uvc_v4l2: Simplify compat ioctl implementation

The uvc compat ioctl implementation seems to have copied user data
for no good reason.  Remove a bunch of copies.
Signed-off-by: Andy Lutomirski <luto@kernel.org>

drivers/media/usb/uvc/uvc_v4l2.c

@@ -1274,8 +1274,6 @@ struct uvc_xu_control_mapping32 {
 static int uvc_v4l2_get_xu_mapping(struct uvc_xu_control_mapping *kp,
 			const struct uvc_xu_control_mapping32 __user *up)
 {
-	struct uvc_menu_info __user *umenus;
-	struct uvc_menu_info __user *kmenus;
 	compat_caddr_t p;
 
 	if (!access_ok(VERIFY_READ, up, sizeof(*up)) ||
@@ -1292,17 +1290,7 @@ static int uvc_v4l2_get_xu_mapping(struct uvc_xu_control_mapping *kp,
 
 	if (__get_user(p, &up->menu_info))
 		return -EFAULT;
-	umenus = compat_ptr(p);
-	if (!access_ok(VERIFY_READ, umenus, kp->menu_count * sizeof(*umenus)))
-		return -EFAULT;
-
-	kmenus = compat_alloc_user_space(kp->menu_count * sizeof(*kmenus));
-	if (kmenus == NULL)
-		return -EFAULT;
-	kp->menu_info = kmenus;
-
-	if (copy_in_user(kmenus, umenus, kp->menu_count * sizeof(*umenus)))
-		return -EFAULT;
+	kp->menu_info = compat_ptr(p);
 
 	return 0;
 }
@@ -1310,10 +1298,6 @@ static int uvc_v4l2_get_xu_mapping(struct uvc_xu_control_mapping *kp,
 static int uvc_v4l2_put_xu_mapping(const struct uvc_xu_control_mapping *kp,
 			struct uvc_xu_control_mapping32 __user *up)
 {
-	struct uvc_menu_info __user *umenus;
-	struct uvc_menu_info __user *kmenus = kp->menu_info;
-	compat_caddr_t p;
-
 	if (!access_ok(VERIFY_WRITE, up, sizeof(*up)) ||
 	    __copy_to_user(up, kp, offsetof(typeof(*up), menu_info)) ||
 	    __put_user(kp->menu_count, &up->menu_count))
@@ -1322,16 +1306,6 @@ static int uvc_v4l2_put_xu_mapping(const struct uvc_xu_control_mapping *kp,
 	if (__clear_user(up->reserved, sizeof(up->reserved)))
 		return -EFAULT;
 
-	if (kp->menu_count == 0)
-		return 0;
-
-	if (get_user(p, &up->menu_info))
-		return -EFAULT;
-	umenus = compat_ptr(p);
-
-	if (copy_in_user(umenus, kmenus, kp->menu_count * sizeof(*umenus)))
-		return -EFAULT;
-
 	return 0;
 }
 
@@ -1346,8 +1320,6 @@ struct uvc_xu_control_query32 {
 static int uvc_v4l2_get_xu_query(struct uvc_xu_control_query *kp,
 			const struct uvc_xu_control_query32 __user *up)
 {
-	u8 __user *udata;
-	u8 __user *kdata;
 	compat_caddr_t p;
 
 	if (!access_ok(VERIFY_READ, up, sizeof(*up)) ||
@@ -1361,17 +1333,7 @@ static int uvc_v4l2_get_xu_query(struct uvc_xu_control_query *kp,
 
 	if (__get_user(p, &up->data))
 		return -EFAULT;
-	udata = compat_ptr(p);
-	if (!access_ok(VERIFY_READ, udata, kp->size))
-		return -EFAULT;
-
-	kdata = compat_alloc_user_space(kp->size);
-	if (kdata == NULL)
-		return -EFAULT;
-	kp->data = kdata;
-
-	if (copy_in_user(kdata, udata, kp->size))
-		return -EFAULT;
+	kp->data = compat_ptr(p);
 
 	return 0;
 }
@@ -1379,26 +1341,10 @@ static int uvc_v4l2_get_xu_query(struct uvc_xu_control_query *kp,
 static int uvc_v4l2_put_xu_query(const struct uvc_xu_control_query *kp,
 			struct uvc_xu_control_query32 __user *up)
 {
-	u8 __user *udata;
-	u8 __user *kdata = kp->data;
-	compat_caddr_t p;
-
 	if (!access_ok(VERIFY_WRITE, up, sizeof(*up)) ||
 	    __copy_to_user(up, kp, offsetof(typeof(*up), data)))
 		return -EFAULT;
 
-	if (kp->size == 0)
-		return 0;
-
-	if (get_user(p, &up->data))
-		return -EFAULT;
-	udata = compat_ptr(p);
-	if (!access_ok(VERIFY_READ, udata, kp->size))
-		return -EFAULT;
-
-	if (copy_in_user(udata, kdata, kp->size))
-		return -EFAULT;
-
 	return 0;
 }