[PATCH v3 0/9] Phy, mdiobus, and netdev struct device fixes

[PATCH v3 0/9] Phy, mdiobus, and netdev struct device fixes

[Russell King - ARM Linux]

Hi,

The third version of this series fixes the build error which David
identified, and drops the broken changes for the Cavium Thunger BGX
ethernet driver as this driver requires some complex changes to
resolve the leakage - and this is best done by people who can test
the driver.

Compared to v2, the only patch which has changed is patch 6
  "net: fix phy refcounting in a bunch of drivers"

I _think_ I've been able to build-test all the drivers touched by
that patch to some degree now, though several of them needed the
Kconfig hacked to allow it (not all had || COMPILE_TEST clause on
their dependencies.)

Previous cover letters below:

This is the second version of the series, with the comments David had
on the first patch fixed up.  Original series description with updated
diffstat below.

While looking at the DSA code, I noticed we have a
of_find_net_device_by_node(), and it looks like users of that are
similarly buggy - it looks like net/dsa/dsa.c is the only user.  Fix
that too.

Hi,

While looking at the phy code, I identified a number of weaknesses
where refcounting on device structures was being leaked, where
modules could be removed while in-use, and where the fixed-phy could
end up having unintended consequences caused by incorrect calls to
fixed_phy_update_state().

This patch series resolves those issues, some of which were discovered
with testing on an Armada 388 board.  Not all patches are fully tested,
particularly the one which touches several network drivers.

When resolving the struct device refcounting problems, several different
solutions were considered before settling on the implementation here -
one of the considerations was to avoid touching many network drivers.
The solution here is:

	phy_attach*() - takes a refcount
	phy_detach*() - drops the phy_attach refcount

Provided drivers always attach and detach their phys, which they should
already be doing, this should change nothing, even if they leak a refcount.

	of_phy_find_device() and of_* functions which use that take
	a refcount.  Arrange for this refcount to be dropped once
	the phy is attached.

This is the reason why the previous change is important - we can't drop
this refcount taken by of_phy_find_device() until something else holds
a reference on the device.  This resolves the leaked refcount caused by
using of_phy_connect() or of_phy_attach().

Even without the above changes, these drivers are leaking by calling
of_phy_find_device().  These drivers are addressed by adding the
appropriate release of that refcount.

The mdiobus code also suffered from the same kind of leak, but thankfully
this only happened in one place - the mdio-mux code.

I also found that the try_module_get() in the phy layer code was utterly
useless: phydev->dev.driver was guaranteed to always be NULL, so
try_module_get() was always being called with a NULL argument.  I proved
this with my SFP code, which declares its own MDIO bus - the module use
count was never incremented irrespective of how I set the MDIO bus up.
This allowed the MDIO bus code to be removed from the kernel while there
were still PHYs attached to it.

One other bug was discovered: while using in-band-status with mvneta, it
was found that if a real phy is attached with in-band-status enabled,
and another ethernet interface is using the fixed-phy infrastructure, the
interface using the fixed-phy infrastructure is configured according to
the other interface using the in-band-status - which is caused by the
fixed-phy code not verifying that the phy_device passed in is actually
a fixed-phy device, rather than a real MDIO phy.

Lastly, having mdio_bus reversing phy_device_register() internals seems
like a layering violation - it's trivial to move that code to the phy
device layer.

 drivers/net/ethernet/apm/xgene/xgene_enet_hw.c | 24 ++++++----
 drivers/net/ethernet/freescale/gianfar.c       |  6 ++-
 drivers/net/ethernet/freescale/ucc_geth.c      |  8 +++-
 drivers/net/ethernet/marvell/mvneta.c          |  2 +
 drivers/net/ethernet/xilinx/xilinx_emaclite.c  |  2 +
 drivers/net/phy/fixed_phy.c                    |  2 +-
 drivers/net/phy/mdio-mux.c                     | 19 +++++---
 drivers/net/phy/mdio_bus.c                     | 24 ++++++----
 drivers/net/phy/phy_device.c                   | 62 ++++++++++++++++++++------
 drivers/of/of_mdio.c                           | 27 +++++++++--
 include/linux/phy.h                            |  6 ++-
 net/core/net-sysfs.c                           |  9 ++++
 net/dsa/dsa.c                                  | 41 ++++++++++++++---
 13 files changed, 181 insertions(+), 51 deletions(-)

-- 
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according to speedtest.net.
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[PATCH 1/9] phy: fix of_mdio_find_bus() device refcount leak

[Russell King]

of_mdio_find_bus() leaks a struct device refcount, caused by using
class_find_device() and not realising that the device reference has
its refcount incremented:

 * Note, you will need to drop the reference with put_device() after use.
...
        while ((dev = class_dev_iter_next(&iter))) {
                if (match(dev, data)) {
                        get_device(dev);
                        break;
                }

Update the comment, and arrange for the phy code to drop this refcount
when disposing of a reference to it.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---
 drivers/net/phy/mdio-mux.c | 19 +++++++++++++------
 drivers/net/phy/mdio_bus.c |  4 +++-
 2 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/drivers/net/phy/mdio-mux.c b/drivers/net/phy/mdio-mux.c
index 4d4d25efc1e1..280c7c311f72 100644
--- a/drivers/net/phy/mdio-mux.c
+++ b/drivers/net/phy/mdio-mux.c
@@ -113,18 +113,18 @@ int mdio_mux_init(struct device *dev,
 	if (!parent_bus_node)
 		return -ENODEV;
 
-	parent_bus = of_mdio_find_bus(parent_bus_node);
-	if (parent_bus == NULL) {
-		ret_val = -EPROBE_DEFER;
-		goto err_parent_bus;
-	}
-
 	pb = devm_kzalloc(dev, sizeof(*pb), GFP_KERNEL);
 	if (pb == NULL) {
 		ret_val = -ENOMEM;
 		goto err_parent_bus;
 	}
 
+	parent_bus = of_mdio_find_bus(parent_bus_node);
+	if (parent_bus == NULL) {
+		ret_val = -EPROBE_DEFER;
+		goto err_parent_bus;
+	}
+
 	pb->switch_data = data;
 	pb->switch_fn = switch_fn;
 	pb->current_child = -1;
@@ -173,6 +173,10 @@ int mdio_mux_init(struct device *dev,
 		dev_info(dev, "Version " DRV_VERSION "\n");
 		return 0;
 	}
+
+	/* balance the reference of_mdio_find_bus() took */
+	put_device(&pb->mii_bus->dev);
+
 err_parent_bus:
 	of_node_put(parent_bus_node);
 	return ret_val;
@@ -189,6 +193,9 @@ void mdio_mux_uninit(void *mux_handle)
 		mdiobus_free(cb->mii_bus);
 		cb = cb->next;
 	}
+
+	/* balance the reference of_mdio_find_bus() in mdio_mux_init() took */
+	put_device(&pb->mii_bus->dev);
 }
 EXPORT_SYMBOL_GPL(mdio_mux_uninit);
 
diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
index 02a4615b65f8..67553e13bd36 100644
--- a/drivers/net/phy/mdio_bus.c
+++ b/drivers/net/phy/mdio_bus.c
@@ -167,7 +167,9 @@ static int of_mdio_bus_match(struct device *dev, const void *mdio_bus_np)
  * of_mdio_find_bus - Given an mii_bus node, find the mii_bus.
  * @mdio_bus_np: Pointer to the mii_bus.
  *
- * Returns a pointer to the mii_bus, or NULL if none found.
+ * Returns a reference to the mii_bus, or NULL if none found.  The
+ * embedded struct device will have its reference count incremented,
+ * and this must be put once the bus is finished with.
  *
  * Because the association of a device_node and mii_bus is made via
  * of_mdiobus_register(), the mii_bus cannot be found before it is
-- 
2.1.0

[PATCH 2/9] net: dsa: fix of_mdio_find_bus() device refcount leak

[Russell King]

Current users of of_mdio_find_bus() leak a struct device refcount, as
they fail to clean up the reference obtained inside class_find_device().

Fix the DSA code to properly refcount the returned MDIO bus by:
1. taking a reference on the struct device whenever we assign it to
   pd->chip[x].host_dev.
2. dropping the reference when we overwrite the existing reference.
3. dropping the reference when we free the data structure.
4. dropping the initial reference we obtained after setting up the
   platform data structure, or on failure.

In step 2 above, where we obtain a new MDIO bus, there is no need to
take a reference on it as we would only have to drop it immediately
after assignment again, iow:

	put_device(cd->host_dev);	/* drop original assignment ref */
	cd->host_dev = get_device(&mdio_bus_switch->dev); /* get our ref */
	put_device(&mdio_bus_switch->dev); /* drop of_mdio_find_bus ref */

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---
 net/dsa/dsa.c | 38 +++++++++++++++++++++++++++++++-------
 1 file changed, 31 insertions(+), 7 deletions(-)

diff --git a/net/dsa/dsa.c b/net/dsa/dsa.c
index 76e3800765f8..bf4ba15fb780 100644
--- a/net/dsa/dsa.c
+++ b/net/dsa/dsa.c
@@ -634,6 +634,10 @@ static void dsa_of_free_platform_data(struct dsa_platform_data *pd)
 			port_index++;
 		}
 		kfree(pd->chip[i].rtable);
+
+		/* Drop our reference to the MDIO bus device */
+		if (pd->chip[i].host_dev)
+			put_device(pd->chip[i].host_dev);
 	}
 	kfree(pd->chip);
 }
@@ -661,16 +665,22 @@ static int dsa_of_probe(struct device *dev)
 		return -EPROBE_DEFER;
 
 	ethernet = of_parse_phandle(np, "dsa,ethernet", 0);
-	if (!ethernet)
-		return -EINVAL;
+	if (!ethernet) {
+		ret = -EINVAL;
+		goto out_put_mdio;
+	}
 
 	ethernet_dev = of_find_net_device_by_node(ethernet);
-	if (!ethernet_dev)
-		return -EPROBE_DEFER;
+	if (!ethernet_dev) {
+		ret = -EPROBE_DEFER;
+		goto out_put_mdio;
+	}
 
 	pd = kzalloc(sizeof(*pd), GFP_KERNEL);
-	if (!pd)
-		return -ENOMEM;
+	if (!pd) {
+		ret = -ENOMEM;
+		goto out_put_mdio;
+	}
 
 	dev->platform_data = pd;
 	pd->of_netdev = ethernet_dev;
@@ -691,7 +701,9 @@ static int dsa_of_probe(struct device *dev)
 		cd = &pd->chip[chip_index];
 
 		cd->of_node = child;
-		cd->host_dev = &mdio_bus->dev;
+
+		/* When assigning the host device, increment its refcount */
+		cd->host_dev = get_device(&mdio_bus->dev);
 
 		sw_addr = of_get_property(child, "reg", NULL);
 		if (!sw_addr)
@@ -711,6 +723,12 @@ static int dsa_of_probe(struct device *dev)
 				ret = -EPROBE_DEFER;
 				goto out_free_chip;
 			}
+
+			/* Drop the mdio_bus device ref, replacing the host
+			 * device with the mdio_bus_switch device, keeping
+			 * the refcount from of_mdio_find_bus() above.
+			 */
+			put_device(cd->host_dev);
 			cd->host_dev = &mdio_bus_switch->dev;
 		}
 
@@ -744,6 +762,10 @@ static int dsa_of_probe(struct device *dev)
 		}
 	}
 
+	/* The individual chips hold their own refcount on the mdio bus,
+	 * so drop ours */
+	put_device(&mdio_bus->dev);
+
 	return 0;
 
 out_free_chip:
@@ -751,6 +773,8 @@ static int dsa_of_probe(struct device *dev)
 out_free:
 	kfree(pd);
 	dev->platform_data = NULL;
+out_put_mdio:
+	put_device(&mdio_bus->dev);
 	return ret;
 }
 
-- 
2.1.0

[PATCH 3/9] phy: fix mdiobus module safety

[Russell King]

Re-implement the mdiobus module refcounting to ensure that we actually
ensure that the mdiobus module code does not go away while we might call
into it.

The old scheme using bus->dev.driver was buggy, because bus->dev is a
class device which never has a struct device_driver associated with it,
and hence the associated code trying to obtain a refcount did nothing
useful.

Instead, take the approach that other subsystems do: pass the module
when calling mdiobus_register(), and record that in the mii_bus struct.
When we need to increment the module use count in the phy code, use
this stored pointer.  When the phy is deteched, drop the module
refcount, remembering that the phy device might go away at that point.

This doesn't stop the mii_bus going away while there are in-use phys -
it merely stops the underlying code vanishing.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---
 drivers/net/phy/mdio_bus.c   |  5 +++--
 drivers/net/phy/phy_device.c | 32 ++++++++++++++++++--------------
 include/linux/phy.h          |  5 ++++-
 3 files changed, 25 insertions(+), 17 deletions(-)

diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
index 67553e13bd36..992406624b7c 100644
--- a/drivers/net/phy/mdio_bus.c
+++ b/drivers/net/phy/mdio_bus.c
@@ -244,7 +244,7 @@ static inline void of_mdiobus_link_phydev(struct mii_bus *mdio,
  *
  * Returns 0 on success or < 0 on error.
  */
-int mdiobus_register(struct mii_bus *bus)
+int __mdiobus_register(struct mii_bus *bus, struct module *owner)
 {
 	int i, err;
 
@@ -255,6 +255,7 @@ int mdiobus_register(struct mii_bus *bus)
 	BUG_ON(bus->state != MDIOBUS_ALLOCATED &&
 	       bus->state != MDIOBUS_UNREGISTERED);
 
+	bus->owner = owner;
 	bus->dev.parent = bus->parent;
 	bus->dev.class = &mdio_bus_class;
 	bus->dev.groups = NULL;
@@ -296,7 +297,7 @@ int mdiobus_register(struct mii_bus *bus)
 	device_del(&bus->dev);
 	return err;
 }
-EXPORT_SYMBOL(mdiobus_register);
+EXPORT_SYMBOL(__mdiobus_register);
 
 void mdiobus_unregister(struct mii_bus *bus)
 {
diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index c0f211127274..03adf328f49b 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -582,10 +582,15 @@ EXPORT_SYMBOL(phy_init_hw);
 int phy_attach_direct(struct net_device *dev, struct phy_device *phydev,
 		      u32 flags, phy_interface_t interface)
 {
+	struct mii_bus *bus = phydev->bus;
 	struct device *d = &phydev->dev;
-	struct module *bus_module;
 	int err;
 
+	if (!try_module_get(bus->owner)) {
+		dev_err(&dev->dev, "failed to get the bus module\n");
+		return -EIO;
+	}
+
 	/* Assume that if there is no driver, that it doesn't
 	 * exist, and we should use the genphy driver.
 	 */
@@ -600,20 +605,13 @@ int phy_attach_direct(struct net_device *dev, struct phy_device *phydev,
 			err = device_bind_driver(d);
 
 		if (err)
-			return err;
+			goto error;
 	}
 
 	if (phydev->attached_dev) {
 		dev_err(&dev->dev, "PHY already attached\n");
-		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;
+		err = -EBUSY;
+		goto error;
 	}
 
 	phydev->attached_dev = dev;
@@ -636,6 +634,10 @@ int phy_attach_direct(struct net_device *dev, struct phy_device *phydev,
 		phy_resume(phydev);
 
 	return err;
+
+error:
+	module_put(bus->owner);
+	return err;
 }
 EXPORT_SYMBOL(phy_attach_direct);
 
@@ -680,11 +682,9 @@ EXPORT_SYMBOL(phy_attach);
  */
 void phy_detach(struct phy_device *phydev)
 {
+	struct mii_bus *bus;
 	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);
@@ -700,6 +700,10 @@ void phy_detach(struct phy_device *phydev)
 			break;
 		}
 	}
+
+	bus = phydev->bus;
+
+	module_put(bus->owner);
 }
 EXPORT_SYMBOL(phy_detach);
 
diff --git a/include/linux/phy.h b/include/linux/phy.h
index 962387a192f1..11bce44f6d65 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -19,6 +19,7 @@
 #include <linux/spinlock.h>
 #include <linux/ethtool.h>
 #include <linux/mii.h>
+#include <linux/module.h>
 #include <linux/timer.h>
 #include <linux/workqueue.h>
 #include <linux/mod_devicetable.h>
@@ -153,6 +154,7 @@ struct sk_buff;
  * PHYs should register using this structure
  */
 struct mii_bus {
+	struct module *owner;
 	const char *name;
 	char id[MII_BUS_ID_SIZE];
 	void *priv;
@@ -198,7 +200,8 @@ static inline struct mii_bus *mdiobus_alloc(void)
 	return mdiobus_alloc_size(0);
 }
 
-int mdiobus_register(struct mii_bus *bus);
+int __mdiobus_register(struct mii_bus *bus, struct module *owner);
+#define mdiobus_register(bus) __mdiobus_register(bus, THIS_MODULE)
 void mdiobus_unregister(struct mii_bus *bus);
 void mdiobus_free(struct mii_bus *bus);
 struct mii_bus *devm_mdiobus_alloc_size(struct device *dev, int sizeof_priv);
-- 
2.1.0

[PATCH 4/9] phy: add proper phy struct device refcounting

[Russell King]

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@arm.linux.org.uk>
---
 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

[PATCH 5/9] of_mdio: fix MDIO phy device refcounting

[Russell King]

bus_find_device() is defined as:

 * This is similar to the bus_for_each_dev() function above, but it
 * returns a reference to a device that is 'found' for later use, as
 * determined by the @match callback.

and it does indeed return a reference-counted pointer to the device:

        while ((dev = next_device(&i)))
                if (match(dev, data) && get_device(dev))
                                        ^^^^^^^^^^^^^^^
                        break;
        klist_iter_exit(&i);
        return dev;

What that means is that when we're done with the struct device, we must
drop that reference.  Neither of_phy_connect() nor of_phy_attach() did
this when phy_connect_direct() or phy_attach_direct() failed.

With our previous patch, phy_connect_direct() and phy_attach_direct()
take a new refcount on the phy device when successful, so we can drop
our local reference immediatley after these functions, whether or not
they succeeded.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---
 drivers/of/of_mdio.c | 27 +++++++++++++++++++++++----
 1 file changed, 23 insertions(+), 4 deletions(-)

diff --git a/drivers/of/of_mdio.c b/drivers/of/of_mdio.c
index 1350fa25cdb0..a87a868fed64 100644
--- a/drivers/of/of_mdio.c
+++ b/drivers/of/of_mdio.c
@@ -197,7 +197,8 @@ static int of_phy_match(struct device *dev, void *phy_np)
  * of_phy_find_device - Give a PHY node, find the phy_device
  * @phy_np: Pointer to the phy's device tree node
  *
- * Returns a pointer to the phy_device.
+ * If successful, returns a pointer to the phy_device with the embedded
+ * struct device refcount incremented by one, or NULL on failure.
  */
 struct phy_device *of_phy_find_device(struct device_node *phy_np)
 {
@@ -217,7 +218,9 @@ EXPORT_SYMBOL(of_phy_find_device);
  * @hndlr: Link state callback for the network device
  * @iface: PHY data interface type
  *
- * Returns a pointer to the phy_device if successful.  NULL otherwise
+ * If successful, returns a pointer to the phy_device with the embedded
+ * struct device refcount incremented by one, or NULL on failure. The
+ * refcount must be dropped by calling phy_disconnect() or phy_detach().
  */
 struct phy_device *of_phy_connect(struct net_device *dev,
 				  struct device_node *phy_np,
@@ -225,13 +228,19 @@ struct phy_device *of_phy_connect(struct net_device *dev,
 				  phy_interface_t iface)
 {
 	struct phy_device *phy = of_phy_find_device(phy_np);
+	int ret;
 
 	if (!phy)
 		return NULL;
 
 	phy->dev_flags = flags;
 
-	return phy_connect_direct(dev, phy, hndlr, iface) ? NULL : phy;
+	ret = phy_connect_direct(dev, phy, hndlr, iface);
+
+	/* refcount is held by phy_connect_direct() on success */
+	put_device(&phy->dev);
+
+	return ret ? NULL : phy;
 }
 EXPORT_SYMBOL(of_phy_connect);
 
@@ -241,17 +250,27 @@ EXPORT_SYMBOL(of_phy_connect);
  * @phy_np: Node pointer for the PHY
  * @flags: flags to pass to the PHY
  * @iface: PHY data interface type
+ *
+ * If successful, returns a pointer to the phy_device with the embedded
+ * struct device refcount incremented by one, or NULL on failure. The
+ * refcount must be dropped by calling phy_disconnect() or phy_detach().
  */
 struct phy_device *of_phy_attach(struct net_device *dev,
 				 struct device_node *phy_np, u32 flags,
 				 phy_interface_t iface)
 {
 	struct phy_device *phy = of_phy_find_device(phy_np);
+	int ret;
 
 	if (!phy)
 		return NULL;
 
-	return phy_attach_direct(dev, phy, flags, iface) ? NULL : phy;
+	ret = phy_attach_direct(dev, phy, flags, iface);
+
+	/* refcount is held by phy_attach_direct() on success */
+	put_device(&phy->dev);
+
+	return ret ? NULL : phy;
 }
 EXPORT_SYMBOL(of_phy_attach);
 
-- 
2.1.0

[PATCH 6/9] net: fix phy refcounting in a bunch of drivers

[Russell King]

of_phy_find_device() increments the phy struct device refcount, which
we need to properly balance.  Add code to network drivers using this
function to ensure that the struct device refcount is correctly
balanced.

For xgene, looking back in the history, we should be able to use
of_phy_connect() with a zero flags argument for the DT case as this is
how the driver used to operate prior to de7b5b3d790a ("net: eth: xgene:
change APM X-Gene SoC platform ethernet to support ACPI").

This leaves the Cavium Thunder BGX unfixed; fixing this driver is a
complicated task, one which the maintainers need to be involved with.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---
 drivers/net/ethernet/apm/xgene/xgene_enet_hw.c | 24 ++++++++++++++++--------
 drivers/net/ethernet/freescale/gianfar.c       |  3 +++
 drivers/net/ethernet/freescale/ucc_geth.c      |  8 +++++++-
 drivers/net/ethernet/marvell/mvneta.c          |  2 ++
 drivers/net/ethernet/xilinx/xilinx_emaclite.c  |  2 ++
 5 files changed, 30 insertions(+), 9 deletions(-)

diff --git a/drivers/net/ethernet/apm/xgene/xgene_enet_hw.c b/drivers/net/ethernet/apm/xgene/xgene_enet_hw.c
index cfa37041ab71..c4bb8027b3fb 100644
--- a/drivers/net/ethernet/apm/xgene/xgene_enet_hw.c
+++ b/drivers/net/ethernet/apm/xgene/xgene_enet_hw.c
@@ -689,16 +689,24 @@ static int xgene_enet_phy_connect(struct net_device *ndev)
 			netdev_dbg(ndev, "No phy-handle found in DT\n");
 			return -ENODEV;
 		}
-		pdata->phy_dev = of_phy_find_device(phy_np);
-	}
 
-	phy_dev = pdata->phy_dev;
+		phy_dev = of_phy_connect(ndev, phy_np, &xgene_enet_adjust_link,
+					 0, pdata->phy_mode);
+		if (!phy_dev) {
+			netdev_err(ndev, "Could not connect to PHY\n");
+			return -ENODEV;
+		}
+
+		pdata->phy_dev = phy_dev;
+	} else {
+		phy_dev = pdata->phy_dev;
 
-	if (!phy_dev ||
-	    phy_connect_direct(ndev, phy_dev, &xgene_enet_adjust_link,
-			       pdata->phy_mode)) {
-		netdev_err(ndev, "Could not connect to PHY\n");
-		return  -ENODEV;
+		if (!phy_dev ||
+		    phy_connect_direct(ndev, phy_dev, &xgene_enet_adjust_link,
+				       pdata->phy_mode)) {
+			netdev_err(ndev, "Could not connect to PHY\n");
+			return  -ENODEV;
+		}
 	}
 
 	pdata->phy_speed = SPEED_UNKNOWN;
diff --git a/drivers/net/ethernet/freescale/gianfar.c b/drivers/net/ethernet/freescale/gianfar.c
index 4b69d061d90f..65a16086faec 100644
--- a/drivers/net/ethernet/freescale/gianfar.c
+++ b/drivers/net/ethernet/freescale/gianfar.c
@@ -1702,6 +1702,7 @@ static void gfar_configure_serdes(struct net_device *dev)
 	tbiphy = of_phy_find_device(priv->tbi_node);
 	if (!tbiphy) {
 		dev_err(&dev->dev, "error: Could not get TBI device\n");
+		put_device(&tbiphy->dev);
 		return;
 	}
 
@@ -1723,6 +1724,8 @@ static void gfar_configure_serdes(struct net_device *dev)
 	phy_write(tbiphy, MII_BMCR,
 		  BMCR_ANENABLE | BMCR_ANRESTART | BMCR_FULLDPLX |
 		  BMCR_SPEED1000);
+
+	put_device(&tbiphy->dev);
 }
 
 static int __gfar_is_rx_idle(struct gfar_private *priv)
diff --git a/drivers/net/ethernet/freescale/ucc_geth.c b/drivers/net/ethernet/freescale/ucc_geth.c
index 4dd40e057f40..650f7888e32b 100644
--- a/drivers/net/ethernet/freescale/ucc_geth.c
+++ b/drivers/net/ethernet/freescale/ucc_geth.c
@@ -1384,6 +1384,8 @@ static int adjust_enet_interface(struct ucc_geth_private *ugeth)
 		value = phy_read(tbiphy, ENET_TBI_MII_CR);
 		value &= ~0x1000;	/* Turn off autonegotiation */
 		phy_write(tbiphy, ENET_TBI_MII_CR, value);
+
+		put_device(&tbiphy->dev);
 	}
 
 	init_check_frame_length_mode(ug_info->lengthCheckRx, &ug_regs->maccfg2);
@@ -1702,8 +1704,10 @@ static void uec_configure_serdes(struct net_device *dev)
 	 * everything for us?  Resetting it takes the link down and requires
 	 * several seconds for it to come back.
 	 */
-	if (phy_read(tbiphy, ENET_TBI_MII_SR) & TBISR_LSTATUS)
+	if (phy_read(tbiphy, ENET_TBI_MII_SR) & TBISR_LSTATUS) {
+		put_device(&tbiphy->dev);
 		return;
+	}
 
 	/* Single clk mode, mii mode off(for serdes communication) */
 	phy_write(tbiphy, ENET_TBI_MII_ANA, TBIANA_SETTINGS);
@@ -1711,6 +1715,8 @@ static void uec_configure_serdes(struct net_device *dev)
 	phy_write(tbiphy, ENET_TBI_MII_TBICON, TBICON_CLK_SELECT);
 
 	phy_write(tbiphy, ENET_TBI_MII_CR, TBICR_SETTINGS);
+
+	put_device(&tbiphy->dev);
 }
 
 /* Configure the PHY for dev.
diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
index fe2299ac4f5c..0dce037a2682 100644
--- a/drivers/net/ethernet/marvell/mvneta.c
+++ b/drivers/net/ethernet/marvell/mvneta.c
@@ -3173,6 +3173,8 @@ static int mvneta_probe(struct platform_device *pdev)
 		struct phy_device *phy = of_phy_find_device(dn);
 
 		mvneta_fixed_link_update(pp, phy);
+
+		put_device(&phy->dev);
 	}
 
 	return 0;
diff --git a/drivers/net/ethernet/xilinx/xilinx_emaclite.c b/drivers/net/ethernet/xilinx/xilinx_emaclite.c
index 6008eee01a33..cf468c87ce57 100644
--- a/drivers/net/ethernet/xilinx/xilinx_emaclite.c
+++ b/drivers/net/ethernet/xilinx/xilinx_emaclite.c
@@ -828,6 +828,8 @@ static int xemaclite_mdio_setup(struct net_local *lp, struct device *dev)
 		if (!phydev)
 			dev_info(dev,
 				 "MDIO of the phy is not registered yet\n");
+		else
+			put_device(&phydev->dev);
 		return 0;
 	}
 
-- 
2.1.0

_______________________________________________
Linuxppc-dev mailing list
Linuxppc-dev@lists.ozlabs.org
https://lists.ozlabs.org/listinfo/linuxppc-dev

[PATCH 7/9] phy: fixed-phy: properly validate phy in fixed_phy_update_state()

[Russell King]

Validate that the phy_device passed into fixed_phy_update_state() is a
fixed-phy device before walking the list of phys for a fixed phy at the
same address.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---
 drivers/net/phy/fixed_phy.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/phy/fixed_phy.c b/drivers/net/phy/fixed_phy.c
index fb1299c6326e..e23bf5b90e17 100644
--- a/drivers/net/phy/fixed_phy.c
+++ b/drivers/net/phy/fixed_phy.c
@@ -220,7 +220,7 @@ int fixed_phy_update_state(struct phy_device *phydev,
 	struct fixed_mdio_bus *fmb = &platform_fmb;
 	struct fixed_phy *fp;
 
-	if (!phydev || !phydev->bus)
+	if (!phydev || phydev->bus != fmb->mii_bus)
 		return -EINVAL;
 
 	list_for_each_entry(fp, &fmb->phys, node) {
-- 
2.1.0

[PATCH 8/9] phy: add phy_device_remove()

[Russell King]

Add a phy_device_remove() function to complement phy_device_register(),
which undoes the effects of phy_device_register() by removing the phy
device from visibility, but not freeing it.

This allows these details to be moved out of the mdio bus code into
the phy code where this action belongs.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---
 drivers/net/ethernet/freescale/gianfar.c |  5 +++--
 drivers/net/phy/mdio_bus.c               | 15 ++++++++++-----
 drivers/net/phy/phy_device.c             | 18 ++++++++++++++++++
 include/linux/phy.h                      |  1 +
 4 files changed, 32 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/freescale/gianfar.c b/drivers/net/ethernet/freescale/gianfar.c
index 65a16086faec..903211df3288 100644
--- a/drivers/net/ethernet/freescale/gianfar.c
+++ b/drivers/net/ethernet/freescale/gianfar.c
@@ -1702,7 +1702,6 @@ static void gfar_configure_serdes(struct net_device *dev)
 	tbiphy = of_phy_find_device(priv->tbi_node);
 	if (!tbiphy) {
 		dev_err(&dev->dev, "error: Could not get TBI device\n");
-		put_device(&tbiphy->dev);
 		return;
 	}
 
@@ -1711,8 +1710,10 @@ static void gfar_configure_serdes(struct net_device *dev)
 	 * everything for us?  Resetting it takes the link down and requires
 	 * several seconds for it to come back.
 	 */
-	if (phy_read(tbiphy, MII_BMSR) & BMSR_LSTATUS)
+	if (phy_read(tbiphy, MII_BMSR) & BMSR_LSTATUS) {
+		put_device(&tbiphy->dev);
 		return;
+	}
 
 	/* Single clk mode, mii mode off(for serdes communication) */
 	phy_write(tbiphy, MII_TBICON, TBICON_CLK_SELECT);
diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
index 992406624b7c..c340e412b38f 100644
--- a/drivers/net/phy/mdio_bus.c
+++ b/drivers/net/phy/mdio_bus.c
@@ -291,8 +291,11 @@ int __mdiobus_register(struct mii_bus *bus, struct module *owner)
 
 error:
 	while (--i >= 0) {
-		if (bus->phy_map[i])
-			device_unregister(&bus->phy_map[i]->dev);
+		struct phy_device *phydev = bus->phy_map[i];
+		if (phydev) {
+			phy_device_remove(phydev);
+			phy_device_free(phydev);
+		}
 	}
 	device_del(&bus->dev);
 	return err;
@@ -307,9 +310,11 @@ void mdiobus_unregister(struct mii_bus *bus)
 	bus->state = MDIOBUS_UNREGISTERED;
 
 	for (i = 0; i < PHY_MAX_ADDR; i++) {
-		if (bus->phy_map[i])
-			device_unregister(&bus->phy_map[i]->dev);
-		bus->phy_map[i] = NULL;
+		struct phy_device *phydev = bus->phy_map[i];
+		if (phydev) {
+			phy_device_remove(phydev);
+			phy_device_free(phydev);
+		}
 	}
 	device_del(&bus->dev);
 }
diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 97a4f52addac..f761288abe66 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -384,6 +384,24 @@ int phy_device_register(struct phy_device *phydev)
 EXPORT_SYMBOL(phy_device_register);
 
 /**
+ * phy_device_remove - Remove a previously registered phy device from the MDIO bus
+ * @phydev: phy_device structure to remove
+ *
+ * This doesn't free the phy_device itself, it merely reverses the effects
+ * of phy_device_register(). Use phy_device_free() to free the device
+ * after calling this function.
+ */
+void phy_device_remove(struct phy_device *phydev)
+{
+	struct mii_bus *bus = phydev->bus;
+	int addr = phydev->addr;
+
+	device_del(&phydev->dev);
+	bus->phy_map[addr] = NULL;
+}
+EXPORT_SYMBOL(phy_device_remove);
+
+/**
  * phy_find_first - finds the first PHY device on the bus
  * @bus: the target MII bus
  */
diff --git a/include/linux/phy.h b/include/linux/phy.h
index 11bce44f6d65..4a4e3a092337 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -745,6 +745,7 @@ struct phy_device *phy_device_create(struct mii_bus *bus, int addr, int phy_id,
 				     struct phy_c45_device_ids *c45_ids);
 struct phy_device *get_phy_device(struct mii_bus *bus, int addr, bool is_c45);
 int phy_device_register(struct phy_device *phy);
+void phy_device_remove(struct phy_device *phydev);
 int phy_init_hw(struct phy_device *phydev);
 int phy_suspend(struct phy_device *phydev);
 int phy_resume(struct phy_device *phydev);
-- 
2.1.0

[PATCH 9/9] net: fix net_device refcounting

[Russell King]

of_find_net_device_by_node() uses class_find_device() internally to
lookup the corresponding network device.  class_find_device() returns
a reference to the embedded struct device, with its refcount
incremented.

Add a comment to the definition in net/core/net-sysfs.c indicating the
need to drop this refcount, and fix the DSA code to drop this refcount
when the OF-generated platform data is cleaned up and freed.  Also
arrange for the ref to be dropped when handling errors.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---
 net/core/net-sysfs.c | 9 +++++++++
 net/dsa/dsa.c        | 5 ++++-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index b279077c3089..805a95a48107 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -1481,6 +1481,15 @@ static int of_dev_node_match(struct device *dev, const void *data)
 	return ret == 0 ? dev->of_node == data : ret;
 }
 
+/*
+ * of_find_net_device_by_node - lookup the net device for the device node
+ * @np: OF device node
+ *
+ * Looks up the net_device structure corresponding with the device node.
+ * If successful, returns a pointer to the net_device with the embedded
+ * struct device refcount incremented by one, or NULL on failure. The
+ * refcount must be dropped when done with the net_device.
+ */
 struct net_device *of_find_net_device_by_node(struct device_node *np)
 {
 	struct device *dev;
diff --git a/net/dsa/dsa.c b/net/dsa/dsa.c
index bf4ba15fb780..c59fa5d9c22c 100644
--- a/net/dsa/dsa.c
+++ b/net/dsa/dsa.c
@@ -679,7 +679,7 @@ static int dsa_of_probe(struct device *dev)
 	pd = kzalloc(sizeof(*pd), GFP_KERNEL);
 	if (!pd) {
 		ret = -ENOMEM;
-		goto out_put_mdio;
+		goto out_put_ethernet;
 	}
 
 	dev->platform_data = pd;
@@ -773,6 +773,8 @@ static int dsa_of_probe(struct device *dev)
 out_free:
 	kfree(pd);
 	dev->platform_data = NULL;
+out_put_ethernet:
+	put_device(&ethernet_dev->dev);
 out_put_mdio:
 	put_device(&mdio_bus->dev);
 	return ret;
@@ -786,6 +788,7 @@ static void dsa_of_remove(struct device *dev)
 		return;
 
 	dsa_of_free_platform_data(pd);
+	put_device(&pd->of_netdev->dev);
 	kfree(pd);
 }
 #else
-- 
2.1.0

Re: [PATCH v3 0/9] Phy, mdiobus, and netdev struct device fixes

[Andrew Lunn]

...

> While looking at the DSA code, I noticed we have a
> of_find_net_device_by_node(), and it looks like users of that are
> similarly buggy - it looks like net/dsa/dsa.c is the only user.  Fix
> that too.

...
 
> The mdiobus code also suffered from the same kind of leak, but thankfully
> this only happened in one place - the mdio-mux code.

Hi Russell

I tested both of these with my board. It is a Freescale Vybrid, using
the FEC ethernet driver, and i have three switches attached, using
mdio-mux to give three mdio busses.

No obvious regressions, my board boots, the switches are all present
and correct. I built the FEC driver as a module, and it won't unload:

 kernel:unregister_netdevice: waiting for eth1 to become free. Usage count = 1
unregister_netdevice: waiting for eth1 to become free. Usage count = 1

i assume because DSA holds a reference. I've not tried a fully module
build, DSA has issues with that.

Tested-by: Andrew Lunn <andrew@lunn.ch>

Thanks
	Andrew

Re: [PATCH v3 0/9] Phy, mdiobus, and netdev struct device fixes

[Russell King - ARM Linux]

On Thu, Sep 24, 2015 at 11:57:31PM +0200, Andrew Lunn wrote:
> Hi Russell
> 
> I tested both of these with my board. It is a Freescale Vybrid, using
> the FEC ethernet driver, and i have three switches attached, using
> mdio-mux to give three mdio busses.
> 
> No obvious regressions, my board boots, the switches are all present
> and correct. I built the FEC driver as a module, and it won't unload:
> 
>  kernel:unregister_netdevice: waiting for eth1 to become free. Usage count = 1
> unregister_netdevice: waiting for eth1 to become free. Usage count = 1
> 
> i assume because DSA holds a reference. I've not tried a fully module
> build, DSA has issues with that.
> 
> Tested-by: Andrew Lunn <andrew@lunn.ch>

Thanks for testing.  Please could you confirm whether the same behaviour
is observed without the patches, just to make absolutely sure that isn't
a regression.

However, I think you are correct - I'm unable to locate where in the
DSA code:
- dst->master_dev's dev_hold() is undone (hence a reference left)
- dst is freed - dsa_probe() allocates it using kzalloc(), but
  dsa_remove() and it's children don't free this structure.

There's no notifier which detects whether the underlying device has
gone away - it registers a netdev notifier (dsa_slave_netdevice_event)
but this only deals with slave devices, not the master device.

Thanks.

-- 
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.

Re: [PATCH v3 0/9] Phy, mdiobus, and netdev struct device fixes

[Andrew Lunn]

> Thanks for testing.  Please could you confirm whether the same behaviour
> is observed without the patches, just to make absolutely sure that isn't
> a regression.

So i tested this now.

I have two FEC interfaces. One i my main access interface, and the
second is used by DSA to access switches. With your patches, the
module Used by count is equal to the number of interfaces which are
up.

Without your patches, the count is always 0.

When i try to remove the fec module, without your patches, but DSA
still using the interface, i get the same

 kernel:unregister_netdevice: waiting for eth1 to become free. Usage count = 1

as with your patch. So this is not a regression.

   Andrew
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Re: [PATCH v3 0/9] Phy, mdiobus, and netdev struct device fixes

[Russell King - ARM Linux]

On Fri, Sep 25, 2015 at 12:50:33AM +0200, Andrew Lunn wrote:
> > Thanks for testing.  Please could you confirm whether the same behaviour
> > is observed without the patches, just to make absolutely sure that isn't
> > a regression.
> 
> So i tested this now.
> 
> I have two FEC interfaces. One i my main access interface, and the
> second is used by DSA to access switches. With your patches, the
> module Used by count is equal to the number of interfaces which are
> up.
> 
> Without your patches, the count is always 0.

That will be as a result of the MDIO bus module refcounting patch -
"phy: fix mdiobus module safety".  The code prior to that patch was
totally useless and ineffectual - it might as well not even have
been present, because it would never have any effect.  bus_module
would always be NULL in phy_attach_direct().

While my change makes the code start to work as originally intended,
it's still unsafe: there's nothing to stop you manually unbinding the
driver providing the MDIO bus from the struct device.  The driver
will then free the resources it claimed in its probe function, which
may include the MMIO mapping for the MDIO bus accessor functions.

If the accessors are then called, despite keeping the mdio bus, phy,
etc data structures properly refcounted, the kernel will oops when
the (many) MDIO bus drivers hit the free'd MMIO mapping.  This is,
unfortunately, just another pre-existing bug in this code.

To stop that, we need some way to say "this MDIO bus has been removed,
prevent further access" and that needs to be done in a race free way.
Right now, that doesn't exist.

-- 
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.

Re: [PATCH v3 0/9] Phy, mdiobus, and netdev struct device fixes

[David Miller]

From: Andrew Lunn <andrew@lunn.ch>
Date: Thu, 24 Sep 2015 23:57:31 +0200

> I built the FEC driver as a module, and it won't unload:
> 
>  kernel:unregister_netdevice: waiting for eth1 to become free. Usage count = 1
> unregister_netdevice: waiting for eth1 to become free. Usage count = 1
> 
> i assume because DSA holds a reference. I've not tried a fully module
> build, DSA has issues with that.
> 
> Tested-by: Andrew Lunn <andrew@lunn.ch>

So, is this a regression?

Please don't provide a "Tested-by: " tag is you encounter a new
problem which could have been introduced by the changes in question.
That _REALLY_ screws everything up for me.

Thank.

Re: [PATCH v3 0/9] Phy, mdiobus, and netdev struct device fixes

[Andrew Lunn]

On Thu, Sep 24, 2015 at 03:15:54PM -0700, David Miller wrote:
> From: Andrew Lunn <andrew-g2DYL2Zd6BY@public.gmane.org>
> Date: Thu, 24 Sep 2015 23:57:31 +0200
> 
> > I built the FEC driver as a module, and it won't unload:
> > 
> >  kernel:unregister_netdevice: waiting for eth1 to become free. Usage count = 1
> > unregister_netdevice: waiting for eth1 to become free. Usage count = 1
> > 
> > i assume because DSA holds a reference. I've not tried a fully module
> > build, DSA has issues with that.
> > 
> > Tested-by: Andrew Lunn <andrew-g2DYL2Zd6BY@public.gmane.org>
> 
> So, is this a regression?

Sorry, worded that badly. Since DSA is still active, it should not be
possible to unload the FEC driver. DSA should have a reference to it,
and mdio-mux also should have a reference to the mdio bus of the FEC
driver.

As Russell requested, i will re-test without his patches, just to make
sure.

	Andrew
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Re: [PATCH v3 0/9] Phy, mdiobus, and netdev struct device fixes

[David Miller]

From: Andrew Lunn <andrew-g2DYL2Zd6BY@public.gmane.org>
Date: Fri, 25 Sep 2015 00:26:54 +0200

> On Thu, Sep 24, 2015 at 03:15:54PM -0700, David Miller wrote:
>> From: Andrew Lunn <andrew-g2DYL2Zd6BY@public.gmane.org>
>> Date: Thu, 24 Sep 2015 23:57:31 +0200
>> 
>> > I built the FEC driver as a module, and it won't unload:
>> > 
>> >  kernel:unregister_netdevice: waiting for eth1 to become free. Usage count = 1
>> > unregister_netdevice: waiting for eth1 to become free. Usage count = 1
>> > 
>> > i assume because DSA holds a reference. I've not tried a fully module
>> > build, DSA has issues with that.
>> > 
>> > Tested-by: Andrew Lunn <andrew-g2DYL2Zd6BY@public.gmane.org>
>> 
>> So, is this a regression?
> 
> Sorry, worded that badly. Since DSA is still active, it should not be
> possible to unload the FEC driver. DSA should have a reference to it,
> and mdio-mux also should have a reference to the mdio bus of the FEC
> driver.
> 
> As Russell requested, i will re-test without his patches, just to make
> sure.

Something needs to hold into the underlying device refcount of a DSA
blob so that an unload can't even be attempted in that state.
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Re: [PATCH v3 0/9] Phy, mdiobus, and netdev struct device fixes

[Russell King - ARM Linux]

On Thu, Sep 24, 2015 at 03:51:37PM -0700, David Miller wrote:
> From: Andrew Lunn <andrew@lunn.ch>
> Date: Fri, 25 Sep 2015 00:26:54 +0200
> 
> > On Thu, Sep 24, 2015 at 03:15:54PM -0700, David Miller wrote:
> >> From: Andrew Lunn <andrew@lunn.ch>
> >> Date: Thu, 24 Sep 2015 23:57:31 +0200
> >> 
> >> > I built the FEC driver as a module, and it won't unload:
> >> > 
> >> >  kernel:unregister_netdevice: waiting for eth1 to become free. Usage count = 1
> >> > unregister_netdevice: waiting for eth1 to become free. Usage count = 1
> >> > 
> >> > i assume because DSA holds a reference. I've not tried a fully module
> >> > build, DSA has issues with that.
> >> > 
> >> > Tested-by: Andrew Lunn <andrew@lunn.ch>
> >> 
> >> So, is this a regression?
> > 
> > Sorry, worded that badly. Since DSA is still active, it should not be
> > possible to unload the FEC driver. DSA should have a reference to it,
> > and mdio-mux also should have a reference to the mdio bus of the FEC
> > driver.
> > 
> > As Russell requested, i will re-test without his patches, just to make
> > sure.
> 
> Something needs to hold into the underlying device refcount of a DSA
> blob so that an unload can't even be attempted in that state.

Holding a reference on a struct device does _not_ stop the device
being unbound or the module driving it being removed.  It merely
stops the struct device from being freed before all references have
been dropped.

Devices are always free to be unbound from their bound drivers
irrespective of the struct device refcount.  Even taking a reference
on the module (via try_module_get()) does not stop this.

-- 
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according to speedtest.net.

Re: [PATCH v3 0/9] Phy, mdiobus, and netdev struct device fixes

[Florian Fainelli]

On 24/09/15 12:17, Russell King - ARM Linux wrote:
> Hi,
> 
> The third version of this series fixes the build error which David
> identified, and drops the broken changes for the Cavium Thunger BGX
> ethernet driver as this driver requires some complex changes to
> resolve the leakage - and this is best done by people who can test
> the driver.
> 
> Compared to v2, the only patch which has changed is patch 6
>   "net: fix phy refcounting in a bunch of drivers"
> 
> I _think_ I've been able to build-test all the drivers touched by
> that patch to some degree now, though several of them needed the
> Kconfig hacked to allow it (not all had || COMPILE_TEST clause on
> their dependencies.)

Tested-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>

Thanks for fixing that.

> 
> Previous cover letters below:
> 
> This is the second version of the series, with the comments David had
> on the first patch fixed up.  Original series description with updated
> diffstat below.
> 
> While looking at the DSA code, I noticed we have a
> of_find_net_device_by_node(), and it looks like users of that are
> similarly buggy - it looks like net/dsa/dsa.c is the only user.  Fix
> that too.
> 
> Hi,
> 
> While looking at the phy code, I identified a number of weaknesses
> where refcounting on device structures was being leaked, where
> modules could be removed while in-use, and where the fixed-phy could
> end up having unintended consequences caused by incorrect calls to
> fixed_phy_update_state().
> 
> This patch series resolves those issues, some of which were discovered
> with testing on an Armada 388 board.  Not all patches are fully tested,
> particularly the one which touches several network drivers.
> 
> When resolving the struct device refcounting problems, several different
> solutions were considered before settling on the implementation here -
> one of the considerations was to avoid touching many network drivers.
> The solution here is:
> 
> 	phy_attach*() - takes a refcount
> 	phy_detach*() - drops the phy_attach refcount
> 
> Provided drivers always attach and detach their phys, which they should
> already be doing, this should change nothing, even if they leak a refcount.
> 
> 	of_phy_find_device() and of_* functions which use that take
> 	a refcount.  Arrange for this refcount to be dropped once
> 	the phy is attached.
> 
> This is the reason why the previous change is important - we can't drop
> this refcount taken by of_phy_find_device() until something else holds
> a reference on the device.  This resolves the leaked refcount caused by
> using of_phy_connect() or of_phy_attach().
> 
> Even without the above changes, these drivers are leaking by calling
> of_phy_find_device().  These drivers are addressed by adding the
> appropriate release of that refcount.
> 
> The mdiobus code also suffered from the same kind of leak, but thankfully
> this only happened in one place - the mdio-mux code.
> 
> I also found that the try_module_get() in the phy layer code was utterly
> useless: phydev->dev.driver was guaranteed to always be NULL, so
> try_module_get() was always being called with a NULL argument.  I proved
> this with my SFP code, which declares its own MDIO bus - the module use
> count was never incremented irrespective of how I set the MDIO bus up.
> This allowed the MDIO bus code to be removed from the kernel while there
> were still PHYs attached to it.
> 
> One other bug was discovered: while using in-band-status with mvneta, it
> was found that if a real phy is attached with in-band-status enabled,
> and another ethernet interface is using the fixed-phy infrastructure, the
> interface using the fixed-phy infrastructure is configured according to
> the other interface using the in-band-status - which is caused by the
> fixed-phy code not verifying that the phy_device passed in is actually
> a fixed-phy device, rather than a real MDIO phy.
> 
> Lastly, having mdio_bus reversing phy_device_register() internals seems
> like a layering violation - it's trivial to move that code to the phy
> device layer.
> 
>  drivers/net/ethernet/apm/xgene/xgene_enet_hw.c | 24 ++++++----
>  drivers/net/ethernet/freescale/gianfar.c       |  6 ++-
>  drivers/net/ethernet/freescale/ucc_geth.c      |  8 +++-
>  drivers/net/ethernet/marvell/mvneta.c          |  2 +
>  drivers/net/ethernet/xilinx/xilinx_emaclite.c  |  2 +
>  drivers/net/phy/fixed_phy.c                    |  2 +-
>  drivers/net/phy/mdio-mux.c                     | 19 +++++---
>  drivers/net/phy/mdio_bus.c                     | 24 ++++++----
>  drivers/net/phy/phy_device.c                   | 62 ++++++++++++++++++++------
>  drivers/of/of_mdio.c                           | 27 +++++++++--
>  include/linux/phy.h                            |  6 ++-
>  net/core/net-sysfs.c                           |  9 ++++
>  net/dsa/dsa.c                                  | 41 ++++++++++++++---
>  13 files changed, 181 insertions(+), 51 deletions(-)
> 


-- 
Florian

Re: [PATCH v3 0/9] Phy, mdiobus, and netdev struct device fixes

[David Miller]

From: Florian Fainelli <f.fainelli-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Date: Thu, 24 Sep 2015 18:39:56 -0700

> On 24/09/15 12:17, Russell King - ARM Linux wrote:
>> Hi,
>> 
>> The third version of this series fixes the build error which David
>> identified, and drops the broken changes for the Cavium Thunger BGX
>> ethernet driver as this driver requires some complex changes to
>> resolve the leakage - and this is best done by people who can test
>> the driver.
>> 
>> Compared to v2, the only patch which has changed is patch 6
>>   "net: fix phy refcounting in a bunch of drivers"
>> 
>> I _think_ I've been able to build-test all the drivers touched by
>> that patch to some degree now, though several of them needed the
>> Kconfig hacked to allow it (not all had || COMPILE_TEST clause on
>> their dependencies.)
> 
> Tested-by: Florian Fainelli <f.fainelli-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> Reviewed-by: Florian Fainelli <f.fainelli-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> 
> Thanks for fixing that.

Series applied, thanks.
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