From b7abb051682263e51866bc78762fd0083d64c5ed Mon Sep 17 00:00:00 2001 From: Desmond Cheong Zhi Xi Date: Sat, 17 Jul 2021 18:07:19 +0800 Subject: mtd: fix lock hierarchy in deregister_mtd_blktrans There is a lock hierarchy of major_names_lock --> mtd_table_mutex. One existing chain is as follows: 1. major_names_lock --> loop_ctl_mutex (when blk_request_module calls loop_probe) 2. loop_ctl_mutex --> bdev->bd_mutex (when loop_control_ioctl calls loop_remove, which then calls del_gendisk) 3. bdev->bd_mutex --> mtd_table_mutex (when blkdev_get_by_dev calls __blkdev_get, which then calls blktrans_open) Since unregister_blkdev grabs the major_names_lock, we need to call it outside the critical section for mtd_table_mutex, otherwise we invert the lock hierarchy. Reported-by: Hillf Danton Signed-off-by: Desmond Cheong Zhi Xi Signed-off-by: Miquel Raynal Link: https://lore.kernel.org/linux-mtd/20210717100719.728829-1-desmondcheongzx@gmail.com --- drivers/mtd/mtd_blkdevs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/mtd') diff --git a/drivers/mtd/mtd_blkdevs.c b/drivers/mtd/mtd_blkdevs.c index 31b208fb225e..44bea3f65060 100644 --- a/drivers/mtd/mtd_blkdevs.c +++ b/drivers/mtd/mtd_blkdevs.c @@ -561,8 +561,8 @@ int deregister_mtd_blktrans(struct mtd_blktrans_ops *tr) list_for_each_entry_safe(dev, next, &tr->devs, list) tr->remove_dev(dev); - unregister_blkdev(tr->major, tr->name); mutex_unlock(&mtd_table_mutex); + unregister_blkdev(tr->major, tr->name); BUG_ON(!list_empty(&tr->devs)); return 0; -- cgit v1.2.3