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| author | Christoph Hellwig <hch@lst.de> | 2021-09-01 14:38:29 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-09-30 11:11:05 +0300 |
| commit | b18ba3f477a2fdd12d2ca2e01d2bd874968714e2 (patch) | |
| tree | f521c4002eb8865406e7a41724a58032d92c5f42 /drivers/md | |
| parent | 568662e37f927e3dc3e475f3ff7cf4ab7719c5e7 (diff) | |
| download | linux-b18ba3f477a2fdd12d2ca2e01d2bd874968714e2.tar.xz | |
md: fix a lock order reversal in md_alloc
[ Upstream commit 7df835a32a8bedf7ce88efcfa7c9b245b52ff139 ]
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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
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 288d26013de2..f16f190546ef 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -5759,10 +5759,6 @@ 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"); @@ -5777,7 +5773,6 @@ 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) { |