4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Greg Kroah-Hartman gregkh@linuxfoundation.org
commit 27cfb3a53be46a54ec5e0bd04e51995b74c90343 upstream.
Some tty line disciplines do not have a receive buf callback, so properly check for that before calling it. If they do not have this callback, just eat the character quietly, as we can't fail this call.
Reported-by: Jann Horn jannh@google.com Cc: stable stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/tty/tty_io.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -2324,7 +2324,8 @@ static int tiocsti(struct tty_struct *tt ld = tty_ldisc_ref_wait(tty); if (!ld) return -EIO; - ld->ops->receive_buf(tty, &ch, &mbz, 1); + if (ld->ops->receive_buf) + ld->ops->receive_buf(tty, &ch, &mbz, 1); tty_ldisc_deref(ld); return 0; }