proc/vmcore: fix clearing user buffer by properly using clear_user()
This is an automated ID intended to aid in discovery of potential security vulnerabilities. The actual impact and attack plausibility have not yet been proven. This ID is fixed in Linux Kernel version v5.4.163 by commit fd7974c547abfb03072a4ee706d3a6f182266f89, it was introduced in version v3.0 by commit 997c136f518c5debd63847e78e2a8694f56dcf90. For more details please see the references link.