security: don't use RCU accessors for cred->session_keyring

sparse complains that a bunch of places in kernel/cred.c access
cred->session_keyring without the RCU helpers required by the __rcu
annotation.

cred->session_keyring is written in the following places:

 - prepare_kernel_cred() [in a new cred struct]
 - keyctl_session_to_parent() [in a new cred struct]
 - prepare_creds [in a new cred struct, via memcpy]
 - install_session_keyring_to_cred()
  - from install_session_keyring() on new creds
  - from join_session_keyring() on new creds [twice]
  - from umh_keys_init()
   - from call_usermodehelper_exec_async() on new creds

All of these writes are before the creds are committed; therefore,
cred->session_keyring doesn't need RCU protection.

Remove the __rcu annotation and fix up all existing users that use __rcu.

Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: James Morris <james.morris@microsoft.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/include/linux/cred.h b/include/linux/cred.h
index ddd45bb74887..efb6edf32de7 100644
--- a/include/linux/cred.h
+++ b/include/linux/cred.h
@@ -138,7 +138,7 @@ struct cred {
 #ifdef CONFIG_KEYS
 	unsigned char	jit_keyring;	/* default keyring to attach requested
 					 * keys to */
-	struct key __rcu *session_keyring; /* keyring inherited over fork */
+	struct key	*session_keyring; /* keyring inherited over fork */
 	struct key	*process_keyring; /* keyring private to this process */
 	struct key	*thread_keyring; /* keyring private to this thread */
 	struct key	*request_key_auth; /* assumed request_key authority */