From: M. Vefa Bicakci Date: Tue, 22 Sep 2020 11:07:02 +0000 (+0300) Subject: usbcore/driver: Fix incorrect downcast X-Git-Tag: v5.10.7~1550^2~2 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=4df30e7603432704380b12fe40a604ee7f66746d;p=platform%2Fkernel%2Flinux-rpi.git usbcore/driver: Fix incorrect downcast This commit resolves a minor bug in the selection/discovery of more specific USB device drivers for devices that are currently bound to generic USB device drivers. The bug is related to the way a candidate USB device driver is compared against the generic USB device driver. The code in is_dev_usb_generic_driver() assumes that the device driver in question is a USB device driver by calling to_usb_device_driver(dev->driver) to downcast; however I have observed that this assumption is not always true, through code instrumentation. This commit avoids the incorrect downcast altogether by comparing the USB device's driver (i.e., dev->driver) to the generic USB device driver directly. This method was suggested by Alan Stern. This bug was found while investigating Andrey Konovalov's report indicating usbip device driver misbehaviour with the recently merged generic USB device driver selection feature. The report is linked below. Fixes: d5643d2249b2 ("USB: Fix device driver race") Cc: # 5.8 Cc: Greg Kroah-Hartman Cc: Alan Stern Cc: Bastien Nocera Cc: Shuah Khan Cc: Valentina Manea Cc: Tested-by: Andrey Konovalov Signed-off-by: M. Vefa Bicakci Link: https://lore.kernel.org/r/20200922110703.720960-4-m.v.b@runbox.com Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c index 7157829..b00b7fb 100644 --- a/drivers/usb/core/driver.c +++ b/drivers/usb/core/driver.c @@ -905,21 +905,14 @@ static int usb_uevent(struct device *dev, struct kobj_uevent_env *env) return 0; } -static bool is_dev_usb_generic_driver(struct device *dev) -{ - struct usb_device_driver *udd = dev->driver ? - to_usb_device_driver(dev->driver) : NULL; - - return udd == &usb_generic_driver; -} - static int __usb_bus_reprobe_drivers(struct device *dev, void *data) { struct usb_device_driver *new_udriver = data; struct usb_device *udev; int ret; - if (!is_dev_usb_generic_driver(dev)) + /* Don't reprobe if current driver isn't usb_generic_driver */ + if (dev->driver != &usb_generic_driver.drvwrap.driver) return 0; udev = to_usb_device(dev);