From 5c7e372caa35d303e414caeb64ee2243fd3cac3d Mon Sep 17 00:00:00 2001 From: Jann Horn Date: Wed, 27 Mar 2019 16:39:38 +0100 Subject: 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 Signed-off-by: James Morris --- security/keys/process_keys.c | 12 ++++-------- security/keys/request_key.c | 9 ++------- 2 files changed, 6 insertions(+), 15 deletions(-) (limited to 'security') diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c index 9320424c4a46..bd7243cb4c85 100644 --- a/security/keys/process_keys.c +++ b/security/keys/process_keys.c @@ -227,6 +227,7 @@ static int install_process_keyring(void) * Install the given keyring as the session keyring of the given credentials * struct, replacing the existing one if any. If the given keyring is NULL, * then install a new anonymous session keyring. + * @cred can not be in use by any task yet. * * Return: 0 on success; -errno on failure. */ @@ -254,7 +255,7 @@ int install_session_keyring_to_cred(struct cred *cred, struct key *keyring) /* install the keyring */ old = cred->session_keyring; - rcu_assign_pointer(cred->session_keyring, keyring); + cred->session_keyring = keyring; if (old) key_put(old); @@ -392,11 +393,8 @@ key_ref_t search_my_process_keyrings(struct keyring_search_context *ctx) /* search the session keyring */ if (ctx->cred->session_keyring) { - rcu_read_lock(); key_ref = keyring_search_aux( - make_key_ref(rcu_dereference(ctx->cred->session_keyring), 1), - ctx); - rcu_read_unlock(); + make_key_ref(ctx->cred->session_keyring, 1), ctx); if (!IS_ERR(key_ref)) goto found; @@ -612,10 +610,8 @@ try_again: goto reget_creds; } - rcu_read_lock(); - key = rcu_dereference(ctx.cred->session_keyring); + key = ctx.cred->session_keyring; __key_get(key); - rcu_read_unlock(); key_ref = make_key_ref(key, 1); break; diff --git a/security/keys/request_key.c b/security/keys/request_key.c index 2f17d84d46f1..db72dc4d7639 100644 --- a/security/keys/request_key.c +++ b/security/keys/request_key.c @@ -142,12 +142,10 @@ static int call_sbin_request_key(struct key *authkey, void *aux) prkey = cred->process_keyring->serial; sprintf(keyring_str[1], "%d", prkey); - rcu_read_lock(); - session = rcu_dereference(cred->session_keyring); + session = cred->session_keyring; if (!session) session = cred->user->session_keyring; sskey = session->serial; - rcu_read_unlock(); sprintf(keyring_str[2], "%d", sskey); @@ -287,10 +285,7 @@ static int construct_get_dest_keyring(struct key **_dest_keyring) /* fall through */ case KEY_REQKEY_DEFL_SESSION_KEYRING: - rcu_read_lock(); - dest_keyring = key_get( - rcu_dereference(cred->session_keyring)); - rcu_read_unlock(); + dest_keyring = key_get(cred->session_keyring); if (dest_keyring) break; -- cgit v1.2.3