This is a note to let you know that I've just added the patch titled
tty: Fix tty_send_xchar() lock order inversion
to the 4.2-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-fix-tty_send_xchar-lock-order-inversion.patch
and it can be found in the queue-4.2 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From ee0c1a65cf95230d5eb3d9de94fd2ead9a428c67 Mon Sep 17 00:00:00 2001
From: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
Date: Wed, 11 Nov 2015 08:03:54 -0500
Subject: tty: Fix tty_send_xchar() lock order inversion
From: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
commit ee0c1a65cf95230d5eb3d9de94fd2ead9a428c67 upstream.
The correct lock order is atomic_write_lock => termios_rwsem, as
established by tty_write() => n_tty_write().
Fixes: c274f6ef1c666 ("tty: Hold termios_rwsem for tcflow(TCIxxx)")
Reported-and-Tested-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Signed-off-by: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/tty/tty_io.c | 4 ++++
drivers/tty/tty_ioctl.c | 4 ----
2 files changed, 4 insertions(+), 4 deletions(-)
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -1279,18 +1279,22 @@ int tty_send_xchar(struct tty_struct *tt
int was_stopped = tty->stopped;
if (tty->ops->send_xchar) {
+ down_read(&tty->termios_rwsem);
tty->ops->send_xchar(tty, ch);
+ up_read(&tty->termios_rwsem);
return 0;
}
if (tty_write_lock(tty, 0) < 0)
return -ERESTARTSYS;
+ down_read(&tty->termios_rwsem);
if (was_stopped)
start_tty(tty);
tty->ops->write(tty, &ch, 1);
if (was_stopped)
stop_tty(tty);
+ up_read(&tty->termios_rwsem);
tty_write_unlock(tty);
return 0;
}
--- a/drivers/tty/tty_ioctl.c
+++ b/drivers/tty/tty_ioctl.c
@@ -1142,16 +1142,12 @@ int n_tty_ioctl_helper(struct tty_struct
spin_unlock_irq(&tty->flow_lock);
break;
case TCIOFF:
- down_read(&tty->termios_rwsem);
if (STOP_CHAR(tty) != __DISABLED_CHAR)
retval = tty_send_xchar(tty, STOP_CHAR(tty));
- up_read(&tty->termios_rwsem);
break;
case TCION:
- down_read(&tty->termios_rwsem);
if (START_CHAR(tty) != __DISABLED_CHAR)
retval = tty_send_xchar(tty, START_CHAR(tty));
- up_read(&tty->termios_rwsem);
break;
default:
return -EINVAL;
Patches currently in stable-queue which might be from peter@xxxxxxxxxxxxxxxxxx are
queue-4.2/tty-fix-tty_send_xchar-lock-order-inversion.patch
queue-4.2/tty-audit-fix-audit-source.patch
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