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SubjectRe: [PATCH] KVM: nVMX: Reset nested_run_pending if the CPU is going to be reset
On Sat, Mar 4, 2017 at 5:03 AM, Wanpeng Li <kernellwp@gmail.com> wrote:
> 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.

Applied on bots. Thanks!

> Reported-by: Dmitry Vyukov <dvyukov@google.com>
> Suggested-by: Radim Krčmář <rkrcmar@redhat.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Radim Krčmář <rkrcmar@redhat.com>
> Cc: Dmitry Vyukov <dvyukov@google.com>
> Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
> ---
> 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 283aa86..b4a757369 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -3310,8 +3310,10 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> FEATURE_CONTROL_LOCKED && !msr_info->host_initiated))
> return 1;
> vmx->msr_ia32_feature_control = data;
> - if (msr_info->host_initiated && data == 0)
> + if (msr_info->host_initiated && data == 0) {
> + vmx->nested.nested_run_pending = 0;
> vmx_leave_nested(vcpu);
> + }
> break;
> case MSR_IA32_VMX_BASIC ... MSR_IA32_VMX_VMFUNC:
> if (!msr_info->host_initiated)
> --
> 2.7.4
>

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