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From: Bryam Vargas <hexlabsecurity@proton.me>
To: Matthieu Buffet <matthieu@buffet.re>
Cc: "Mickaël Salaün" <mic@digikod.net>,
	"Günther Noack" <gnoack@google.com>,
	"Mikhail Ivanov" <ivanov.mikhail1@huawei-partners.com>,
	"Paul Moore" <paul@paul-moore.com>,
	"Eric Dumazet" <edumazet@google.com>,
	"Neal Cardwell" <ncardwell@google.com>,
	linux-security-module@vger.kernel.org, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 1/2] landlock: fix TCP Fast Open connection bypass
Date: Thu, 18 Jun 2026 01:25:33 +0000	[thread overview]
Message-ID: <20260618012527.34964-1-hexlabsecurity@proton.me> (raw)
In-Reply-To: <20260617180526.15627-2-matthieu@buffet.re>

Thanks Matthieu, your #41, so no competing patch from me. I built your v0
(Landlock + MPTCP) and ran an A/B: without it, a confined task with CONNECT_TCP
denied still reaches the port via sendto(MSG_FASTOPEN); with it, that path is now
denied too, on IPv4 and IPv6.

Tested-by: Bryam Vargas <hexlabsecurity@proton.me>

One scope note, since you mention MPTCP: an MPTCP socket isn't covered.
sk_is_tcp() is false for the mptcp parent (sk_protocol is IPPROTO_MPTCP), so
neither the new sendmsg hook nor the existing socket_connect one mediates it. On
the patched kernel my MPTCP arm still reaches the blocked port via both connect()
and MSG_FASTOPEN. If MPTCP is meant to be in scope for CONNECT_TCP, the guard
wants `|| sk->sk_protocol == IPPROTO_MPTCP` (not sk_is_mptcp(), which is the
subflow flag).

Bryam


  reply	other threads:[~2026-06-18  1:25 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-06-16 20:16 Landlock: LANDLOCK_ACCESS_NET_CONNECT_TCP bypass via TCP Fast Open Bryam Vargas
2026-06-17 14:22 ` Mickaël Salaün
2026-06-17 18:05   ` Matthieu Buffet
2026-06-17 18:05     ` [RFC PATCH 1/2] landlock: fix TCP Fast Open connection bypass Matthieu Buffet
2026-06-18  1:25       ` Bryam Vargas [this message]
2026-06-19  0:34         ` Matthieu Buffet
2026-06-19  1:39           ` Bryam Vargas
2026-06-26 20:40       ` Mickaël Salaün
2026-07-01 21:42         ` Matthieu Buffet
2026-07-01 21:46           ` [PATCH v2 " Matthieu Buffet
2026-07-01 21:46             ` [PATCH v2 2/2] selftests/landlock: Add test for TCP fast open Matthieu Buffet
2026-07-02 14:59             ` [PATCH v2 1/2] landlock: fix TCP Fast Open connection bypass Mickaël Salaün
2026-06-17 18:05     ` [RFC PATCH 2/2] selftests/landlock: Add test for TCP fast open Matthieu Buffet
2026-06-26 21:19       ` Mickaël Salaün

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