KVM: x86: Add a helper to retrieve userspace address from kvm_device_attr

mainline inclusion
from mainline-v5.17-rc2
commit 56f289a8
category: feature
bugzilla: https://gitee.com/openeuler/intel-kernel/issues/I5RQLJ
CVE: NA

Intel-SIG: commit 56f289a8 KVM: x86: Add a helper to retrieve userspace address from kvm_device_attr.

--------------------------------

Add a helper to handle converting the u64 userspace address embedded in
struct kvm_device_attr into a userspace pointer, it's all too easy to
forget the intermediate "unsigned long" cast as well as the truncation
check.

No functional change intended.
Signed-off-by: NSean Christopherson <seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NLin Wang <lin.x.wang@intel.com>

arch/x86/kvm/x86.c

@@ -4006,7 +4006,15 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 		break;
 	}
 	return r;
+}
+
+static inline void __user *kvm_get_attr_addr(struct kvm_device_attr *attr)
+{
+	void __user *uaddr = (void __user*)(unsigned long)attr->addr;
 
+	if ((u64)(unsigned long)uaddr != attr->addr)
+		return ERR_PTR(-EFAULT);
+	return uaddr;
 }
 
 long kvm_arch_dev_ioctl(struct file *filp,