[PATCH] selinux: fix avc_alloc_node() oom with no policy loaded

This patch should fix the avc_alloc_node() oom condition that Andrew
reported when no policy is loaded in SELinux.

Prior to this patch, when no policy was loaded, the SELinux "security
server" (policy engine) was only returning allowed decisions for the
requested permissions for each access check.  This caused the cache to
thrash when trying to use SELinux for real work with no policy loaded
(typically, the no policy loaded state is only for bootstrapping to the
point where we can load an initial policy).

This patch changes the SELinux security server to return the complete
allowed access vector at once, and then to reset the cache after the
initial policy load to flush the initial cache state created during
bootstrapping.

Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

security/selinux/ss/services.c

@@ -476,8 +476,8 @@ int security_compute_av(u32 ssid,
 	int rc = 0;
 
 	if (!ss_initialized) {
-		avd->allowed = requested;
-		avd->decided = requested;
+		avd->allowed = 0xffffffff;
+		avd->decided = 0xffffffff;
 		avd->auditallow = 0;
 		avd->auditdeny = 0xffffffff;
 		avd->seqno = latest_granting;
@@ -1196,9 +1196,11 @@ int security_load_policy(void *data, size_t len)
 		}
 		policydb_loaded_version = policydb.policyvers;
 		ss_initialized = 1;
-
+		seqno = ++latest_granting;
 		LOAD_UNLOCK;
 		selinux_complete_init();
+		avc_ss_reset(seqno);
+		selnl_notify_policyload(seqno);
 		return 0;
 	}