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

[Roman Gushchin <guro@fb.com>]

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