CVE-2024-44954

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

ALSA: line6: Fix racy access to midibuf

There can be concurrent accesses to line6 midibuf from both the URB
completion callback and the rawmidi API access. This could be a cause
of KMSAN warning triggered by syzkaller below (so put as reported-by
here).

This patch protects the midibuf call of the former code path with a
spinlock for avoiding the possible races.