linux-kernel - Re: [PATCH] media/cec/core: fix task hung in cec_claim_log

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Date: Thu, 22 Feb 2024 13:16:05 +0100
From: Hans Verkuil <hverkuil-cisco@...all.nl>
To: Hillf Danton <hdanton@...a.com>
Cc: Edward Adam Davis <eadavis@...com>,
 syzbot+116b65a23bc791ae49a6@...kaller.appspotmail.com,
 linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
 mchehab@...nel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH] media/cec/core: fix task hung in cec_claim_log_addrs

On 22/02/2024 11:43, Hillf Danton wrote:
> On Wed, 21 Feb 2024 15:38:47 +0100 Hans Verkuil <hverkuil-cisco@...all.nl>
>> On 21/02/2024 15:20, Edward Adam Davis wrote:
>>> After unlocking adap->lock in cec_claim_log_addrs(), cec_claim_log_addrs() may
>>> re-enter, causing this issue to occur.
>>
>> But if it is called again, then it should hit this at the start of the function:
>>
>>         if (WARN_ON(adap->is_configuring || adap->is_configured))
>>                 return;
>>
>> I'm still not sure what causes the KASAN hung task since I cannot seem to reproduce
>> it, and because it is hard for me to find enough time to dig into this.
> 
> Likely because of the window for initializing completion more than once [1].
> 
> [1] https://lore.kernel.org/lkml/00000000000054a54e0611f1bc01@google.com/

I have been able to reproduce this by adding msleeps in several places.

When I have some more time I will start digging into this.

Regards,

	Hans