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From 19e08b371b6795e009f09cdcf30f76ad0f1db037 Mon Sep 17 00:00:00 2001
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: Sun, 20 Jan 2019 10:46:58 +0100
Subject: [PATCH 08/11] 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 <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
@@ -2189,7 +2189,8 @@ 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;
}
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