netdev - Re: [PATCH bpf] tools/bpf: fix selftest get_cgroup_id

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Message-ID: <a4bc77b6-1467-52fd-46db-f1b25f2764ad@iogearbox.net>
Date:   Fri, 8 Jun 2018 00:15:53 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Yonghong Song <yhs@...com>, ast@...com, netdev@...r.kernel.org
Cc:     kernel-team@...com
Subject: Re: [PATCH bpf] tools/bpf: fix selftest get_cgroup_id_user

On 06/06/2018 06:12 PM, Yonghong Song wrote:
> Commit f269099a7e7a ("tools/bpf: add a selftest for
> bpf_get_current_cgroup_id() helper") added a test
> for bpf_get_current_cgroup_id() helper. The bpf program
> is attached to tracepoint syscalls/sys_enter_nanosleep
> and will record the cgroup id if the tracepoint is hit.
> The test program creates a cgroup and attachs itself to
> this cgroup and expects that the test program process
> cgroup id is the same as the cgroup_id retrieved
> by the bpf program.
> 
> In a light system where no other processes called
> nanosleep syscall, the test case can pass.
> In a busy system where many different processes can hit
> syscalls/sys_enter_nanosleep tracepoint, the cgroup id
> recorded by bpf program may not match the test program
> process cgroup_id.
> 
> This patch fixed an issue by communicating the test program
> pid to bpf program. The bpf program only records
> cgroup id if the current task pid is the same as
> passed-in pid. This ensures that the recorded cgroup_id
> is for the cgroup within which the test program resides.
> 
> Fixes: f269099a7e7a ("tools/bpf: add a selftest for bpf_get_current_cgroup_id() helper")
> Signed-off-by: Yonghong Song <yhs@...com>

Applied to bpf, thanks Yonghong!