ubi: Fix race condition between ubi volume creation and udev

commit a51a0c8d upstream.

Similar to commit 714fb87e ("ubi: Fix race condition between ubi
device creation and udev"), we should make the volume active before
registering it.
Signed-off-by: Clay McClure <clay@daemons.net>
Cc: <stable@vger.kernel.org>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/mtd/ubi/vmt.c

@@ -265,6 +265,12 @@ int ubi_create_volume(struct ubi_device *ubi, struct ubi_mkvol_req *req)
 			vol->last_eb_bytes = vol->usable_leb_size;
 	}
 
+	/* Make volume "available" before it becomes accessible via sysfs */
+	spin_lock(&ubi->volumes_lock);
+	ubi->volumes[vol_id] = vol;
+	ubi->vol_count += 1;
+	spin_unlock(&ubi->volumes_lock);
+
 	/* Register character device for the volume */
 	cdev_init(&vol->cdev, &ubi_vol_cdev_operations);
 	vol->cdev.owner = THIS_MODULE;
@@ -304,11 +310,6 @@ int ubi_create_volume(struct ubi_device *ubi, struct ubi_mkvol_req *req)
 	if (err)
 		goto out_sysfs;
 
-	spin_lock(&ubi->volumes_lock);
-	ubi->volumes[vol_id] = vol;
-	ubi->vol_count += 1;
-	spin_unlock(&ubi->volumes_lock);
-
 	ubi_volume_notify(ubi, vol, UBI_VOLUME_ADDED);
 	self_check_volumes(ubi);
 	return err;
@@ -328,6 +329,10 @@ int ubi_create_volume(struct ubi_device *ubi, struct ubi_mkvol_req *req)
 out_cdev:
 	cdev_del(&vol->cdev);
 out_mapping:
+	spin_lock(&ubi->volumes_lock);
+	ubi->volumes[vol_id] = NULL;
+	ubi->vol_count -= 1;
+	spin_unlock(&ubi->volumes_lock);
 	if (do_free)
 		kfree(vol->eba_tbl);
 out_acc: