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    Subject[PATCH v2 12/16] KVM: Do not partially reinitialize gfn=>pfn cache during activation
    From
    Don't partially reinitialize a gfn=>pfn cache when activating the cache,
    and instead assert that the cache is not valid during activation. Bug
    the VM if the assertion fails, as use-after-free and/or data corruption
    is all but guaranteed if KVM ends up with a valid-but-inactive cache.

    Signed-off-by: Sean Christopherson <seanjc@google.com>
    ---
    virt/kvm/pfncache.c | 9 +++++----
    1 file changed, 5 insertions(+), 4 deletions(-)

    diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c
    index 62b47feed36c..2d5b417e50ac 100644
    --- a/virt/kvm/pfncache.c
    +++ b/virt/kvm/pfncache.c
    @@ -342,6 +342,9 @@ void kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm,
    gpc->vcpu = vcpu;
    gpc->usage = usage;
    gpc->len = len;
    + gpc->pfn = KVM_PFN_ERR_FAULT;
    + gpc->uhva = KVM_HVA_ERR_BAD;
    +
    }
    EXPORT_SYMBOL_GPL(kvm_gpc_init);

    @@ -350,10 +353,8 @@ int kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa)
    struct kvm *kvm = gpc->kvm;

    if (!gpc->active) {
    - gpc->khva = NULL;
    - gpc->pfn = KVM_PFN_ERR_FAULT;
    - gpc->uhva = KVM_HVA_ERR_BAD;
    - gpc->valid = false;
    + if (KVM_BUG_ON(gpc->valid, kvm))
    + return -EIO;

    spin_lock(&kvm->gpc_lock);
    list_add(&gpc->list, &kvm->gpc_list);
    --
    2.38.0.413.g74048e4d9e-goog
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