linux-kernel - Re: [PATCH v3 1/1] bpf: Drop unprotected find_vpid() in favour of find_get

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Message-ID: <YxmbwRkJB3yJ58TM@google.com>
Date:   Thu, 8 Sep 2022 08:37:37 +0100
From:   Lee Jones <lee@...nel.org>
To:     linux-kernel@...r.kernel.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>, Yonghong Song <yhs@...com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, bpf@...r.kernel.org,
        Jiri Olsa <jolsa@...nel.org>
Subject: Re: [PATCH v3 1/1] bpf: Drop unprotected find_vpid() in favour of
 find_get_pid()

On Thu, 08 Sep 2022, Lee Jones wrote:

> On Tue, 09 Aug 2022, Lee Jones wrote:
> 
> > The documentation for find_vpid() clearly states:
> > 
> >   "Must be called with the tasklist_lock or rcu_read_lock() held."
> > 
> > Presently we do neither.
> > 
> > Let's use find_get_pid() which searches for the vpid, then takes a
> > reference to it preventing early free, all within the safety of
> > rcu_read_lock().  Once we have our reference we can safely make use of
> > it up until the point it is put.
> > 
> > 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")
> > Acked-by: Jiri Olsa <jolsa@...nel.org>
> > Signed-off-by: Lee Jones <lee@...nel.org>
> > ---
> > 
> > v1 => v2:
> >   * Commit log update - description - no code differences
> > 
> > v2 => v3:
> >   * Commit log update - spelling of find_vpid() - no code differences
> 
> Did anyone get a chance to look at this please?
> 
> Would you like a [RESEND]?

Scrap that.  I've just seen the last replies to v2.

Leave it with me.

-- 
Lee Jones [李琼斯]