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

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: md/dm-raid: don't call md_reap_sync_thread() directly Currently md_reap_sync_thread() is called from raid_message() directly without holding 'reconfig_mutex', this is definitely unsafe because md_reap_sync_thread() can change many fields that is protected by 'reconfig_mutex'. However, hold 'reconfig_mutex' here is still problematic because this will cause deadlock, for example, commit 130443d60b1b ("md: refactor idle/frozen_sync_thread() to fix deadlock"). Fix this problem by using stop_sync_thread() to unregister sync_thread, like md/raid did.

References

• https://git.kernel.org/stable/c/347dcdc15a1706f61aa545ae498ededdf31aeebc
• https://git.kernel.org/stable/c/9e59b8d76ff511505eb0dd1478329f09e0f04669
• https://git.kernel.org/stable/c/cd32b27a66db8776d8b8e82ec7d7dde97a8693b0