From aea850cd35ae3d266fe6f93fb9edb25e4a555230 Mon Sep 17 00:00:00 2001 From: "M. Vefa Bicakci" Date: Tue, 22 Sep 2020 14:07:01 +0300 Subject: usbcore/driver: Fix specific driver selection This commit resolves a 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 in the logic that determines whether a device currently bound to a generic USB device driver should be re-probed by a more specific USB device driver or not. The code in __usb_bus_reprobe_drivers() used to have the following lines: if (usb_device_match_id(udev, new_udriver->id_table) == NULL && (!new_udriver->match || new_udriver->match(udev) != 0)) return 0; ret = device_reprobe(dev); As the reader will notice, the code checks whether the USB device in consideration matches the identifier table (id_table) of a specific USB device_driver (new_udriver), followed by a similar check, but this time with the USB device driver's match function. However, the match function's return value is not checked correctly. When match() returns zero, it means that the specific USB device driver is *not* applicable to the USB device in question, but the code then goes on to reprobe the device with the new USB device driver under consideration. All this to say, the logic is inverted. This bug was found by code inspection and instrumentation while investigating the root cause of the issue reported by Andrey Konovalov, where usbip took over syzkaller's virtual USB devices in an undesired manner. 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/20200922110703.720960-3-m.v.b@runbox.com Signed-off-by: Greg Kroah-Hartman --- drivers/usb/core/driver.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/usb/core') diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c index 7e73e989645b..715782995428 100644 --- a/drivers/usb/core/driver.c +++ b/drivers/usb/core/driver.c @@ -924,7 +924,7 @@ static int __usb_bus_reprobe_drivers(struct device *dev, void *data) udev = to_usb_device(dev); if (usb_device_match_id(udev, new_udriver->id_table) == NULL && - (!new_udriver->match || new_udriver->match(udev) != 0)) + (!new_udriver->match || new_udriver->match(udev) == 0)) return 0; ret = device_reprobe(dev); -- cgit v1.2.3 From 4df30e7603432704380b12fe40a604ee7f66746d Mon Sep 17 00:00:00 2001 From: "M. Vefa Bicakci" Date: Tue, 22 Sep 2020 14:07:02 +0300 Subject: 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 --- drivers/usb/core/driver.c | 11 ++--------- 1 file changed, 2 insertions(+), 9 deletions(-) (limited to 'drivers/usb/core') diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c index 715782995428..b00b7fb1aad1 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); -- cgit v1.2.3 From 3fce39601a1a34d940cf62858ee01ed9dac5d459 Mon Sep 17 00:00:00 2001 From: "M. Vefa Bicakci" Date: Tue, 22 Sep 2020 14:07:03 +0300 Subject: usbcore/driver: Accommodate usbip Commit 88b7381a939d ("USB: Select better matching USB drivers when available") inadvertently broke usbip functionality. The commit in question allows USB device drivers to be explicitly matched with USB devices via the use of driver-provided identifier tables and match functions, which is useful for a specialised device driver to be chosen for a device that can also be handled by another, more generic, device driver. Prior, the USB device section of usb_device_match() had an unconditional "return 1" statement, which allowed user-space to bind USB devices to the usbip_host device driver, if desired. However, the aforementioned commit changed the default/fallback return value to zero. This breaks device drivers such as usbip_host, so this commit restores the legacy behaviour, but only if a device driver does not have an id_table and a match() function. In addition, if usb_device_match is called for a device driver and device pair where the device does not match the id_table of the device driver in question, then the device driver will be disqualified for the device. This allows avoiding the default case of "return 1", which prevents undesirable probe() calls to a driver even though its id_table did not match the device. Finally, this commit changes the specialised-driver-to-generic-driver transition code so that when a device driver returns -ENODEV, a more generic device driver is only considered if the current device driver does not have an id_table and a match() function. This ensures that "generic" drivers such as usbip_host will not be considered specialised device drivers and will not cause the device to be locked in to the generic device driver, when a more specialised device driver could be tried. All of these changes restore usbip functionality without regressions, ensure that the specialised/generic device driver selection logic works as expected with the usb and apple-mfi-fastcharge drivers, and do not negatively affect the use of devices provided by dummy_hcd. Fixes: 88b7381a939d ("USB: Select better matching USB drivers when available") Cc: # 5.8 Cc: Bastien Nocera Cc: Valentina Manea Cc: Shuah Khan Cc: Greg Kroah-Hartman Cc: Alan Stern Cc: Tested-by: Andrey Konovalov Acked-by: Shuah Khan Signed-off-by: M. Vefa Bicakci Link: https://lore.kernel.org/r/20200922110703.720960-5-m.v.b@runbox.com Signed-off-by: Greg Kroah-Hartman --- drivers/usb/core/driver.c | 37 +++++++++++++++++++++++++++++++------ 1 file changed, 31 insertions(+), 6 deletions(-) (limited to 'drivers/usb/core') diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c index b00b7fb1aad1..b351962279e4 100644 --- a/drivers/usb/core/driver.c +++ b/drivers/usb/core/driver.c @@ -269,8 +269,30 @@ static int usb_probe_device(struct device *dev) if (error) return error; + /* Probe the USB device with the driver in hand, but only + * defer to a generic driver in case the current USB + * device driver has an id_table or a match function; i.e., + * when the device driver was explicitly matched against + * a device. + * + * If the device driver does not have either of these, + * then we assume that it can bind to any device and is + * not truly a more specialized/non-generic driver, so a + * return value of -ENODEV should not force the device + * to be handled by the generic USB driver, as there + * can still be another, more specialized, device driver. + * + * This accommodates the usbip driver. + * + * TODO: What if, in the future, there are multiple + * specialized USB device drivers for a particular device? + * In such cases, there is a need to try all matching + * specialised device drivers prior to setting the + * use_generic_driver bit. + */ error = udriver->probe(udev); - if (error == -ENODEV && udriver != &usb_generic_driver) { + if (error == -ENODEV && udriver != &usb_generic_driver && + (udriver->id_table || udriver->match)) { udev->use_generic_driver = 1; return -EPROBE_DEFER; } @@ -831,14 +853,17 @@ static int usb_device_match(struct device *dev, struct device_driver *drv) udev = to_usb_device(dev); udrv = to_usb_device_driver(drv); - if (udrv->id_table && - usb_device_match_id(udev, udrv->id_table) != NULL) { - return 1; - } + if (udrv->id_table) + return usb_device_match_id(udev, udrv->id_table) != NULL; if (udrv->match) return udrv->match(udev); - return 0; + + /* If the device driver under consideration does not have a + * id_table or a match function, then let the driver's probe + * function decide. + */ + return 1; } else if (is_usb_interface(dev)) { struct usb_interface *intf; -- cgit v1.2.3