diff options
| author | Christoph Hellwig <hch@lst.de> | 2021-09-01 13:38:29 +0200 |
|---|---|---|
| committer | Song Liu <songliubraving@fb.com> | 2021-09-22 08:45:58 -0700 |
| commit | 7df835a32a8bedf7ce88efcfa7c9b245b52ff139 (patch) | |
| tree | 6f2a1d6487894719f55610f8ce743a4e6efe8739 /drivers/md | |
| parent | 858560b27645e7e97aca37ee8f232cccd658fbd2 (diff) | |
md: fix a lock order reversal in md_alloc
Commit b0140891a8cea3 ("md: Fix race when creating a new md device.")
not only moved assigning mddev->gendisk before calling add_disk, which
fixes the races described in the commit log, but also added a
mddev->open_mutex critical section over add_disk and creation of the
md kobj. Adding a kobject after add_disk is racy vs deleting the gendisk
right after adding it, but md already prevents against that by holding
a mddev->active reference.
On the other hand taking this lock added a lock order reversal with what
is not disk->open_mutex (used to be bdev->bd_mutex when the commit was
added) for partition devices, which need that lock for the internal open
for the partition scan, and a recent commit also takes it for
non-partitioned devices, leading to further lockdep splatter.
Fixes: b0140891a8ce ("md: Fix race when creating a new md device.")
Fixes: d62633873590 ("block: support delayed holder registration")
Reported-by: syzbot+fadc0aaf497e6a493b9f@syzkaller.appspotmail.com
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: syzbot+fadc0aaf497e6a493b9f@syzkaller.appspotmail.com
Reviewed-by: NeilBrown <neilb@suse.de>
Signed-off-by: Song Liu <songliubraving@fb.com>
Diffstat (limited to 'drivers/md')
| -rw-r--r-- | drivers/md/md.c | 5 |
1 files changed, 0 insertions, 5 deletions
diff --git a/drivers/md/md.c b/drivers/md/md.c index ae8fe54ea358..6c0c3d0d905a 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -5700,10 +5700,6 @@ static int md_alloc(dev_t dev, char *name) disk->flags |= GENHD_FL_EXT_DEVT; disk->events |= DISK_EVENT_MEDIA_CHANGE; mddev->gendisk = disk; - /* As soon as we call add_disk(), another thread could get - * through to md_open, so make sure it doesn't get too far - */ - mutex_lock(&mddev->open_mutex); add_disk(disk); error = kobject_add(&mddev->kobj, &disk_to_dev(disk)->kobj, "%s", "md"); @@ -5718,7 +5714,6 @@ static int md_alloc(dev_t dev, char *name) if (mddev->kobj.sd && sysfs_create_group(&mddev->kobj, &md_bitmap_group)) pr_debug("pointless warning\n"); - mutex_unlock(&mddev->open_mutex); abort: mutex_unlock(&disks_mutex); if (!error && mddev->kobj.sd) { |