| Message ID | 20250113222740.1481934-2-seanjc@google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | KVM: x86: Hyper-V SEND_IPI fix and partial testcase | expand |
On Mon, Jan 13, 2025, Sean Christopherson wrote: > 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 Argh, I missed the ".org". Paolo, if you end up applying this instead of me, can you fixup the email?
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c index 4f0a94346d00..44c88537448c 100644 --- a/arch/x86/kvm/hyperv.c +++ b/arch/x86/kvm/hyperv.c @@ -2226,6 +2226,9 @@ static u64 kvm_hv_send_ipi(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc) 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, @@ -2852,7 +2855,8 @@ int kvm_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;
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 Signed-off-by: Sean Christopherson <seanjc@google.com> --- arch/x86/kvm/hyperv.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)