[PATCH] selinux: fix tty locking

Take tty_mutex when accessing ->signal->tty in selinux code.  Noted by Alan
Cox.  Longer term, we are looking at refactoring the code to provide better
encapsulation of the tty layer, but this is a simple fix that addresses the
immediate bug.

Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Acked-by: Alan Cox <alan@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 4 insertions, 1 deletions

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 55cec4d6f117..e4d81a42fca4 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -1689,10 +1689,12 @@ static inline void flush_unauthorized_files(struct files_struct * files)
 {
         struct avc_audit_data ad;
         struct file *file, *devnull = NULL;
-        struct tty_struct *tty = current->signal->tty;
+        struct tty_struct *tty;
         struct fdtable *fdt;
         long j = -1;
 
+        mutex_lock(&tty_mutex);
+        tty = current->signal->tty;
         if (tty) {
                 file_list_lock();
                 file = list_entry(tty->tty_files.next, typeof(*file), f_u.fu_list);
@@ -1712,6 +1714,7 @@ static inline void flush_unauthorized_files(struct files_struct * files)
                 }
                 file_list_unlock();
         }
+        mutex_unlock(&tty_mutex);
 
         /* Revalidate access to inherited open files. */