Re: [syzbot] BUG: sleeping function called from invalid context in _copy_to_iter

From: Shoaib Rao <rao.shoaib@oracle.com>
To: Eric Dumazet <edumazet@google.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>,
	Dmitry Vyukov <dvyukov@google.com>,
	syzbot <syzbot+8760ca6c1ee783ac4abd@syzkaller.appspotmail.com>,
	Andrii Nakryiko <andrii@kernel.org>,
	Alexei Starovoitov <ast@kernel.org>, bpf <bpf@vger.kernel.org>,
	Christian Brauner <christian.brauner@ubuntu.com>,
	Cong Wang <cong.wang@bytedance.com>,
	Daniel Borkmann <daniel@iogearbox.net>,
	David Miller <davem@davemloft.net>,
	jamorris@linux.microsoft.com,
	John Fastabend <john.fastabend@gmail.com>,
	Martin KaFai Lau <kafai@fb.com>,
	kpsingh@kernel.org, Jakub Kicinski <kuba@kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	"open list:KERNEL SELFTEST FRAMEWORK" 
	<linux-kselftest@vger.kernel.org>,
	netdev <netdev@vger.kernel.org>, Shuah Khan <shuah@kernel.org>,
	Song Liu <songliubraving@fb.com>,
	syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
	Al Viro <viro@zeniv.linux.org.uk>, Yonghong Song <yhs@fb.com>
Subject: Re: [syzbot] BUG: sleeping function called from invalid context in _copy_to_iter
Date: Tue, 10 Aug 2021 11:29:43 -0700	[thread overview]
Message-ID: <53cda27e-418f-40e6-b33e-ba891fde655b@oracle.com> (raw)
In-Reply-To: <CANn89iJOFoMa2-Dx+_b8p0-FNNKhYn4DsB3AbtL7zR4bvNR5DA@mail.gmail.com>

On 8/10/21 11:02 AM, Eric Dumazet wrote:
> On Tue, Aug 10, 2021 at 7:50 PM Shoaib Rao <rao.shoaib@oracle.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