linux-kernel - [PATCH] KEYS: trusted: Remove redundant static calls usage

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Message-Id: <20231005133306.379718-1-sumit.garg@linaro.org>
Date:   Thu,  5 Oct 2023 19:03:06 +0530
From:   Sumit Garg <sumit.garg@...aro.org>
To:     torvalds@...ux-foundation.org, jarkko@...nel.org,
        peterz@...radead.org
Cc:     linux-kernel@...r.kernel.org, linux-integrity@...r.kernel.org,
        jejb@...ux.ibm.com, zohar@...ux.ibm.com, David.Kaplan@....com,
        bp@...en8.de, mingo@...nel.org, x86@...nel.org,
        regressions@...mhuis.info, Sumit Garg <sumit.garg@...aro.org>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>
Subject: [PATCH] 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() doesn't adds any value neither from performance
point and nor there is any security benefit. Hence switch to use indirect
function calls instead.

Note here that although it will fix the current crash reported. But
ultimately we need fix up static calls infrastructure to either support
its future usage from module __init and __exit functions or not.

Reported-by: Hyeonggon Yoo <42.hyeyoo@...il.com>
Closes: https://lore.kernel.org/lkml/ZRhKq6e5nF%2F4ZIV1@fedora/#t
Fixes: 5d0682be3189 ("KEYS: trusted: Add generic trusted keys framework")
Signed-off-by: Sumit Garg <sumit.garg@...aro.org>
---
 security/keys/trusted-keys/trusted_core.c | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/security/keys/trusted-keys/trusted_core.c b/security/keys/trusted-keys/trusted_core.c
index c6fc50d67214..85fb5c22529a 100644
--- a/security/keys/trusted-keys/trusted_core.c
+++ b/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);
-- 
2.34.1