Input: joydev - validate axis/button maps before clobbering current ones

Up to now axis and button map validation was done after the user-supplied
values were copied over the driver's map. This patch copies the
user-supplied values into temporary buffers and validated them before
overwriting the driver's permanent maps.

Also change JSIOCGBTNMAP and JSIOCGAXMAP to return number of bytes returned
to userspace instead of 0.
Signed-off-by: Stephen Kitt <steve@sk2.org>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

drivers/input/joydev.c

@@ -452,6 +452,76 @@ static unsigned int joydev_poll(struct file *file, poll_table *wait)
 		(joydev->exist ?  0 : (POLLHUP | POLLERR));
 }
 
+static int joydev_handle_JSIOCSAXMAP(struct joydev *joydev,
+				     void __user *argp, size_t len)
+{
+	__u8 *abspam;
+	int i;
+	int retval = 0;
+
+	len = min(len, sizeof(joydev->abspam));
+
+	/* Validate the map. */
+	abspam = kmalloc(len, GFP_KERNEL);
+	if (!abspam)
+		return -ENOMEM;
+
+	if (copy_from_user(abspam, argp, len)) {
+		retval = -EFAULT;
+		goto out;
+	}
+
+	for (i = 0; i < joydev->nabs; i++) {
+		if (abspam[i] > ABS_MAX) {
+			retval = -EINVAL;
+			goto out;
+		}
+	}
+
+	memcpy(joydev->abspam, abspam, len);
+
+ out:
+	kfree(abspam);
+	return retval;
+}
+
+static int joydev_handle_JSIOCSBTNMAP(struct joydev *joydev,
+				      void __user *argp, size_t len)
+{
+	__u16 *keypam;
+	int i;
+	int retval = 0;
+
+	len = min(len, sizeof(joydev->keypam));
+
+	/* Validate the map. */
+	keypam = kmalloc(len, GFP_KERNEL);
+	if (!keypam)
+		return -ENOMEM;
+
+	if (copy_from_user(keypam, argp, len)) {
+		retval = -EFAULT;
+		goto out;
+	}
+
+	for (i = 0; i < joydev->nkey; i++) {
+		if (keypam[i] > KEY_MAX || keypam[i] < BTN_MISC) {
+			retval = -EINVAL;
+			goto out;
+		}
+	}
+
+	memcpy(joydev->keypam, keypam, len);
+
+	for (i = 0; i < joydev->nkey; i++)
+		joydev->keymap[keypam[i] - BTN_MISC] = i;
+
+ out:
+	kfree(keypam);
+	return retval;
+}
+
+
 static int joydev_ioctl_common(struct joydev *joydev,
 				unsigned int cmd, void __user *argp)
 {
@@ -512,46 +582,18 @@ static int joydev_ioctl_common(struct joydev *joydev,
 	switch (cmd & ~IOCSIZE_MASK) {
 
 	case (JSIOCSAXMAP & ~IOCSIZE_MASK):
-		len = min_t(size_t, _IOC_SIZE(cmd), sizeof(joydev->abspam));
-		/*
-		 * FIXME: we should not copy into our axis map before
-		 * validating the data.
-		 */
-		if (copy_from_user(joydev->abspam, argp, len))
-			return -EFAULT;
-
-		for (i = 0; i < joydev->nabs; i++) {
-			if (joydev->abspam[i] > ABS_MAX)
-				return -EINVAL;
-			joydev->absmap[joydev->abspam[i]] = i;
-		}
-		return 0;
+		return joydev_handle_JSIOCSAXMAP(joydev, argp, _IOC_SIZE(cmd));
 
 	case (JSIOCGAXMAP & ~IOCSIZE_MASK):
 		len = min_t(size_t, _IOC_SIZE(cmd), sizeof(joydev->abspam));
-		return copy_to_user(argp, joydev->abspam, len) ? -EFAULT : 0;
+		return copy_to_user(argp, joydev->abspam, len) ? -EFAULT : len;
 
 	case (JSIOCSBTNMAP & ~IOCSIZE_MASK):
-		len = min_t(size_t, _IOC_SIZE(cmd), sizeof(joydev->keypam));
-		/*
-		 * FIXME: we should not copy into our keymap before
-		 * validating the data.
-		 */
-		if (copy_from_user(joydev->keypam, argp, len))
-			return -EFAULT;
-
-		for (i = 0; i < joydev->nkey; i++) {
-			if (joydev->keypam[i] > KEY_MAX ||
-			    joydev->keypam[i] < BTN_MISC)
-				return -EINVAL;
-			joydev->keymap[joydev->keypam[i] - BTN_MISC] = i;
-		}
-
-		return 0;
+		return joydev_handle_JSIOCSBTNMAP(joydev, argp, _IOC_SIZE(cmd));
 
 	case (JSIOCGBTNMAP & ~IOCSIZE_MASK):
 		len = min_t(size_t, _IOC_SIZE(cmd), sizeof(joydev->keypam));
-		return copy_to_user(argp, joydev->keypam, len) ? -EFAULT : 0;
+		return copy_to_user(argp, joydev->keypam, len) ? -EFAULT : len;
 
 	case JSIOCGNAME(0):
 		name = dev->name;