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 <gqjiang@xxxxxxxx>
Signed-off-by: NeilBrown <neilb@xxxxxxxx>
---
drivers/md/md.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 01175dac0db6..8926fb781cdc 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);
--
2.11.0
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