linux-kernel - Re: [PATCH 2/3] bpf: bpf_iter_task_next: use __next_thread() rather than next

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Message-ID: <95c2b494-ce8a-422b-918e-8ae4853ab9f0@linux.dev>
Date:   Wed, 15 Nov 2023 22:34:10 -0500
From:   Yonghong Song <yonghong.song@...ux.dev>
To:     Oleg Nesterov <oleg@...hat.com>,
        Alexei Starovoitov <ast@...nel.org>
Cc:     Chuyi Zhou <zhouchuyi@...edance.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kui-Feng Lee <kuifeng@...com>, linux-kernel@...r.kernel.org,
        bpf@...r.kernel.org
Subject: Re: [PATCH 2/3] bpf: bpf_iter_task_next: use __next_thread() rather
 than next_thread()


On 11/14/23 11:32 AM, Oleg Nesterov wrote:
> Lockless use of next_thread() should be avoided, kernel/bpf/task_iter.c
> is the last user and the usage is wrong.
>
> bpf_iter_task_next() can loop forever, "kit->pos == kit->task" can never
> happen if kit->pos execs. Change this code to use __next_thread().
>
> With or without this change the usage of kit->pos/task and next_task()
> doesn't look nice, see the next patch.
>
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>

Acked-by: Yonghong Song <yonghong.song@...ux.dev>