Improper Locking

Summary

In the Linux kernel, the following vulnerability has been resolved: ALSA: timer: Don't take register_mutex with copy_from/to_user() The infamous mmap_lock taken in copy_from/to_user() can be often problematic when it's called inside another mutex, as they might lead to deadlocks. In the case of ALSA timer code, the bad pattern is with guard(mutex)(&register_mutex) that covers copy_from/to_user() -- which was mistakenly introduced at converting to guard(), and it had been carefully worked around in the past. This patch fixes those pieces simply by moving copy_from/to_user() out of the register mutex lock again.