3 files changed, 27 insertions, 21 deletions

diff --git a/fs/proc/array.c b/fs/proc/array.c
index 9b58d38bc911..fff6572676ae 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -176,7 +176,7 @@ static inline void task_state(struct seq_file *m, struct pid_namespace *ns,
                 if (tracer)
                         tpid = task_pid_nr_ns(tracer, ns);
         }
-        cred = get_cred((struct cred *) __task_cred(p));
+        cred = get_task_cred(p);
         seq_printf(m,
                 "State:\t%s\n"
                 "Tgid:\t%d\n"
diff --git a/include/linux/cred.h b/include/linux/cred.h
index 75c0fa881308..ce40cbc791e2 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);
@@ -282,26 +283,6 @@ static inline void put_cred(const struct cred *_cred)
         ((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;                                         \
-})
-
-/**
  * get_current_cred - Get the current task's subjective credentials
  *
  * Get the subjective credentials of the current task, pinning them so that
diff --git a/kernel/cred.c b/kernel/cred.c
index a2d5504fbcc2..60bc8b1e32e6 100644
--- 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.