diff options
Diffstat (limited to 'Documentation/credentials.txt')
| -rw-r--r-- | Documentation/credentials.txt | 17 |
1 files changed, 8 insertions, 9 deletions
diff --git a/Documentation/credentials.txt b/Documentation/credentials.txt index df03169782e..995baf379c0 100644 --- a/Documentation/credentials.txt +++ b/Documentation/credentials.txt @@ -408,9 +408,6 @@ This should be used inside the RCU read lock, as in the following example: ... } -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: @@ -420,23 +417,25 @@ 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: |