Recent changes in the usbhid layer exposed a bug in usbcore.  If
CONFIG_USB_DYNAMIC_MINORS is enabled then an interface may be assigned
a minor number of 0.  However interfaces that aren't registered as USB
class devices also have their minor number set to 0, during
initialization.  As a result usb_find_interface() may return the
wrong interface, leading to a crash.

This patch (as1418) fixes the problem by initializing every
interface's minor number to -1.  It also cleans up the
usb_register_dev() function, which besides being somewhat awkwardly
written, does not unwind completely on all its error paths.
Signed-off-by: NAlan Stern <stern@rowland.harvard.edu>
Tested-by: NPhilip J. Turmel <philip@turmel.org>
Tested-by: NGabriel Craciunescu <nix.or.die@googlemail.com>
Tested-by: NAlex Riesen <raa.lkml@gmail.com>
Tested-by: NMatthias Bayer <jackdachef@gmail.com>
CC: Jiri Kosina <jkosina@suse.cz>
Cc: stable <stable@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>