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Force enable PTI on ARM64 CPUs #333

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Merged
adrelanos merged 3 commits into from
Dec 3, 2025
Merged

Force enable PTI on ARM64 CPUs #333

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5e87c9b
Set `kpti=1`
raja-grewal Nov 3, 2025
322584d
Update docs on `pti=on`
raja-grewal Nov 3, 2025
53d90b1
Update docs on `ssbd=force-on`
raja-grewal Nov 3, 2025
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6 changes: 4 additions & 2 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -156,6 +156,8 @@ CPU mitigations:

- Spectre Side Channels (BTI and BHI)

- Meltdown

- Speculative Store Bypass (SSB)

- L1 Terminal Fault (L1TF)
Expand Down Expand Up @@ -206,8 +208,8 @@ Kernel space:
- Enable the kernel page allocator to randomize free lists to limit some data
exfiltration and ROP attacks, especially during the early boot process.

- Enable kernel page table isolation to increase KASLR effectiveness and also
mitigate the Meltdown CPU vulnerability.
- Enable kernel page table isolation on X86_64 CPUs to increase KASLR effectiveness
and also mitigate the Meltdown CPU vulnerability.

- Enable randomization of the kernel stack offset on syscall entries to harden
against memory corruption attacks.
Expand Down
16 changes: 15 additions & 1 deletion etc/default/grub.d/40_cpu_mitigations.cfg#security-misc-shared
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Expand Up @@ -71,10 +71,24 @@ GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX nosmt=force"
GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX spectre_v2=on"
GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX spectre_bhi=on"

## Meltdown:
## Mitigate Spectre Variant 3 using kernel page table isolation (PTI).
## Force enable PTI of user and kernel address spaces on all cores.
## Mitigations for X86_64 CPUs are done in /etc/default/grub.d/40_kernel_hardening.cfg using "pti=on".
## Currently affects ARM64 CPUs.
##
## https://en.wikipedia.org/wiki/Meltdown_(security_vulnerability)
## https://en.wikipedia.org/wiki/Kernel_page-table_isolation
##
## KSPP=yes
## KSPP sets CONFIG_UNMAP_KERNEL_AT_EL0=y.
##
GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX kpti=1"

## Speculative Store Bypass (SSB):
## Mitigate Spectre Variant 4 by disabling speculative store bypass system-wide.
## Unconditionally enable the mitigation for both kernel and userspace.
## Currently affects both AMD and Intel CPUs.
## Currently affects AMD, ARM64, and Intel CPUs.
##
## https://en.wikipedia.org/wiki/Speculative_Store_Bypass
## https://www.suse.com/support/kb/doc/?id=000019189
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4 changes: 3 additions & 1 deletion etc/default/grub.d/40_kernel_hardening.cfg#security-misc-shared
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Expand Up @@ -83,8 +83,10 @@ GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX init_on_free=1"
GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX page_alloc.shuffle=1"

## Enable kernel page table isolation to harden against kernel ASLR (KASLR) bypasses.
## Mitigates the Meltdown CPU vulnerability.
## Mitigates the Meltdown (Spectre Variant 3) CPU vulnerability.
## Mitigations for ARM64 CPUs are done in /etc/default/grub.d/40_cpu_mitigations.cfg using "kpti=1".
##
## https://en.wikipedia.org/wiki/Meltdown_(security_vulnerability)
## https://en.wikipedia.org/wiki/Kernel_page-table_isolation
##
## KSPP=yes
Expand Down