Vulnerability Discussion

Kernel page-table isolation is a kernel feature that mitigates the Meltdown security vulnerability and hardens the kernel against attempts to bypass kernel address space layout randomization (KASLR).

Check

Verify AlmaLinux OS 9 enables kernel page-table isolation with the following command:

$ grubby --info=ALL | grep pti

args="ro audit=1 selinux=1 enforcing=1 audit_backlog_limit=8192 page_poison=1 vsyscall=none slub_debug=P pti=on iommu=force resume=/dev/mapper/luks-88bf0df8-547f-4613-af07-215e5f62e9a9 rd.luks.uuid=luks-8a7154ec-8eeb-47c8-9d75-66fd4b80d665 rd.lvm.lv=rootvg/root rd.luks.uuid=luks-89bf0df8-547f-4613-af07-215e5f62e9a9 rd.lvm.lv=rootvg/swap rd.shell=0 quiet splash fips=1 boot=UUID=eda01e9b-b7e1-431b-9549-16d5dcddf665"

If the "pti" entry does not equal "on", or is missing, this is a finding.

Check that kernel page-table isolation is enabled by default to persist in kernel updates:

$ grep pti /etc/default/grub

GRUB_CMDLINE_LINUX="pti=on"

If "pti" is not set to "on", is missing or commented out, this is a finding.

Fix

Configure AlmaLinux OS 9 to enable kernel page-table isolation with the following command:

$ grubby --update-kernel=ALL --args="pti=on"

Add or modify the following line in "/etc/default/grub" to ensure the configuration survives kernel updates:

GRUB_CMDLINE_LINUX="pti=on"