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| author | Peter Hurley <peter@hurleysoftware.com> | 2015-11-11 08:03:54 -0500 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-12-09 14:31:25 -0500 |
| commit | 0163804569a78f87cf47cf5a0891c7e829bd101c (patch) | |
| tree | b88364bb8b77a8aeea10187f57bd24f3db047978 | |
| parent | b7861b3137c40241cc299345a47be7f7d1efae10 (diff) | |
| download | lwn-0163804569a78f87cf47cf5a0891c7e829bd101c.tar.gz lwn-0163804569a78f87cf47cf5a0891c7e829bd101c.zip | |
tty: Fix tty_send_xchar() lock order inversion
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@google.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/tty/tty_io.c | 4 | ||||
| -rw-r--r-- | 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 774df354af55..1aa028638120 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -1279,18 +1279,22 @@ 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 5232fb60b0b1..043e332e7423 100644 --- a/drivers/tty/tty_ioctl.c +++ b/drivers/tty/tty_ioctl.c @@ -1142,16 +1142,12 @@ 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; |