4.4-stable review patch. If anyone has any objections, please let me know.
------------------ From: Peter Hurley <[email protected]> commit 7f22f6c935cda600660e623a411fe380015d28d9 upstream. 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 <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- drivers/tty/tty_io.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -1462,13 +1462,13 @@ static int tty_reopen(struct tty_struct { 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; @@ -2092,7 +2092,11 @@ 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);
