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>

1 files changed, 13 insertions, 0 deletions

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 35d753d22f78..74a82328dd49 100644
--- 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);