Fix a NULL pointer deref due to exposing Hyper-V enlightments to a guest
without an in-kernel local APIC (found by syzkaller, highly unlikely to
affect any "real" VMMs).  Expand the Hyper-V CPUID test to verify that KVM
doesn't incorrectly advertise support.

v2
 - Fix the stable@ email.  Hilariously, I was _this_ close to sending this
   with stable@vger.kernel@kernel.org instead of stable@vger.kernel.org,
   *after* I wrote this exact blurb about fat-fingering the email a second
   time.  Thankfully, git send-email told me I was being stupid :-)
 - Don't free the system-scoped CPUID entries object. [Vitaly]
 - Collect reviews. [Vitaly] 

v1: https://lore.kernel.org/all/20250113222740.1481934-1-seanjc@google.com

Sean Christopherson (4):
  KVM: x86: Reject Hyper-V's SEND_IPI hypercalls if local APIC isn't
    in-kernel
  KVM: selftests: Mark test_hv_cpuid_e2big() static in Hyper-V CPUID
    test
  KVM: selftests: Manage CPUID array in Hyper-V CPUID test's core helper
  KVM: selftests: Add CPUID tests for Hyper-V features that need
    in-kernel APIC

 arch/x86/kvm/hyperv.c                         |  6 ++-
 .../selftests/kvm/x86_64/hyperv_cpuid.c       | 47 +++++++++++++------
 2 files changed, 37 insertions(+), 16 deletions(-)


base-commit: a5546c2f0dc4f84727a4bb8a91633917929735f5
-- 
2.48.0.rc2.279.g1de40edade-goog

On Fri, 17 Jan 2025 16:34:50 -0800, Sean Christopherson wrote:
> Fix a NULL pointer deref due to exposing Hyper-V enlightments to a guest
> without an in-kernel local APIC (found by syzkaller, highly unlikely to
> affect any "real" VMMs).  Expand the Hyper-V CPUID test to verify that KVM
> doesn't incorrectly advertise support.
> 
> v2
>  - Fix the stable@ email.  Hilariously, I was _this_ close to sending this
>    with stable@vger.kernel@kernel.org instead of stable@vger.kernel.org,
>    *after* I wrote this exact blurb about fat-fingering the email a second
>    time.  Thankfully, git send-email told me I was being stupid :-)
>  - Don't free the system-scoped CPUID entries object. [Vitaly]
>  - Collect reviews. [Vitaly]
> 
> [...]

Applied to kvm-x86 fixes, thanks!

[1/4] KVM: x86: Reject Hyper-V's SEND_IPI hypercalls if local APIC isn't in-kernel
      https://github.com/kvm-x86/linux/commit/a8de7f100bb5
[2/4] KVM: selftests: Mark test_hv_cpuid_e2big() static in Hyper-V CPUID test
      https://github.com/kvm-x86/linux/commit/0b6db0dc43ee
[3/4] KVM: selftests: Manage CPUID array in Hyper-V CPUID test's core helper
      https://github.com/kvm-x86/linux/commit/cd5a0c2f0fae
[4/4] KVM: selftests: Add CPUID tests for Hyper-V features that need in-kernel APIC
      https://github.com/kvm-x86/linux/commit/e36454461c5e

--
https://github.com/kvm-x86/linux/tree/next