...
}
-A function need not get RCU read lock to use __task_cred() if it is holding a
-spinlock at the time as this implicitly holds the RCU read lock.
-
Should it be necessary to hold another task's credentials for a long period of
time, and possibly to sleep whilst doing so, then the caller should get a
reference on them using:
This does all the RCU magic inside of it. The caller must call put_cred() on
the credentials so obtained when they're finished with.
+ [*] Note: The result of __task_cred() should not be passed directly to
+ get_cred() as this may race with commit_cred().
+
There are a couple of convenience functions to access bits of another task's
credentials, hiding the RCU magic from the caller:
uid_t task_uid(task) Task's real UID
uid_t task_euid(task) Task's effective UID
-If the caller is holding a spinlock or the RCU read lock at the time anyway,
-then:
+If the caller is holding the RCU read lock at the time anyway, then:
__task_cred(task)->uid
__task_cred(task)->euid
should be used instead. Similarly, if multiple aspects of a task's credentials
-need to be accessed, RCU read lock or a spinlock should be used, __task_cred()
-called, the result stored in a temporary pointer and then the credential
-aspects called from that before dropping the lock. This prevents the
-potentially expensive RCU magic from being invoked multiple times.
+need to be accessed, RCU read lock should be used, __task_cred() called, the
+result stored in a temporary pointer and then the credential aspects called
+from that before dropping the lock. This prevents the potentially expensive
+RCU magic from being invoked multiple times.
Should some other single aspect of another task's credentials need to be
accessed, then this can be used: