From: Cong Wang <xiyou.wangcong@gmail.com>
To: Roman Gushchin <guro@fb.com>
Cc: "Zefan Li" <lizefan@huawei.com>,
"Linux Kernel Network Developers" <netdev@vger.kernel.org>,
"Cameron Berkenpas" <cam@neo-zeon.de>,
"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: Thu, 18 Jun 2020 14:09:43 -0700 [thread overview]
Message-ID: <CAM_iQpWuNnHqNHKz5FMgAXoqQ5qGDEtNbBKDXpmpeNSadCZ-1w@mail.gmail.com> (raw)
In-Reply-To: <20200618193611.GE24694@carbon.DHCP.thefacebook.com>
On Thu, Jun 18, 2020 at 12:36 PM Roman Gushchin <guro@fb.com> wrote:
>
> On Thu, Jun 18, 2020 at 12:19:13PM -0700, Cong Wang wrote:
> > On Wed, Jun 17, 2020 at 6:44 PM Zefan Li <lizefan@huawei.com> wrote:
> > >
> > > Cc: Roman Gushchin <guro@fb.com>
> > >
> > > Thanks for fixing this.
> > >
> > > On 2020/6/17 2:03, Cong Wang wrote:
> > > > When we clone a socket in sk_clone_lock(), its sk_cgrp_data is
> > > > copied, so the cgroup refcnt must be taken too. And, unlike the
> > > > sk_alloc() path, sock_update_netprioidx() is not called here.
> > > > Therefore, it is safe and necessary to grab the cgroup refcnt
> > > > even when cgroup_sk_alloc is disabled.
> > > >
> > > > sk_clone_lock() is in BH context anyway, the in_interrupt()
> > > > would terminate this function if called there. And for sk_alloc()
> > > > skcd->val is always zero. So it's safe to factor out the code
> > > > to make it more readable.
> > > >
> > > > Fixes: 090e28b229af92dc5b ("netprio_cgroup: Fix unlimited memory leak of v2 cgroups")
> > >
> > > but I don't think the bug was introduced by this commit, because there
> > > are already calls to cgroup_sk_alloc_disable() in write_priomap() and
> > > write_classid(), which can be triggered by writing to ifpriomap or
> > > classid in cgroupfs. This commit just made it much easier to happen
> > > with systemd invovled.
> > >
> > > I think it's 4bfc0bb2c60e2f4c ("bpf: decouple the lifetime of cgroup_bpf from cgroup itself"),
> > > which added cgroup_bpf_get() in cgroup_sk_alloc().
> >
> > Good point.
> >
> > I take a deeper look, it looks like commit d979a39d7242e06
> > is the one to blame, because it is the first commit that began to
> > hold cgroup refcnt in cgroup_sk_alloc().
>
> I agree, ut seems that the issue is not related to bpf and probably
> can be reproduced without CONFIG_CGROUP_BPF. d979a39d7242e06 indeed
> seems closer to the origin.
Yeah, I will update the Fixes tag and send V2.
>
> Btw, based on the number of reported-by tags it seems that there was
> a real issue which the patch is fixing. Maybe you'll a couple of words
> about how it reveals itself in the real life?
I still have no idea how exactly this is triggered. According to the
people who reported this bug, they just need to wait for some hours
to trigger. So I am not sure what to add here, just the stack trace?
Thanks.
next prev parent reply other threads:[~2020-06-18 21:09 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 [this message]
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
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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