Extend struct landlock_cred_security with a domain_exec bitmask to identify which Landlock domain were created by the current task's bprm. This is reset on each execve(2) call.
Cc: Günther Noack <[email protected]> Cc: Paul Moore <[email protected]> Signed-off-by: Mickaël Salaün <[email protected]> Link: https://lore.kernel.org/r/[email protected] --- Changes since v5: - Add documentation and pack struct landlock_cred_security to minimize struct landlock_file_security. Changes since v4: - New patch. --- security/landlock/cred.c | 26 ++++++++++++++++++++++---- security/landlock/cred.h | 32 +++++++++++++++++++++++++++++++- security/landlock/syscalls.c | 5 +++++ 3 files changed, 58 insertions(+), 5 deletions(-) diff --git a/security/landlock/cred.c b/security/landlock/cred.c index db9fe7d906ba..a22756fe3b71 100644 --- a/security/landlock/cred.c +++ b/security/landlock/cred.c @@ -4,8 +4,10 @@ * * Copyright © 2017-2020 Mickaël Salaün <[email protected]> * Copyright © 2018-2020 ANSSI + * Copyright © 2025 Microsoft Corporation */ +#include <linux/binfmts.h> #include <linux/cred.h> #include <linux/lsm_hooks.h> @@ -17,11 +19,12 @@ static void hook_cred_transfer(struct cred *const new, const struct cred *const old) { - struct landlock_ruleset *const old_dom = landlock_cred(old)->domain; + const struct landlock_cred_security *const old_llcred = + landlock_cred(old); - if (old_dom) { - landlock_get_ruleset(old_dom); - landlock_cred(new)->domain = old_dom; + if (old_llcred->domain) { + landlock_get_ruleset(old_llcred->domain); + *landlock_cred(new) = *old_llcred; } } @@ -40,10 +43,25 @@ static void hook_cred_free(struct cred *const cred) landlock_put_ruleset_deferred(dom); } +#ifdef CONFIG_AUDIT + +static int hook_bprm_creds_for_exec(struct linux_binprm *const bprm) +{ + /* Resets for each execution. */ + landlock_cred(bprm->cred)->domain_exec = 0; + return 0; +} + +#endif /* CONFIG_AUDIT */ + static struct security_hook_list landlock_hooks[] __ro_after_init = { LSM_HOOK_INIT(cred_prepare, hook_cred_prepare), LSM_HOOK_INIT(cred_transfer, hook_cred_transfer), LSM_HOOK_INIT(cred_free, hook_cred_free), + +#ifdef CONFIG_AUDIT + LSM_HOOK_INIT(bprm_creds_for_exec, hook_bprm_creds_for_exec), +#endif /* CONFIG_AUDIT */ }; __init void landlock_add_cred_hooks(void) diff --git a/security/landlock/cred.h b/security/landlock/cred.h index fdbbaf66d151..cf38caf77adc 100644 --- a/security/landlock/cred.h +++ b/security/landlock/cred.h @@ -9,17 +9,47 @@ #ifndef _SECURITY_LANDLOCK_CRED_H #define _SECURITY_LANDLOCK_CRED_H +#include <linux/container_of.h> #include <linux/cred.h> #include <linux/init.h> #include <linux/rcupdate.h> #include "access.h" +#include "limits.h" #include "ruleset.h" #include "setup.h" +/** + * struct landlock_cred_security - Credential security blob + * + * This structure is packed to minimize the size of struct + * landlock_file_security. However, it is always aligned in the LSM cred blob, + * see lsm_set_blob_size(). + */ struct landlock_cred_security { + /** + * @domain: Immutable ruleset enforced on a task. + */ struct landlock_ruleset *domain; -}; + +#ifdef CONFIG_AUDIT + /** + * @domain_exec: Bitmask identifying the domain layers that were enforced by + * the current task's executed file (i.e. no new execve(2) since + * landlock_restrict_self(2)). + */ + u16 domain_exec; +#endif /* CONFIG_AUDIT */ +} __packed; + +#ifdef CONFIG_AUDIT + +/* Makes sure all layer executions can be stored. */ +static_assert(BITS_PER_TYPE(typeof_member(struct landlock_cred_security, + domain_exec)) >= + LANDLOCK_MAX_NUM_LAYERS); + +#endif /* CONFIG_AUDIT */ static inline struct landlock_cred_security * landlock_cred(const struct cred *cred) diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c index a9760d252fc2..5129981fec8b 100644 --- a/security/landlock/syscalls.c +++ b/security/landlock/syscalls.c @@ -496,5 +496,10 @@ SYSCALL_DEFINE2(landlock_restrict_self, const int, ruleset_fd, const __u32, /* Replaces the old (prepared) domain. */ landlock_put_ruleset(new_llcred->domain); new_llcred->domain = new_dom; + +#ifdef CONFIG_AUDIT + new_llcred->domain_exec |= 1 << (new_dom->num_layers - 1); +#endif /* CONFIG_AUDIT */ + return commit_creds(new_cred); } -- 2.48.1
