1 files changed, 21 insertions, 2 deletions

diff --git a/drivers/char/tty_ldisc.c b/drivers/char/tty_ldisc.c
index feb55075819b..3f653f7d849f 100644
--- a/drivers/char/tty_ldisc.c
+++ b/drivers/char/tty_ldisc.c
@@ -34,6 +34,8 @@
 #include <linux/vt_kern.h>
 #include <linux/selection.h>
 
+#include <linux/smp_lock.h>     /* For the moment */
+
 #include <linux/kmod.h>
 #include <linux/nsproxy.h>
 
@@ -443,8 +445,14 @@ static void tty_set_termios_ldisc(struct tty_struct *tty, int num)
 static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld)
 {
         WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags));
-        if (ld->ops->open)
-                return ld->ops->open(tty);
+        if (ld->ops->open) {
+                int ret;
+                /* BKL here locks verus a hangup event */
+                lock_kernel();
+                ret = ld->ops->open(tty);
+                unlock_kernel();
+                return ret;
+        }
         return 0;
 }
 
@@ -545,6 +553,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
         if (IS_ERR(new_ldisc))
                 return PTR_ERR(new_ldisc);
 
+        lock_kernel();
         /*
          *      We need to look at the tty locking here for pty/tty pairs
          *      when both sides try to change in parallel.
@@ -558,10 +567,12 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
          */
 
         if (tty->ldisc->ops->num == ldisc) {
+                unlock_kernel();
                 tty_ldisc_put(new_ldisc);
                 return 0;
         }
 
+        unlock_kernel();
         /*
          *      Problem: What do we do if this blocks ?
          *      We could deadlock here
@@ -582,6 +593,9 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
                         test_bit(TTY_LDISC_CHANGING, &tty->flags) == 0);
                 mutex_lock(&tty->ldisc_mutex);
         }
+
+        lock_kernel();
+
         set_bit(TTY_LDISC_CHANGING, &tty->flags);
 
         /*
@@ -592,6 +606,8 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
         tty->receive_room = 0;
 
         o_ldisc = tty->ldisc;
+
+        unlock_kernel();
         /*
          *      Make sure we don't change while someone holds a
          *      reference to the line discipline. The TTY_LDISC bit
@@ -617,12 +633,14 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
         flush_scheduled_work();
 
         mutex_lock(&tty->ldisc_mutex);
+        lock_kernel();
         if (test_bit(TTY_HUPPED, &tty->flags)) {
                 /* We were raced by the hangup method. It will have stomped
                    the ldisc data and closed the ldisc down */
                 clear_bit(TTY_LDISC_CHANGING, &tty->flags);
                 mutex_unlock(&tty->ldisc_mutex);
                 tty_ldisc_put(new_ldisc);
+                unlock_kernel();
                 return -EIO;
         }
 
@@ -664,6 +682,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
         if (o_work)
                 schedule_delayed_work(&o_tty->buf.work, 1);
         mutex_unlock(&tty->ldisc_mutex);
+        unlock_kernel();
         return retval;
 }