linux-kernel - Re: [PATCH v3 1/1] bpf: Ensure correct locking around vulnerable function find

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Message-ID: <a6e56396-f1f9-d939-cc25-201db242e3b8@fb.com>
Date:   Mon, 12 Sep 2022 17:02:22 +0100
From:   Yonghong Song <yhs@...com>
To:     Lee Jones <lee@...nel.org>
Cc:     linux-kernel@...r.kernel.org, Jiri Olsa <jolsa@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        John Fastabend <john.fastabend@...il.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>, KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, bpf@...r.kernel.org
Subject: Re: [PATCH v3 1/1] bpf: Ensure correct locking around vulnerable
 function find_vpid()



On 9/12/22 4:14 PM, Lee Jones wrote:
> On Mon, 12 Sep 2022, Yonghong Song wrote:
>> On 9/12/22 2:38 PM, Lee Jones wrote:
>>> The documentation for find_vpid() clearly states:
>>>
>>
>> No need for the above extra line.
> 
> The intentional blank formatting line?
> 
> The commit message would look worse without it.
> 
> Is this really a blocker?

Not a blocker. Just a suggestion. I won't enforce it
if you do have this extra line.

> 
>>>     "Must be called with the tasklist_lock or rcu_read_lock() held."
>>>
>>> Presently we do neither.
>>
>> Presently we do neither for find_vpid() instance in bpf_task_fd_query().
>> Add proper rcu_read_lock/unlock() to fix the issue.
> 
> I can expand this.
> 
>>> Cc: Jiri Olsa <jolsa@...nel.org>
>>> Cc: Alexei Starovoitov <ast@...nel.org>
>>> Cc: Daniel Borkmann <daniel@...earbox.net>
>>> Cc: John Fastabend <john.fastabend@...il.com>
>>> Cc: Andrii Nakryiko <andrii@...nel.org>
>>> Cc: Martin KaFai Lau <martin.lau@...ux.dev>
>>> Cc: Song Liu <song@...nel.org>
>>> Cc: Yonghong Song <yhs@...com>
>>> Cc: KP Singh <kpsingh@...nel.org>
>>> Cc: Stanislav Fomichev <sdf@...gle.com>
>>> Cc: Hao Luo <haoluo@...gle.com>
>>> Cc: bpf@...r.kernel.org
>>> Fixes: 41bdc4b40ed6f ("bpf: introduce bpf subcommand BPF_TASK_FD_QUERY")
>>> Signed-off-by: Lee Jones <lee@...nel.org>
>>
>> Ack with above a few suggestions for the commit message.
>>
>> Acked-by: Yonghong Song <yhs@...com>
>