This is a conceptual cherry-pick of commit a51a0c8d213594bc094cb8e54aad0cb6d7f7b9a6 upstream.

Similar to commit 714fb87e8bc0 ("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 (clay: massaged to apply to 4.9.y) Signed-off-by: Clay McClure clay@daemons.net --- Hello,

The race fixed by this upstream patch also occurs in 4.9, 4.4, and at least as far back as 3.14 (where we originally found it). This massaged patch applies cleanly to 4.9.y and 4.4.y and possibly to earlier kernels.

Thanks,

Clay --- drivers/mtd/ubi/vmt.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/mtd/ubi/vmt.c b/drivers/mtd/ubi/vmt.c index 7ac78c13dd1c..1bcb25bc35ef 100644 --- a/drivers/mtd/ubi/vmt.c +++ b/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) ubi_eba_destroy_table(eba_tbl); out_acc: