selinux: change handling of invalid classes (Was: Re: 2.6.26-rc5-mm1 selinux whine)

On Mon, 2008-06-09 at 01:24 -0700, Andrew Morton wrote:
> Getting a few of these with FC5:
>
> SELinux: context_struct_compute_av:  unrecognized class 69
> SELinux: context_struct_compute_av:  unrecognized class 69
>
> one came out when I logged in.
>
> No other symptoms, yet.

Change handling of invalid classes by SELinux, reporting class values
unknown to the kernel as errors (w/ ratelimit applied) and handling
class values unknown to policy as normal denials.
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Acked-by: Eric Paris <eparis@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>

security/selinux/ss/services.c

@@ -407,9 +407,19 @@ static int context_struct_compute_av(struct context *scontext,
 	return 0;
 
 inval_class:
-	printk(KERN_ERR "SELinux: %s:  unrecognized class %d\n", __func__,
-		tclass);
-	return -EINVAL;
+	if (!tclass || tclass > kdefs->cts_len ||
+	    !kdefs->class_to_string[tclass]) {
+		if (printk_ratelimit())
+			printk(KERN_ERR "SELinux: %s:  unrecognized class %d\n",
+			       __func__, tclass);
+		return -EINVAL;
+	}
+
+	/*
+	 * Known to the kernel, but not to the policy.
+	 * Handle as a denial (allowed is 0).
+	 */
+	return 0;
 }
 
 /*