linux-kernel - Re: [PATCH] memcg: net: do not associate sock with unrelated memcg

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Message-ID: <20200214214730.GA99109@carbon.DHCP.thefacebook.com>
Date:   Fri, 14 Feb 2020 13:47:30 -0800
From:   Roman Gushchin <guro@...com>
To:     Shakeel Butt <shakeelb@...gle.com>
CC:     Johannes Weiner <hannes@...xchg.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Greg Thelen <gthelen@...gle.com>,
        Michal Hocko <mhocko@...nel.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        <cgroups@...r.kernel.org>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] memcg: net: do not associate sock with unrelated memcg

Hello, Shakeel!

On Thu, Feb 13, 2020 at 11:12:33PM -0800, Shakeel Butt wrote:
> We are testing network memory accounting in our setup and noticed
> inconsistent network memory usage and often unrelated memcgs network
> usage correlates with testing workload. On further inspection, it seems
> like mem_cgroup_sk_alloc() is broken in irq context specially for
> cgroup v1.

A great catch!

> 
> mem_cgroup_sk_alloc() can be called in irq context and kind
> of assumes that it can only happen from sk_clone_lock() and the source
> sock object has already associated memcg. However in cgroup v1, where
> network memory accounting is opt-in, the source sock can be not
> associated with any memcg and the new cloned sock can get associated
> with unrelated interrupted memcg.
> 
> Cgroup v2 can also suffer if the source sock object was created by
> process in the root memcg or if sk_alloc() is called in irq context.

Do you mind sharing a call trace?

Also, shouldn't cgroup_sk_alloc() be changed in a similar way?

Thanks!

Roman