net: phy: Ensure the MDIO bus module is held

This commit adds proper module_{get,put} to prevent the MDIO bus module
from being unloaded while the phydev is connected. By doing so, we fix
a kernel panic produced when a MDIO driver is removed, but the phydev
that relies on it is attached and running.

Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Tested-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 35d753d..74a8232 100644 (file)
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -575,6 +575,7 @@ int phy_attach_direct(struct net_device *dev, struct phy_device *phydev,
                      u32 flags, phy_interface_t interface)
 {
        struct device *d = &phydev->dev;
+       struct module *bus_module;
        int err;
 
        /* Assume that if there is no driver, that it doesn't
@@ -599,6 +600,14 @@ int phy_attach_direct(struct net_device *dev, struct phy_device *phydev,
                return -EBUSY;
        }
 
+       /* Increment the bus module reference count */
+       bus_module = phydev->bus->dev.driver ?
+                    phydev->bus->dev.driver->owner : NULL;
+       if (!try_module_get(bus_module)) {
+               dev_err(&dev->dev, "failed to get the bus module\n");
+               return -EIO;
+       }
+
        phydev->attached_dev = dev;
        dev->phydev = phydev;
 
@@ -664,6 +673,10 @@ EXPORT_SYMBOL(phy_attach);
 void phy_detach(struct phy_device *phydev)
 {
        int i;
+
+       if (phydev->bus->dev.driver)
+               module_put(phydev->bus->dev.driver->owner);
+
        phydev->attached_dev->phydev = NULL;
        phydev->attached_dev = NULL;
        phy_suspend(phydev);