netdev - Re: [Patch net v2] cgroup: fix cgroup_sk_alloc() for sk_clone

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Date:   Wed, 8 Jul 2020 12:07:07 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Cameron Berkenpas <cam@...-zeon.de>,
        Peter Geis <pgwipeout@...il.com>,
        Lu Fengqi <lufq.fnst@...fujitsu.com>,
        Daniël Sonck <dsonck92@...il.com>,
        Zhang Qiang <qiang.zhang@...driver.com>,
        Thomas Lamprecht <t.lamprecht@...xmox.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Zefan Li <lizefan@...wei.com>, Tejun Heo <tj@...nel.org>,
        Roman Gushchin <guro@...com>
Subject: Re: [Patch net v2] cgroup: fix cgroup_sk_alloc() for sk_clone_lock()

On 7/8/20 11:34 AM, Cong Wang wrote:
> Hi,
> 
> On Wed, Jul 8, 2020 at 8:33 AM Guenter Roeck <linux@...ck-us.net> wrote:
>> This patch causes all my s390 boot tests to crash. Reverting it fixes
>> the problem. Please see bisect results and and crash log below.
>>
> ...
>> Crash log:
> 
> Interesting. I don't see how unix socket is any special here, it creates
> a peer sock with sk_alloc(), but this is not any different from two separated
> sockets.
> 
> What is your kernel config? Do you enable CONFIG_CGROUP_NET_PRIO
> or CONFIG_CGROUP_NET_CLASSID? I can see there might be a problem
> if you don't enable either of them but enable CONFIG_CGROUP_BPF.
> 

cgroup specific configuration bits:

CONFIG_CGROUPS=y
CONFIG_BLK_CGROUP=y
CONFIG_CGROUP_WRITEBACK=y
CONFIG_CGROUP_SCHED=y
CONFIG_CGROUP_PIDS=y
CONFIG_CGROUP_RDMA=y
CONFIG_CGROUP_FREEZER=y
CONFIG_CGROUP_HUGETLB=y
CONFIG_CGROUP_DEVICE=y
CONFIG_CGROUP_CPUACCT=y
CONFIG_CGROUP_PERF=y
CONFIG_CGROUP_BPF=y
# CONFIG_CGROUP_DEBUG is not set
CONFIG_SOCK_CGROUP_DATA=y
CONFIG_BLK_CGROUP_RWSTAT=y
CONFIG_BLK_CGROUP_IOLATENCY=y
CONFIG_BLK_CGROUP_IOCOST=y
# CONFIG_BFQ_CGROUP_DEBUG is not set
# CONFIG_NETFILTER_XT_MATCH_CGROUP is not set
CONFIG_NET_CLS_CGROUP=y
CONFIG_CGROUP_NET_PRIO=y
CONFIG_CGROUP_NET_CLASSID=y

This originates from arch/s390/configs/defconfig; I don't touch
any cgroup specific configuration in my tests.

> And if you have the full kernel log, it would be helpful too.
> 

https://kerneltests.org/builders/qemu-s390-pending-fixes/builds/222/steps/qemubuildcommand/logs/stdio

Interestingly, enabling CONFIG_BFQ_CGROUP_DEBUG makes the problem disappear.

Guenter