Messages in this thread Patch in this message | | | From | Wanpeng Li <> | Subject | [PATCH] KVM: LAPIC: Fix SynIC Timers inject timer interrupt w/o LAPIC present | Date | Thu, 5 Sep 2019 18:44:30 +0800 |
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From: Wanpeng Li <wanpengli@tencent.com>
Reported by syzkaller:
kasan: GPF could be caused by NULL-ptr deref or user memory access general protection fault: 0000 [#1] PREEMPT SMP KASAN RIP: 0010:__apic_accept_irq+0x46/0x740 arch/x86/kvm/lapic.c:1029 Call Trace: kvm_apic_set_irq+0xb4/0x140 arch/x86/kvm/lapic.c:558 stimer_notify_direct arch/x86/kvm/hyperv.c:648 [inline] stimer_expiration arch/x86/kvm/hyperv.c:659 [inline] kvm_hv_process_stimers+0x594/0x1650 arch/x86/kvm/hyperv.c:686 vcpu_enter_guest+0x2b2a/0x54b0 arch/x86/kvm/x86.c:7896 vcpu_run+0x393/0xd40 arch/x86/kvm/x86.c:8152 kvm_arch_vcpu_ioctl_run+0x636/0x900 arch/x86/kvm/x86.c:8360 kvm_vcpu_ioctl+0x6cf/0xaf0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2765
The testcase programs HV_X64_MSR_STIMERn_CONFIG/HV_X64_MSR_STIMERn_COUNT, in addition, there is no lapic in the kernel, the counters value are small enough in order that kvm_hv_process_stimers() inject this already-expired timer interrupt into the guest through lapic in the kernel which triggers the NULL deferencing. This patch fixes it by checking lapic_in_kernel, discarding the inject if it is 0.
Reported-by: syzbot+dff25ee91f0c7d5c1695@syzkaller.appspotmail.com Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Radim Krčmář <rkrcmar@redhat.com> Cc: Vitaly Kuznetsov <vkuznets@redhat.com> Signed-off-by: Wanpeng Li <wanpengli@tencent.com> --- arch/x86/kvm/hyperv.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c index c10a8b1..461fcc5 100644 --- a/arch/x86/kvm/hyperv.c +++ b/arch/x86/kvm/hyperv.c @@ -645,7 +645,9 @@ static int stimer_notify_direct(struct kvm_vcpu_hv_stimer *stimer) .vector = stimer->config.apic_vector }; - return !kvm_apic_set_irq(vcpu, &irq, NULL); + if (lapic_in_kernel(vcpu)) + return !kvm_apic_set_irq(vcpu, &irq, NULL); + return 0; } static void stimer_expiration(struct kvm_vcpu_hv_stimer *stimer) -- 2.7.4
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