CVE-2022-49943: In the Linux kernel, the following vulnerability has been resolved:  USB: gadget: Fix obscure lockdep violation for udc_mutex  A recent commit expanding the scope of the udc_lock mutex in the gadget core managed to cause an obscure and slightly bizarre lockdep violation.  In abbreviated form:  ====================================================== WARNING: possible circular locking dependency detected 5.19.0-rc7+ #12510 Not tainted ------------------------------------------------------ udevadm/312 is trying to acquire lock: ffff80000aae1058 (udc_lock){+.+.}-{3:3}, at: usb_udc_uevent+0x54/0xe0  but task is already holding lock: ffff000002277548 (kn->active#4){++++}-{0:0}, at: kernfs_seq_start+0x34/0xe0  which lock already depends on the new lock.  the existing dependency chain (in reverse order) is:  -> #3 (kn->active#4){++++}-{0:0}:         lock_acquire+0x68/0x84         __kernfs_remove+0x268/0x380         kernfs_remove_by_name_ns+0x58/0xac         sysfs_remove_file_ns+0x18/0x24         device_del+0x15c/0x440  -> #2 (device_links_lock){+.+.}-{3:3}:         lock_acquire+0x68/0x84         __mutex_lock+0x9c/0x430         mutex_lock_nested+0x38/0x64         device_link_remove+0x3c/0xa0         _regulator_put.part.0+0x168/0x190         regulator_put+0x3c/0x54         devm_regulator_release+0x14/0x20  -> #1 (regulator_list_mutex){+.+.}-{3:3}:         lock_acquire+0x68/0x84         __mutex_lock+0x9c/0x430         mutex_lock_nested+0x38/0x64         regulator_lock_dependent+0x54/0x284         regulator_enable+0x34/0x80         phy_power_on+0x24/0x130         __dwc2_lowlevel_hw_enable+0x100/0x130         dwc2_lowlevel_hw_enable+0x18/0x40         dwc2_hsotg_udc_start+0x6c/0x2f0         gadget_bind_driver+0x124/0x1f4  -> #0 (udc_lock){+.+.}-{3:3}:         __lock_acquire+0x1298/0x20cc         lock_acquire.part.0+0xe0/0x230         lock_acquire+0x68/0x84         __mutex_lock+0x9c/0x430         mutex_lock_nested+0x38/0x64         usb_udc_uevent+0x54/0xe0  Evidently this was caused by the scope of udc_mutex being too large. The mutex is only meant to protect udc->driver along with a few other things.  As far as I can tell, there's no reason for the mutex to be held while the gadget core calls a gadget driver's ->bind or ->unbind routine, or while a UDC is being started or stopped.  (This accounts for link #1 in the chain above, where the mutex is held while the dwc2_hsotg_udc is started as part of driver probing.)  Gadget drivers' ->disconnect callbacks are problematic.  Even though usb_gadget_disconnect() will now acquire the udc_mutex, there's a window in usb_gadget_bind_driver() between the times when the mutex is released and the ->bind callback is invoked.  If a disconnect occurred during that window, we could call the driver's ->disconnect routine before its ->bind routine.  To prevent this from happening, it will be necessary to prevent a UDC from connecting while it has no gadget driver.  This should be done already but it doesn't seem to be; currently usb_gadget_connect() has no check for this.  Such a check will have to be added later.  Some degree of mutual exclusion is required in soft_connect_store(), which can dereference udc->driver at arbitrary times since it is a sysfs callback.  The solution here is to acquire the gadget's device lock rather than the udc_mutex.  Since the driver core guarantees that the device lock is always held during driver binding and unbinding, this will make the accesses in soft_connect_store() mutually exclusive with any changes to udc->driver.  Lastly, it turns out there is one place which should hold the udc_mutex but currently does not: The function_show() routine needs protection while it dereferences udc->driver.  The missing lock and unlock calls are added.