CVE-2024-35808

In the Linux kernel, the following vulnerability has been resolved:

md/dm-raid: don't call mdreapsync_thread() directly

Currently mdreapsyncthread() is called from raidmessage() directly without holding 'reconfigmutex', this is definitely unsafe because mdreapsyncthread() can change many fields that is protected by 'reconfig_mutex'.

However, hold 'reconfigmutex' here is still problematic because this will cause deadlock, for example, commit 130443d60b1b ("md: refactor idle/frozensync_thread() to fix deadlock").

Fix this problem by using stopsyncthread() to unregister sync_thread, like md/raid did.