apparmor: fix SECURITY_APPARMOR_HASH_DEFAULT parameter handling

The newly added Kconfig option could never work and just causes a build error
when disabled:

security/apparmor/lsm.c:675:25: error: 'CONFIG_SECURITY_APPARMOR_HASH_DEFAULT' undeclared here (not in a function)
 bool aa_g_hash_policy = CONFIG_SECURITY_APPARMOR_HASH_DEFAULT;

The problem is that the macro undefined in this case, and we need to use the IS_ENABLED()
helper to turn it into a boolean constant.

Another minor problem with the original patch is that the option is even offered
in sysfs when SECURITY_APPARMOR_HASH is not enabled, so this also hides the option
in that case.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: 6059f71f1e94 ("apparmor: add parameter to control whether policy hashing is used")
Signed-off-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>

security/apparmor/crypto.c

@@ -39,6 +39,9 @@ int aa_calc_profile_hash(struct aa_profile *profile, u32 version, void *start,
 	int error = -ENOMEM;
 	u32 le32_version = cpu_to_le32(version);
 
+	if (!aa_g_hash_policy)
+		return 0;
+
 	if (!apparmor_tfm)
 		return 0;
 

security/apparmor/lsm.c

@@ -671,9 +671,11 @@ enum profile_mode aa_g_profile_mode = APPARMOR_ENFORCE;
 module_param_call(mode, param_set_mode, param_get_mode,
 		  &aa_g_profile_mode, S_IRUSR | S_IWUSR);
 
+#ifdef CONFIG_SECURITY_APPARMOR_HASH
 /* whether policy verification hashing is enabled */
-bool aa_g_hash_policy = CONFIG_SECURITY_APPARMOR_HASH_DEFAULT;
+bool aa_g_hash_policy = IS_ENABLED(CONFIG_SECURITY_APPARMOR_HASH_DEFAULT);
 module_param_named(hash_policy, aa_g_hash_policy, aabool, S_IRUSR | S_IWUSR);
+#endif
 
 /* Debug mode */
 bool aa_g_debug;

security/apparmor/policy_unpack.c

@@ -778,8 +778,7 @@ int aa_unpack(void *udata, size_t size, struct list_head *lh, const char **ns)
 		if (error)
 			goto fail_profile;
 
-		if (aa_g_hash_policy)
-			error = aa_calc_profile_hash(profile, e.version, start,
+		error = aa_calc_profile_hash(profile, e.version, start,
 						     e.pos - start);
 		if (error)
 			goto fail_profile;