From 24d406a6bf736f7aebdc8fa0f0ec86e0890c6d24 Mon Sep 17 00:00:00 2001 From: Jiri Slaby Date: Wed, 10 Aug 2011 14:59:28 +0200 Subject: TTY: pty, fix pty counting tty_operations->remove is normally called like: queue_release_one_tty ->tty_shutdown ->tty_driver_remove_tty ->tty_operations->remove However tty_shutdown() is called from queue_release_one_tty() only if tty_operations->shutdown is NULL. But for pty, it is not. pty_unix98_shutdown() is used there as ->shutdown. So tty_operations->remove of pty (i.e. pty_unix98_remove()) is never called. This results in invalid pty_count. I.e. what can be seen in /proc/sys/kernel/pty/nr. I see this was already reported at: https://lkml.org/lkml/2009/11/5/370 But it was not fixed since then. This patch is kind of a hackish way. The problem lies in ->install. We allocate there another tty (so-called tty->link). So ->install is called once, but ->remove twice, for both tty and tty->link. The fix here is to count both tty and tty->link and divide the count by 2 for user. And to have ->remove called, let's make tty_driver_remove_tty() global and call that from pty_unix98_shutdown() (tty_operations->shutdown). While at it, let's document that when ->shutdown is defined, tty_shutdown() is not called. Signed-off-by: Jiri Slaby Cc: Alan Cox Cc: "H. Peter Anvin" Cc: stable Signed-off-by: Greg Kroah-Hartman --- include/linux/tty.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux/tty.h') diff --git a/include/linux/tty.h b/include/linux/tty.h index 44bc0c5617e1..5f2ede82b3d6 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -421,6 +421,8 @@ extern void tty_driver_flush_buffer(struct tty_struct *tty); extern void tty_throttle(struct tty_struct *tty); extern void tty_unthrottle(struct tty_struct *tty); extern int tty_do_resize(struct tty_struct *tty, struct winsize *ws); +extern void tty_driver_remove_tty(struct tty_driver *driver, + struct tty_struct *tty); extern void tty_shutdown(struct tty_struct *tty); extern void tty_free_termios(struct tty_struct *tty); extern int is_current_pgrp_orphaned(void); -- cgit v1.2.3