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From: Bart Van Assche <bvanassche@acm.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: mingo@redhat.com, tj@kernel.org, longman@redhat.com,
	johannes.berg@intel.com, linux-kernel@vger.kernel.org,
	Johannes Berg <johannes@sipsolutions.net>
Subject: Re: [PATCH v3 17/24] locking/lockdep: Free lock classes that are no longer in use
Date: Fri, 07 Dec 2018 08:27:32 -0800	[thread overview]
Message-ID: <1544200052.185366.308.camel@acm.org> (raw)
In-Reply-To: <20181207121429.GI2237@hirez.programming.kicks-ass.net>

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.

  reply	other threads:[~2018-12-07 16:27 UTC|newest]

Thread overview: 49+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-12-07  1:11 [PATCH v3 00/24] locking/lockdep: Add support for dynamic keys Bart Van Assche
2018-12-07  1:11 ` [PATCH v3 01/24] lockdep tests: Display compiler warning and error messages Bart Van Assche
2018-12-11 15:22   ` [tip:locking/core] tools/lib/lockdep/tests: " tip-bot for Bart Van Assche
2018-12-07  1:11 ` [PATCH v3 02/24] lockdep tests: Fix shellcheck warnings Bart Van Assche
2018-12-11 15:23   ` [tip:locking/core] tools/lib/lockdep/tests: " tip-bot for Bart Van Assche
2018-12-07  1:11 ` [PATCH v3 03/24] lockdep tests: Improve testing accuracy Bart Van Assche
2018-12-11 15:23   ` [tip:locking/core] tools/lib/lockdep/tests: " tip-bot for Bart Van Assche
2018-12-07  1:11 ` [PATCH v3 04/24] lockdep tests: Run lockdep tests a second time under Valgrind Bart Van Assche
2018-12-11 15:24   ` [tip:locking/core] tools/lib/lockdep/tests: " tip-bot for Bart Van Assche
2018-12-07  1:11 ` [PATCH v3 05/24] liblockdep: Rename "trywlock" into "trywrlock" Bart Van Assche
2018-12-11 15:24   ` [tip:locking/core] tools/lib/lockdep: " tip-bot for Bart Van Assche
2018-12-11 17:19   ` [PATCH v3 05/24] liblockdep: " Sasha Levin
2018-12-11 17:38     ` Bart Van Assche
2018-12-13 19:41       ` Sasha Levin
2018-12-07  1:11 ` [PATCH v3 06/24] liblockdep: Add dummy print_irqtrace_events() implementation Bart Van Assche
2018-12-11 15:25   ` [tip:locking/core] tools/lib/lockdep: " tip-bot for Bart Van Assche
2018-12-07  1:11 ` [PATCH v3 07/24] lockdep tests: Test the lockdep_reset_lock() implementation Bart Van Assche
2018-12-11 15:26   ` [tip:locking/core] tools/lib/lockdep/tests: " tip-bot for Bart Van Assche
2018-12-07  1:11 ` [PATCH v3 08/24] locking/lockdep: Declare local symbols static Bart Van Assche
2018-12-11 15:26   ` [tip:locking/core] " tip-bot for Bart Van Assche
2018-12-07  1:11 ` [PATCH v3 09/24] locking/lockdep: Inline __lockdep_init_map() Bart Van Assche
2018-12-11 15:27   ` [tip:locking/core] " tip-bot for Bart Van Assche
2018-12-07  1:11 ` [PATCH v3 10/24] locking/lockdep: Introduce lock_class_cache_is_registered() Bart Van Assche
2018-12-11 15:27   ` [tip:locking/core] " tip-bot for Bart Van Assche
2018-12-07  1:11 ` [PATCH v3 11/24] locking/lockdep: Remove a superfluous INIT_LIST_HEAD() statement Bart Van Assche
2018-12-11 15:28   ` [tip:locking/core] " tip-bot for Bart Van Assche
2018-12-07  1:11 ` [PATCH v3 12/24] locking/lockdep: Make concurrent lockdep_reset_lock() calls safe Bart Van Assche
2018-12-11 15:29   ` [tip:locking/core] " tip-bot for Bart Van Assche
2018-12-07  1:11 ` [PATCH v3 13/24] locking/lockdep: Stop using RCU primitives to access all_lock_classes Bart Van Assche
2018-12-11 15:29   ` [tip:locking/core] locking/lockdep: Stop using RCU primitives to access 'all_lock_classes' tip-bot for Bart Van Assche
2018-12-07  1:11 ` [PATCH v3 14/24] locking/lockdep: Make zap_class() remove all matching lock order entries Bart Van Assche
2018-12-07  1:11 ` [PATCH v3 15/24] locking/lockdep: Reorder struct lock_class members Bart Van Assche
2018-12-07  1:11 ` [PATCH v3 16/24] locking/lockdep: Retain the class key and name while freeing a lock class Bart Van Assche
2018-12-07 10:21   ` Peter Zijlstra
2018-12-07 14:50     ` Waiman Long
2018-12-07 16:23       ` Bart Van Assche
2018-12-07  1:11 ` [PATCH v3 17/24] locking/lockdep: Free lock classes that are no longer in use Bart Van Assche
2018-12-07 12:14   ` Peter Zijlstra
2018-12-07 16:27     ` Bart Van Assche [this message]
2018-12-07  1:11 ` [PATCH v3 18/24] locking/lockdep: Reuse list entries " Bart Van Assche
2018-12-07  1:11 ` [PATCH v3 19/24] locking/lockdep: Check data structure consistency Bart Van Assche
2018-12-07  1:11 ` [PATCH v3 20/24] locking/lockdep: Introduce __lockdep_free_key_range() Bart Van Assche
2018-12-07  1:11 ` [PATCH v3 21/24] locking/lockdep: Verify whether lock objects are small enough to be used as class keys Bart Van Assche
2018-12-07  1:11 ` [PATCH v3 22/24] locking/lockdep: Add support for dynamic keys Bart Van Assche
2018-12-07  1:11 ` [PATCH v3 23/24] kernel/workqueue: Use dynamic lockdep keys for workqueues Bart Van Assche
2018-12-07  1:11 ` [PATCH v3 24/24] lockdep tests: Test dynamic key registration Bart Van Assche
2018-12-07 12:23 ` [PATCH v3 00/24] locking/lockdep: Add support for dynamic keys Peter Zijlstra
2018-12-07 16:35   ` Bart Van Assche
2018-12-08 10:26     ` Peter Zijlstra

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