ALSA: seq: Avoid concurrent access to queue flags

commit bb51e669

 upstream.

The queue flags are represented in bit fields and the concurrent
access may result in unexpected results.  Although the current code
should be mostly OK as it's only reading a field while writing other
fields as KCSAN reported, it's safer to cover both with a proper
spinlock protection.

This patch fixes the possible concurrent read by protecting with
q->owner_lock.  Also the queue owner field is protected as well since
it's the field to be protected by the lock itself.

Reported-by:  <syzbot+65c6c92d04304d0a8efc@syzkaller.appspotmail.com>
Reported-by:  <syzbot+e60ddfa48717579799dd@syzkaller.appspotmail.com>
Link: https://lore.kernel.org/r/20200214111316.26939-2-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>