[PATCH] tty: fix the locking for signal->session in disassociate_ctty

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>

1 files changed, 1 insertions, 3 deletions

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index ac937f767f23..abfe24d28c51 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -1496,7 +1496,6 @@ void disassociate_ctty(int on_exit)
 {
         struct tty_struct *tty;
         int tty_pgrp = -1;
-        int session;
 
         lock_kernel();
 
@@ -1530,7 +1529,6 @@ void disassociate_ctty(int on_exit)
 
         spin_lock_irq(&current->sighand->siglock);
         current->signal->tty_old_pgrp = 0;
-        session = process_session(current);
         spin_unlock_irq(&current->sighand->siglock);
 
         mutex_lock(&tty_mutex);
@@ -1549,7 +1547,7 @@ void disassociate_ctty(int on_exit)
 
         /* Now clear signal->tty under the lock */
         read_lock(&tasklist_lock);
-        session_clear_tty(session);
+        session_clear_tty(process_session(current));
         read_unlock(&tasklist_lock);
         unlock_kernel();
 }