[patch 1/1] selinux: fix tty locking

[Stephen Smalley <sds@tycho.nsa.gov>]

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>

---

 security/selinux/hooks.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 5d1b8c7..4b0f904 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -1711,10 +1711,12 @@ static inline void flush_unauthorized_fi
 {
 	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);
@@ -1734,6 +1736,7 @@ static inline void flush_unauthorized_fi
 		}
 		file_list_unlock();
 	}
+	mutex_unlock(&tty_mutex);
 
 	/* Revalidate access to inherited open files. */
 

-- 
Stephen Smalley
National Security Agency

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