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874c8f8382
hook_cred_transfer() only copies the Landlock security blob when the
source credential has a domain. This is inconsistent with
landlock_restrict_self() which can set LOG_SUBDOMAINS_OFF on a
credential without creating a domain (via the ruleset_fd=-1 path): the
field is committed but not preserved across fork() because the child's
prepare_creds() calls hook_cred_transfer() which skips the copy when
domain is NULL.
This breaks the documented use case where a process mutes subdomain logs
before forking sandboxed children: the children lose the muting and
their domains produce unexpected audit records.
Fix this by unconditionally copying the Landlock credential blob.
Cc: Günther Noack <gnoack@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: stable@vger.kernel.org
Fixes: ead9079f75 ("landlock: Add LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF")
Reviewed-by: Günther Noack <gnoack3000@gmail.com>
Link: https://lore.kernel.org/r/20260407164107.2012589-1-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>
70 lines
1.6 KiB
C
70 lines
1.6 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Landlock - Credential hooks
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*
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* Copyright © 2017-2020 Mickaël Salaün <mic@digikod.net>
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* Copyright © 2018-2020 ANSSI
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* Copyright © 2024-2025 Microsoft Corporation
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*/
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#include <linux/binfmts.h>
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#include <linux/cred.h>
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#include <linux/lsm_hooks.h>
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#include "common.h"
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#include "cred.h"
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#include "ruleset.h"
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#include "setup.h"
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static void hook_cred_transfer(struct cred *const new,
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const struct cred *const old)
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{
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const struct landlock_cred_security *const old_llcred =
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landlock_cred(old);
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landlock_get_ruleset(old_llcred->domain);
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*landlock_cred(new) = *old_llcred;
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}
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static int hook_cred_prepare(struct cred *const new,
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const struct cred *const old, const gfp_t gfp)
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{
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hook_cred_transfer(new, old);
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return 0;
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}
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static void hook_cred_free(struct cred *const cred)
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{
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struct landlock_ruleset *const dom = landlock_cred(cred)->domain;
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if (dom)
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landlock_put_ruleset_deferred(dom);
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}
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#ifdef CONFIG_AUDIT
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static int hook_bprm_creds_for_exec(struct linux_binprm *const bprm)
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{
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/* Resets for each execution. */
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landlock_cred(bprm->cred)->domain_exec = 0;
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return 0;
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}
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#endif /* CONFIG_AUDIT */
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static struct security_hook_list landlock_hooks[] __ro_after_init = {
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LSM_HOOK_INIT(cred_prepare, hook_cred_prepare),
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LSM_HOOK_INIT(cred_transfer, hook_cred_transfer),
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LSM_HOOK_INIT(cred_free, hook_cred_free),
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#ifdef CONFIG_AUDIT
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LSM_HOOK_INIT(bprm_creds_for_exec, hook_bprm_creds_for_exec),
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#endif /* CONFIG_AUDIT */
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};
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__init void landlock_add_cred_hooks(void)
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{
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security_add_hooks(landlock_hooks, ARRAY_SIZE(landlock_hooks),
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&landlock_lsmid);
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}
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