[PATCH 4.4 15/65] tty: Handle problem if line discipline does not have receive_buf

Greg Kroah-Hartman
2019-02-04T10:39:53Z

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
@@ -2297,7 +2297,8 @@ static int tiocsti(struct tty_struct *tt
return -EFAULT;
tty_audit_tiocsti(tty, ch);
ld = tty_ldisc_ref_wait(tty);
- 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;
}