[PATCH] Driver Core: fix bk-driver-core kills ppc64

There's no check to see if the device is already bound to a driver, which
could do bad things.  The first thing to go wrong is that it will try to match
a driver with a device already bound to one.  In some cases (it appears with
USB with drivers/usb/core/usb.c::usb_match_id()), some drivers will match a
device based on the class type, so it would be common (especially for HID
devices) to match a device that is already bound.

The fun comes when ->probe() is called, it fails, then
driver_probe_device() does this:

	dev->driver = NULL;

Later on, that pointer could be be dereferenced without checking and cause
hell to break loose.

This problem could be nasty. It's very hardware dependent, since some
devices could have a different set of matching qualifiers than others.

Now, I don't quite see exactly where/how you were getting that crash.
You're dereferencing bad memory, but I'm not sure which pointer was bad
and where it came from, but it could have come from a couple of different
places.

The patch below will hopefully fix it all up for you. It's against
2.6.12-rc2-mm1, and does the following:

- Move logic to driver_probe_device() and comments uncommon returns:
  1 - If device is bound
  0 - If device not bound, and no error
  error - If there was an error.

- Move locking to caller of that function, since we want to lock a
  device for the entire time we're trying to bind it to a driver (to
  prevent against a driver being loaded at the same time).

- Update __device_attach() and __driver_attach() to do that locking.

- Check if device is already bound in __driver_attach()

- Update the converse device_release_driver() so it locks the device
  around all of the operations.

- Mark driver_probe_device() as static and remove export. It's an
  internal function, it should stay that way, and there are no other
  callers. If there is ever a need to export it, we can audit it as
  necessary.

Signed-off-by: Andrew Morton <akpm@osdl.org>

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index dd2a8a7..8510918 100644 (file)
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -35,6 +35,8 @@
  *     nor take the bus's rwsem. Please verify those are accounted
  *     for before calling this. (It is ok to call with no other effort
  *     from a driver's probe() method.)
+ *
+ *     This function must be called with @dev->sem held.
  */
 void device_bind_driver(struct device * dev)
 {
@@ -57,54 +59,56 @@ void device_bind_driver(struct device * dev)
  *     because we don't know the format of the ID structures, nor what
  *     is to be considered a match and what is not.
  *
- *     If we find a match, we call @drv->probe(@dev) if it exists, and
- *     call device_bind_driver() above.
+ *
+ *     This function returns 1 if a match is found, an error if one
+ *     occurs (that is not -ENODEV or -ENXIO), and 0 otherwise.
+ *
+ *     This function must be called with @dev->sem held.
  */
-int driver_probe_device(struct device_driver * drv, struct device * dev)
+static int driver_probe_device(struct device_driver * drv, struct device * dev)
 {
-       int error = 0;
+       int ret = 0;
 
        if (drv->bus->match && !drv->bus->match(dev, drv))
-               return -ENODEV;
+               goto Done;
 
-       down(&dev->sem);
+       pr_debug("%s: Matched Device %s with Driver %s\n",
+                drv->bus->name, dev->bus_id, drv->name);
        dev->driver = drv;
        if (drv->probe) {
-               error = drv->probe(dev);
-               if (error) {
+               ret = drv->probe(dev);
+               if (ret) {
                        dev->driver = NULL;
-                       up(&dev->sem);
-                       return error;
+                       goto ProbeFailed;
                }
        }
-       up(&dev->sem);
        device_bind_driver(dev);
-       return 0;
+       ret = 1;
+       pr_debug("%s: Bound Device %s to Driver %s\n",
+                drv->bus->name, dev->bus_id, drv->name);
+       goto Done;
+
+ ProbeFailed:
+       if (ret == -ENODEV || ret == -ENXIO) {
+               /* Driver matched, but didn't support device
+                * or device not found.
+                * Not an error; keep going.
+                */
+               ret = 0;
+       } else {
+               /* driver matched but the probe failed */
+               printk(KERN_WARNING
+                      "%s: probe of %s failed with error %d\n",
+                      drv->name, dev->bus_id, ret);
+       }
+ Done:
+       return ret;
 }
 
 static int __device_attach(struct device_driver * drv, void * data)
 {
        struct device * dev = data;
-       int error;
-
-       error = driver_probe_device(drv, dev);
-       if (error) {
-               if ((error == -ENODEV) || (error == -ENXIO)) {
-                       /* Driver matched, but didn't support device
-                        * or device not found.
-                        * Not an error; keep going.
-                        */
-                       error = 0;
-               } else {
-                       /* driver matched but the probe failed */
-                       printk(KERN_WARNING
-                              "%s: probe of %s failed with error %d\n",
-                              drv->name, dev->bus_id, error);
-               }
-               return error;
-       }
-       /* stop looking, this device is attached */
-       return 1;
+       return driver_probe_device(drv, dev);
 }
 
 /**
@@ -114,37 +118,43 @@ static int __device_attach(struct device_driver * drv, void * data)
  *     Walk the list of drivers that the bus has and call
  *     driver_probe_device() for each pair. If a compatible
  *     pair is found, break out and return.
+ *
+ *     Returns 1 if the device was bound to a driver; 0 otherwise.
  */
 int device_attach(struct device * dev)
 {
+       int ret = 0;
+
+       down(&dev->sem);
        if (dev->driver) {
                device_bind_driver(dev);
-               return 1;
-       }
-
-       return bus_for_each_drv(dev->bus, NULL, dev, __device_attach);
+               ret = 1;
+       } else
+               ret = bus_for_each_drv(dev->bus, NULL, dev, __device_attach);
+       up(&dev->sem);
+       return ret;
 }
 
 static int __driver_attach(struct device * dev, void * data)
 {
        struct device_driver * drv = data;
-       int error = 0;
-
-       if (!dev->driver) {
-               error = driver_probe_device(drv, dev);
-               if (error) {
-                       if (error != -ENODEV) {
-                               /* driver matched but the probe failed */
-                               printk(KERN_WARNING
-                                      "%s: probe of %s failed with error %d\n",
-                                      drv->name, dev->bus_id, error);
-                       } else
-                               error = 0;
-                       return error;
-               }
-               /* stop looking, this driver is attached */
-               return 1;
-       }
+
+       /*
+        * Lock device and try to bind to it. We drop the error
+        * here and always return 0, because we need to keep trying
+        * to bind to devices and some drivers will return an error
+        * simply if it didn't support the device.
+        *
+        * driver_probe_device() will spit a warning if there
+        * is an error.
+        */
+
+       down(&dev->sem);
+       if (!dev->driver)
+               driver_probe_device(drv, dev);
+       up(&dev->sem);
+
+
        return 0;
 }
 
@@ -156,9 +166,6 @@ static int __driver_attach(struct device * dev, void * data)
  *     match the driver with each one.  If driver_probe_device()
  *     returns 0 and the @dev->driver is set, we've found a
  *     compatible pair.
- *
- *     Note that we ignore the -ENODEV error from driver_probe_device(),
- *     since it's perfectly valid for a driver not to bind to any devices.
  */
 void driver_attach(struct device_driver * drv)
 {
@@ -176,19 +183,19 @@ void driver_attach(struct device_driver * drv)
  */
 void device_release_driver(struct device * dev)
 {
-       struct device_driver * drv = dev->driver;
-
-       if (!drv)
-               return;
-
-       sysfs_remove_link(&drv->kobj, kobject_name(&dev->kobj));
-       sysfs_remove_link(&dev->kobj, "driver");
-       klist_del(&dev->knode_driver);
+       struct device_driver * drv;
 
        down(&dev->sem);
-       if (drv->remove)
-               drv->remove(dev);
-       dev->driver = NULL;
+       if (dev->driver) {
+               drv = dev->driver;
+               sysfs_remove_link(&drv->kobj, kobject_name(&dev->kobj));
+               sysfs_remove_link(&dev->kobj, "driver");
+               klist_del(&dev->knode_driver);
+
+               if (drv->remove)
+                       drv->remove(dev);
+               dev->driver = NULL;
+       }
        up(&dev->sem);
 }
 
@@ -208,7 +215,6 @@ void driver_detach(struct device_driver * drv)
 }
 
 
-EXPORT_SYMBOL_GPL(driver_probe_device);
 EXPORT_SYMBOL_GPL(device_bind_driver);
 EXPORT_SYMBOL_GPL(device_release_driver);
 EXPORT_SYMBOL_GPL(device_attach);

diff --git a/include/linux/device.h b/include/linux/device.h
index 4324926..91aac34 100644 (file)
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -325,7 +325,6 @@ extern int device_for_each_child(struct device *, void *,
  * Manual binding of a device to driver. See drivers/base/bus.c
  * for information on use.
  */
-extern int  driver_probe_device(struct device_driver * drv, struct device * dev);
 extern void device_bind_driver(struct device * dev);
 extern void device_release_driver(struct device * dev);
 extern int  device_attach(struct device * dev);