[PATCH] USB: usbfs: Don't leak uninitialized data

This patch fixes an information leak in the usbfs snoop facility:
uninitialized data from __get_free_page can be returned to userspace and
written to the system log.  It also improves the snoop output by printing
the wLength value.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/usb/core/devio.c

@@ -569,8 +569,11 @@ static int proc_control(struct dev_state *ps, void __user *arg)
 			free_page((unsigned long)tbuf);
 			return -EINVAL;
 		}
-		snoop(&dev->dev, "control read: bRequest=%02x bRrequestType=%02x wValue=%04x wIndex=%04x\n", 
-			ctrl.bRequest, ctrl.bRequestType, ctrl.wValue, ctrl.wIndex);
+		snoop(&dev->dev, "control read: bRequest=%02x "
+				"bRrequestType=%02x wValue=%04x "
+				"wIndex=%04x wLength=%04x\n",
+			ctrl.bRequest, ctrl.bRequestType, ctrl.wValue,
+				ctrl.wIndex, ctrl.wLength);
 
 		usb_unlock_device(dev);
 		i = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0), ctrl.bRequest, ctrl.bRequestType,
@@ -579,11 +582,11 @@ static int proc_control(struct dev_state *ps, void __user *arg)
 		if ((i > 0) && ctrl.wLength) {
 			if (usbfs_snoop) {
 				dev_info(&dev->dev, "control read: data ");
-				for (j = 0; j < ctrl.wLength; ++j)
+				for (j = 0; j < i; ++j)
 					printk ("%02x ", (unsigned char)(tbuf)[j]);
 				printk("\n");
 			}
-			if (copy_to_user(ctrl.data, tbuf, ctrl.wLength)) {
+			if (copy_to_user(ctrl.data, tbuf, i)) {
 				free_page((unsigned long)tbuf);
 				return -EFAULT;
 			}
@@ -595,8 +598,11 @@ static int proc_control(struct dev_state *ps, void __user *arg)
 				return -EFAULT;
 			}
 		}
-		snoop(&dev->dev, "control write: bRequest=%02x bRrequestType=%02x wValue=%04x wIndex=%04x\n", 
-			ctrl.bRequest, ctrl.bRequestType, ctrl.wValue, ctrl.wIndex);
+		snoop(&dev->dev, "control write: bRequest=%02x "
+				"bRrequestType=%02x wValue=%04x "
+				"wIndex=%04x wLength=%04x\n",
+			ctrl.bRequest, ctrl.bRequestType, ctrl.wValue,
+				ctrl.wIndex, ctrl.wLength);
 		if (usbfs_snoop) {
 			dev_info(&dev->dev, "control write: data: ");
 			for (j = 0; j < ctrl.wLength; ++j)