Take a refcount on the phy struct device when the phy device is attached
to a network device, and drop it after it's detached. This ensures that
a refcount is held on the phy device while the device is being used by
a network device, thereby preventing the phy_device from being
unexpectedly kfree()'d by phy_device_release().
Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
---
drivers/net/phy/phy_device.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 03adf328f49b..97a4f52addac 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -578,6 +578,7 @@ EXPORT_SYMBOL(phy_init_hw);
* generic driver is used. The phy_device is given a ptr to
* the attaching device, and given a callback for link status
* change. The phy_device is returned to the attaching driver.
+ * This function takes a reference on the phy device.
*/
int phy_attach_direct(struct net_device *dev, struct phy_device *phydev,
u32 flags, phy_interface_t interface)
@@ -591,6 +592,8 @@ int phy_attach_direct(struct net_device *dev, struct phy_device *phydev,
return -EIO;
}
+ get_device(d);
+
/* Assume that if there is no driver, that it doesn't
* exist, and we should use the genphy driver.
*/
@@ -636,6 +639,7 @@ int phy_attach_direct(struct net_device *dev, struct phy_device *phydev,
return err;
error:
+ put_device(d);
module_put(bus->owner);
return err;
}
@@ -679,6 +683,9 @@ EXPORT_SYMBOL(phy_attach);
/**
* phy_detach - detach a PHY device from its network device
* @phydev: target phy_device struct
+ *
+ * This detaches the phy device from its network device and the phy
+ * driver, and drops the reference count taken in phy_attach_direct().
*/
void phy_detach(struct phy_device *phydev)
{
@@ -701,8 +708,13 @@ void phy_detach(struct phy_device *phydev)
}
}
+ /*
+ * The phydev might go away on the put_device() below, so avoid
+ * a use-after-free bug by reading the underlying bus first.
+ */
bus = phydev->bus;
+ put_device(&phydev->dev);
module_put(bus->owner);
}
EXPORT_SYMBOL(phy_detach);
--
2.1.0
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