This fixes a use-after-free bug in the usb-serial core.  It is simple to
trigger this (open a usb-serial port, then yank the device out before
closing the port.)  Thanks to Stefan Seyfried <seife@suse.de> for
reporting this, and to the slab debugging code which enabled it to be
tracked down.
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>