Patch "tty: Retry failed reopen if tty teardown in-progress" has been added to the 4.3-stable tree

This is a note to let you know that I've just added the patch titled

tty: Retry failed reopen if tty teardown in-progress

to the 4.3-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
tty-retry-failed-reopen-if-tty-teardown-in-progress.patch
and it can be found in the queue-4.3 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Peter Hurley <[email protected]>
Date: Sat, 9 Jan 2016 21:13:45 -0800
Subject: tty: Retry failed reopen if tty teardown in-progress

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.

---
 drivers/tty/tty_io.c |   12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

@@ -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;
 

@@ -2087,7 +2087,11 @@ 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);

Patches currently in stable-queue which might be from [email protected] are

queue-4.3/n_tty-fix-unsafe-reference-to-other-ldisc.patch queue-4.3/tty-fix-unsafe-ldisc-reference-via-ioctl-tiocgetd.patch queue-4.3/n_tty-fix-poll-after-buffer-limited-eof-push-read.patch queue-4.3/tty-fix-gpf-in-flush_to_ldisc.patch queue-4.3/tty-retry-failed-reopen-if-tty-teardown-in-progress.patch