6.16-stable review patch. If anyone has any objections, please let me know.
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From: Yu Kuai yukuai3@huawei.com
commit 1df1fc845d221eb646539836dbf509eb96b41afd upstream.
Commit 9e59d609763f ("md: call del_gendisk in control path") moves setting MD_DELETED from __mddev_put() to do_md_stop(), however, for the case create on open, mddev can be freed without do_md_stop():
1) open
md_probe md_alloc_and_put md_alloc mddev_alloc atomic_set(&mddev->active, 1); mddev->hold_active = UNTIL_IOCTL mddev_put atomic_dec_and_test(&mddev->active) if (mddev->hold_active) -> active is 0, hold_active is set md_open mddev_get atomic_inc(&mddev->active);
2) ioctl that is not STOP_ARRAY, for example, GET_ARRAY_INFO:
md_ioctl mddev->hold_active = 0
3) close
md_release mddev_put(mddev); atomic_dec_and_lock(&mddev->active, &all_mddevs_lock) __mddev_put -> hold_active is cleared, mddev will be freed queue_work(md_misc_wq, &mddev->del_work)
Now that MD_DELETED is not set, before mddev is freed by mddev_delayed_delete(), md_open can still succeed and break mddev lifetime, causing mddev->kobj refcount underflow or mddev uaf problem.
Fix this problem by setting MD_DELETED before queuing del_work.
Reported-by: syzbot+9921e319bd6168140b40@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/68894408.a00a0220.26d0e1.0012.GAE@google.com/ Reported-by: syzbot+fa3a12519f0d3fd4ec16@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/68894408.a00a0220.26d0e1.0013.GAE@google.com/ Fixes: 9e59d609763f ("md: call del_gendisk in control path") Link: https://lore.kernel.org/linux-raid/20250730073321.2583158-1-yukuai1@huaweicl... Signed-off-by: Yu Kuai yukuai3@huawei.com Reviewed-by: Paul Menzel pmenzel@molgen.mpg.de Reviewed-by: Xiao Ni xni@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/md/md.c | 6 ++++++ 1 file changed, 6 insertions(+)
--- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -637,6 +637,12 @@ static void __mddev_put(struct mddev *md return;
/* + * If array is freed by stopping array, MD_DELETED is set by + * do_md_stop(), MD_DELETED is still set here in case mddev is freed + * directly by closing a mddev that is created by create_on_open. + */ + set_bit(MD_DELETED, &mddev->flags); + /* * Call queue_work inside the spinlock so that flush_workqueue() after * mddev_find will succeed in waiting for the work to be done. */