From 7f22f6c935cda600660e623a411fe380015d28d9 Mon Sep 17 00:00:00 2001 From: Peter Hurley Date: Sat, 9 Jan 2016 21:13:45 -0800 Subject: [PATCH] tty: Retry failed reopen if tty teardown in-progress A small window exists where a tty reopen will observe the tty just prior to imminent teardown (tty->count == 0); in this case, open() returns EIO to userspace. Instead, retry the open after checking for signals and yielding; this interruptible retry loop allows teardown to commence and initialize a new tty on retry. Never retry the BSD master pty reopen; there is no guarantee the pty pair teardown is imminent since the slave file descriptors may remain open indefinitely. Signed-off-by: Peter Hurley Cc: stable # 4.4 Signed-off-by: Greg Kroah-Hartman --- drivers/tty/tty_io.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index 765935b144d6..a1b36bf545e8 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -1463,13 +1463,13 @@ static int tty_reopen(struct tty_struct *tty) { struct tty_driver *driver = tty->driver; - if (!tty->count) - return -EIO; - if (driver->type == TTY_DRIVER_TYPE_PTY && driver->subtype == PTY_TYPE_MASTER) return -EIO; + if (!tty->count) + return -EAGAIN; + if (test_bit(TTY_EXCLUSIVE, &tty->flags) && !capable(CAP_SYS_ADMIN)) return -EBUSY; @@ -2088,7 +2088,11 @@ retry_open: if (IS_ERR(tty)) { retval = PTR_ERR(tty); - goto err_file; + if (retval != -EAGAIN || signal_pending(current)) + goto err_file; + tty_free_file(filp); + schedule(); + goto retry_open; } tty_add_file(tty, filp);