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From: Waiman Long <longman@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>,
	Bart Van Assche <bvanassche@acm.org>
Cc: mingo@redhat.com, tj@kernel.org, johannes.berg@intel.com,
	linux-kernel@vger.kernel.org,
	Johannes Berg <johannes@sipsolutions.net>
Subject: Re: [PATCH v3 16/24] locking/lockdep: Retain the class key and name while freeing a lock class
Date: Fri, 7 Dec 2018 09:50:49 -0500	[thread overview]
Message-ID: <a681e9d4-7bf8-d919-f0ce-f4990f34d3af@redhat.com> (raw)
In-Reply-To: <20181207102143.GH2237@hirez.programming.kicks-ass.net>

On 12/07/2018 05:21 AM, Peter Zijlstra wrote:
> On Thu, Dec 06, 2018 at 05:11:40PM -0800, Bart Van Assche wrote:
>> The next patch in this series uses the class name in code that
>> detects calls to lock_acquire() while a class key is being freed. Hence
>> retain the class name for lock classes that are being freed.
> From readin the discussion with v2; you meant to say: 'uses the class
> name pointer', right? You're not actually ever going to dereference it,
> since that would be a UaF.
>
>> Cc: Peter Zijlstra <peterz@infradead.org>
>> Cc: Waiman Long <longman@redhat.com>
>> Cc: Johannes Berg <johannes@sipsolutions.net>
>> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
>> ---
>>  kernel/locking/lockdep.c | 4 +---
>>  1 file changed, 1 insertion(+), 3 deletions(-)
>>
>> diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
>> index ecd92969674c..92bdb187987f 100644
>> --- a/kernel/locking/lockdep.c
>> +++ b/kernel/locking/lockdep.c
>> @@ -4147,10 +4147,8 @@ static void zap_class(struct lock_class *class)
>>  	 * Unhash the class and remove it from the all_lock_classes list:
>>  	 */
>>  	hlist_del_rcu(&class->hash_entry);
>> +	class->hash_entry.pprev = NULL;
>>  	list_del(&class->lock_entry);
>> -
>> -	RCU_INIT_POINTER(class->key, NULL);
>> -	RCU_INIT_POINTER(class->name, NULL);
>>  }
>>  
>>  static inline int within(const void *addr, void *start, unsigned long size)
>> -- 
>> 2.20.0.rc2.403.gdbc3b29805-goog
>>
I still prefer keeping the clearing statements. Leaving key behind
should be OK as it is just a long value to be compared against. The
variable name is a different story as it is a pointer that will
reference bytes that it points to unless you save the name in a safe
storage area and change the pointer to point there.

Cheers,
Longman


  reply	other threads:[~2018-12-07 14:50 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 [this message]
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
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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