Re: [PATCH v2 2/2] Revert "KVM: x86: work around leak of uninitialized stack contents"

From: Paolo Bonzini
Date: Fri Jun 05 2020 - 13:34:07 EST


On 05/06/20 13:59, Vitaly Kuznetsov wrote:
> handle_vmptrst()/handle_vmread() stopped injecting #PF unconditionally
> and switched to nested_vmx_handle_memory_failure() which just kills the
> guest with KVM_EXIT_INTERNAL_ERROR in case of MMIO access, zeroing
> 'exception' in kvm_write_guest_virt_system() is not needed anymore.
>
> This reverts commit 541ab2aeb28251bf7135c7961f3a6080eebcc705.
>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
> ---
> arch/x86/kvm/x86.c | 7 -------
> 1 file changed, 7 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 9e41b5135340..0097a97d331f 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -5647,13 +5647,6 @@ int kvm_write_guest_virt_system(struct kvm_vcpu *vcpu, gva_t addr, void *val,
> /* kvm_write_guest_virt_system can pull in tons of pages. */
> vcpu->arch.l1tf_flush_l1d = true;
>
> - /*
> - * FIXME: this should call handle_emulation_failure if X86EMUL_IO_NEEDED
> - * is returned, but our callers are not ready for that and they blindly
> - * call kvm_inject_page_fault. Ensure that they at least do not leak
> - * uninitialized kernel stack memory into cr2 and error code.
> - */
> - memset(exception, 0, sizeof(*exception));
> return kvm_write_guest_virt_helper(addr, val, bytes, vcpu,
> PFERR_WRITE_MASK, exception);
> }
>

Queued, thanks.

Paolo