tty: Fix a USB serial crash/scribble
tty: Fix a USB serial crash/scribble

The port lock is used to protect the port state. However the port structure
is freed on a hangup, then the lock taken on a close. The right fix is to
drop the port on tty->shutdown() but we can't yet do that due to sleep v
non-sleeping rules. Instead do the next best thing and fix it up when we are
not in -rc season.

Reported-by: Daniel Mack <3d0f3b9ddcacec30c4008c5e030e6c13a478cb4f@caiaq.de>
Signed-off-by: Alan Cox <91e38e63b890fbb214c8914809fde03c73e7f24d@linux.intel.com>
Tested-by: Daniel Mack <3d0f3b9ddcacec30c4008c5e030e6c13a478cb4f@caiaq.de>
Signed-off-by: Linus Torvalds <69652caca27c8b940640ad396ab71f93cacec34f@linux-foundation.org>

KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs