2 files changed, 12 insertions, 25 deletions

diff --git a/include/linux/cred.h b/include/linux/cred.h
index 75c0fa881308..4d2c39573f36 100644
--- a/include/linux/cred.h
+++ b/include/linux/cred.h
@@ -153,6 +153,7 @@ struct cred {
 extern void __put_cred(struct cred *);
 extern void exit_creds(struct task_struct *);
 extern int copy_creds(struct task_struct *, unsigned long);
+extern const struct cred *get_task_cred(struct task_struct *);
 extern struct cred *cred_alloc_blank(void);
 extern struct cred *prepare_creds(void);
 extern struct cred *prepare_exec_creds(void);
@@ -273,33 +274,18 @@ static inline void put_cred(const struct cred *_cred)
  * @task: The task to query
  *
  * Access the objective credentials of a task.  The caller must hold the RCU
- * readlock.
+ * readlock or the task must be dead and unable to change its own credentials.
  *
- * The caller must make sure task doesn't go away, either by holding a ref on
- * task or by holding tasklist_lock to prevent it from being unlinked.
+ * The result of this function should not be passed directly to get_cred();
+ * rather get_task_cred() should be used instead.
  */
-#define __task_cred(task) \
-        ((const struct cred *)(rcu_dereference_check((task)->real_cred, rcu_read_lock_held() || lockdep_tasklist_lock_is_held())))
-
-/**
- * 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 make sure task doesn't go away, either by holding a ref on
- * task or by holding tasklist_lock to prevent it from being unlinked.
- */
-#define get_task_cred(task)                             \
-({                                                      \
-        struct cred *__cred;                            \
-        rcu_read_lock();                                \
-        __cred = (struct cred *) __task_cred((task));   \
-        get_cred(__cred);                               \
-        rcu_read_unlock();                              \
-        __cred;                                         \
-})
+#define __task_cred(task)                                               \
+        ({                                                              \
+                const struct task_struct *__t = (task);                 \
+                rcu_dereference_check(__t->real_cred,                   \
+                                      rcu_read_lock_held() ||           \
+                                      task_is_dead(__t));               \
+        })
 
 /**
  * get_current_cred - Get the current task's subjective credentials
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 747fcaedddb7..0478888c6899 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -214,6 +214,7 @@ extern char ___assert_task_state[1 - 2*!!(
 
 #define task_is_traced(task)    ((task->state & __TASK_TRACED) != 0)
 #define task_is_stopped(task)   ((task->state & __TASK_STOPPED) != 0)
+#define task_is_dead(task)      ((task)->exit_state != 0)
 #define task_is_stopped_or_traced(task) \
                         ((task->state & (__TASK_STOPPED | __TASK_TRACED)) != 0)
 #define task_contributes_to_load(task)  \