[PATCH 4.9 037/108] net: phy: Fix PHY module checks and NULL deref in phy_attach_direct()

Greg Kroah-Hartman
2017-06-15T18:21:48Z

From: Florian Fainelli <f.fainelli@gmail.com>

[ Upstream commit 6d9f66ac7fec2a6ccd649e5909806dfe36f1fc25 ]

The Generic PHY drivers gets assigned after we checked that the current
PHY driver is NULL, so we need to check a few things before we can
safely dereference d->driver. This would be causing a NULL deference to
occur when a system binds to the Generic PHY driver. Update
phy_attach_direct() to do the following:

- grab the driver module reference after we have assigned the Generic
PHY drivers accordingly, and remember we came from the generic PHY
path

- update the error path to clean up the module reference in case the
Generic PHY probe function fails

- split the error path involving phy_detacht() to avoid double free/put
since phy_detach() does all the clean up

- finally, have phy_detach() drop the module reference count before we
call device_release_driver() for the Generic PHY driver case

Fixes: cafe8df8b9bc ("net: phy: Fix lack of reference count on PHY driver")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/phy/phy_device.c | 29 +++++++++++++++++++++--------
1 file changed, 21 insertions(+), 8 deletions(-)

--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -860,6 +860,7 @@ int phy_attach_direct(struct net_device
struct module *ndev_owner = dev->dev.parent->driver->owner;
struct mii_bus *bus = phydev->mdio.bus;
struct device *d = &phydev->mdio.dev;
+ bool using_genphy = false;
int err;

/* For Ethernet device drivers that register their own MDIO bus, we
@@ -872,11 +873,6 @@ int phy_attach_direct(struct net_device
return -EIO;
}

- if (!try_module_get(d->driver->owner)) {
- dev_err(&dev->dev, "failed to get the device driver module\n");
- return -EIO;
- }
-
get_device(d);

/* Assume that if there is no driver, that it doesn't
@@ -890,12 +886,22 @@ int phy_attach_direct(struct net_device
d->driver =
&genphy_driver[GENPHY_DRV_1G].mdiodrv.driver;

+ using_genphy = true;
+ }
+
+ if (!try_module_get(d->driver->owner)) {
+ dev_err(&dev->dev, "failed to get the device driver module\n");
+ err = -EIO;
+ goto error_put_device;
+ }
+
+ if (using_genphy) {
err = d->driver->probe(d);
if (err >= 0)
err = device_bind_driver(d);

if (err)
- goto error;
+ goto error_module_put;
}

if (phydev->attached_dev) {
@@ -931,8 +937,14 @@ int phy_attach_direct(struct net_device
return err;

error:
- put_device(d);
+ /* phy_detach() does all of the cleanup below */
+ phy_detach(phydev);
+ return err;
+
+error_module_put:
module_put(d->driver->owner);
+error_put_device:
+ put_device(d);
if (ndev_owner != bus->owner)
module_put(bus->owner);
return err;
@@ -993,6 +1005,8 @@ void phy_detach(struct phy_device *phyde
phydev->attached_dev = NULL;
phy_suspend(phydev);

+ module_put(phydev->mdio.dev.driver->owner);
+
/* If the device had no specific driver before (i.e. - it
* was using the generic driver), we unbind the device
* from the generic driver so that there's a chance a
@@ -1013,7 +1027,6 @@ void phy_detach(struct phy_device *phyde
bus = phydev->mdio.bus;

put_device(&phydev->mdio.dev);
- module_put(phydev->mdio.dev.driver->owner);
if (ndev_owner != bus->owner)
module_put(bus->owner);
}