tty: Fix GPF in flush_to_ldisc(), part 2

Orabug: 23331050

[ Upstream commit f33798deecbd59a2955f40ac0ae2bc7dff54c069 ]

commit 9ce119f318ba ("tty: Fix GPF in flush_to_ldisc()") fixed a
GPF caused by a line discipline which does not define a receive_buf()
method.

However, the vt driver (and speakup driver also) pushes selection
data directly to the line discipline receive_buf() method via
tty_ldisc_receive_buf(). Fix the same problem in tty_ldisc_receive_buf().

Cc: <stable@vger.kernel.org>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
(cherry picked from commit 3beac2b0bffd8e977ef1d464dd424f22af965a96)

Signed-off-by: Dan Duval <dan.duval@oracle.com>

diff --git a/include/linux/tty.h b/include/linux/tty.h
index 9580c09afdbe613e9d189e35c9a6a17fac8d353b..5e704e26f9a2dc7a7c40573f9cfcea5909a4e2dd 100644 (file)
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -592,7 +592,7 @@ static inline int tty_ldisc_receive_buf(struct tty_ldisc *ld, unsigned char *p,
                count = ld->ops->receive_buf2(ld->tty, p, f, count);
        else {
                count = min_t(int, count, ld->tty->receive_room);
-               if (count)
+               if (count && ld->ops->receive_buf)
                        ld->ops->receive_buf(ld->tty, p, f, count);
        }
        return count;