[PATCH v6 06/13] KEYS: trusted: Update static calls before init

[Jarkko Sakkinen <jarkko@kernel.org>]

Given that the static calls are updated only after ->init() returns, an
added trusted key can race with the callback initializations. This can
ultimately lead into null dereference as static_call() is used unchecked.

Address the bug by updating the static calls before invoking ->init(), and
roll back on failure.

Cc: stable@vger.kernel.org # v5.15+
Fixes: 31de287345f4 ("KEYS: trusted: Rollback init_trusted() consistently")
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
 security/keys/trusted-keys/trusted_core.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/security/keys/trusted-keys/trusted_core.c b/security/keys/trusted-keys/trusted_core.c
index 0509d9955f2a..11d7d296d063 100644
--- a/security/keys/trusted-keys/trusted_core.c
+++ b/security/keys/trusted-keys/trusted_core.c
@@ -373,14 +373,19 @@ static int __init init_trusted(void)
 		if (!get_random)
 			get_random = kernel_get_random;
 
+		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);
+		migratable = trusted_key_sources[i].ops->migratable;
+
 		ret = trusted_key_sources[i].ops->init();
 		if (!ret) {
-			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);
-
 			trusted_key_exit = trusted_key_sources[i].ops->exit;
-			migratable = trusted_key_sources[i].ops->migratable;
+		} else {
+			static_call_update(trusted_key_seal, NULL);
+			static_call_update(trusted_key_unseal, NULL);
+			static_call_update(trusted_key_get_random, NULL);
+			migratable = 0;
 		}
 
 		if (!ret || ret != -ENODEV)
-- 
2.47.3