ubi: Fix race condition between ubi device creation and udev

[ Upstream commit 714fb87e ]

Install the UBI device object before we arm sysfs.
Otherwise udev tries to read sysfs attributes before UBI is ready and
udev rules will not match.

Cc: <stable@vger.kernel.org>
Signed-off-by: Iosif Harutyunov <iharutyunov@sonicwall.com>
[rw: massaged commit message]
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>

drivers/mtd/ubi/build.c

@@ -1005,6 +1005,9 @@ int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num,
 			goto out_detach;
 	}
 
+	/* Make device "available" before it becomes accessible via sysfs */
+	ubi_devices[ubi_num] = ubi;
+
 	err = uif_init(ubi, &ref);
 	if (err)
 		goto out_detach;
@@ -1049,7 +1052,6 @@ int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num,
 	wake_up_process(ubi->bgt_thread);
 	spin_unlock(&ubi->wl_lock);
 
-	ubi_devices[ubi_num] = ubi;
 	ubi_notify_all(ubi, UBI_VOLUME_ADDED, NULL);
 	return ubi_num;
 
@@ -1060,6 +1062,7 @@ int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num,
 	ubi_assert(ref);
 	uif_close(ubi);
 out_detach:
+	ubi_devices[ubi_num] = NULL;
 	ubi_wl_close(ubi);
 	ubi_free_internal_volumes(ubi);
 	vfree(ubi->vtbl);