2017-03-06 04:03-0800, Wanpeng Li:
> From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
>
> Reported by syzkaller:
>
> WARNING: CPU: 1 PID: 27742 at arch/x86/kvm/vmx.c:11029
> nested_vmx_vmexit+0x5c35/0x74d0 arch/x86/kvm/vmx.c:11029
> CPU: 1 PID: 27742 Comm: a.out Not tainted 4.10.0+ #229
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
> Call Trace:
> __dump_stack lib/dump_stack.c:15 [inline]
> dump_stack+0x2ee/0x3ef lib/dump_stack.c:51
> panic+0x1fb/0x412 kernel/panic.c:179
> __warn+0x1c4/0x1e0 kernel/panic.c:540
> warn_slowpath_null+0x2c/0x40 kernel/panic.c:583
> nested_vmx_vmexit+0x5c35/0x74d0 arch/x86/kvm/vmx.c:11029
> vmx_leave_nested arch/x86/kvm/vmx.c:11136 [inline]
> vmx_set_msr+0x1565/0x1910 arch/x86/kvm/vmx.c:3324
> kvm_set_msr+0xd4/0x170 arch/x86/kvm/x86.c:1099
> do_set_msr+0x11e/0x190 arch/x86/kvm/x86.c:1128
> __msr_io arch/x86/kvm/x86.c:2577 [inline]
> msr_io+0x24b/0x450 arch/x86/kvm/x86.c:2614
> kvm_arch_vcpu_ioctl+0x35b/0x46a0 arch/x86/kvm/x86.c:3497
> kvm_vcpu_ioctl+0x232/0x1120 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2721
> vfs_ioctl fs/ioctl.c:43 [inline]
> do_vfs_ioctl+0x1bf/0x1790 fs/ioctl.c:683
> SYSC_ioctl fs/ioctl.c:698 [inline]
> SyS_ioctl+0x8f/0xc0 fs/ioctl.c:689
> entry_SYSCALL_64_fastpath+0x1f/0xc2
>
> The syzkaller folks reported a nested_run_pending warning during userspace
> clear VMX capability which is exposed to L1 before.
>
> The warning gets thrown while doing
>
> (*(uint32_t*)0x20aecfe8 = (uint32_t)0x1);
> (*(uint32_t*)0x20aecfec = (uint32_t)0x0);
> (*(uint32_t*)0x20aecff0 = (uint32_t)0x3a);
> (*(uint32_t*)0x20aecff4 = (uint32_t)0x0);
> (*(uint64_t*)0x20aecff8 = (uint64_t)0x0);
> r[29] = syscall(__NR_ioctl, r[4], 0x4008ae89ul,
> 0x20aecfe8ul, 0, 0, 0, 0, 0, 0);
>
> i.e. KVM_SET_MSR ioctl with
>
> struct kvm_msrs {
> .nmsrs = 1,
> .pad = 0,
> .entries = {
> {.index = MSR_IA32_FEATURE_CONTROL,
> .reserved = 0,
> .data = 0}
> }
> }
>
> The VMLANCH/VMRESUME emulation should be stopped since the CPU is going to
> reset here. This patch resets the nested_run_pending since the CPU is going
> to be reset hence there should be nothing pending.
>
> Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
> Suggested-by: Radim Krčmář <rkrcmar@xxxxxxxxxx>
> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx>
> Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
> Cc: David Hildenbrand <david@xxxxxxxxxx>
> Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
> ---
Queued for 4.11-rc2, thanks.
> v2 -> v3:
> * move the reset to vmx_leave_nested()
> v1 -> v2:
> * cleanup comments format
>
> arch/x86/kvm/vmx.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 3b626d6..ab33858 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -11107,8 +11107,10 @@ static void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 exit_reason,
> */
> static void vmx_leave_nested(struct kvm_vcpu *vcpu)
> {
> - if (is_guest_mode(vcpu))
> + if (is_guest_mode(vcpu)) {
> + to_vmx(vcpu)->nested.nested_run_pending = 0;
> nested_vmx_vmexit(vcpu, -1, 0, 0);
> + }
> free_nested(to_vmx(vcpu));
> }
>
> --
> 2.7.4
>
