coredump: Do not lock during 'comm' reporting

coredump: Do not lock during 'comm' reporting

The 'comm' member will always be NUL terminated, and this is not
fast-path, so we can just perform a direct memcpy during a coredump
instead of potentially deadlocking while holding the task struct lock.

Reported-by: Vegard Nossum <vegard.nossum@oracle.com>
Closes: https://lore.kernel.org/all/d122ece6-3606-49de-ae4d-8da88846bef2@oracle.com
Fixes: c114e9948c2b ("coredump: Standartize and fix logging")
Tested-by: Vegard Nossum <vegard.nossum@oracle.com>
Link: https://lore.kernel.org/r/20240928210830.work.307-kees@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>