SELinux: security_load_policy: Silence frame-larger-than warning

Dynamically allocate a couple of the larger stack variables in order to
reduce the stack footprint below 1024. gcc-4.8

security/selinux/ss/services.c: In function 'security_load_policy':
security/selinux/ss/services.c:1964:1: warning: the frame size of 1104 bytes is larger than 1024 bytes [-Wframe-larger-than=]
 }

Also silence a couple of checkpatch warnings at the same time.

WARNING: sizeof policydb should be sizeof(policydb)
+	memcpy(oldpolicydb, &policydb, sizeof policydb);

WARNING: sizeof policydb should be sizeof(policydb)
+	memcpy(&policydb, newpolicydb, sizeof policydb);

Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: James Morris <james.l.morris@oracle.com>
Cc: Eric Paris <eparis@parisplace.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Paul Moore <pmoore@redhat.com>

security/selinux/ss/services.c

@@ -1831,7 +1831,7 @@ static int security_preserve_bools(struct policydb *p);
  */
 int security_load_policy(void *data, size_t len)
 {
-	struct policydb oldpolicydb, newpolicydb;
+	struct policydb *oldpolicydb, *newpolicydb;
 	struct sidtab oldsidtab, newsidtab;
 	struct selinux_mapping *oldmap, *map = NULL;
 	struct convert_context_args args;
@@ -1840,12 +1840,19 @@ int security_load_policy(void *data, size_t len)
 	int rc = 0;
 	struct policy_file file = { data, len }, *fp = &file;
 
+	oldpolicydb = kzalloc(2 * sizeof(*oldpolicydb), GFP_KERNEL);
+	if (!oldpolicydb) {
+		rc = -ENOMEM;
+		goto out;
+	}
+	newpolicydb = oldpolicydb + 1;
+
 	if (!ss_initialized) {
 		avtab_cache_init();
 		rc = policydb_read(&policydb, fp);
 		if (rc) {
 			avtab_cache_destroy();
-			return rc;
+			goto out;
 		}
 
 		policydb.len = len;
@@ -1855,14 +1862,14 @@ int security_load_policy(void *data, size_t len)
 		if (rc) {
 			policydb_destroy(&policydb);
 			avtab_cache_destroy();
-			return rc;
+			goto out;
 		}
 
 		rc = policydb_load_isids(&policydb, &sidtab);
 		if (rc) {
 			policydb_destroy(&policydb);
 			avtab_cache_destroy();
-			return rc;
+			goto out;
 		}
 
 		security_load_policycaps();
@@ -1874,36 +1881,36 @@ int security_load_policy(void *data, size_t len)
 		selinux_status_update_policyload(seqno);
 		selinux_netlbl_cache_invalidate();
 		selinux_xfrm_notify_policyload();
-		return 0;
+		goto out;
 	}
 
 #if 0
 	sidtab_hash_eval(&sidtab, "sids");
 #endif
 
-	rc = policydb_read(&newpolicydb, fp);
+	rc = policydb_read(newpolicydb, fp);
 	if (rc)
-		return rc;
+		goto out;
 
-	newpolicydb.len = len;
+	newpolicydb->len = len;
 	/* If switching between different policy types, log MLS status */
-	if (policydb.mls_enabled && !newpolicydb.mls_enabled)
+	if (policydb.mls_enabled && !newpolicydb->mls_enabled)
 		printk(KERN_INFO "SELinux: Disabling MLS support...\n");
-	else if (!policydb.mls_enabled && newpolicydb.mls_enabled)
+	else if (!policydb.mls_enabled && newpolicydb->mls_enabled)
 		printk(KERN_INFO "SELinux: Enabling MLS support...\n");
 
-	rc = policydb_load_isids(&newpolicydb, &newsidtab);
+	rc = policydb_load_isids(newpolicydb, &newsidtab);
 	if (rc) {
 		printk(KERN_ERR "SELinux:  unable to load the initial SIDs\n");
-		policydb_destroy(&newpolicydb);
+		policydb_destroy(newpolicydb);
-		return rc;
+		goto out;
 	}
 
-	rc = selinux_set_mapping(&newpolicydb, secclass_map, &map, &map_size);
+	rc = selinux_set_mapping(newpolicydb, secclass_map, &map, &map_size);
 	if (rc)
 		goto err;
 
-	rc = security_preserve_bools(&newpolicydb);
+	rc = security_preserve_bools(newpolicydb);
 	if (rc) {
 		printk(KERN_ERR "SELinux:  unable to preserve booleans\n");
 		goto err;
@@ -1921,7 +1928,7 @@ int security_load_policy(void *data, size_t len)
 	 * in the new SID table.
 	 */
 	args.oldp = &policydb;
-	args.newp = &newpolicydb;
+	args.newp = newpolicydb;
 	rc = sidtab_map(&newsidtab, convert_context, &args);
 	if (rc) {
 		printk(KERN_ERR "SELinux:  unable to convert the internal"
@@ -1931,12 +1938,12 @@ int security_load_policy(void *data, size_t len)
 	}
 
 	/* Save the old policydb and SID table to free later. */
-	memcpy(&oldpolicydb, &policydb, sizeof policydb);
+	memcpy(oldpolicydb, &policydb, sizeof(policydb));
 	sidtab_set(&oldsidtab, &sidtab);
 
 	/* Install the new policydb and SID table. */
 	write_lock_irq(&policy_rwlock);
-	memcpy(&policydb, &newpolicydb, sizeof policydb);
+	memcpy(&policydb, newpolicydb, sizeof(policydb));
 	sidtab_set(&sidtab, &newsidtab);
 	security_load_policycaps();
 	oldmap = current_mapping;
@@ -1946,7 +1953,7 @@ int security_load_policy(void *data, size_t len)
 	write_unlock_irq(&policy_rwlock);
 
 	/* Free the old policydb and SID table. */
-	policydb_destroy(&oldpolicydb);
+	policydb_destroy(oldpolicydb);
 	sidtab_destroy(&oldsidtab);
 	kfree(oldmap);
 
@@ -1956,14 +1963,17 @@ int security_load_policy(void *data, size_t len)
 	selinux_netlbl_cache_invalidate();
 	selinux_xfrm_notify_policyload();
 
-	return 0;
+	rc = 0;
+	goto out;
 
 err:
 	kfree(map);
 	sidtab_destroy(&newsidtab);
-	policydb_destroy(&newpolicydb);
+	policydb_destroy(newpolicydb);
-	return rc;
 
+out:
+	kfree(oldpolicydb);
+	return rc;
 }
 
 size_t security_policydb_len(void)