1 files changed, 28 insertions, 12 deletions

diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index eeae7fafe9a7..59af3945ea85 100644
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c
@@ -26,11 +26,13 @@
 #include <linux/bitops.h>
 #include <linux/devpts_fs.h>
 #include <linux/slab.h>
+#include <linux/mutex.h>
 
 
 #ifdef CONFIG_UNIX98_PTYS
 static struct tty_driver *ptm_driver;
 static struct tty_driver *pts_driver;
+static DEFINE_MUTEX(devpts_mutex);
 #endif
 
 static void pty_close(struct tty_struct *tty, struct file *filp)
@@ -45,6 +47,7 @@ static void pty_close(struct tty_struct *tty, struct file *filp)
         wake_up_interruptible(&tty->read_wait);
         wake_up_interruptible(&tty->write_wait);
         tty->packet = 0;
+        /* Review - krefs on tty_link ?? */
         if (!tty->link)
                 return;
         tty->link->packet = 0;
@@ -54,12 +57,15 @@ static void pty_close(struct tty_struct *tty, struct file *filp)
         if (tty->driver->subtype == PTY_TYPE_MASTER) {
                 set_bit(TTY_OTHER_CLOSED, &tty->flags);
 #ifdef CONFIG_UNIX98_PTYS
-                if (tty->driver == ptm_driver)
+                if (tty->driver == ptm_driver) {
+                        mutex_lock(&devpts_mutex);
                         devpts_pty_kill(tty->link);
+                        mutex_unlock(&devpts_mutex);
+                }
 #endif
-                tty_unlock();
+                tty_unlock(tty);
                 tty_vhangup(tty->link);
-                tty_lock();
+                tty_lock(tty);
         }
 }
 
@@ -475,13 +481,17 @@ static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
  *      @idx: tty index
  *
  *      Look up a pty master device. Called under the tty_mutex for now.
- *      This provides our locking.
+ *      This provides our locking for the tty pointer.
  */
 
 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
                 struct inode *pts_inode, int idx)
 {
-        struct tty_struct *tty = devpts_get_tty(pts_inode, idx);
+        struct tty_struct *tty;
+
+        mutex_lock(&devpts_mutex);
+        tty = devpts_get_tty(pts_inode, idx);
+        mutex_unlock(&devpts_mutex);
         /* Master must be open before slave */
         if (!tty)
                 return ERR_PTR(-EIO);
@@ -613,24 +623,29 @@ static int ptmx_open(struct inode *inode, struct file *filp)
                 return retval;
 
         /* find a device that is not in use. */
-        tty_lock();
+        mutex_lock(&devpts_mutex);
         index = devpts_new_index(inode);
-        tty_unlock();
         if (index < 0) {
                 retval = index;
                 goto err_file;
         }
 
+        mutex_unlock(&devpts_mutex);
+
         mutex_lock(&tty_mutex);
-        tty_lock();
+        mutex_lock(&devpts_mutex);
         tty = tty_init_dev(ptm_driver, index);
-        mutex_unlock(&tty_mutex);
 
         if (IS_ERR(tty)) {
                 retval = PTR_ERR(tty);
                 goto out;
         }
 
+        /* The tty returned here is locked so we can safely
+           drop the mutex */
+        mutex_unlock(&devpts_mutex);
+        mutex_unlock(&tty_mutex);
+
         set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
 
         tty_add_file(tty, filp);
@@ -643,16 +658,17 @@ static int ptmx_open(struct inode *inode, struct file *filp)
         if (retval)
                 goto err_release;
 
-        tty_unlock();
+        tty_unlock(tty);
         return 0;
 err_release:
-        tty_unlock();
+        tty_unlock(tty);
         tty_release(inode, filp);
         return retval;
 out:
+        mutex_unlock(&tty_mutex);
         devpts_kill_index(inode, index);
-        tty_unlock();
 err_file:
+        mutex_unlock(&devpts_mutex);
         tty_free_file(filp);
         return retval;
 }