b51d1d87f Richard Cochran 2010-07-17 1753 phydev->attached_dev->phydev = NULL;
e13934563db047 Andy Fleming 2005-08-24 1754 phydev->attached_dev = NULL;
2db2d9d1ac3722 Ioana Ciornei 2019-05-28 1755 }
9525ae83959b60 Russell King 2017-07-25 1756 phydev->phylink = NULL;
e13934563db047 Andy Fleming 2005-08-24 1757
0075bd692dca03 Geert Uytterhoeven 2016-11-28 1758 phy_led_triggers_unregister(phydev);
0075bd692dca03 Geert Uytterhoeven 2016-11-28 1759
c2b727df7caa33 Florian Fainelli 2020-09-16 1760 if (phydev->mdio.dev.driver)
6d9f66ac7fec2a Florian Fainelli 2017-02-08 1761 module_put(phydev->mdio.dev.driver->owner);
6d9f66ac7fec2a Florian Fainelli 2017-02-08 1762
e13934563db047 Andy Fleming 2005-08-24 1763 /* If the device had no specific driver before (i.e. - it
e13934563db047 Andy Fleming 2005-08-24 1764 * was using the generic driver), we unbind the device
e13934563db047 Andy Fleming 2005-08-24 1765 * from the generic driver so that there's a chance a
2f53e9047e79b6 Sergei Shtylyov 2014-01-05 1766 * real driver could be loaded
2f53e9047e79b6 Sergei Shtylyov 2014-01-05 1767 */
5db5ea995fc2fa Florian Fainelli 2019-01-15 1768 if (phy_driver_is_genphy(phydev) ||
5db5ea995fc2fa Florian Fainelli 2019-01-15 1769 phy_driver_is_genphy_10g(phydev))
e5a03bfd873c29 Andrew Lunn 2016-01-06 1770 device_release_driver(&phydev->mdio.dev);
3e3aaf64941698 Russell King 2015-09-24 1771
898624b63a3362 Dongjin Kim 2021-11-17 @1772 if (!dev->wol_enabled) {

Unchecked dereference

cbda1b16687580 Marek Behún 2022-01-19 1773 /* Assert the reset signal */
cbda1b16687580 Marek Behún 2022-01-19 1774 phy_device_reset(phydev, 1);
898624b63a3362 Dongjin Kim 2021-11-17 1775 }
cbda1b16687580 Marek Behún 2022-01-19 1776
7322967bc1bd97 Russell King 2015-09-24 1777 /*
7322967bc1bd97 Russell King 2015-09-24 1778 * The phydev might go away on the put_device() below, so avoid
7322967bc1bd97 Russell King 2015-09-24 1779 * a use-after-free bug by reading the underlying bus first.
7322967bc1bd97 Russell King 2015-09-24 1780 */
e5a03bfd873c29 Andrew Lunn 2016-01-06 1781 bus = phydev->mdio.bus;
3e3aaf64941698 Russell King 2015-09-24 1782
e5a03bfd873c29 Andrew Lunn 2016-01-06 1783 put_device(&phydev->mdio.dev);
2db2d9d1ac3722 Ioana Ciornei 2019-05-28 @1784 if (dev)

A third check for NULL

2db2d9d1ac3722 Ioana Ciornei 2019-05-28 1785 ndev_owner = dev->dev.parent->driver->owner;
ec988ad78ed6d1 Florian Fainelli 2016-12-06 1786 if (ndev_owner != bus->owner)
3e3aaf64941698 Russell King 2015-09-24 1787 module_put(bus->owner);
e13934563db047 Andy Fleming 2005-08-24 1788 }

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