KVM: Explicitly initialize all fields at the start of kvm_vcpu_map()

Explicitly initialize the entire kvm_host_map structure when mapping a
pfn, as some callers declare their struct on the stack, i.e. don't
zero-initialize the struct, which makes the map->hva in kvm_vcpu_unmap()
*very* suspect.

Tested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241010182427.1434605-22-seanjc@google.com>

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 90e2a1f1de606915fe254c3742b1498a611915ef..4074f49eb3f17928aa793a111a8375313c0ef6ae 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3061,32 +3061,24 @@ void kvm_release_pfn(kvm_pfn_t pfn, bool dirty)
 
 int kvm_vcpu_map(struct kvm_vcpu *vcpu, gfn_t gfn, struct kvm_host_map *map)
 {
-       kvm_pfn_t pfn;
-       void *hva = NULL;
-       struct page *page = KVM_UNMAPPED_PAGE;
+       map->page = KVM_UNMAPPED_PAGE;
+       map->hva = NULL;
+       map->gfn = gfn;
 
-       pfn = gfn_to_pfn(vcpu->kvm, gfn);
-       if (is_error_noslot_pfn(pfn))
+       map->pfn = gfn_to_pfn(vcpu->kvm, gfn);
+       if (is_error_noslot_pfn(map->pfn))
                return -EINVAL;
 
-       if (pfn_valid(pfn)) {
-               page = pfn_to_page(pfn);
-               hva = kmap(page);
+       if (pfn_valid(map->pfn)) {
+               map->page = pfn_to_page(map->pfn);
+               map->hva = kmap(map->page);
 #ifdef CONFIG_HAS_IOMEM
        } else {
-               hva = memremap(pfn_to_hpa(pfn), PAGE_SIZE, MEMREMAP_WB);
+               map->hva = memremap(pfn_to_hpa(map->pfn), PAGE_SIZE, MEMREMAP_WB);
 #endif
        }
 
-       if (!hva)
-               return -EFAULT;
-
-       map->page = page;
-       map->hva = hva;
-       map->pfn = pfn;
-       map->gfn = gfn;
-
-       return 0;
+       return map->hva ? 0 : -EFAULT;
 }
 EXPORT_SYMBOL_GPL(kvm_vcpu_map);