From 9356863c9409efc79029c01a85d015efae977e69 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Mon, 6 Feb 2017 13:41:39 +1100 Subject: [PATCH] md: ensure md devices are freed before module is unloaded. Commit: cbd199837750 ("md: Fix unfortunate interaction with evms") change mddev_put() so that it would not destroy an md device while ->ctime was non-zero. Unfortunately, we didn't make sure to clear ->ctime when unloading the module, so it is possible for an md device to remain after module unload. An attempt to open such a device will trigger an invalid memory reference in: get_gendisk -> kobj_lookup -> exact_lock -> get_disk when tring to access disk->fops, which was in the module that has been removed. So ensure we clear ->ctime in md_exit(), and explain how that is useful, as it isn't immediately obvious when looking at the code. Fixes: cbd199837750 ("md: Fix unfortunate interaction with evms") Tested-by: Guoqing Jiang Signed-off-by: NeilBrown Signed-off-by: Shaohua Li --- drivers/md/md.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/drivers/md/md.c b/drivers/md/md.c index 01175da..13020e5 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -8980,7 +8980,14 @@ static __exit void md_exit(void) for_each_mddev(mddev, tmp) { export_array(mddev); + mddev->ctime = 0; mddev->hold_active = 0; + /* + * for_each_mddev() will call mddev_put() at the end of each + * iteration. As the mddev is now fully clear, this will + * schedule the mddev for destruction by a workqueue, and the + * destroy_workqueue() below will wait for that to complete. + */ } destroy_workqueue(md_misc_wq); destroy_workqueue(md_wq); -- 2.7.4