On Thu, Jun 17, 2021 at 05:20:16PM +0800, Desmond Cheong Zhi Xi wrote: > mutex_lock(&major_names_lock); > for (n = &major_names[major_to_index(major)]; *n; n = &(*n)->next) { > if ((*n)->major == major && (*n)->probe) { > - (*n)->probe(devt); > + probe = (*n)->probe; > mutex_unlock(&major_names_lock); > + probe(devt); And now you can all probe after it has been freed and/or the module has been unloaded. The obviously correct fix is to only hold mtd_table_mutex for the actually required critical section: diff --git a/drivers/mtd/mtd_blkdevs.c b/drivers/mtd/mtd_blkdevs.c index fb8e12d590a1..065d94f9b1fb 100644 --- a/drivers/mtd/mtd_blkdevs.c +++ b/drivers/mtd/mtd_blkdevs.c @@ -529,13 +529,11 @@ int register_mtd_blktrans(struct mtd_blktrans_ops *tr) register_mtd_user(&blktrans_notifier); - mutex_lock(&mtd_table_mutex); ret = register_blkdev(tr->major, tr->name); if (ret < 0) { printk(KERN_WARNING "Unable to register %s block device on major %d: %d\n", tr->name, tr->major, ret); - mutex_unlock(&mtd_table_mutex); return ret; } @@ -545,12 +543,12 @@ int register_mtd_blktrans(struct mtd_blktrans_ops *tr) tr->blkshift = ffs(tr->blksize) - 1; INIT_LIST_HEAD(&tr->devs); - list_add(&tr->list, &blktrans_majors); + mutex_lock(&mtd_table_mutex); + list_add(&tr->list, &blktrans_majors); mtd_for_each_device(mtd) if (mtd->type != MTD_ABSENT) tr->add_mtd(tr, mtd); - mutex_unlock(&mtd_table_mutex); return 0; }