linux-kernel - Re: [syzbot] [net?] possible deadlock in inet

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Message-ID: <51adf9cb-619e-9646-36f0-1362828e801e@huaweicloud.com>
Date: Mon, 8 Sep 2025 17:34:30 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: Eric Dumazet <edumazet@...gle.com>, Yu Kuai <yukuai1@...weicloud.com>
Cc: syzbot <syzbot+e1cd6bd8493060bd701d@...kaller.appspotmail.com>,
 Josef Bacik <josef@...icpanda.com>, Jens Axboe <axboe@...nel.dk>,
 davem@...emloft.net, dsahern@...nel.org, horms@...nel.org, kuba@...nel.org,
 linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
 ming.lei@...hat.com, netdev@...r.kernel.org, pabeni@...hat.com,
 syzkaller-bugs@...glegroups.com, thomas.hellstrom@...ux.intel.com,
 "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [syzbot] [net?] possible deadlock in inet_shutdown

Hi,

在 2025/09/08 17:07, Eric Dumazet 写道:
> On Mon, Sep 8, 2025 at 1:52 AM Yu Kuai <yukuai1@...weicloud.com> wrote:
>>
>> Hi,
>>
>> 在 2025/09/06 17:16, Eric Dumazet 写道:
>>> On Fri, Sep 5, 2025 at 1:03 PM Eric Dumazet <edumazet@...gle.com> wrote:
>>>>
>>>> On Fri, Sep 5, 2025 at 1:00 PM syzbot
>>>> <syzbot+e1cd6bd8493060bd701d@...kaller.appspotmail.com> wrote:
>>>
>>> Note to NBD maintainers : I held about  20 syzbot reports all pointing
>>> to NBD accepting various sockets, I  can release them if needed, if you prefer
>>> to triage them.
>>>
>> I'm not NBD maintainer, just trying to understand the deadlock first.
>>
>> Is this deadlock only possible for some sepecific socket types? Take
>> a look at the report here:
>>
>> Usually issue IO will require the order:
>>
>> q_usage_counter -> cmd lock -> tx lock -> sk lock
>>
> 
> I have not seen the deadlock being reported with normal TCP sockets.
> 
> NBD sets sk->sk_allocation to  GFP_NOIO | __GFP_MEMALLOC;
> from __sock_xmit(), and TCP seems to respect this.
> .
> 

What aboud iscsi and nvme-tcp? and probably other drivers, where
sk_allocation is GFP_ATOMIC, do they have similar problem?

Thanks,
Kuai