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KVM: nSVM: call nested_svm_load_cr3 on nested state load

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While KVM's MMU should be fully reset by loading of nested CR0/CR3/CR4
by KVM_SET_SREGS, we are not in nested mode yet when we do it and therefore
only root_mmu is reset.

On regular nested entries we call nested_svm_load_cr3 which both updates
the guest's CR3 in the MMU when it is needed, and it also initializes
the mmu again which makes it initialize the walk_mmu as well when nested
paging is enabled in both host and guest.

Since we don't call nested_svm_load_cr3 on nested state load,
the walk_mmu can be left uninitialized, which can lead to a NULL pointer
dereference while accessing it if we happen to get a nested page fault
right after entering the nested guest first time after the migration and
we decide to emulate it, which leads to the emulator trying to access
walk_mmu->gva_to_gpa which is NULL.

Therefore we should call this function on nested state load as well.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20210401141814.1029036-3-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Maxim Levitsky 2021-04-01 17:18:10 +03:00 committed by Paolo Bonzini
parent 8486039a6c
commit 232f75d3b4
1 changed files with 22 additions and 18 deletions
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40
arch/x86/kvm/svm/nested.c
View File

@ -215,24 +215,6 @@ static bool nested_svm_vmrun_msrpm(struct vcpu_svm *svm)
return true;
}
static bool svm_get_nested_state_pages(struct kvm_vcpu *vcpu)
{
struct vcpu_svm *svm = to_svm(vcpu);
if (WARN_ON(!is_guest_mode(vcpu)))
return true;
if (!nested_svm_vmrun_msrpm(svm)) {
vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
vcpu->run->internal.suberror =
KVM_INTERNAL_ERROR_EMULATION;
vcpu->run->internal.ndata = 0;
return false;
}
return true;
}
static bool nested_vmcb_check_controls(struct vmcb_control_area *control)
{
if (CC(!vmcb_is_intercept(control, INTERCEPT_VMRUN)))
@ -1330,6 +1312,28 @@ out_free:
return ret;
}
static bool svm_get_nested_state_pages(struct kvm_vcpu *vcpu)
{
struct vcpu_svm *svm = to_svm(vcpu);
if (WARN_ON(!is_guest_mode(vcpu)))
return true;
if (nested_svm_load_cr3(&svm->vcpu, vcpu->arch.cr3,
nested_npt_enabled(svm)))
return false;
if (!nested_svm_vmrun_msrpm(svm)) {
vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
vcpu->run->internal.suberror =
KVM_INTERNAL_ERROR_EMULATION;
vcpu->run->internal.ndata = 0;
return false;
}
return true;
}
struct kvm_x86_nested_ops svm_nested_ops = {
.check_events = svm_check_nested_events,
.triple_fault = nested_svm_triple_fault,