From 4469315439827290923fce4f3f672599cabeb366 Mon Sep 17 00:00:00 2001 From: Yu Kuai Date: Tue, 23 May 2023 10:10:17 +0800 Subject: md: protect md_thread with rcu Currently, there are many places that md_thread can be accessed without protection, following are known scenarios that can cause null-ptr-dereference or uaf: 1) sync_thread that is allocated and started from md_start_sync() 2) mddev->thread can be accessed directly from timeout_store() and md_bitmap_daemon_work() 3) md_unregister_thread() from action_store(). Currently, a global spinlock 'pers_lock' is borrowed to protect 'mddev->thread' in some places, this problem can be fixed likewise, however, use a global lock for all the cases is not good. Fix this problem by protecting all md_thread with rcu. Signed-off-by: Yu Kuai Signed-off-by: Song Liu Link: https://lore.kernel.org/r/20230523021017.3048783-6-yukuai1@huaweicloud.com --- drivers/md/md-multipath.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'drivers/md/md-multipath.c') diff --git a/drivers/md/md-multipath.c b/drivers/md/md-multipath.c index 66edf5e72bd6..92c45be203d7 100644 --- a/drivers/md/md-multipath.c +++ b/drivers/md/md-multipath.c @@ -400,8 +400,8 @@ static int multipath_run (struct mddev *mddev) if (ret) goto out_free_conf; - mddev->thread = md_register_thread(multipathd, mddev, - "multipath"); + rcu_assign_pointer(mddev->thread, + md_register_thread(multipathd, mddev, "multipath")); if (!mddev->thread) goto out_free_conf; -- cgit