From 8f92054e7ca1d3a3ae50fb42d2253ac8730d9b2a Mon Sep 17 00:00:00 2001 From: David Howells Date: Thu, 29 Jul 2010 12:45:55 +0100 Subject: CRED: Fix __task_cred()'s lockdep check and banner comment Fix __task_cred()'s lockdep check by removing the following validation condition: lockdep_tasklist_lock_is_held() as commit_creds() does not take the tasklist_lock, and nor do most of the functions that call it, so this check is pointless and it can prevent detection of the RCU lock not being held if the tasklist_lock is held. Instead, add the following validation condition: task->exit_state >= 0 to permit the access if the target task is dead and therefore unable to change its own credentials. Fix __task_cred()'s comment to: (1) discard the bit that says that the caller must prevent the target task from being deleted. That shouldn't need saying. (2) Add a comment indicating the result of __task_cred() should not be passed directly to get_cred(), but rather than get_task_cred() should be used instead. Also put a note into the documentation to enforce this point there too. Signed-off-by: David Howells Acked-by: Jiri Olsa Cc: Paul E. McKenney Signed-off-by: Linus Torvalds --- Documentation/credentials.txt | 3 +++ 1 file changed, 3 insertions(+) (limited to 'Documentation/credentials.txt') diff --git a/Documentation/credentials.txt b/Documentation/credentials.txt index a2db35287003..995baf379c07 100644 --- a/Documentation/credentials.txt +++ b/Documentation/credentials.txt @@ -417,6 +417,9 @@ 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: -- cgit v1.2.1