[PATCH v2 0/2] KVM: arm64: Validate host pointers in __kvm_adjust_pc() under pKVM

[Fuad Tabba]

Hi folks,

Changes since v1 [1]:
  - New patch 1: enter_exception64() reads the VM's MTE flag through a
    host-writable vcpu->kvm that nothing validates. It goes first,
    since pinning the vCPU alone leaves that read on an unmapped VM.
    (sashiko)
  - Dropped the VM pin the fix carried in v1, patch 1 validating that
    read at its site.

Two host pointers reach EL2 unvalidated on the __kvm_adjust_pc() path
under pKVM, and this series fixes both. The host vCPU isn't mapped at
EL2 until its first KVM_RUN pins it, and KVM_SET_VCPU_EVENTS with
ext_dabt_pending reaches the hypercall before that. The vcpu->kvm the
exception entry reads the MTE flag from is host-writable, and nothing
checks it. Either one panics the hypervisor, and on MTE-capable
hardware the flag read leaks one bit of hyp memory the host chose,
through PSR_TCO.

These are patches 2 and 3 of the pKVM core series [2], which carries
them so that it applies as is. They're respun here so they can be
applied on their own.

Based on v7.3-rc3 (fd73f4a665989).

Cheers,
/fuad

[1] https://lore.kernel.org/all/20260914065136.3418404-1-fuad.tabba@xxxxxxxxx/
[2] https://lore.kernel.org/all/20260914113338.159227-1-fuad.tabba@xxxxxxxxx/

Fuad Tabba (2):
  KVM: arm64: Validate the host vCPU's VM before reading it under pKVM
  KVM: arm64: Pin the host vCPU before adjusting its PC under pKVM

 arch/arm64/kvm/hyp/exception.c             |  5 ++-
 arch/arm64/kvm/hyp/include/hyp/adjust_pc.h | 18 ++++++++++
 arch/arm64/kvm/hyp/nvhe/hyp-main.c         | 19 ++++++++++-
 arch/arm64/kvm/hyp/nvhe/pkvm.c             | 39 ++++++++++++++++++++++
 4 files changed, 79 insertions(+), 2 deletions(-)


base-commit: fd73f4a6659897191fa0d40695fe370925dd3780
-- 
2.39.5