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From: Oleg Nesterov <oleg@redhat.com>
To: Yafang Shao <laoar.shao@gmail.com>
Cc: ast@kernel.org, daniel@iogearbox.net, john.fastabend@gmail.com,
	andrii@kernel.org, martin.lau@linux.dev, eddyz87@gmail.com,
	song@kernel.org, yonghong.song@linux.dev, kpsingh@kernel.org,
	sdf@google.com, haoluo@google.com, jolsa@kernel.org,
	bpf@vger.kernel.org, Chuyi Zhou <zhouchuyi@bytedance.com>
Subject: Re: [PATCH v2 bpf-next 1/2] bpf: Fix an issue due to uninitialized bpf_iter_task
Date: Sat, 17 Feb 2024 17:43:01 +0100	[thread overview]
Message-ID: <20240217164300.GA22909@redhat.com> (raw)
In-Reply-To: <CALOAHbCNs4VvVoKGTyw9E5oK=nh4v8+7A=EOt9pmj-n5DTYABQ@mail.gmail.com>

On 02/17, Yafang Shao wrote:
>
> On Sat, Feb 17, 2024 at 8:05 PM Oleg Nesterov <oleg@redhat.com> wrote:
> >
> > > Fixes: ac8148d957f5 ("bpf: bpf_iter_task_next: use next_task(kit->task) rather than next_task(kit->pos)")
> >
> > Confused...
> >
> > Does this mean that bpf_iter_task_next() (the only user of ->pos) can be
> > called even if bpf_iter_task_new() returns -EINVAL ?
>
> Right. The bpf_for_each() doesn't check the return value of bpf_iter_task_new
> (), see also https://lore.kernel.org/bpf/20240208090906.56337-4-laoar.shao@gmail.com/
>
> Even if we check the return value of bpf_iter_task_new() in
> bpf_for_each(), we still need to fix it in the kernel.

Hmm, OK. Somehow I naively thought there must be an in-kernel check that
would that prevent bpf_iter_task_next() if bpf_iter_task_new() failed.

Thanks for your explanations. FWIW,

Acked-by: Oleg Nesterov <oleg@redhat.com>


  reply	other threads:[~2024-02-17 16:44 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-02-17 11:41 [PATCH v2 bpf-next 0/2] bpf: Fix an issue in bpf_iter_task Yafang Shao
2024-02-17 11:41 ` [PATCH v2 bpf-next 1/2] bpf: Fix an issue due to uninitialized bpf_iter_task Yafang Shao
2024-02-17 12:03   ` Oleg Nesterov
2024-02-17 13:11     ` Yafang Shao
2024-02-17 16:43       ` Oleg Nesterov [this message]
2024-02-17 11:41 ` [PATCH v2 bpf-next 2/2] selftests/bpf: Add negtive test cases for task iter Yafang Shao
2024-02-19 11:40 ` [PATCH v2 bpf-next 0/2] bpf: Fix an issue in bpf_iter_task patchwork-bot+netdevbpf

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