diff options
author | David Howells <dhowells@redhat.com> | 2010-07-29 07:45:55 -0400 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-07-29 18:16:18 -0400 |
commit | 8f92054e7ca1d3a3ae50fb42d2253ac8730d9b2a (patch) | |
tree | 29d1bcf78bf04fe41c7e811f806f58d655c41f9f /include | |
parent | de09a9771a5346029f4d11e4ac886be7f9bfdd75 (diff) |
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 <dhowells@redhat.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r-- | include/linux/cred.h | 15 | ||||
-rw-r--r-- | include/linux/sched.h | 1 |
2 files changed, 11 insertions, 5 deletions
diff --git a/include/linux/cred.h b/include/linux/cred.h index ce40cbc791e2..4d2c39573f36 100644 --- a/include/linux/cred.h +++ b/include/linux/cred.h | |||
@@ -274,13 +274,18 @@ static inline void put_cred(const struct cred *_cred) | |||
274 | * @task: The task to query | 274 | * @task: The task to query |
275 | * | 275 | * |
276 | * Access the objective credentials of a task. The caller must hold the RCU | 276 | * Access the objective credentials of a task. The caller must hold the RCU |
277 | * readlock. | 277 | * readlock or the task must be dead and unable to change its own credentials. |
278 | * | 278 | * |
279 | * The caller must make sure task doesn't go away, either by holding a ref on | 279 | * The result of this function should not be passed directly to get_cred(); |
280 | * task or by holding tasklist_lock to prevent it from being unlinked. | 280 | * rather get_task_cred() should be used instead. |
281 | */ | 281 | */ |
282 | #define __task_cred(task) \ | 282 | #define __task_cred(task) \ |
283 | ((const struct cred *)(rcu_dereference_check((task)->real_cred, rcu_read_lock_held() || lockdep_tasklist_lock_is_held()))) | 283 | ({ \ |
284 | const struct task_struct *__t = (task); \ | ||
285 | rcu_dereference_check(__t->real_cred, \ | ||
286 | rcu_read_lock_held() || \ | ||
287 | task_is_dead(__t)); \ | ||
288 | }) | ||
284 | 289 | ||
285 | /** | 290 | /** |
286 | * get_current_cred - Get the current task's subjective credentials | 291 | * get_current_cred - Get the current task's subjective credentials |
diff --git a/include/linux/sched.h b/include/linux/sched.h index 747fcaedddb7..0478888c6899 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h | |||
@@ -214,6 +214,7 @@ extern char ___assert_task_state[1 - 2*!!( | |||
214 | 214 | ||
215 | #define task_is_traced(task) ((task->state & __TASK_TRACED) != 0) | 215 | #define task_is_traced(task) ((task->state & __TASK_TRACED) != 0) |
216 | #define task_is_stopped(task) ((task->state & __TASK_STOPPED) != 0) | 216 | #define task_is_stopped(task) ((task->state & __TASK_STOPPED) != 0) |
217 | #define task_is_dead(task) ((task)->exit_state != 0) | ||
217 | #define task_is_stopped_or_traced(task) \ | 218 | #define task_is_stopped_or_traced(task) \ |
218 | ((task->state & (__TASK_STOPPED | __TASK_TRACED)) != 0) | 219 | ((task->state & (__TASK_STOPPED | __TASK_TRACED)) != 0) |
219 | #define task_contributes_to_load(task) \ | 220 | #define task_contributes_to_load(task) \ |