path: root/kernel/lockdep.c
diff options
authorHitoshi Mitake <mitake@dcl.info.waseda.ac.jp>2010-10-13 17:30:26 +0900
committerIngo Molnar <mingo@elte.hu>2010-10-18 18:44:26 +0200
commit4ba053c04aece1f4734056f21b751eee47ea3fb1 (patch)
tree2386ea00022684cd8a9ff811bee2cd8cc7229001 /kernel/lockdep.c
parent620162505e5d46bc4494b1761743e4b0b3bf8e16 (diff)
lockdep: Check the depth of subclass
Current look_up_lock_class() doesn't check the parameter "subclass". This rarely rises problems because the main caller of this function, register_lock_class(), checks it. But register_lock_class() is not the only function which calls look_up_lock_class(). lock_set_class() and its callees also call it. And lock_set_class() doesn't check this parameter. This will rise problems when the the value of subclass is larger than MAX_LOCKDEP_SUBCLASSES. Because the address (used as the key of class) caliculated with too large subclass has a probability to point another key in different lock_class_key. Of course this problem depends on the memory layout and occurs with really low probability. Signed-off-by: Hitoshi Mitake <mitake@dcl.info.waseda.ac.jp> Cc: Dmitry Torokhov <dtor@mail.ru> Cc: Vojtech Pavlik <vojtech@ucw.cz> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <1286958626-986-1-git-send-email-mitake@dcl.info.waseda.ac.jp> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/lockdep.c')
1 files changed, 10 insertions, 8 deletions
diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index bc4d32871f9..42ba65dff7d 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -639,6 +639,16 @@ look_up_lock_class(struct lockdep_map *lock, unsigned int subclass)
+ if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
+ debug_locks_off();
+ printk(KERN_ERR
+ "BUG: looking up invalid subclass: %u\n", subclass);
+ printk(KERN_ERR
+ "turning off the locking correctness validator.\n");
+ dump_stack();
+ return NULL;
+ }
* Static locks do not have their class-keys yet - for them the key
* is the lock object itself:
@@ -2745,14 +2755,6 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
return 0;
- if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
- debug_locks_off();
- printk("BUG: MAX_LOCKDEP_SUBCLASSES too low!\n");
- printk("turning off the locking correctness validator.\n");
- dump_stack();
- return 0;
- }
if (lock->key == &__lockdep_no_validate__)
check = 1;