usb: core: add option of only authorizing internal devices

On Chrome OS we want to use USBguard to potentially limit access to USB
devices based on policy. We however to do not want to wait for userspace to
come up before initializing fixed USB devices to not regress our boot
times.

This patch adds option to instruct the kernel to only authorize devices
connected to the internal ports. Previously we could either authorize
all or none (or, by default, we'd only authorize wired devices).

The behavior is controlled via usbcore.authorized_default command line
option.

Signed-off-by: Dmitry Torokhov <dtor@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 57 insertions, 27 deletions

diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index 86f39e44f98a..3b6e3e25f59e 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -373,13 +373,19 @@ static const u8 ss_rh_config_descriptor[] = {
  * -1 is authorized for all devices except wireless (old behaviour)
  * 0 is unauthorized for all devices
  * 1 is authorized for all devices
+ * 2 is authorized for internal devices
  */
-static int authorized_default = -1;
+#define USB_AUTHORIZE_WIRED	-1
+#define USB_AUTHORIZE_NONE	0
+#define USB_AUTHORIZE_ALL	1
+#define USB_AUTHORIZE_INTERNAL	2
+
+static int authorized_default = USB_AUTHORIZE_WIRED;
 module_param(authorized_default, int, S_IRUGO|S_IWUSR);
 MODULE_PARM_DESC(authorized_default,
 		"Default USB device authorization: 0 is not authorized, 1 is "
-		"authorized, -1 is authorized except for wireless USB (default, "
-		"old behaviour");
+		"authorized, 2 is authorized for internal devices, -1 is "
+		"authorized except for wireless USB (default, old behaviour");
 /*-------------------------------------------------------------------------*/
 
 /**
@@ -884,7 +890,7 @@ static ssize_t authorized_default_show(struct device *dev,
 	struct usb_hcd *hcd;
 
 	hcd = bus_to_hcd(usb_bus);
-	return snprintf(buf, PAGE_SIZE, "%u\n", !!HCD_DEV_AUTHORIZED(hcd));
+	return snprintf(buf, PAGE_SIZE, "%u\n", hcd->dev_policy);
 }
 
 static ssize_t authorized_default_store(struct device *dev,
@@ -900,11 +906,8 @@ static ssize_t authorized_default_store(struct device *dev,
 	hcd = bus_to_hcd(usb_bus);
 	result = sscanf(buf, "%u\n", &val);
 	if (result == 1) {
-		if (val)
-			set_bit(HCD_FLAG_DEV_AUTHORIZED, &hcd->flags);
-		else
-			clear_bit(HCD_FLAG_DEV_AUTHORIZED, &hcd->flags);
-
+		hcd->dev_policy = val <= USB_DEVICE_AUTHORIZE_INTERNAL ?
+			val : USB_DEVICE_AUTHORIZE_ALL;
 		result = size;
 	} else {
 		result = -EINVAL;
@@ -2748,18 +2751,26 @@ int usb_add_hcd(struct usb_hcd *hcd,
 
 	dev_info(hcd->self.controller, "%s\n", hcd->product_desc);
 
-	/* Keep old behaviour if authorized_default is not in [0, 1]. */
-	if (authorized_default < 0 || authorized_default > 1) {
-		if (hcd->wireless)
-			clear_bit(HCD_FLAG_DEV_AUTHORIZED, &hcd->flags);
-		else
-			set_bit(HCD_FLAG_DEV_AUTHORIZED, &hcd->flags);
-	} else {
-		if (authorized_default)
-			set_bit(HCD_FLAG_DEV_AUTHORIZED, &hcd->flags);
-		else
-			clear_bit(HCD_FLAG_DEV_AUTHORIZED, &hcd->flags);
+	switch (authorized_default) {
+	case USB_AUTHORIZE_NONE:
+		hcd->dev_policy = USB_DEVICE_AUTHORIZE_NONE;
+		break;
+
+	case USB_AUTHORIZE_ALL:
+		hcd->dev_policy = USB_DEVICE_AUTHORIZE_ALL;
+		break;
+
+	case USB_AUTHORIZE_INTERNAL:
+		hcd->dev_policy = USB_DEVICE_AUTHORIZE_INTERNAL;
+		break;
+
+	case USB_AUTHORIZE_WIRED:
+	default:
+		hcd->dev_policy = hcd->wireless ?
+			USB_DEVICE_AUTHORIZE_NONE : USB_DEVICE_AUTHORIZE_ALL;
+		break;
 	}
+
 	set_bit(HCD_FLAG_HW_ACCESSIBLE, &hcd->flags);
 
 	/* per default all interfaces are authorized */
diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
index 4ebfbd737905..9b5852e313f5 100644
--- a/drivers/usb/core/usb.c
+++ b/drivers/usb/core/usb.c
@@ -46,8 +46,7 @@
 #include <linux/mm.h>
 #include <linux/dma-mapping.h>
 
-#include "usb.h"
-
+#include "hub.h"
 
 const char *usbcore_name = "usbcore";
 
@@ -536,6 +535,27 @@ static unsigned usb_bus_is_wusb(struct usb_bus *bus)
 	return hcd->wireless;
 }
 
+static bool usb_dev_authorized(struct usb_device *dev, struct usb_hcd *hcd)
+{
+	struct usb_hub *hub;
+
+	if (!dev->parent)
+		return true; /* Root hub always ok [and always wired] */
+
+	switch (hcd->dev_policy) {
+	case USB_DEVICE_AUTHORIZE_NONE:
+	default:
+		return false;
+
+	case USB_DEVICE_AUTHORIZE_ALL:
+		return true;
+
+	case USB_DEVICE_AUTHORIZE_INTERNAL:
+		hub = usb_hub_to_struct_hub(dev->parent);
+		return hub->ports[dev->portnum - 1]->connect_type ==
+				USB_PORT_CONNECT_TYPE_HARD_WIRED;
+	}
+}
 
 /**
  * usb_alloc_dev - usb device constructor (usbcore-internal)
@@ -663,12 +683,11 @@ struct usb_device *usb_alloc_dev(struct usb_device *parent,
 	dev->connect_time = jiffies;
 	dev->active_duration = -jiffies;
 #endif
-	if (root_hub)	/* Root hub always ok [and always wired] */
-		dev->authorized = 1;
-	else {
-		dev->authorized = !!HCD_DEV_AUTHORIZED(usb_hcd);
+
+	dev->authorized = usb_dev_authorized(dev, usb_hcd);
+	if (!root_hub)
 		dev->wusb = usb_bus_is_wusb(bus) ? 1 : 0;
-	}
+
 	return dev;
 }
 EXPORT_SYMBOL_GPL(usb_alloc_dev);