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".

Satisfies: SRG-OS-000132-GPOS-00067, SRG-OS-000433-GPOS-00192

Check

Verify Amazon Linux 2023 restricts exposed kernel pointer addresses access by validating the runtime status of the Amazon Linux 2023 kernel.kptr_restrict kernel parameter with the following command:

$ sudo sysctl kernel.kptr_restrict
kernel.kptr_restrict = 1

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

Fix

Configure Amazon Linux 2023 to restrict exposed kernel pointer addresses access.

Add or edit the following line in a system configuration file in the "/etc/sysctl.d/" directory:

kernel.kptr_restrict = 1

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

$ sudo sysctl --system