netdev - Re: [PATCH net-next v2 2/4] bpf: test_run: Use system page pool for XDP live frame mode

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Date: Thu, 4 Apr 2024 13:23:53 +0200
From: Jesper Dangaard Brouer <hawk@...nel.org>
To: Toke Høiland-Jørgensen <toke@...hat.com>,
 Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>,
 Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau
 <martin.lau@...ux.dev>, Eduard Zingerman <eddyz87@...il.com>,
 Song Liu <song@...nel.org>, Yonghong Song <yonghong.song@...ux.dev>,
 John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>,
 Stanislav Fomichev <sdf@...gle.com>, Hao Luo <haoluo@...gle.com>,
 Jiri Olsa <jolsa@...nel.org>, "David S. Miller" <davem@...emloft.net>,
 Jakub Kicinski <kuba@...nel.org>
Cc: Alexander Lobakin <aleksander.lobakin@...el.com>,
 Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
 bpf@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH net-next v2 2/4] bpf: test_run: Use system page pool for
 XDP live frame mode

On 21/02/2024 15.48, Toke Høiland-Jørgensen wrote:
> Toke Høiland-Jørgensen <toke@...hat.com> writes:
> 
>> The cookie is a random 128-bit value, which means the probability that
>> we will get accidental collisions (which would lead to recycling the
>> wrong page values and reading garbage) is on the order of 2^-128. This
>> is in the "won't happen before the heat death of the universe" range, so
>> this marking is safe for the intended usage.
> 
> Alright, got a second opinion on this from someone better at security
> than me; I'll go try out some different ideas :)

It is a general security concern for me that BPF test_run gets access to
memory used by 'system page pool', with the concern of leaking data
(from real traffic) to an attacker than can inject a BPF test_run
program via e.g. a CI pipeline.

I'm not saying we leaking data today in BPF/XDP progs, but there is a
potential, because to gain performance in XDP and page_pool we don't
clear memory to avoid cache line performance issues.
I guess today, I could BPF tail extend and read packet data from older
frames, in this way, if I get access to 'system page pool'.

--Jesper