Re: [PATCH 4/4] task_work: kill task_work->data

[Oleg Nesterov <oleg@redhat.com>]

On 06/27, Oleg Nesterov wrote:
>
> Turn cred->rcu into rcu_head/task_work union for keyctl_session_to_parent().

I tried to make the minimal patch, but perhaps with this change we
can also simplify the error handling in keyctl_session_to_parent()
a little bit.

We can do cred_alloc_blank() before lookup_user_key() and remove
error_keyring/key_ref_put.

IOW, on top of this patch:

--- x/security/keys/keyctl.c
+++ x/security/keys/keyctl.c
@@ -1461,17 +1461,18 @@ long keyctl_session_to_parent(void)
 	struct cred *cred;
 	int ret;
 
-	keyring_r = lookup_user_key(KEY_SPEC_SESSION_KEYRING, 0, KEY_LINK);
-	if (IS_ERR(keyring_r))
-		return PTR_ERR(keyring_r);
-
 	/* our parent is going to need a new cred struct, a new tgcred struct
 	 * and new security data, so we allocate them here to prevent ENOMEM in
 	 * our parent */
-	ret = -ENOMEM;
 	cred = cred_alloc_blank();
 	if (!cred)
-		goto error_keyring;
+		return -ENOMEM;
+
+	keyring_r = lookup_user_key(KEY_SPEC_SESSION_KEYRING, 0, KEY_LINK);
+	if (IS_ERR(keyring_r)) {
+		ret = PTR_ERR(keyring_r);
+		goto free_cred;
+	}
 
 	cred->tgcred->session_keyring = key_ref_to_ptr(keyring_r);
 	init_task_work(&cred->twork, key_change_session_keyring);
@@ -1532,13 +1533,10 @@ unlock:
 
 	if (oldwork)
 		put_cred(container_of(oldwork, struct cred, twork));
+free_cred:
 	if (cred)
 		put_cred(cred);
 	return ret;
-
-error_keyring:
-	key_ref_put(keyring_r);
-	return ret;
 }
 
 /*