Messages in this thread | | | Subject | Re: [PATCH v3 17/24] locking/lockdep: Free lock classes that are no longer in use | From | Bart Van Assche <> | Date | Fri, 07 Dec 2018 08:27:32 -0800 |
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On Fri, 2018-12-07 at 13:14 +0100, Peter Zijlstra wrote: > On Thu, Dec 06, 2018 at 05:11:41PM -0800, Bart Van Assche wrote: > > + if (WARN_ON_ONCE(!hlock_class(prev)->hash_entry.pprev) || > > + WARN_ONCE(!hlock_class(next)->hash_entry.pprev, > > + KERN_INFO "Detected use-after-free of lock class %s\n", > > + hlock_class(next)->name)) { > > + return 2; > > + } > > Ah, this is that UaF on ->name, but it only happens when there's already > been a UaF, so that's fine I suppose. Still a note on that earlier > Changelog would've been nice I suppose.
How about reporting the class pointer only as is done elsewhere in the lockdep code?
> > +/* Must be called with the graph lock held. */ > > +static void remove_class_from_lock_chain(struct lock_chain *chain, > > + struct lock_class *class) > > +{ > > + u64 chain_key; > > + int i; > > + > > +#ifdef CONFIG_PROVE_LOCKING > > + for (i = chain->base; i < chain->base + chain->depth; i++) { > > + if (chain_hlocks[i] != class - lock_classes) > > + continue; > > + if (--chain->depth > 0) > > { > > + memmove(&chain_hlocks[i], &chain_hlocks[i + 1], > > + (chain->base + chain->depth - i) * > > + sizeof(chain_hlocks[0])); > > } > > Also, I suppose a comment here that notes we 'leak' chain_hlock[] > entries would be appropriate here.
OK, I will add such a comment.
> If Waiman cares, it is possible to reclaim then by extending the above > memmove() to cover the _entire_ tail of the array and then going around > and fixing up all the chain->base 'pointers' that are in the moved part.
Since that change is outside the scope of what I want to realize I will leave this to Waiman.
Bart.
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