[PATCH 5.10.y] KVM: x86: Reject Hyper-V's SEND_IPI hypercalls if local APIC isn't in-kernel
From: Sean Christopherson seanjc@google.com
commit a8de7f100bb5989d9c3627d3a223ee1c863f3b69 upstream.
Advertise support for Hyper-V's SEND_IPI and SEND_IPI_EX hypercalls if and only if the local API is emulated/virtualized by KVM, and explicitly reject said hypercalls if the local APIC is emulated in userspace, i.e. don't rely on userspace to opt-in to KVM_CAP_HYPERV_ENFORCE_CPUID.
Rejecting SEND_IPI and SEND_IPI_EX fixes a NULL-pointer dereference if Hyper-V enlightenments are exposed to the guest without an in-kernel local APIC:
dump_stack+0xbe/0xfd __kasan_report.cold+0x34/0x84 kasan_report+0x3a/0x50 __apic_accept_irq+0x3a/0x5c0 kvm_hv_send_ipi.isra.0+0x34e/0x820 kvm_hv_hypercall+0x8d9/0x9d0 kvm_emulate_hypercall+0x506/0x7e0 __vmx_handle_exit+0x283/0xb60 vmx_handle_exit+0x1d/0xd0 vcpu_enter_guest+0x16b0/0x24c0 vcpu_run+0xc0/0x550 kvm_arch_vcpu_ioctl_run+0x170/0x6d0 kvm_vcpu_ioctl+0x413/0xb20 __se_sys_ioctl+0x111/0x160 do_syscal1_64+0x30/0x40 entry_SYSCALL_64_after_hwframe+0x67/0xd1
Note, checking the sending vCPU is sufficient, as the per-VM irqchip_mode can't be modified after vCPUs are created, i.e. if one vCPU has an in-kernel local APIC, then all vCPUs have an in-kernel local APIC.
Reported-by: Dongjie Zou zoudongjie@huawei.com Fixes: 214ff83d4473 ("KVM: x86: hyperv: implement PV IPI send hypercalls") Fixes: 2bc39970e932 ("x86/kvm/hyper-v: Introduce KVM_GET_SUPPORTED_HV_CPUID") Cc: stable@vger.kernel.org Reviewed-by: Vitaly Kuznetsov vkuznets@redhat.com Link: https://lore.kernel.org/r/20250118003454.2619573-2-seanjc@google.com Signed-off-by: Sean Christopherson seanjc@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org [Conflict due to 72167a9d7da2 ("KVM: x86: hyper-v: Stop shadowing global 'current_vcpu' variable") not in the tree] Signed-off-by: Abdelkareem Abdelsaamad kareemem@amazon.com --- arch/x86/kvm/hyperv.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c index 20eb8f55e1f1..e097faf12c82 100644 --- a/arch/x86/kvm/hyperv.c +++ b/arch/x86/kvm/hyperv.c @@ -1618,6 +1618,9 @@ static u64 kvm_hv_send_ipi(struct kvm_vcpu *current_vcpu, u64 ingpa, u64 outgpa, u32 vector; bool all_cpus;
+ if (!lapic_in_kernel(current_vcpu)) + return HV_STATUS_INVALID_HYPERCALL_INPUT; + if (!ex) { if (!fast) { if (unlikely(kvm_read_guest(kvm, ingpa, &send_ipi, @@ -2060,7 +2063,8 @@ int kvm_vcpu_ioctl_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid, ent->eax |= HV_X64_REMOTE_TLB_FLUSH_RECOMMENDED; ent->eax |= HV_X64_APIC_ACCESS_RECOMMENDED; ent->eax |= HV_X64_RELAXED_TIMING_RECOMMENDED; - ent->eax |= HV_X64_CLUSTER_IPI_RECOMMENDED; + if (!vcpu || lapic_in_kernel(vcpu)) + ent->eax |= HV_X64_CLUSTER_IPI_RECOMMENDED; ent->eax |= HV_X64_EX_PROCESSOR_MASKS_RECOMMENDED; if (evmcs_ver) ent->eax |= HV_X64_ENLIGHTENED_VMCS_RECOMMENDED;
[ Sasha's backport helper bot ]
Hi,
✅ All tests passed successfully. No issues detected. No action required from the submitter.
The upstream commit SHA1 provided is correct: a8de7f100bb5989d9c3627d3a223ee1c863f3b69
WARNING: Author mismatch between patch and upstream commit: Backport author: Abdelkareem Abdelsaamadkareemem@amazon.com Commit author: Sean Christophersonseanjc@google.com
Status in newer kernel trees: 6.13.y | Present (different SHA1: ca29f58ca374) 6.12.y | Present (different SHA1: aca8be4403fb) 6.6.y | Present (different SHA1: 874ff13c73c4) 6.1.y | Present (different SHA1: 5393cf223124) 5.15.y | Present (different SHA1: 8c0bc4fec456)
Note: The patch differs from the upstream commit: --- 1: a8de7f100bb59 ! 1: 26c34724741d5 KVM: x86: Reject Hyper-V's SEND_IPI hypercalls if local APIC isn't in-kernel @@ Metadata ## Commit message ## KVM: x86: Reject Hyper-V's SEND_IPI hypercalls if local APIC isn't in-kernel
+ commit a8de7f100bb5989d9c3627d3a223ee1c863f3b69 upstream. + Advertise support for Hyper-V's SEND_IPI and SEND_IPI_EX hypercalls if and only if the local API is emulated/virtualized by KVM, and explicitly reject said hypercalls if the local APIC is emulated in userspace, i.e. don't rely @@ Commit message Reviewed-by: Vitaly Kuznetsov vkuznets@redhat.com Link: https://lore.kernel.org/r/20250118003454.2619573-2-seanjc@google.com Signed-off-by: Sean Christopherson seanjc@google.com + Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org + [Conflict due to + 72167a9d7da2 ("KVM: x86: hyper-v: Stop shadowing global 'current_vcpu' + variable") + not in the tree] + Signed-off-by: Abdelkareem Abdelsaamad kareemem@amazon.com
## arch/x86/kvm/hyperv.c ## -@@ arch/x86/kvm/hyperv.c: static u64 kvm_hv_send_ipi(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc) +@@ arch/x86/kvm/hyperv.c: static u64 kvm_hv_send_ipi(struct kvm_vcpu *current_vcpu, u64 ingpa, u64 outgpa, u32 vector; bool all_cpus;
-+ if (!lapic_in_kernel(vcpu)) ++ if (!lapic_in_kernel(current_vcpu)) + return HV_STATUS_INVALID_HYPERCALL_INPUT; + - if (hc->code == HVCALL_SEND_IPI) { - if (!hc->fast) { - if (unlikely(kvm_read_guest(kvm, hc->ingpa, &send_ipi, -@@ arch/x86/kvm/hyperv.c: int kvm_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid, + if (!ex) { + if (!fast) { + if (unlikely(kvm_read_guest(kvm, ingpa, &send_ipi, +@@ arch/x86/kvm/hyperv.c: int kvm_vcpu_ioctl_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid, ent->eax |= HV_X64_REMOTE_TLB_FLUSH_RECOMMENDED; ent->eax |= HV_X64_APIC_ACCESS_RECOMMENDED; ent->eax |= HV_X64_RELAXED_TIMING_RECOMMENDED; ---
Results of testing on various branches:
| Branch | Patch Apply | Build Test | |---------------------------|-------------|------------| | stable/linux-5.10.y | Success | Success |
linux-stable-mirror@lists.linaro.org
-
Abdelkareem Abdelsaamad -
Sasha Levin