KEYS: trusted: Remove redundant static calls usage

Static calls invocations aren't well supported from module __init and
__exit functions. Especially the static call from cleanup_trusted() led
to a crash on x86 kernel with CONFIG_DEBUG_VIRTUAL=y.

However, the usage of static call invocations for trusted_key_init()
and trusted_key_exit() don't add any value from either a performance or
security perspective. Hence switch to use indirect function calls instead.

Note here that although it will fix the current crash report, ultimately
the static call infrastructure should be fixed to either support its
future usage from module __init and __exit functions or not.
Reported-and-tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Link: https://lore.kernel.org/lkml/ZRhKq6e5nF%2F4ZIV1@fedora/#t
Fixes: 5d0682be ("KEYS: trusted: Add generic trusted keys framework")
Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

security/keys/trusted-keys/trusted_core.c

@@ -44,13 +44,12 @@ static const struct trusted_key_source trusted_key_sources[] = {
 #endif
 };
 
-DEFINE_STATIC_CALL_NULL(trusted_key_init, *trusted_key_sources[0].ops->init);
 DEFINE_STATIC_CALL_NULL(trusted_key_seal, *trusted_key_sources[0].ops->seal);
 DEFINE_STATIC_CALL_NULL(trusted_key_unseal,
 			*trusted_key_sources[0].ops->unseal);
 DEFINE_STATIC_CALL_NULL(trusted_key_get_random,
 			*trusted_key_sources[0].ops->get_random);
-DEFINE_STATIC_CALL_NULL(trusted_key_exit, *trusted_key_sources[0].ops->exit);
+static void (*trusted_key_exit)(void);
 static unsigned char migratable;
 
 enum {
@@ -359,19 +358,16 @@ static int __init init_trusted(void)
 		if (!get_random)
 			get_random = kernel_get_random;
 
-		static_call_update(trusted_key_init,
-				   trusted_key_sources[i].ops->init);
 		static_call_update(trusted_key_seal,
 				   trusted_key_sources[i].ops->seal);
 		static_call_update(trusted_key_unseal,
 				   trusted_key_sources[i].ops->unseal);
 		static_call_update(trusted_key_get_random,
 				   get_random);
-		static_call_update(trusted_key_exit,
-				   trusted_key_sources[i].ops->exit);
+		trusted_key_exit = trusted_key_sources[i].ops->exit;
 		migratable = trusted_key_sources[i].ops->migratable;
 
-		ret = static_call(trusted_key_init)();
+		ret = trusted_key_sources[i].ops->init();
 		if (!ret)
 			break;
 	}
@@ -388,7 +384,8 @@ static int __init init_trusted(void)
 
 static void __exit cleanup_trusted(void)
 {
-	static_call_cond(trusted_key_exit)();
+	if (trusted_key_exit)
+		(*trusted_key_exit)();
 }
 
 late_initcall(init_trusted);