Merge branch 'net-phy-fix-a-second-attach-of-an-attached-phy-and-the-module-put-on-detach'

Aleksei Sviridkin says:

====================
net: phy: fix a second attach of an attached PHY and the module put on detach

Two phylib fixes found on a Keenetic KN-1012 (MT7981) while chasing a
PHY driver unbind race. A second attach of an attached PHY tears down
the first consumer, and a detach after a driver unbind leaks the module
reference.

1: refuse a second attach before the driver module is taken or the
   generic driver bound.
2: put the module the attach pinned, not whatever driver is bound at
   detach.

Patch 1 goes first: with patch 2 alone, the second attach error path
leaves the first consumer's module reference pinned.
====================

Link: https://patch.msgid.link/20261013151200.2473464-1-f@lex.la
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

2 files changed, 17 insertions, 10 deletions

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index bfce8b893644..68691c487eee 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -1728,8 +1728,8 @@ static void phy_detach_internal(struct phy_device *phydev, bool notify_bus)
 	phydev->phy_link_change = NULL;
 	phydev->phylink = NULL;
 
-	if (phydev->mdio.dev.driver)
-		module_put(phydev->mdio.dev.driver->owner);
+	module_put(phydev->drv_owner);
+	phydev->drv_owner = NULL;
 
 	/* If the device had no specific driver before (i.e. - it
 	 * was using the generic driver), we unbind the device
@@ -1794,6 +1794,7 @@ int phy_attach_direct(struct net_device *dev, struct phy_device *phydev,
 	struct mii_bus *bus = phydev->mdio.bus;
 	struct device *d = &phydev->mdio.dev;
 	struct module *ndev_owner = NULL;
+	struct module *drv_owner;
 	int irq = phydev->irq;
 	int err;
 
@@ -1811,6 +1812,13 @@ int phy_attach_direct(struct net_device *dev, struct phy_device *phydev,
 
 	get_device(d);
 
+	/* Set by every attach, with or without a netdev */
+	if (phydev->phy_link_change) {
+		phydev_err(phydev, "PHY already attached\n");
+		err = -EBUSY;
+		goto error_put_device;
+	}
+
 	/* Assume that if there is no driver, that it doesn't
 	 * exist, and we should use the genphy driver.
 	 */
@@ -1823,11 +1831,13 @@ int phy_attach_direct(struct net_device *dev, struct phy_device *phydev,
 		phydev->is_genphy_driven = 1;
 	}
 
-	if (!try_module_get(d->driver->owner)) {
+	drv_owner = d->driver->owner;
+	if (!try_module_get(drv_owner)) {
 		phydev_err(phydev, "failed to get the device driver module\n");
 		err = -EIO;
 		goto error_put_device;
 	}
+	phydev->drv_owner = drv_owner;
 
 	if (phydev->is_genphy_driven) {
 		err = d->driver->probe(d);
@@ -1838,12 +1848,6 @@ int phy_attach_direct(struct net_device *dev, struct phy_device *phydev,
 			goto error_module_put;
 	}
 
-	if (phydev->attached_dev) {
-		dev_err(&dev->dev, "PHY already attached\n");
-		err = -EBUSY;
-		goto error;
-	}
-
 	phydev->phy_link_change = phy_link_change;
 	if (dev) {
 		phydev->attached_dev = dev;
@@ -1941,7 +1945,8 @@ error:
 	return err;
 
 error_module_put:
-	module_put(d->driver->owner);
+	module_put(phydev->drv_owner);
+	phydev->drv_owner = NULL;
 	phydev->irq = irq;
 	phydev->is_genphy_driven = 0;
 	d->driver = NULL;
diff --git a/include/linux/phy.h b/include/linux/phy.h
index 7c5098a0dd6c..a5a419bc400e 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -578,6 +578,7 @@ struct phy_oatc14_sqi_capability {
  *
  * @mdio: MDIO bus this PHY is on
  * @drv: Pointer to the driver for this PHY instance
+ * @drv_owner: Driver module phy_attach_direct() took a reference on
  * @devlink: Create a link between phy dev and mac dev, if the external phy
  *           used by current mac interface is managed by another mac interface.
  * @phyindex: Unique id across the phy's parent tree of phys to address the PHY
@@ -689,6 +690,7 @@ struct phy_device {
 	/* Information about the PHY type */
 	/* And management functions */
 	const struct phy_driver *drv;
+	struct module *drv_owner;
 
 	struct device_link *devlink;