diff options
author | Russ Dill <russ.dill@gmail.com> | 2009-11-18 18:02:13 (GMT) |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@suse.de> | 2009-12-11 19:55:20 (GMT) |
commit | a2582bd478c13c574d4c16ef1209d333f2a25935 (patch) | |
tree | 77fd2b7ab8b5f6696872f3cf7151ff3ae0c02554 /drivers/usb/core/usb.c | |
parent | 22a627ba81e0f75b994d37adb68761a9b9ef7186 (diff) | |
download | linux-a2582bd478c13c574d4c16ef1209d333f2a25935.tar.xz |
USB: Close usb_find_interface race
USB drivers that create character devices call usb_register_dev in their
probe function. This associates the usb_interface device with that minor
number and creates the character device and announces it to the world.
However, the driver's probe function is called before the new
usb_interface is added to the driver's klist_devices.
This is a problem because userspace will respond to the character device
creation announcement by opening the character device. The driver's open
function will the call usb_find_interface to find the usb_interface
associated with that minor number. usb_find_interface will walk the
driver's list of devices and find the usb_interface with the matching
minor number.
Because the announcement happens before the usb_interface is added to the
driver's klist_devices, a race condition exists. A straightforward fix
is to walk the list of devices on usb_bus_type instead since the device
is added to that list before the announcement occurs.
bus_find_device calls get_device to bump the reference count on the found
device. It is arguable that the reference count should be dropped by the
caller of usb_find_interface instead of usb_find_interface, however,
the current users of usb_find_interface do not expect this.
Signed-off-by: Russ Dill <Russ.Dill@gmail.com>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'drivers/usb/core/usb.c')
-rw-r--r-- | drivers/usb/core/usb.c | 28 |
1 files changed, 10 insertions, 18 deletions
diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c index b1b85ab..d1e9440 100644 --- a/drivers/usb/core/usb.c +++ b/drivers/usb/core/usb.c @@ -130,24 +130,17 @@ struct usb_host_interface *usb_altnum_to_altsetting( } EXPORT_SYMBOL_GPL(usb_altnum_to_altsetting); -struct find_interface_arg { - int minor; - struct usb_interface *interface; -}; - static int __find_interface(struct device *dev, void *data) { - struct find_interface_arg *arg = data; + int *minor = data; struct usb_interface *intf; if (!is_usb_interface(dev)) return 0; intf = to_usb_interface(dev); - if (intf->minor != -1 && intf->minor == arg->minor) { - arg->interface = intf; + if (intf->minor != -1 && intf->minor == *minor) return 1; - } return 0; } @@ -156,21 +149,20 @@ static int __find_interface(struct device *dev, void *data) * @drv: the driver whose current configuration is considered * @minor: the minor number of the desired device * - * This walks the driver device list and returns a pointer to the interface + * This walks the bus device list and returns a pointer to the interface * with the matching minor. Note, this only works for devices that share the * USB major number. */ struct usb_interface *usb_find_interface(struct usb_driver *drv, int minor) { - struct find_interface_arg argb; - int retval; + struct device *dev; + + dev = bus_find_device(&usb_bus_type, NULL, &minor, __find_interface); + + /* Drop reference count from bus_find_device */ + put_device(dev); - argb.minor = minor; - argb.interface = NULL; - /* eat the error, it will be in argb.interface */ - retval = driver_for_each_device(&drv->drvwrap.driver, NULL, &argb, - __find_interface); - return argb.interface; + return dev ? to_usb_interface(dev) : NULL; } EXPORT_SYMBOL_GPL(usb_find_interface); |