+/**
+ * prepare_creds - Prepare a new set of credentials for modification
+ *
+ * Prepare a new set of task credentials for modification. A task's creds
+ * shouldn't generally be modified directly, therefore this function is used to
+ * prepare a new copy, which the caller then modifies and then commits by
+ * calling commit_creds().
+ *
+ * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
+ *
+ * Call commit_creds() or abort_creds() to clean up.
+ */
+struct cred *prepare_creds(void)
+{
+ struct task_struct *task = current;
+ const struct cred *old;
+ struct cred *new;
+
+ BUG_ON(atomic_read(&task->cred->usage) < 1);
+
+ new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
+ if (!new)
+ return NULL;
+
+ old = task->cred;
+ memcpy(new, old, sizeof(struct cred));
+
+ atomic_set(&new->usage, 1);
+ get_group_info(new->group_info);
+ get_uid(new->user);
+
+#ifdef CONFIG_KEYS
+ key_get(new->thread_keyring);
+ key_get(new->request_key_auth);
+ atomic_inc(&new->tgcred->usage);
+#endif
+
+#ifdef CONFIG_SECURITY
+ new->security = NULL;
+#endif
+
+ if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
+ goto error;
+ return new;
+
+error:
+ abort_creds(new);
+ return NULL;
+}
+EXPORT_SYMBOL(prepare_creds);
+
+/*
+ * prepare new credentials for the usermode helper dispatcher
+ */
+struct cred *prepare_usermodehelper_creds(void)
+{
+#ifdef CONFIG_KEYS
+ struct thread_group_cred *tgcred = NULL;
+#endif
+ struct cred *new;
+
+#ifdef CONFIG_KEYS
+ tgcred = kzalloc(sizeof(*new->tgcred), GFP_ATOMIC);
+ if (!tgcred)
+ return NULL;
+#endif
+
+ new = kmem_cache_alloc(cred_jar, GFP_ATOMIC);
+ if (!new)
+ return NULL;
+
+ memcpy(new, &init_cred, sizeof(struct cred));
+
+ atomic_set(&new->usage, 1);
+ get_group_info(new->group_info);
+ get_uid(new->user);
+
+#ifdef CONFIG_KEYS
+ new->thread_keyring = NULL;
+ new->request_key_auth = NULL;
+ new->jit_keyring = KEY_REQKEY_DEFL_DEFAULT;
+
+ atomic_set(&tgcred->usage, 1);
+ spin_lock_init(&tgcred->lock);
+ new->tgcred = tgcred;
+#endif
+
+#ifdef CONFIG_SECURITY
+ new->security = NULL;
+#endif
+ if (security_prepare_creds(new, &init_cred, GFP_ATOMIC) < 0)
+ goto error;
+
+ BUG_ON(atomic_read(&new->usage) != 1);
+ return new;
+
+error:
+ put_cred(new);
+ return NULL;
+}
+