Messages in this thread Patch in this message | | | From | Ben Hutchings <> | Date | Thu, 01 Jun 2017 16:43:16 +0100 | Subject | [PATCH 3.16 121/212] md: ensure md devices are freed before module is unloaded. |
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3.16.44-rc1 review patch. If anyone has any objections, please let me know.
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From: NeilBrown <neilb@suse.com>
commit 9356863c9409efc79029c01a85d015efae977e69 upstream.
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@suse.com> Signed-off-by: NeilBrown <neilb@suse.com> Signed-off-by: Shaohua Li <shli@fb.com> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- drivers/md/md.c | 7 +++++++ 1 file changed, 7 insertions(+)
--- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -8714,7 +8714,14 @@ 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);
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