linux-kernel - Re: [PATCH bpf/for-next] cgroup: Make current_cgns_cgroup_dfl() safe to call after exit_task

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Date:   Wed, 15 Mar 2023 00:00:18 +0000
From:   patchwork-bot+netdevbpf@...nel.org
To:     Tejun Heo <tj@...nel.org>
Cc:     ast@...nel.org, bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...a.com
Subject: Re: [PATCH bpf/for-next] cgroup: Make current_cgns_cgroup_dfl() safe to
 call after exit_task_namespace()

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Alexei Starovoitov <ast@...nel.org>:

On Tue, 14 Mar 2023 11:59:49 -1000 you wrote:
> 332ea1f697be ("bpf: Add bpf_cgroup_from_id() kfunc") added
> bpf_cgroup_from_id() which calls current_cgns_cgroup_dfl() through
> cgroup_get_from_id(). However, BPF programs may be attached to a point where
> current->nsproxy has already been cleared to NULL by exit_task_namespace()
> and calling bpf_cgroup_from_id() would cause an oops.
> 
> Just return the system-wide root if nsproxy has been cleared. This allows
> all cgroups to be looked up after the task passed through
> exit_task_namespace(), which semantically makes sense. Given that the only
> way to get this behavior is through BPF programs, it seems safe but let's
> see what others think.
> 
> [...]

Here is the summary with links:
  - [bpf/for-next] cgroup: Make current_cgns_cgroup_dfl() safe to call after exit_task_namespace()
    https://git.kernel.org/bpf/bpf-next/c/b8a2e3f93d41

You are awesome, thank you!
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