From c874cde1a49694c863acf7921da32769187f4fc9 Mon Sep 17 00:00:00 2001 From: Johan Hovold Date: Thu, 12 Jan 2017 14:56:11 +0100 Subject: [PATCH] USB: serial: ftdi_sio: fix modem-status error handling commit 427c3a95e3e29e65f59d99aaf320d7506f3eed57 upstream. Make sure to detect short responses when fetching the modem status in order to avoid parsing uninitialised buffer data and having bits of it leak to user space. Note that we still allow for short 1-byte responses. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reviewed-by: Greg Kroah-Hartman Signed-off-by: Johan Hovold [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings --- drivers/usb/serial/ftdi_sio.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c index dbc437c61fb5..43e1c392817c 100644 --- a/drivers/usb/serial/ftdi_sio.c +++ b/drivers/usb/serial/ftdi_sio.c @@ -2542,8 +2542,13 @@ static int ftdi_tiocmget(struct tty_struct *tty) FTDI_SIO_GET_MODEM_STATUS_REQUEST_TYPE, 0, priv->interface, buf, len, WDR_TIMEOUT); - if (ret < 0) + + /* NOTE: We allow short responses and handle that below. */ + if (ret < 1) { + if (ret >= 0) + ret = -EIO; goto out; + } ret = (buf[0] & FTDI_SIO_DSR_MASK ? TIOCM_DSR : 0) | (buf[0] & FTDI_SIO_CTS_MASK ? TIOCM_CTS : 0) | -- 2.39.2