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 my tty git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git
in the tty-linus branch.
The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)
The patch will hopefully also be merged in Linus's tree for the
next -rc kernel release.
If you have any questions about this process, please let me know.
>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
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>
Cc: stable <stable@xxxxxxxxxxxxxxx> # 4.4
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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);
--
2.7.0
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