Re: [PATCH] locking/lockdep: Add debug_locks check in __lock_downgrade()

[Tetsuo Handa]

Peter, will this fix be sent to linux.git shortly?
syzbot is generating many corrupted reports due to this race.

On 2019/01/14 22:36, Peter Zijlstra wrote:
> On Thu, Jan 10, 2019 at 11:21:13AM +0100, Dmitry Vyukov wrote:
>> On Thu, Jan 10, 2019 at 5:04 AM Waiman Long <longman@xxxxxxxxxx> wrote:
>>>
>>> Tetsuo Handa had reported he saw an incorrect "downgrading a read lock"
>>> warning right after a previous lockdep warning. It is likely that the
>>> previous warning turned off lock debugging causing the lockdep to have
>>> inconsistency states leading to the lock downgrade warning.
>>>
>>> Fix that by add a check for debug_locks at the beginning of
>>> __lock_downgrade().
>>>
>>> Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
>>> Reported-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
>>
>> Please also add:
>>
>> Reported-by: syzbot+53383ae265fb161ef488@xxxxxxxxxxxxxxxxxxxxxxxxx
>>
>> for tracking purposes. But Tetsuo deserves lots of credit for debugging it.
> 
> I made that:
> 
> Reported-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
> Debugged-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
> Reported-by: syzbot+53383ae265fb161ef488@xxxxxxxxxxxxxxxxxxxxxxxxx