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 Signed-off-by: Johan Hovold johan@kernel.org --- drivers/usb/serial/option.c | 23 +++++++++++++++++++++-- 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/serial/option.c b/drivers/usb/serial/option.c index 2a3bfd6f867e..c5908c4f2046 100644 --- a/drivers/usb/serial/option.c +++ b/drivers/usb/serial/option.c @@ -561,6 +561,9 @@ static void option_instat_callback(struct urb *urb);

/* 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)

@@ -2089,6 +2092,14 @@ static struct usb_serial_driver * const serial_drivers[] = {

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) { @@ -2105,7 +2116,7 @@ static int option_probe(struct usb_serial *serial, * 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;

/* @@ -2121,6 +2132,14 @@ static int option_probe(struct usb_serial *serial, 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; @@ -2136,7 +2155,7 @@ static int option_attach(struct usb_serial *serial)

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)