On Wed, 11 Nov 2020 10:53:37 -0800
Ben Gardon <[email protected]> wrote:
> When PAE is in use, the root_hpa will not have a shadow page
> assoicated with it. In this case the kernel will crash with a NULL
> pointer dereference. Add checks to ensure is_tdp_mmu_root works as
> intended even when using PAE.
>
> Tested: compiles
>
> Fixes: 02c00b3a2f7e ("kvm: x86/mmu: Allocate and free TDP MMU roots")
> Reported-by: Zdenek Kaspar <[email protected]>
> Signed-off-by: Ben Gardon <[email protected]>
> ---
> arch/x86/kvm/mmu/tdp_mmu.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
> index 27e381c9da6c..13013f4d98ad 100644
> --- a/arch/x86/kvm/mmu/tdp_mmu.c
> +++ b/arch/x86/kvm/mmu/tdp_mmu.c
> @@ -49,8 +49,18 @@ bool is_tdp_mmu_root(struct kvm *kvm, hpa_t hpa)
> {
> struct kvm_mmu_page *sp;
>
> + if (WARN_ON(!VALID_PAGE(hpa)))
> + return false;
> +
> sp = to_shadow_page(hpa);
>
> + /*
> + * If this VM is being run with PAE, the TDP MMU will not be
> enabled
> + * and the root HPA will not have a shadow page associated
> with it.
> + */
> + if (!sp)
> + return false;
> +
> return sp->tdp_mmu_page && sp->root_count;
> }
>
Fixes is_tdp_mmu_root NULL pointer dereference
Tested on: Intel(R) Core(TM)2 CPU 6600 @ 2.40GHz
Tested-by: Zdenek Kaspar <[email protected]>
