lockdep: Check the depth of subclass
authorHitoshi Mitake <mitake@dcl.info.waseda.ac.jp>
Wed, 13 Oct 2010 08:30:26 +0000 (17:30 +0900)
committerIngo Molnar <mingo@elte.hu>
Mon, 18 Oct 2010 16:44:26 +0000 (18:44 +0200)
commit4ba053c04aece1f4734056f21b751eee47ea3fb1
tree2386ea00022684cd8a9ff811bee2cd8cc7229001
parent620162505e5d46bc4494b1761743e4b0b3bf8e16
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>
kernel/lockdep.c