USB: whiteheat: Added bounds checking for bulk command response

This patch fixes a potential security issue in the whiteheat USB driver
which might allow a local attacker to cause kernel memory corrpution. This
is due to an unchecked memcpy into a fixed size buffer (of 64 bytes). On
EHCI and XHCI busses it's possible to craft responses greater than 64
bytes leading a buffer overflow.

Signed-off-by: James Forshaw <forshaw@google.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/serial/whiteheat.c b/drivers/usb/serial/whiteheat.c
index e62f2df..6c3734d 100644 (file)
--- a/drivers/usb/serial/whiteheat.c
+++ b/drivers/usb/serial/whiteheat.c
@@ -514,6 +514,10 @@ static void command_port_read_callback(struct urb *urb)
                dev_dbg(&urb->dev->dev, "%s - command_info is NULL, exiting.\n", __func__);
                return;
        }
+       if (!urb->actual_length) {
+               dev_dbg(&urb->dev->dev, "%s - empty response, exiting.\n", __func__);
+               return;
+       }
        if (status) {
                dev_dbg(&urb->dev->dev, "%s - nonzero urb status: %d\n", __func__, status);
                if (status != -ENOENT)
@@ -534,7 +538,8 @@ static void command_port_read_callback(struct urb *urb)
                /* These are unsolicited reports from the firmware, hence no
                   waiting command to wakeup */
                dev_dbg(&urb->dev->dev, "%s - event received\n", __func__);
-       } else if (data[0] == WHITEHEAT_GET_DTR_RTS) {
+       } else if ((data[0] == WHITEHEAT_GET_DTR_RTS) &&
+               (urb->actual_length - 1 <= sizeof(command_info->result_buffer))) {
                memcpy(command_info->result_buffer, &data[1],
                                                urb->actual_length - 1);
                command_info->command_finished = WHITEHEAT_CMD_COMPLETE;