Merge branch 'master' into for-linus

1 files changed, 25 insertions, 0 deletions

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.