From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 070823B71DF; Mon, 31 Aug 2026 04:09:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788149347; cv=none; b=Sh3aP7SjJJ49uZ1FALH7VhdMggnHiCz4Sl1LR8MLQQdhQynJpPvSplYz9YjQkg6CPEYasH8pkMzERvGa0uW+SpKYFqHrsFEFRSIfeHSzcfbATw9/7QlZAaZYYAf6EDfKvE39MxOPusH1vjcntY7UYW+z+hXUwsZBGYFEivPjpc4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788149347; c=relaxed/simple; bh=SYLPKJwPVb8TOL1Tnw+rYAn2PAvvHlPtxwfP85MImHs=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=YqDHuQBrqZ1LMZhrSsiANx2leq1v3WTxvTNSWJYBlRmNSy8kn5z05DoZoXpU3xjOkDihKoaBpngzIBftDSIIs8nTUXw18pCuyI4GLMJPZe0G7SbzHS+40sAv/QuCnSdEispSln4JUiVZL3OmXc8hEiotJZaCtVdT5z4ohTw1/+g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=OOnDKeaO; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="OOnDKeaO" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 147071F00A3E; Mon, 31 Aug 2026 04:09:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788149345; bh=/ph9w7cuFjdMlI9pMSwhn/gmRZwiHl3sIDZaHz+Xc6Y=; h=Subject:From:To:Cc:Date:In-Reply-To:References; b=OOnDKeaO4dBtt5gbCQXNC0+03hVmoc2n3c80kAeOrNZeUeD8fe/QLzoorm5Noxf0L qUuPpioWzCAx0SSwgL096WSDZcHWli8AXYfaJy9LA4vq0zy3EmMOgOB85MJ8aSqxqG scd27akD3Kjsi7+o6U1GLwZqjRn+T556bFch2xVZlrEIw8Hl+4pOidM0jRuKx20ehZ Z2w3YGObrYDS8A5EdmU8jEZ5UyQzk9MkfSZZqGtklpm2RIAqAS1NXKUAP1GSk1e3x0 +SlkXhwdCAtKe/sHXAMPidw2UzzyKX1d91Ap53AtONPd95mKjHF5nZ3UDfvM0puGar E59fs7PVyzBRA== Message-ID: Subject: Re: [PATCH 3/6] landlock: Add MPTCP bind and connect access rights From: Geliang Tang To: =?ISO-8859-1?Q?G=FCnther?= Noack , =?ISO-8859-1?Q?Micka=EBl_Sala=FCn?= Cc: Matthieu Baerts , Mat Martineau , Mikhail Ivanov , mptcp@lists.linux.dev, netdev@vger.kernel.org, linux-security-module@vger.kernel.org Date: Mon, 31 Aug 2026 12:09:00 +0800 In-Reply-To: <20260830201650.67050-4-gnoack3000@gmail.com> References: <20260830201650.67050-1-gnoack3000@gmail.com> <20260830201650.67050-4-gnoack3000@gmail.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.56.2-9 Precedence: bulk X-Mailing-List: linux-security-module@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hi Günther, On Sun, 2026-08-30 at 22:16 +0200, Günther Noack wrote: > MPTCP sockets have equivalent bind(2) and connect(2) operations as > TCP > sockets, but can not currently be restricted with Landlock without > explicit MPTCP access rights.  As MPTCP operates on the same TCP port > number space as TCP, this is a gap in Landlock's policies. > > Add access rights for MPTCP bind(2) and connect(2) operations > and document them in the header. > > Treat TCP Fast Open the same as done for plain TCP in > commit 33cb713db016 ("landlock: Fix TCP Fast Open connection bypass") > > The port numbers used in MPTCP subflows are negotiated by the kernel > and therefore not subject to these access rights. > > Bump the Landlock ABI version to 12. > > Closes: https://github.com/landlock-lsm/linux/issues/54 > Signed-off-by: Günther Noack > --- >  include/linux/landlock.h                     |  5 +- >  include/uapi/linux/landlock.h                | 24 +++++++ >  security/landlock/limits.h                   |  2 +- >  security/landlock/net.c                      | 68 ++++++++++++++---- > -- >  security/landlock/syscalls.c                 |  2 +- >  tools/testing/selftests/landlock/base_test.c |  2 +- >  6 files changed, 79 insertions(+), 24 deletions(-) > > diff --git a/include/linux/landlock.h b/include/linux/landlock.h > index 004cbd0b9298..b04ffc7caa21 100644 > --- a/include/linux/landlock.h > +++ b/include/linux/landlock.h > @@ -46,7 +46,10 @@ >   _LANDLOCK_NAME_ENTRY(LANDLOCK_ACCESS_NET_CONNECT_TCP, > "connect_tcp"), \ >   _LANDLOCK_NAME_ENTRY(LANDLOCK_ACCESS_NET_BIND_UDP, > "bind_udp"), \ >   _LANDLOCK_NAME_ENTRY(LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP, \ > -      "connect_send_udp") > +      "connect_send_udp"), \ > + _LANDLOCK_NAME_ENTRY(LANDLOCK_ACCESS_NET_BIND_MPTCP, > "bind_mptcp"), \ > + _LANDLOCK_NAME_ENTRY(LANDLOCK_ACCESS_NET_CONNECT_MPTCP, \ > +      "connect_mptcp") >   >  #define _LANDLOCK_SCOPE_NAMES \ >   _LANDLOCK_NAME_ENTRY(LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET, \ > diff --git a/include/uapi/linux/landlock.h > b/include/uapi/linux/landlock.h > index cceda3b3b961..2a953ba7ce25 100644 > --- a/include/uapi/linux/landlock.h > +++ b/include/uapi/linux/landlock.h > @@ -448,6 +448,9 @@ struct landlock_net_port_attr { >   * - %LANDLOCK_ACCESS_NET_CONNECT_TCP: Connect TCP sockets to the > given >   *   remote port. Support added in Landlock ABI version 4. >   * > + * .. note:: These rights do not apply to MPTCP sockets, which have > their own > + *   access rights (see below). > + * >   * And similarly for UDP port numbers: >   * >   * - %LANDLOCK_ACCESS_NET_BIND_UDP: Bind UDP sockets to the given > local > @@ -474,12 +477,33 @@ struct landlock_net_port_attr { >   * .. note:: Sending datagrams to an ``AF_UNSPEC`` destination > address >   *   family is not supported for IPv6 UDP sockets: you will need to > use a >   *   ``NULL`` address instead. > + * > + * MPTCP sockets (created with ``IPPROTO_MPTCP``) use TCP port > numbers, but > + * they are controlled by their own access rights: > + * > + * - %LANDLOCK_ACCESS_NET_BIND_MPTCP: Bind MPTCP sockets to the > given local > + *   port. Support added in Landlock ABI version 12. > + * - %LANDLOCK_ACCESS_NET_CONNECT_MPTCP: Connect MPTCP sockets to > the given > + *   remote port. Support added in Landlock ABI version 12. > + * > + * .. note:: The TCP and the MPTCP access rights are independent, > even though > + *   they refer to the same port number space. Handling only > + *   %LANDLOCK_ACCESS_NET_BIND_TCP and > %LANDLOCK_ACCESS_NET_CONNECT_TCP leaves > + *   MPTCP sockets unrestricted, and vice versa. A sandbox that > wants to > + *   control all TCP-based traffic needs to handle both sets. > + * > + * .. note:: These MPTCP access rights restrict the ports passed to > + *   :manpage:`bind(2)` and :manpage:`connect(2)`. The ports used in > MPTCP > + *   subflows are negotiated in the MPTCP protocol by the kernel and > are not > + *   subject to these restrictions. >   */ >  /* clang-format off */ >  #define LANDLOCK_ACCESS_NET_BIND_TCP (1ULL << 0) >  #define > LANDLOCK_ACCESS_NET_CONNECT_TCP (1ULL << 1) >  #define LANDLOCK_ACCESS_NET_BIND_UDP (1ULL << 2) >  #define LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP (1ULL << 3) > +#define LANDLOCK_ACCESS_NET_BIND_MPTCP (1ULL << 4) > +#define LANDLOCK_ACCESS_NET_CONNECT_MPTCP (1ULL << 5) >  /* clang-format on */ >   >  /** > diff --git a/security/landlock/limits.h b/security/landlock/limits.h > index 1a7c5fb8f6fd..d25e056b7ca2 100644 > --- a/security/landlock/limits.h > +++ b/security/landlock/limits.h > @@ -23,7 +23,7 @@ >  #define > LANDLOCK_MASK_ACCESS_FS ((LANDLOCK_LAST_ACCESS_FS << 1) - 1) >  #define > LANDLOCK_NUM_ACCESS_FS __const_hweight64(LANDLOCK_MASK_ACCESS_FS) >   > -#define > LANDLOCK_LAST_ACCESS_NET LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP > +#define > LANDLOCK_LAST_ACCESS_NET LANDLOCK_ACCESS_NET_CONNECT_MPTCP >  #define LANDLOCK_MASK_ACCESS_NET ((LANDLOCK_LAST_ACCESS_NET > << 1) - 1) >  #define > LANDLOCK_NUM_ACCESS_NET __const_hweight64(LANDLOCK_MASK_ACCESS_NET) >   > diff --git a/security/landlock/net.c b/security/landlock/net.c > index 8f2aaac54b33..8541b0c07d64 100644 > --- a/security/landlock/net.c > +++ b/security/landlock/net.c > @@ -11,6 +11,7 @@ >  #include >  #include >  #include > +#include >   >  #include "common.h" >  #include "cred.h" > @@ -53,6 +54,26 @@ int landlock_append_net_rule(struct > landlock_ruleset *const ruleset, >   return err; >  } >   > +static bool sk_is_mptcp_socket(const struct sock *sk) > +{ > + return sk_is_inet(sk) && sk->sk_type == SOCK_STREAM && > +        sk->sk_protocol == IPPROTO_MPTCP; > +} This helper should be placed in include/net/mptcp.h. I had already implemented one in [1], called sk_is_msk(), to differentiate it from sk_is_mptcp(). If you have no concerns with my implementation, please feel free to pick it up and use it in your series. Thanks, -Geliang [1] https://patchwork.kernel.org/project/mptcp/patch/e2727ba40084f261545f1cbb140a3fb9d295ba25.1765505775.git.tanggeliang@kylinos.cn/ > + > +static bool is_connect_access(const access_mask_t access_request) > +{ > + return access_request == LANDLOCK_ACCESS_NET_CONNECT_TCP || > +        access_request == LANDLOCK_ACCESS_NET_CONNECT_MPTCP > || > +        access_request == > LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP; > +} > + > +static bool is_bind_access(const access_mask_t access_request) > +{ > + return access_request == LANDLOCK_ACCESS_NET_BIND_TCP || > +        access_request == LANDLOCK_ACCESS_NET_BIND_MPTCP || > +        access_request == LANDLOCK_ACCESS_NET_BIND_UDP; > +} > + >  static bool unmask_layers_net(const struct landlock_domain *const > domain, >         const struct landlock_id id, >         struct layer_masks *masks, > @@ -104,6 +125,7 @@ static int current_check_access_socket(struct > socket *const sock, >   switch (address->sa_family) { >   case AF_UNSPEC: >   if (access_request == > LANDLOCK_ACCESS_NET_CONNECT_TCP || > +     access_request == > LANDLOCK_ACCESS_NET_CONNECT_MPTCP || >       (access_request == > LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP && >        connecting)) { >   /* > @@ -147,17 +169,15 @@ static int current_check_access_socket(struct > socket *const sock, >   }); >   return -EACCES; >   } > - } else if (access_request == > LANDLOCK_ACCESS_NET_BIND_TCP || > -    access_request == > LANDLOCK_ACCESS_NET_BIND_UDP) { > + } else if (is_bind_access(access_request)) { >   /* >   * Binding to an AF_UNSPEC address is > treated >   * differently by IPv4 and IPv6 sockets. The > socket's >   * family may change under our feet due to >   * setsockopt(IPV6_ADDRFORM), but that's ok: > we either > - * reject entirely for IPv6 or require > - * %LANDLOCK_ACCESS_NET_BIND_TCP or > - * %LANDLOCK_ACCESS_NET_BIND_UDP for IPv4, > so it cannot > - * be used to bypass the policy. > + * reject entirely for IPv6 or require the > relevant bind > + * access right for IPv4, so it cannot be > used to bypass > + * the policy. >   * >   * IPv4 sockets map AF_UNSPEC to AF_INET for >   * retrocompatibility for bind accesses, > only if the > @@ -204,12 +224,10 @@ static int current_check_access_socket(struct > socket *const sock, >   addr4 = (struct sockaddr_in *)address; >   port = addr4->sin_port; >   > - if (access_request == > LANDLOCK_ACCESS_NET_CONNECT_TCP || > -     access_request == > LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP) { > + if (is_connect_access(access_request)) { >   audit_net.dport = port; >   audit_net.v4info.daddr = addr4- > >sin_addr.s_addr; > - } else if (access_request == > LANDLOCK_ACCESS_NET_BIND_TCP || > -    access_request == > LANDLOCK_ACCESS_NET_BIND_UDP) { > + } else if (is_bind_access(access_request)) { >   audit_net.sport = port; >   audit_net.v4info.saddr = addr4- > >sin_addr.s_addr; >   } else { > @@ -228,12 +246,10 @@ static int current_check_access_socket(struct > socket *const sock, >   addr6 = (struct sockaddr_in6 *)address; >   port = addr6->sin6_port; >   > - if (access_request == > LANDLOCK_ACCESS_NET_CONNECT_TCP || > -     access_request == > LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP) { > + if (is_connect_access(access_request)) { >   audit_net.dport = port; >   audit_net.v6info.daddr = addr6->sin6_addr; > - } else if (access_request == > LANDLOCK_ACCESS_NET_BIND_TCP || > -    access_request == > LANDLOCK_ACCESS_NET_BIND_UDP) { > + } else if (is_bind_access(access_request)) { >   audit_net.sport = port; >   audit_net.v6info.saddr = addr6->sin6_addr; >   } else { > @@ -331,6 +347,8 @@ static int hook_socket_bind(struct socket *const > sock, >   >   if (sk_is_tcp(sock->sk)) >   access_request = LANDLOCK_ACCESS_NET_BIND_TCP; > + else if (sk_is_mptcp_socket(sock->sk)) > + access_request = LANDLOCK_ACCESS_NET_BIND_MPTCP; >   else if (sk_is_udp(sock->sk)) >   access_request = LANDLOCK_ACCESS_NET_BIND_UDP; >   else > @@ -349,6 +367,8 @@ static int hook_socket_connect(struct socket > *const sock, >   >   if (sk_is_tcp(sock->sk)) >   access_request = LANDLOCK_ACCESS_NET_CONNECT_TCP; > + else if (sk_is_mptcp_socket(sock->sk)) > + access_request = LANDLOCK_ACCESS_NET_CONNECT_MPTCP; >   else if (sk_is_udp(sock->sk)) >   access_request = > LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP; >   else > @@ -377,12 +397,20 @@ static int hook_socket_sendmsg(struct socket > *const sock, >   access_mask_t access_request; >   int ret = 0; >   > - if ((msg->msg_flags & MSG_FASTOPEN) && address && > sk_is_tcp(sock->sk)) { > - ret = current_check_access_socket( > - sock, address, addrlen, > LANDLOCK_ACCESS_NET_CONNECT_TCP, > - true); > - if (ret != 0) > - return ret; > + if ((msg->msg_flags & MSG_FASTOPEN) && address) { > + access_mask_t fastopen_access = 0; > + > + if (sk_is_tcp(sock->sk)) > + fastopen_access = > LANDLOCK_ACCESS_NET_CONNECT_TCP; > + else if (sk_is_mptcp_socket(sock->sk)) > + fastopen_access = > LANDLOCK_ACCESS_NET_CONNECT_MPTCP; > + > + if (fastopen_access) { > + ret = current_check_access_socket( > + sock, address, addrlen, > fastopen_access, true); > + if (ret != 0) > + return ret; > + } >   } >   >   if (sk_is_udp(sock->sk)) > diff --git a/security/landlock/syscalls.c > b/security/landlock/syscalls.c > index 1d02d57f4c48..cc54d4f1d502 100644 > --- a/security/landlock/syscalls.c > +++ b/security/landlock/syscalls.c > @@ -172,7 +172,7 @@ static const struct file_operations ruleset_fops > = { >   * If the change involves a fix that requires userspace awareness, > also update >   * the errata documentation in Documentation/userspace- > api/landlock.rst . >   */ > -const int landlock_abi_version = 11; > +const int landlock_abi_version = 12; >   >  /** >   * sys_landlock_create_ruleset - Create a new ruleset > diff --git a/tools/testing/selftests/landlock/base_test.c > b/tools/testing/selftests/landlock/base_test.c > index d20ab8f0862c..58fe322d8637 100644 > --- a/tools/testing/selftests/landlock/base_test.c > +++ b/tools/testing/selftests/landlock/base_test.c > @@ -76,7 +76,7 @@ TEST(abi_version) >   const struct landlock_ruleset_attr ruleset_attr = { >   .handled_access_fs = LANDLOCK_ACCESS_FS_READ_FILE, >   }; > - ASSERT_EQ(11, landlock_create_ruleset(NULL, 0, > + ASSERT_EQ(12, landlock_create_ruleset(NULL, 0, >         > LANDLOCK_CREATE_RULESET_VERSION)); >   >   ASSERT_EQ(-1, landlock_create_ruleset(&ruleset_attr, 0,