[PATCH v2 4/6] USB: hub: fix non-SS hub-descriptor handling

[Johan Hovold <johan@kernel.org>]

Add missing sanity check on the non-SuperSpeed hub-descriptor length in
order to avoid parsing and leaking two bytes of uninitialised slab data
through sysfs removable-attributes (or a compound-device debug
statement).

Note that we only make sure that the DeviceRemovable field is always
present (and specifically ignore the unused PortPwrCtrlMask field) in
order to continue support any hubs with non-compliant descriptors. As a
further safeguard, the descriptor buffer is also cleared.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable <stable@vger.kernel.org>     # 2.6.12
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/usb/core/hub.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 3ff1e9f89f2d..f77a4ebde7d5 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -362,7 +362,8 @@ static void usb_set_lpm_parameters(struct usb_device *udev)
 }
 
 /* USB 2.0 spec Section 11.24.4.5 */
-static int get_hub_descriptor(struct usb_device *hdev, void *data)
+static int get_hub_descriptor(struct usb_device *hdev,
+		struct usb_hub_descriptor *desc)
 {
 	int i, ret, size;
 	unsigned dtype;
@@ -378,12 +379,16 @@ static int get_hub_descriptor(struct usb_device *hdev, void *data)
 	for (i = 0; i < 3; i++) {
 		ret = usb_control_msg(hdev, usb_rcvctrlpipe(hdev, 0),
 			USB_REQ_GET_DESCRIPTOR, USB_DIR_IN | USB_RT_HUB,
-			dtype << 8, 0, data, size,
+			dtype << 8, 0, desc, size,
 			USB_CTRL_GET_TIMEOUT);
 		if (hub_is_superspeed(hdev)) {
 			if (ret == size)
 				return ret;
-		} else if (ret >= (USB_DT_HUB_NONVAR_SIZE + 2)) {
+		} else if (ret >= USB_DT_HUB_NONVAR_SIZE + 2) {
+			/* Make sure we have the DeviceRemovable field. */
+			size = USB_DT_HUB_NONVAR_SIZE + desc->bNbrPorts / 8 + 1;
+			if (ret < size)
+				return -EMSGSIZE;
 			return ret;
 		}
 	}
@@ -1317,7 +1322,7 @@ static int hub_configure(struct usb_hub *hub,
 	}
 	mutex_init(&hub->status_mutex);
 
-	hub->descriptor = kmalloc(sizeof(*hub->descriptor), GFP_KERNEL);
+	hub->descriptor = kzalloc(sizeof(*hub->descriptor), GFP_KERNEL);
 	if (!hub->descriptor) {
 		ret = -ENOMEM;
 		goto fail;
-- 
2.13.0