From 42fc7e6543f6d17d2cf9ed3e5021f103a3d11182 Mon Sep 17 00:00:00 2001 From: Günther Noack Date: Thu, 27 Nov 2025 12:51:34 +0100 Subject: landlock: Multithreading support for landlock_restrict_self() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Introduce the LANDLOCK_RESTRICT_SELF_TSYNC flag. With this flag, a given Landlock ruleset is applied to all threads of the calling process, instead of only the current one. Without this flag, multithreaded userspace programs currently resort to using the nptl(7)/libpsx hack for multithreaded policy enforcement, which is also used by libcap and for setuid(2). Using this userspace-based scheme, the threads of a process enforce the same Landlock policy, but the resulting Landlock domains are still separate. The domains being separate causes multiple problems: * When using Landlock's "scoped" access rights, the domain identity is used to determine whether an operation is permitted. As a result, when using LANLDOCK_SCOPE_SIGNAL, signaling between sibling threads stops working. This is a problem for programming languages and frameworks which are inherently multithreaded (e.g. Go). * In audit logging, the domains of separate threads in a process will get logged with different domain IDs, even when they are based on the same ruleset FD, which might confuse users. Cc: Andrew G. Morgan Cc: John Johansen Cc: Paul Moore Suggested-by: Jann Horn Signed-off-by: Günther Noack Link: https://lore.kernel.org/r/20251127115136.3064948-2-gnoack@google.com [mic: Fix restrict_self_flags test, clean up Makefile, allign comments, reduce local variable scope, add missing includes] Closes: https://github.com/landlock-lsm/linux/issues/2 Signed-off-by: Mickaël Salaün --- include/uapi/linux/landlock.h | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'include/uapi/linux') diff --git a/include/uapi/linux/landlock.h b/include/uapi/linux/landlock.h index 75fd7f5e6cc3..d5081ab4e5ef 100644 --- a/include/uapi/linux/landlock.h +++ b/include/uapi/linux/landlock.h @@ -117,11 +117,24 @@ struct landlock_ruleset_attr { * future nested domains, not the one being created. It can also be used * with a @ruleset_fd value of -1 to mute subdomain logs without creating a * domain. + * + * The following flag supports policy enforcement in multithreaded processes: + * + * %LANDLOCK_RESTRICT_SELF_TSYNC + * Applies the new Landlock configuration atomically to all threads of the + * current process, including the Landlock domain and logging + * configuration. This overrides the Landlock configuration of sibling + * threads, irrespective of previously established Landlock domains and + * logging configurations on these threads. + * + * If the calling thread is running with no_new_privs, this operation + * enables no_new_privs on the sibling threads as well. */ /* clang-format off */ #define LANDLOCK_RESTRICT_SELF_LOG_SAME_EXEC_OFF (1U << 0) #define LANDLOCK_RESTRICT_SELF_LOG_NEW_EXEC_ON (1U << 1) #define LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF (1U << 2) +#define LANDLOCK_RESTRICT_SELF_TSYNC (1U << 3) /* clang-format on */ /** -- cgit v1.2.3 From bbb6f53e905ca119f99ccab8496f8921d9db9c50 Mon Sep 17 00:00:00 2001 From: Matthieu Buffet Date: Fri, 12 Dec 2025 17:36:57 +0100 Subject: landlock: Minor reword of docs for TCP access rights MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit - Move ABI requirement next to each access right to prepare adding more access rights; - Mention the possibility to remove the random component of a socket's ephemeral port choice within the netns-wide ephemeral port range, since it allows choosing the "random" ephemeral port. Signed-off-by: Matthieu Buffet Link: https://lore.kernel.org/r/20251212163704.142301-2-matthieu@buffet.re Signed-off-by: Mickaël Salaün --- include/uapi/linux/landlock.h | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) (limited to 'include/uapi/linux') diff --git a/include/uapi/linux/landlock.h b/include/uapi/linux/landlock.h index d5081ab4e5ef..f88fa1f68b77 100644 --- a/include/uapi/linux/landlock.h +++ b/include/uapi/linux/landlock.h @@ -195,11 +195,13 @@ struct landlock_net_port_attr { * It should be noted that port 0 passed to :manpage:`bind(2)` will bind * to an available port from the ephemeral port range. This can be * configured with the ``/proc/sys/net/ipv4/ip_local_port_range`` sysctl - * (also used for IPv6). + * (also used for IPv6), and within that range, on a per-socket basis + * with ``setsockopt(IP_LOCAL_PORT_RANGE)``. * - * A Landlock rule with port 0 and the ``LANDLOCK_ACCESS_NET_BIND_TCP`` + * A Landlock rule with port 0 and the %LANDLOCK_ACCESS_NET_BIND_TCP * right means that requesting to bind on port 0 is allowed and it will - * automatically translate to binding on the related port range. + * automatically translate to binding on a kernel-assigned ephemeral + * port. */ __u64 port; }; @@ -342,13 +344,12 @@ struct landlock_net_port_attr { * These flags enable to restrict a sandboxed process to a set of network * actions. * - * This is supported since Landlock ABI version 4. - * * The following access rights apply to TCP port numbers: * - * - %LANDLOCK_ACCESS_NET_BIND_TCP: Bind a TCP socket to a local port. - * - %LANDLOCK_ACCESS_NET_CONNECT_TCP: Connect an active TCP socket to - * a remote port. + * - %LANDLOCK_ACCESS_NET_BIND_TCP: Bind TCP sockets to the given local + * port. Support added in Landlock ABI version 4. + * - %LANDLOCK_ACCESS_NET_CONNECT_TCP: Connect TCP sockets to the given + * remote port. Support added in Landlock ABI version 4. */ /* clang-format off */ #define LANDLOCK_ACCESS_NET_BIND_TCP (1ULL << 0) -- cgit v1.2.3