commit 24ec839c431eb79bb8f6abc00c4e1eb3b8c4d517 while fixing the locking for
signal->tty got the locking wrong for signal->session. This places our
accesses of signal->session back under the tasklist_lock where they belong.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Cc: Oleg Nesterov <oleg@tv-sign.ru> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>