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From: Zefan Li <lizefan@huawei.com>
To: Roman Gushchin <guro@fb.com>, Cong Wang <xiyou.wangcong@gmail.com>
Cc: "Cameron Berkenpas" <cam@neo-zeon.de>,
	"Linux Kernel Network Developers" <netdev@vger.kernel.org>,
	"Peter Geis" <pgwipeout@gmail.com>,
	"Lu Fengqi" <lufq.fnst@cn.fujitsu.com>,
	"Daniël Sonck" <dsonck92@gmail.com>,
	"Daniel Borkmann" <daniel@iogearbox.net>,
	"Tejun Heo" <tj@kernel.org>
Subject: Re: [Patch net] cgroup: fix cgroup_sk_alloc() for sk_clone_lock()
Date: Fri, 3 Jul 2020 09:17:09 +0800	[thread overview]
Message-ID: <42baf0f8-627b-0ab8-72fc-12d24667ad0a@huawei.com> (raw)
In-Reply-To: <20200702160242.GA91667@carbon.dhcp.thefacebook.com>

On 2020/7/3 0:02, Roman Gushchin wrote:
> On Wed, Jul 01, 2020 at 09:48:48PM -0700, Cong Wang wrote:
>> On Tue, Jun 30, 2020 at 3:48 PM Roman Gushchin <guro@fb.com> wrote:
>>>
>>> Btw if we want to backport the problem but can't blame a specific commit,
>>> we can always use something like "Cc: <stable@vger.kernel.org>    [3.1+]".
>>
>> Sure, but if we don't know which is the right commit to blame, then how
>> do we know which stable version should the patch target? :)
>>
>> I am open to all options here, including not backporting to stable at all.
> 
> It seems to be that the issue was there from bd1060a1d671 ("sock, cgroup: add sock->sk_cgroup"),
> so I'd go with it. Otherwise we can go with 5.4+, as I understand before that it was
> hard to reproduce it.
> 

Actually I think it should be very easy to reproduce the bug.

suppose default cgroup and netcls cgroup are mounted in /cgroup/default and
/cgroup/netcls respectively, and then:

1. mkdir /cgroup/default/sub1
2. mkdir /cgroup/default/sub2
3. attach some tasks into sub1/ and sub2/
4. attach bpf program to sub1/ and sub2/ # get bpf refcnt for those cgroups
5. echo 1 > /cgroup/netcls/classid       # this will disable cgroup_sk_alloc
6. kill all tasks in sub1/ and sub2/
7. rmdir sub1/ sub2/

The last step will deref bpf for the default root cgroup instead of sub1/
and sub2/, and should trigger the bug.

FYI I never use bpf, so I might be wrong.

  parent reply	other threads:[~2020-07-03  1:17 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-16 18:03 [Patch net] cgroup: fix cgroup_sk_alloc() for sk_clone_lock() Cong Wang
2020-06-18  1:44 ` Zefan Li
2020-06-18 19:19   ` Cong Wang
2020-06-18 19:36     ` Roman Gushchin
2020-06-18 21:09       ` Cong Wang
2020-06-18 21:26         ` Roman Gushchin
2020-06-18 22:45           ` Peter Geis
2020-06-19  6:40         ` Zefan Li
2020-06-19 19:51           ` Cong Wang
2020-06-20  0:45             ` Zefan Li
2020-06-20  0:51               ` Zefan Li
2020-06-20  3:31                 ` Cong Wang
2020-06-20  7:52                   ` Zefan Li
2020-06-20 16:04                     ` Roman Gushchin
2020-06-23 22:21                   ` Roman Gushchin
2020-06-26  5:23                     ` Cameron Berkenpas
2020-06-26 17:58                       ` Cong Wang
2020-06-26 22:03                         ` Cameron Berkenpas
2020-06-27 22:59                           ` Cameron Berkenpas
2020-06-30 22:16                             ` Cong Wang
2020-06-27 23:41                         ` Roman Gushchin
2020-06-30 22:22                           ` Cong Wang
2020-06-30 22:48                             ` Roman Gushchin
2020-07-01  1:18                               ` Zefan Li
2020-07-02  4:48                               ` Cong Wang
2020-07-02  8:12                                 ` Thomas Lamprecht
2020-07-02 16:02                                 ` Roman Gushchin
2020-07-02 16:24                                   ` Peter Geis
2020-07-03  1:17                                   ` Zefan Li [this message]
2020-06-20  0:51           ` Roman Gushchin
2020-06-20  1:00             ` Zefan Li
2020-06-20  1:14               ` Roman Gushchin
2020-06-20  2:48                 ` Zefan Li
2020-06-20  3:00                 ` Cong Wang
2020-06-20 15:57                   ` Roman Gushchin
2020-06-22 18:14                     ` Cong Wang
2020-06-22 20:39                       ` Roman Gushchin
2020-06-23  8:45                         ` Zhang,Qiang
2020-06-23 17:56                           ` Cong Wang
2020-06-23  8:54                         ` Zhang,Qiang
2020-06-23  9:01                         ` Zhang,Qiang

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