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From:   Eric Biggers <ebiggers@kernel.org>
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jiri Slaby <jslaby@suse.com>
Cc:     linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com,
        Al Viro <viro@zeniv.linux.org.uk>
Subject: [PATCH v2 2/2] tty: fix compat TIOCGSERIAL checking wrong function ptr
Date:   Mon, 24 Feb 2020 10:20:44 -0800
Message-Id: <20200224182044.234553-3-ebiggers@kernel.org>
In-Reply-To: <20200224182044.234553-1-ebiggers@kernel.org>
References: <20200224181532.GA109047@gmail.com>
 <20200224182044.234553-1-ebiggers@kernel.org>
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From: Eric Biggers <ebiggers@google.com>

Commit 77654350306a ("take compat TIOC[SG]SERIAL treatment into
tty_compat_ioctl()") changed the compat version of TIOCGSERIAL to start
checking for the presence of the ->set_serial function pointer rather
than ->get_serial.  This appears to be a copy-and-paste error, since
->get_serial is the function pointer that is called as well as the
pointer that is checked by the non-compat version of TIOCGSERIAL.

Fix this by checking the correct function pointer.

Fixes: 77654350306a ("take compat TIOC[SG]SERIAL treatment into tty_compat_ioctl()")
Cc: <stable@vger.kernel.org> # v4.20+
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 drivers/tty/tty_io.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index db4a13bc855ed6..5a6f36b391d95d 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -2734,7 +2734,7 @@ static int compat_tty_tiocgserial(struct tty_struct *tty,
 	memset(&v, 0, sizeof(v));
 	memset(&v32, 0, sizeof(v32));
 
-	if (!tty->ops->set_serial)
+	if (!tty->ops->get_serial)
 		return -ENOTTY;
 	err = tty->ops->get_serial(tty, &v);
 	if (!err) {
-- 
2.25.0.265.gbab2e86ba0-goog