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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 <morgan@kernel.org> Cc: John Johansen <john.johansen@canonical.com> Cc: Paul Moore <paul@paul-moore.com> Suggested-by: Jann Horn <jannh@google.com> Signed-off-by: Günther Noack <gnoack@google.com> 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 <mic@digikod.net>
16 lines
378 B
C
16 lines
378 B
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Landlock - Cross-thread ruleset enforcement
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*
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* Copyright © 2025 Google LLC
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*/
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#ifndef _SECURITY_LANDLOCK_TSYNC_H
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#define _SECURITY_LANDLOCK_TSYNC_H
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#include <linux/cred.h>
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int landlock_restrict_sibling_threads(const struct cred *old_cred,
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const struct cred *new_cred);
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#endif /* _SECURITY_LANDLOCK_TSYNC_H */
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