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 4.4-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-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 7f22f6c935cda600660e623a411fe380015d28d9 Mon Sep 17 00:00:00 2001
From: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
Date: Sat, 9 Jan 2016 21:13:45 -0800
Subject: tty: Retry failed reopen if tty teardown in-progress
From: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
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 <peter@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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);
Patches currently in stable-queue which might be from peter@xxxxxxxxxxxxxxxxxx are
queue-4.4/tty-wait-interruptibly-for-tty-lock-on-reopen.patch
queue-4.4/n_tty-fix-unsafe-reference-to-other-ldisc.patch
queue-4.4/tty-fix-unsafe-ldisc-reference-via-ioctl-tiocgetd.patch
queue-4.4/tty-retry-failed-reopen-if-tty-teardown-in-progress.patch
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