6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Sean Christopherson <seanjc@xxxxxxxxxx>
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@xxxxxxxxxx>
Fixes: 214ff83d4473 ("KVM: x86: hyperv: implement PV IPI send hypercalls")
Fixes: 2bc39970e932 ("x86/kvm/hyper-v: Introduce KVM_GET_SUPPORTED_HV_CPUID")
Cc: stable@xxxxxxxxxxxxxxx
Reviewed-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20250118003454.2619573-2-seanjc@xxxxxxxxxx
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kvm/hyperv.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -2175,6 +2175,9 @@ static u64 kvm_hv_send_ipi(struct kvm_vc
u32 vector;
bool all_cpus;
+ if (!lapic_in_kernel(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,
@@ -2801,7 +2804,8 @@ int kvm_get_hv_cpuid(struct kvm_vcpu *vc
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;
