KVM: Validate hva in kvm_gpc_activate_hva() to fix __kvm_gpc_refresh() WARN

Check that the virtual address is "ok" when activating a gfn_to_pfn_cache
with a host VA to ensure that KVM never attempts to use a bad address.

This fixes a bug where KVM fails to check the incoming address when
handling KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO_HVA in kvm_xen_vcpu_set_attr().

Reported-by: syzbot+fd555292a1da3180fc82@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=fd555292a1da3180fc82
Tested-by: syzbot+fd555292a1da3180fc82@syzkaller.appspotmail.com
Signed-off-by: Pei Li <peili.dev@gmail.com>
Reviewed-by: Paul Durrant <paul@xen.org>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
Link: https://lore.kernel.org/r/20240627-bug5-v2-1-2c63f7ee6739@gmail.com
[sean: rewrite changelog with --verbose]
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index f65b35a05d91687b3a159af967a7408c8d73c27c..67bb4e89c399f1cf0c0400caf00423b611609679 100644 (file)
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -741,7 +741,7 @@ int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data)
                } else {
                        void __user * hva = u64_to_user_ptr(data->u.shared_info.hva);
 
-                       if (!PAGE_ALIGNED(hva) || !access_ok(hva, PAGE_SIZE)) {
+                       if (!PAGE_ALIGNED(hva)) {
                                r = -EINVAL;
                        } else if (!hva) {
                                kvm_gpc_deactivate(&kvm->arch.xen.shinfo_cache);

diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c
index e3453e869e92c8f6546b7aa76ce8b3a2b486df4f..f0039efb9e1e34315450bcb589429a8cecb37a73 100644 (file)
--- a/virt/kvm/pfncache.c
+++ b/virt/kvm/pfncache.c
@@ -430,6 +430,9 @@ int kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len)
 
 int kvm_gpc_activate_hva(struct gfn_to_pfn_cache *gpc, unsigned long uhva, unsigned long len)
 {
+       if (!access_ok((void __user *)uhva, len))
+               return -EINVAL;
+
        return __kvm_gpc_activate(gpc, INVALID_GPA, uhva, len);
 }