[PATCH 3.16 017/136] USB: serial: keyspan: fix NULL-derefs on open() and write()

Ben Hutchings
2019-12-17T00:51:45Z

From: Johan Hovold <johan@kernel.org>

commit 7d7e21fafdbc7fcf0854b877bd0975b487ed2717 upstream.

Fix NULL-pointer dereferences on open() and write() which can be
triggered by a malicious USB device.

The current URB allocation helper would fail to initialise the newly
allocated URB if the device has unexpected endpoint descriptors,
something which could lead NULL-pointer dereferences in a number of
open() and write() paths when accessing the URB. For example:

BUG: kernel NULL pointer dereference, address: 0000000000000000
...
RIP: 0010:usb_clear_halt+0x11/0xc0
...
Call Trace:
? tty_port_open+0x4d/0xd0
keyspan_open+0x70/0x160 [keyspan]
serial_port_activate+0x5b/0x80 [usbserial]
tty_port_open+0x7b/0xd0
? check_tty_count+0x43/0xa0
tty_open+0xf1/0x490

BUG: kernel NULL pointer dereference, address: 0000000000000000
...
RIP: 0010:keyspan_write+0x14e/0x1f3 [keyspan]
...
Call Trace:
serial_write+0x43/0xa0 [usbserial]
n_tty_write+0x1af/0x4f0
? do_wait_intr_irq+0x80/0x80
? process_echoes+0x60/0x60
tty_write+0x13f/0x2f0

BUG: kernel NULL pointer dereference, address: 0000000000000000
...
RIP: 0010:keyspan_usa26_send_setup+0x298/0x305 [keyspan]
...
Call Trace:
keyspan_open+0x10f/0x160 [keyspan]
serial_port_activate+0x5b/0x80 [usbserial]
tty_port_open+0x7b/0xd0
? check_tty_count+0x43/0xa0
tty_open+0xf1/0x490

Fixes: fdcba53e2d58 ("fix for bugzilla #7544 (keyspan USB-to-serial converter)")
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/usb/serial/keyspan.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/usb/serial/keyspan.c
+++ b/drivers/usb/serial/keyspan.c
@@ -1249,8 +1249,8 @@ static struct urb *keyspan_setup_urb(str

ep_desc = find_ep(serial, endpoint);
if (!ep_desc) {
- /* leak the urb, something's wrong and the callers don't care */
- return urb;
+ usb_free_urb(urb);
+ return NULL;
}
if (usb_endpoint_xfer_int(ep_desc)) {
ep_type_name = "INT";