[PATCH 5.10 06/40] USB: serial: option: add interface-number sanity check to flag handling

Greg Kroah-Hartman
2020-12-23T15:35:17Z

From: Johan Hovold <johan@kernel.org>

commit a251963f76fa0226d0fdf0c4f989496f18d9ae7f upstream.

Add an interface-number sanity check before testing the device flags to
avoid relying on undefined behaviour when left shifting in case a device
uses an interface number greater than or equal to BITS_PER_LONG (i.e. 64
or 32).

Reported-by: syzbot+8881b478dad0a7971f79@syzkaller.appspotmail.com
Fixes: c3a65808f04a ("USB: serial: option: reimplement interface masking")
Cc: stable@vger.kernel.org
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/usb/serial/option.c | 23 +++++++++++++++++++++--
1 file changed, 21 insertions(+), 2 deletions(-)

--- a/drivers/usb/serial/option.c
+++ b/drivers/usb/serial/option.c
@@ -563,6 +563,9 @@ static void option_instat_callback(struc

/* Device flags */

+/* Highest interface number which can be used with NCTRL() and RSVD() */
+#define FLAG_IFNUM_MAX 7
+
/* Interface does not support modem-control requests */
#define NCTRL(ifnum) ((BIT(ifnum) & 0xff) << 8)

@@ -2101,6 +2104,14 @@ static struct usb_serial_driver * const

module_usb_serial_driver(serial_drivers, option_ids);

+static bool iface_is_reserved(unsigned long device_flags, u8 ifnum)
+{
+ if (ifnum > FLAG_IFNUM_MAX)
+ return false;
+
+ return device_flags & RSVD(ifnum);
+}
+
static int option_probe(struct usb_serial *serial,
const struct usb_device_id *id)
{
@@ -2117,7 +2128,7 @@ static int option_probe(struct usb_seria
* the same class/subclass/protocol as the serial interfaces. Look at
* the Windows driver .INF files for reserved interface numbers.
*/
- if (device_flags & RSVD(iface_desc->bInterfaceNumber))
+ if (iface_is_reserved(device_flags, iface_desc->bInterfaceNumber))
return -ENODEV;

/*
@@ -2133,6 +2144,14 @@ static int option_probe(struct usb_seria
return 0;
}

+static bool iface_no_modem_control(unsigned long device_flags, u8 ifnum)
+{
+ if (ifnum > FLAG_IFNUM_MAX)
+ return false;
+
+ return device_flags & NCTRL(ifnum);
+}
+
static int option_attach(struct usb_serial *serial)
{
struct usb_interface_descriptor *iface_desc;
@@ -2148,7 +2167,7 @@ static int option_attach(struct usb_seri

iface_desc = &serial->interface->cur_altsetting->desc;

- if (!(device_flags & NCTRL(iface_desc->bInterfaceNumber)))
+ if (!iface_no_modem_control(device_flags, iface_desc->bInterfaceNumber))
data->use_send_setup = 1;

if (device_flags & ZLP)