Vulnerability Discussion

Exposing kernel pointers (through procfs or "seq_printf()") exposes kernel writeable structures, which may contain functions pointers. If a write vulnerability occurs in the kernel, allowing write access to any of this structure, the kernel can be compromised.

This option disallows any program without the CAP_SYSLOG capability to get the addresses of kernel pointers by replacing them with "0".

Check

Verify the runtime status of the kernel.kptr_restrict kernel parameter with the following command:

$ sysctl kernel.kptr_restrict

kernel.kptr_restrict = 1

Verify the configuration of the kernel.kptr_restrict kernel parameter with the following command:

$ /usr/lib/systemd/systemd-sysctl --cat-config | egrep -v '^(#|;)' | grep -F kernel.kptr_restrict | tail -1

kernel.kptr_restrict =1

If "kernel.kptr_restrict" is not set to "1" or is missing, this is a finding.

Fix

Configure AlmaLinux OS 9 to restrict exposed kernel pointer addresses access with the following command:

$ echo "kernel.kptr_restrict = 1" > /etc/sysctl.d/60-kptr.conf

Load settings from all system configuration files with the following command:

$ sysctl --system