tty: Make get_current_tty use a kref

We now return a kref covered tty reference. That ensures the tty structure
doesn't go away when you have a return from get_current_tty. This is not
enough to protect you from most of the resources being freed behind your
back - yet.

[Updated to include fixes for SELinux problems found by Andrew Morton and
 an s390 leak found while debugging the former]

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 4a7374c12d9c..089d61a23952 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2123,6 +2123,7 @@ static inline void flush_unauthorized_files(struct files_struct *files)
 
         mutex_lock(&tty_mutex);
         tty = get_current_tty();
+        mutex_unlock(&tty_mutex);
         if (tty) {
                 file_list_lock();
                 file = list_entry(tty->tty_files.next, typeof(*file), f_u.fu_list);
@@ -2139,8 +2140,8 @@ static inline void flush_unauthorized_files(struct files_struct *files)
                         }
                 }
                 file_list_unlock();
+                tty_kref_put(tty);
         }
-        mutex_unlock(&tty_mutex);
         /* Reset controlling tty. */
         if (drop_tty)
                 no_tty();