From 27cfb3a53be46a54ec5e0bd04e51995b74c90343 Mon Sep 17 00:00:00 2001 From: Greg Kroah-Hartman Date: Sun, 20 Jan 2019 10:46:58 +0100 Subject: [PATCH] tty: Handle problem if line discipline does not have receive_buf 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 Cc: stable Signed-off-by: Greg Kroah-Hartman --- drivers/tty/tty_io.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index 23c6fd2..21ffcce 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -2189,7 +2189,8 @@ static int tiocsti(struct tty_struct *tty, char __user *p) 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; } -- 2.7.4