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 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 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
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>
Cc: <stable@xxxxxxxxxxxxxxx> # v3.18+
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(-)
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 0c41dbcb90b8..bcc8e1e8bb72 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -1282,18 +1282,22 @@ int tty_send_xchar(struct tty_struct *tty, char ch)
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;
}
diff --git a/drivers/tty/tty_ioctl.c b/drivers/tty/tty_ioctl.c
index 9c5aebfe7053..1445dd39aa62 100644
--- a/drivers/tty/tty_ioctl.c
+++ b/drivers/tty/tty_ioctl.c
@@ -1147,16 +1147,12 @@ int n_tty_ioctl_helper(struct tty_struct *tty, struct file *file,
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;
--
2.6.2
--
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