Sean Christopherson <sean.j.christopherson@xxxxxxxxx> writes:
> Use an unsigned long for 'exit_qual' in nested_vmx_reflect_vmexit(), the
> EXIT_QUALIFICATION field is naturally sized, not a 32-bit field.
>
> The bug is most easily observed by doing VMXON (or any VMX instruction)
> in L2 with a negative displacement, in which case dropping the upper
> bits on nested VM-Exit results in L1 calculating the wrong virtual
> address for the memory operand, e.g. "vmxon -0x8(%rbp)" yields:
>
> Unhandled cpu exception 14 #PF at ip 0000000000400553
> rbp=0000000000537000 cr2=0000000100536ff8
>
> Fixes: fbdd50250396d ("KVM: nVMX: Move VM-Fail check out of nested_vmx_exit_reflected()")
> Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> ---
>
> Sadly (for me), I can't blame a mishandled merge on this one. Even more
> embarassing is that this is actually the second instance where I botched
> the size for exit_qual, you'd think I'd have double-checked everything
> after the first one...
>
> arch/x86/kvm/vmx/nested.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index f228339cd0a0..3f32f81f5c59 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -5814,7 +5814,8 @@ bool nested_vmx_reflect_vmexit(struct kvm_vcpu *vcpu)
> {
> struct vcpu_vmx *vmx = to_vmx(vcpu);
> u32 exit_reason = vmx->exit_reason;
> - u32 exit_intr_info, exit_qual;
> + unsigned long exit_qual;
> + u32 exit_intr_info;
>
> WARN_ON_ONCE(vmx->nested.nested_run_pending);
Too late but
Reviewed-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
I also did 'git grep -W 'u32.*exit_qual' kvm/queue' and I can see a few
more places where 'exit_qual' is u32:
nested_vmx_check_guest_state()
nested_vmx_enter_non_root_mode()
vmx_set_nested_state()
Being too lazy to check an even if there are no immediate issues with
that, should we just use 'unsigned long' everywhere?
--
Vitaly
