Input: joydev - decouple axis and button map ioctls from input constants

The KEY_MAX change in 2.6.28 changed the values of the JSIOCSBTNMAP and
JSIOCGBTNMAP constants; software compiled with the old values no longer
works with kernels following 2.6.28, because the ioctl switch statement
no longer matches the values given by the software. This patch handles
these ioctls independently of the length of data specified, and applies the
same treatment to JSIOCSAXMAP and JSIOCGAXMAP which currently depend on
ABS_MAX.
Signed-off-by: Stephen Kitt <steve@sk2.org>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

drivers/input/joydev.c

@@ -456,8 +456,11 @@ static int joydev_ioctl_common(struct joydev *joydev,
 				unsigned int cmd, void __user *argp)
 {
 	struct input_dev *dev = joydev->handle.dev;
+	size_t len;
 	int i, j;
+	const char *name;
 
+	/* Process fixed-sized commands. */
 	switch (cmd) {
 
 	case JS_SET_CAL:
@@ -499,9 +502,22 @@ static int joydev_ioctl_common(struct joydev *joydev,
 		return copy_to_user(argp, joydev->corr,
 			sizeof(joydev->corr[0]) * joydev->nabs) ? -EFAULT : 0;
 
-	case JSIOCSAXMAP:
-		if (copy_from_user(joydev->abspam, argp,
-				   sizeof(__u8) * (ABS_MAX + 1)))
+	}
+
+	/*
+	 * Process variable-sized commands (the axis and button map commands
+	 * are considered variable-sized to decouple them from the values of
+	 * ABS_MAX and KEY_MAX).
+	 */
+	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++) {
@@ -511,13 +527,17 @@ static int joydev_ioctl_common(struct joydev *joydev,
 		}
 		return 0;
 
-	case JSIOCGAXMAP:
-		return copy_to_user(argp, joydev->abspam,
-			sizeof(__u8) * (ABS_MAX + 1)) ? -EFAULT : 0;
-
-	case JSIOCSBTNMAP:
-		if (copy_from_user(joydev->keypam, argp,
-				   sizeof(__u16) * (KEY_MAX - BTN_MISC + 1)))
+	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;
+
+	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++) {
@@ -529,25 +549,19 @@ static int joydev_ioctl_common(struct joydev *joydev,
 
 		return 0;
 
-	case JSIOCGBTNMAP:
-		return copy_to_user(argp, joydev->keypam,
-			sizeof(__u16) * (KEY_MAX - BTN_MISC + 1)) ? -EFAULT : 0;
+	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;
 
-	default:
-		if ((cmd & ~IOCSIZE_MASK) == JSIOCGNAME(0)) {
-			int len;
-			const char *name = dev->name;
-
-			if (!name)
-				return 0;
-			len = strlen(name) + 1;
-			if (len > _IOC_SIZE(cmd))
-				len = _IOC_SIZE(cmd);
-			if (copy_to_user(argp, name, len))
-				return -EFAULT;
-			return len;
-		}
+	case JSIOCGNAME(0):
+		name = dev->name;
+		if (!name)
+			return 0;
+
+		len = min_t(size_t, _IOC_SIZE(cmd), strlen(name) + 1);
+		return copy_to_user(argp, name, len) ? -EFAULT : len;
 	}
+
 	return -EINVAL;
 }