linux-kernel - Re: [syzbot] BUG: sleeping function called from invalid context in _copy_to

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Message-ID: <53cda27e-418f-40e6-b33e-ba891fde655b@oracle.com>
Date:   Tue, 10 Aug 2021 11:29:43 -0700
From:   Shoaib Rao <rao.shoaib@...cle.com>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     Eric Dumazet <eric.dumazet@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        syzbot <syzbot+8760ca6c1ee783ac4abd@...kaller.appspotmail.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>, bpf <bpf@...r.kernel.org>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Cong Wang <cong.wang@...edance.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        David Miller <davem@...emloft.net>,
        jamorris@...ux.microsoft.com,
        John Fastabend <john.fastabend@...il.com>,
        Martin KaFai Lau <kafai@...com>, kpsingh@...nel.org,
        Jakub Kicinski <kuba@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>, netdev <netdev@...r.kernel.org>,
        Shuah Khan <shuah@...nel.org>,
        Song Liu <songliubraving@...com>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Al Viro <viro@...iv.linux.org.uk>, Yonghong Song <yhs@...com>
Subject: Re: [syzbot] BUG: sleeping function called from invalid context in
 _copy_to_iter


On 8/10/21 11:02 AM, Eric Dumazet wrote:
> On Tue, Aug 10, 2021 at 7:50 PM Shoaib Rao <rao.shoaib@...cle.com> wrote:
>>
>> On 8/10/21 2:19 AM, Eric Dumazet wrote:
>>> On 8/9/21 10:31 PM, Shoaib Rao wrote:
>>>> On 8/9/21 1:09 PM, Eric Dumazet wrote:
>>>>> I am guessing that even your test would trigger the warning,
>>>>> if you make sure to include CONFIG_DEBUG_ATOMIC_SLEEP=y in your kernel build.
>>>> Eric,
>>>>
>>>> Thanks for the pointer, have you ever over looked at something when coding?
>>>>
>>> I _think_ I was trying to help, not shaming you in any way.
>> How did the previous email help? I did not get any reply when I asked
>> what could be the cause.
> Which previous email ? Are you expecting immediate answers to your emails ?
> I am not working for Oracle.
>
>>> My question about spinlock/mutex was not sarcastic, you authored
>>> 6 official linux patches, there is no evidence for linux kernel expertise.
>> That is no measure of someones understanding. There are other OS's as
>> well. I have worked on Solaris and other *unix* OS's for over 20+ years.
>> This was an oversight on my part and I apologize, but instead of
>> questioning my expertise it would have been helpful to say what might
>> have caused it.
>
> I sent two emails with _useful_ _information_.
>
> If you felt you were attacked, I suggest you take a deep breath,
> and read my emails without trying to change their intention and meaning.
>
> If you think my emails were not useful, just ignore them, this is fine by me.

Hi Eric,

I went back and looked at the two emails. You are correct.

> Are you aware of the difference between a mutex and a spinlock ?
>
> When copying data from/to user, you can not hold a spinlock.
The second line is useful but the first one was not necessary.

Shoaib