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authorPeter Hurley <peter@hurleysoftware.com>2015-11-11 08:03:54 -0500
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2015-12-09 14:03:27 -0500
commitff4fcbdf43bc4ae760ef1e7782e233156ed90a75 (patch)
tree0f1ea82bf4026196484f9bc30a7bd072800c0368
parent8d0fe5721d2725e58429a9b54149a20f9f590451 (diff)
downloadlinux-linaro-stable-ff4fcbdf43bc4ae760ef1e7782e233156ed90a75.tar.gz
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.c4
-rw-r--r--drivers/tty/tty_ioctl.c4
2 files changed, 4 insertions, 4 deletions
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 21837f14a403..5a5c1ab5a375 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -1287,18 +1287,22 @@ 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 8e53fe469664..7bbf86b94716 100644
--- a/drivers/tty/tty_ioctl.c
+++ b/drivers/tty/tty_ioctl.c
@@ -1144,16 +1144,12 @@ 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;