The bug was caused by dev_release() failing to turn off its
gadget_registered flag after unregistering the gadget driver. As a
result, when a later user closed the device file before writing a
valid set of descriptors, dev_release() thought the gadget had been
registered and tried to unregister it, even though it had not been.
This led to the NULL pointer dereference.
The fix is simple: turn off the flag when the gadget is unregistered.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Reported-and-tested-by: Andrey Konovalov <andreyknvl@google.com> CC: <stable@vger.kernel.org> Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>