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SubjectRe: lockdep: Warning & NULL ptr deref
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On Tue, 2012-02-28 at 10:24 -0500, Sasha Levin wrote:
>
> I'll send some patches to prevent the NULL deref itself which happens
> since a chunk of the code in lockdep.c assumed hlock_class() can't
> return NULL.
>
There's tons of code actually assuming that..

> This won't fix the actual problem though, I'm not sure exactly how a
> held lock wouldn't have a class initialized to it.

static inline struct lock_class *hlock_class(struct held_lock *hlock)
{
if (!hlock->class_idx) {
/*
* Someone passed in garbage, we give up.
*/
DEBUG_LOCKS_WARN_ON(1);
return NULL;
}
return lock_classes + hlock->class_idx - 1;
}

Typically that translates to severe memory corruption.


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