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    Subject[PATCH AUTOSEL for 4.4 17/32] KVM: nVMX: reset nested_run_pending if the vCPU is going to be reset
    Date
    From: Wanpeng Li <wanpeng.li@hotmail.com>

    [ Upstream commit 2f707d97982286b307ef2a9b034e19aabc1abb56 ]

    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@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>
    Cc: David Hildenbrand <david@redhat.com>
    Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
    Reviewed-by: David Hildenbrand <david@redhat.com>
    Reviewed-by: Jim Mattson <jmattson@google.com>
    Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
    Signed-off-by: Sasha Levin <alexander.levin@verizon.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 aa8776848183..88b92d948b41 100644
    --- a/arch/x86/kvm/vmx.c
    +++ b/arch/x86/kvm/vmx.c
    @@ -10556,8 +10556,10 @@ 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));
    }

    --
    2.11.0
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