[PATCH 09/12] tty: Re-define tty driver remove() interface

[Peter Hurley]

The tty driver remove() method is used exclusively by the BSD and Unix98
pty drivers to release the tty index; the BSD drivers clear the tty tables
for the pty pair @index, while the Unix98 drivers free the devpts index.

Although the remove() method is intended as the symmetric operation to the
lookup() method (ie., the index obtained via the lookup() is released by
the remove() method). the actual interface isn't defined reflexively.

This causes cleanup problems for ptmx_open() if initialization fails in
tty_init_dev(): ptmx_open() releases the devpts index, but the index may
have been already been released by release_tty() during cleanup in
tty_init_dev() instead. This will cause mismatched devpts counts and
duplicate removal of the devpts index.

Re-define the driver remove() method as the symmetric operation to the
lookup() method. Propagate the inode parameter dependency from the
file operation to the tty driver method:

 tty_open()  -+
              +-> tty_init_dev() +-> release_tty() -> tty_driver_remove_tty()
 ptmx_open() -+                  |
                                 |
 tty_release() ------------------+

Signed-off-by: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
---
 drivers/tty/pty.c          | 13 ++++++-------
 drivers/tty/tty_io.c       | 24 ++++++++++++++----------
 include/linux/tty.h        |  3 ++-
 include/linux/tty_driver.h |  4 ++--
 4 files changed, 24 insertions(+), 20 deletions(-)

diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index 2680044..c71a1ab 100644
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c
@@ -461,10 +461,10 @@ static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
 	return pty_common_install(driver, tty, true);
 }
 
-static void pty_remove(struct tty_driver *driver, struct tty_struct *tty)
+static void pty_remove(struct tty_driver *driver, struct inode *inode, int idx)
 {
-	driver->ttys[tty->index] = NULL;
-	driver->other->ttys[tty->index] = NULL;
+	driver->ttys[idx] = NULL;
+	driver->other->ttys[idx] = NULL;
 }
 
 static int pty_bsd_ioctl(struct tty_struct *tty,
@@ -660,9 +660,9 @@ static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
 }
 
 /* this is called once with whichever end is closed last */
-static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
+static void pty_unix98_remove(struct tty_driver *driver, struct inode *inode, int idx)
 {
-	devpts_kill_index(tty->driver_data, tty->index);
+	devpts_kill_index(inode, idx);
 }
 
 static const struct tty_operations ptm_unix98_ops = {
@@ -738,7 +738,7 @@ static int ptmx_open(struct inode *inode, struct file *filp)
 	mutex_unlock(&devpts_mutex);
 
 	mutex_lock(&tty_mutex);
-	tty = tty_init_dev(ptm_driver, index);
+	tty = tty_init_dev(ptm_driver, inode, index);
 
 	if (IS_ERR(tty)) {
 		retval = PTR_ERR(tty);
@@ -777,7 +777,6 @@ err_release:
 	return retval;
 out:
 	mutex_unlock(&tty_mutex);
-	devpts_kill_index(inode, index);
 err_file:
 	tty_free_file(filp);
 	return retval;
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index afd378e..2a6d40c 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -158,7 +158,7 @@ static long tty_compat_ioctl(struct file *file, unsigned int cmd,
 #endif
 static int __tty_fasync(int fd, struct file *filp, int on);
 static int tty_fasync(int fd, struct file *filp, int on);
-static void release_tty(struct tty_struct *tty, int idx);
+static void release_tty(struct tty_struct *tty, struct inode *inode, int idx);
 
 /**
  *	free_tty_struct		-	free a disused tty
@@ -1435,6 +1435,7 @@ static int tty_driver_install_tty(struct tty_driver *driver,
 /**
  *	tty_driver_remove_tty() - remove a tty from the driver tables
  *	@driver: the driver for the tty
+ *	@inode:	 device file inode
  *	@idx:	 the minor number
  *
  *	Remvoe a tty object from the driver tables. The tty->index field
@@ -1442,12 +1443,13 @@ static int tty_driver_install_tty(struct tty_driver *driver,
  *
  *	Locking: tty_mutex for now
  */
-static void tty_driver_remove_tty(struct tty_driver *driver, struct tty_struct *tty)
+static void tty_driver_remove_tty(struct tty_driver *driver,
+				  struct inode *inode, int idx)
 {
 	if (driver->ops->remove)
-		driver->ops->remove(driver, tty);
+		driver->ops->remove(driver, inode, idx);
 	else
-		driver->ttys[tty->index] = NULL;
+		driver->ttys[idx] = NULL;
 }
 
 /*
@@ -1505,7 +1507,8 @@ static int tty_reopen(struct tty_struct *tty)
  * relaxed for the (most common) case of reopening a tty.
  */
 
-struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx)
+struct tty_struct *tty_init_dev(struct tty_driver *driver,
+				struct inode *inode, int idx)
 {
 	struct tty_struct *tty;
 	int retval;
@@ -1557,6 +1560,7 @@ err_free_tty:
 	free_tty_struct(tty);
 err_module_put:
 	module_put(driver->owner);
+	tty_driver_remove_tty(driver, inode, idx);
 	return ERR_PTR(retval);
 
 	/* call the tty release_tty routine to clean out this slot */
@@ -1564,7 +1568,7 @@ err_release_tty:
 	tty_unlock(tty);
 	tty_info_ratelimited(tty, "ldisc open failed (%d), clearing slot %d\n",
 			     retval, idx);
-	release_tty(tty, idx);
+	release_tty(tty, inode, idx);
 	return ERR_PTR(retval);
 }
 
@@ -1679,7 +1683,7 @@ EXPORT_SYMBOL(tty_kref_put);
  *	of ttys that the driver keeps.
  *
  */
-static void release_tty(struct tty_struct *tty, int idx)
+static void release_tty(struct tty_struct *tty, struct inode *inode, int idx)
 {
 	/* This should always be true but check for the moment */
 	WARN_ON(tty->index != idx);
@@ -1687,7 +1691,7 @@ static void release_tty(struct tty_struct *tty, int idx)
 	if (tty->ops->shutdown)
 		tty->ops->shutdown(tty);
 	tty_free_termios(tty);
-	tty_driver_remove_tty(tty->driver, tty);
+	tty_driver_remove_tty(tty->driver, inode, idx);
 	tty->port->itty = NULL;
 	if (tty->link)
 		tty->link->port->itty = NULL;
@@ -1910,7 +1914,7 @@ int tty_release(struct inode *inode, struct file *filp)
 	 * unlock never unlocks a freed tty).
 	 */
 	mutex_lock(&tty_mutex);
-	release_tty(tty, idx);
+	release_tty(tty, inode, idx);
 	mutex_unlock(&tty_mutex);
 
 	return 0;
@@ -2078,7 +2082,7 @@ retry_open:
 				tty = ERR_PTR(retval);
 			}
 		} else { /* Returns with the tty_lock held for now */
-			tty = tty_init_dev(driver, index);
+			tty = tty_init_dev(driver, inode, index);
 			mutex_unlock(&tty_mutex);
 		}
 
diff --git a/include/linux/tty.h b/include/linux/tty.h
index c7c5d3c..94c3983 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -506,7 +506,8 @@ extern struct tty_struct *alloc_tty_struct(struct tty_driver *driver, int idx);
 extern int tty_alloc_file(struct file *file);
 extern void tty_add_file(struct tty_struct *tty, struct file *file);
 extern void tty_free_file(struct file *file);
-extern struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx);
+extern struct tty_struct *tty_init_dev(struct tty_driver *driver,
+				       struct inode *inode, int idx);
 extern int tty_release(struct inode *inode, struct file *filp);
 extern void tty_init_termios(struct tty_struct *tty);
 extern int tty_standard_install(struct tty_driver *driver,
diff --git a/include/linux/tty_driver.h b/include/linux/tty_driver.h
index 1610524..c7aa71c 100644
--- a/include/linux/tty_driver.h
+++ b/include/linux/tty_driver.h
@@ -22,7 +22,7 @@
  *
  *	Optional method. Default behaviour is to use the ttys array
  *
- * void (*remove)(struct tty_driver *self, struct tty_struct *tty)
+ * void (*remove)(struct tty_driver *self, struct inode *inode, int idx)
  *
  *	Remove a closed tty from the tty driver internal tables. Used in
  *	conjunction with lookup and remove methods.
@@ -252,7 +252,7 @@ struct tty_operations {
 	struct tty_struct * (*lookup)(struct tty_driver *driver,
 			struct inode *inode, int idx);
 	int  (*install)(struct tty_driver *driver, struct tty_struct *tty);
-	void (*remove)(struct tty_driver *driver, struct tty_struct *tty);
+	void (*remove)(struct tty_driver *driver, struct inode *inode, int idx);
 	int  (*open)(struct tty_struct * tty, struct file * filp);
 	void (*close)(struct tty_struct * tty, struct file * filp);
 	void (*shutdown)(struct tty_struct *tty);
-- 
2.6.3

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