CRED: Fix get_task_cred() and task_state() to not resurrect dead credentials

[net-next-2.6.git] / kernel / cred.c

diff --git a/kernel/cred.c b/kernel/cred.c
index 2c24870c55d1279995379980766dd792f8671ebd..60bc8b1e32e632eb2a51b318f1ae35486d01174f 100644 (file)
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -209,6 +209,31 @@ void exit_creds(struct task_struct *tsk)
        }
 }
 
+/**
+ * get_task_cred - Get another task's objective credentials
+ * @task: The task to query
+ *
+ * Get the objective credentials of a task, pinning them so that they can't go
+ * away.  Accessing a task's credentials directly is not permitted.
+ *
+ * The caller must also make sure task doesn't get deleted, either by holding a
+ * ref on task or by holding tasklist_lock to prevent it from being unlinked.
+ */
+const struct cred *get_task_cred(struct task_struct *task)
+{
+       const struct cred *cred;
+
+       rcu_read_lock();
+
+       do {
+               cred = __task_cred((task));
+               BUG_ON(!cred);
+       } while (!atomic_inc_not_zero(&((struct cred *)cred)->usage));
+
+       rcu_read_unlock();
+       return cred;
+}
+
 /*
  * Allocate blank credentials, such that the credentials can be filled in at a
  * later date without risk of ENOMEM.
@@ -346,66 +371,6 @@ struct cred *prepare_exec_creds(void)
        return new;
 }
 
-/*
- * 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)
-               goto free_tgcred;
-
-       kdebug("prepare_usermodehelper_creds() alloc %p", new);
-
-       memcpy(new, &init_cred, sizeof(struct cred));
-
-       atomic_set(&new->usage, 1);
-       set_cred_subscribers(new, 0);
-       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;
-       validate_creds(new);
-
-       BUG_ON(atomic_read(&new->usage) != 1);
-       return new;
-
-error:
-       put_cred(new);
-       return NULL;
-
-free_tgcred:
-#ifdef CONFIG_KEYS
-       kfree(tgcred);
-#endif
-       return NULL;
-}
-
 /*
  * Copy credentials for the new process created by fork()
  *