From fe81536af3978f26a1383e4da7f135b973eb4209 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= Date: Mon, 31 Mar 2025 12:47:07 +0200 Subject: [PATCH 1/7] landlock: Remove incorrect warning MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit landlock_put_hierarchy() can be called when an error occurs in landlock_merge_ruleset() due to insufficient memory. In this case, the domain's audit details might not have been allocated yet, which would cause landlock_free_hierarchy_details() to print a warning (but still safely handle this case). We could keep the WARN_ON_ONCE(!hierarchy) but it's not worth it for this kind of function, so let's remove it entirely. Cc: Paul Moore Reported-by: syzbot+8bca99e91de7e060e4ea@syzkaller.appspotmail.com Link: https://lore.kernel.org/r/20250331104709.897062-1-mic@digikod.net Reviewed-by: Günther Noack Signed-off-by: Mickaël Salaün --- security/landlock/domain.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/security/landlock/domain.h b/security/landlock/domain.h index ed0d348e214c..7fb70b25f85a 100644 --- a/security/landlock/domain.h +++ b/security/landlock/domain.h @@ -130,7 +130,7 @@ int landlock_init_hierarchy_log(struct landlock_hierarchy *const hierarchy); static inline void landlock_free_hierarchy_details(struct landlock_hierarchy *const hierarchy) { - if (WARN_ON_ONCE(!hierarchy || !hierarchy->details)) + if (!hierarchy || !hierarchy->details) return; put_pid(hierarchy->details->pid); From 4767af82a08ffaa5e55fe71febfa8cdef201b620 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= Date: Thu, 10 Apr 2025 19:17:21 +0200 Subject: [PATCH 2/7] landlock: Log the TGID of the domain creator MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit As for other Audit's "pid" fields, Landlock should use the task's TGID instead of its TID. Fix this issue by keeping a reference to the TGID of the domain creator. Existing tests already check for the PID but only with the thread group leader, so always the TGID. A following patch adds dedicated tests for non-leader thread. Remove the current_real_cred() check which does not make sense because we only reference a struct pid, whereas a previous version did reference a struct cred instead. Cc: Christian Brauner Cc: Paul Moore Reviewed-by: Günther Noack Link: https://lore.kernel.org/r/20250410171725.1265860-1-mic@digikod.net Signed-off-by: Mickaël Salaün --- security/landlock/domain.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/security/landlock/domain.c b/security/landlock/domain.c index bae2e9909013..a647b68e8d06 100644 --- a/security/landlock/domain.c +++ b/security/landlock/domain.c @@ -16,6 +16,7 @@ #include #include #include +#include #include #include "access.h" @@ -99,8 +100,7 @@ static struct landlock_details *get_current_details(void) return ERR_PTR(-ENOMEM); memcpy(details->exe_path, path_str, path_size); - WARN_ON_ONCE(current_cred() != current_real_cred()); - details->pid = get_pid(task_pid(current)); + details->pid = get_pid(task_tgid(current)); details->uid = from_kuid(&init_user_ns, current_uid()); get_task_comm(details->comm, current); return details; From e4a0f9e0cacd93094b619616426a273e0bc9107e Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= Date: Thu, 10 Apr 2025 19:17:22 +0200 Subject: [PATCH 3/7] selftests/landlock: Factor out audit fixture in audit_test MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The audit fixture needlessly stores and manages domain_stack. Move it to the audit.layers tests. This will be useful to reuse the audit fixture with the next patch. Cc: Günther Noack Link: https://lore.kernel.org/r/20250410171725.1265860-2-mic@digikod.net Signed-off-by: Mickaël Salaün --- tools/testing/selftests/landlock/audit_test.c | 27 +++++++++---------- 1 file changed, 12 insertions(+), 15 deletions(-) diff --git a/tools/testing/selftests/landlock/audit_test.c b/tools/testing/selftests/landlock/audit_test.c index a0643070c403..815c0f03e1fb 100644 --- a/tools/testing/selftests/landlock/audit_test.c +++ b/tools/testing/selftests/landlock/audit_test.c @@ -40,7 +40,6 @@ FIXTURE(audit) { struct audit_filter audit_filter; int audit_fd; - __u64(*domain_stack)[16]; }; FIXTURE_SETUP(audit) @@ -60,18 +59,10 @@ FIXTURE_SETUP(audit) TH_LOG("Failed to initialize audit: %s", error_msg); } clear_cap(_metadata, CAP_AUDIT_CONTROL); - - self->domain_stack = mmap(NULL, sizeof(*self->domain_stack), - PROT_READ | PROT_WRITE, - MAP_SHARED | MAP_ANONYMOUS, -1, 0); - ASSERT_NE(MAP_FAILED, self->domain_stack); - memset(self->domain_stack, 0, sizeof(*self->domain_stack)); } FIXTURE_TEARDOWN(audit) { - EXPECT_EQ(0, munmap(self->domain_stack, sizeof(*self->domain_stack))); - set_cap(_metadata, CAP_AUDIT_CONTROL); EXPECT_EQ(0, audit_cleanup(self->audit_fd, &self->audit_filter)); clear_cap(_metadata, CAP_AUDIT_CONTROL); @@ -83,9 +74,15 @@ TEST_F(audit, layers) .scoped = LANDLOCK_SCOPE_SIGNAL, }; int status, ruleset_fd, i; + __u64(*domain_stack)[16]; __u64 prev_dom = 3; pid_t child; + domain_stack = mmap(NULL, sizeof(*domain_stack), PROT_READ | PROT_WRITE, + MAP_SHARED | MAP_ANONYMOUS, -1, 0); + ASSERT_NE(MAP_FAILED, domain_stack); + memset(domain_stack, 0, sizeof(*domain_stack)); + ruleset_fd = landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0); ASSERT_LE(0, ruleset_fd); @@ -94,7 +91,7 @@ TEST_F(audit, layers) child = fork(); ASSERT_LE(0, child); if (child == 0) { - for (i = 0; i < ARRAY_SIZE(*self->domain_stack); i++) { + for (i = 0; i < ARRAY_SIZE(*domain_stack); i++) { __u64 denial_dom = 1; __u64 allocated_dom = 2; @@ -115,7 +112,7 @@ TEST_F(audit, layers) /* Checks that the new domain is younger than the previous one. */ EXPECT_GT(allocated_dom, prev_dom); prev_dom = allocated_dom; - (*self->domain_stack)[i] = allocated_dom; + (*domain_stack)[i] = allocated_dom; } /* Checks that we reached the maximum number of layers. */ @@ -142,20 +139,20 @@ TEST_F(audit, layers) /* Purges log from deallocated domains. */ EXPECT_EQ(0, setsockopt(self->audit_fd, SOL_SOCKET, SO_RCVTIMEO, &audit_tv_dom_drop, sizeof(audit_tv_dom_drop))); - for (i = ARRAY_SIZE(*self->domain_stack) - 1; i >= 0; i--) { + for (i = ARRAY_SIZE(*domain_stack) - 1; i >= 0; i--) { __u64 deallocated_dom = 2; EXPECT_EQ(0, matches_log_domain_deallocated(self->audit_fd, 1, &deallocated_dom)); - EXPECT_EQ((*self->domain_stack)[i], deallocated_dom) + EXPECT_EQ((*domain_stack)[i], deallocated_dom) { TH_LOG("Failed to match domain %llx (#%d)", - (*self->domain_stack)[i], i); + (*domain_stack)[i], i); } } + EXPECT_EQ(0, munmap(domain_stack, sizeof(*domain_stack))); EXPECT_EQ(0, setsockopt(self->audit_fd, SOL_SOCKET, SO_RCVTIMEO, &audit_tv_default, sizeof(audit_tv_default))); - EXPECT_EQ(0, close(ruleset_fd)); } From 6b4566400a2919e6c1137404c53d7cf1ada559aa Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= Date: Thu, 10 Apr 2025 19:17:23 +0200 Subject: [PATCH 4/7] selftests/landlock: Add PID tests for audit records MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add audit.thread tests to check that the PID tied to a domain is not a thread ID but the thread group ID. These new tests would not pass without the previous TGID fix. Extend matches_log_domain_allocated() to check against the PID that created the domain. Test coverage for security/landlock is 93.6% of 1524 lines according to gcc/gcov-14. Cc: Christian Brauner Cc: Günther Noack Cc: Paul Moore Link: https://lore.kernel.org/r/20250410171725.1265860-3-mic@digikod.net Signed-off-by: Mickaël Salaün --- tools/testing/selftests/landlock/audit.h | 21 ++- tools/testing/selftests/landlock/audit_test.c | 127 +++++++++++++++++- tools/testing/selftests/landlock/fs_test.c | 3 +- 3 files changed, 141 insertions(+), 10 deletions(-) diff --git a/tools/testing/selftests/landlock/audit.h b/tools/testing/selftests/landlock/audit.h index b9054086a0c9..18a6014920b5 100644 --- a/tools/testing/selftests/landlock/audit.h +++ b/tools/testing/selftests/landlock/audit.h @@ -300,15 +300,22 @@ static int audit_match_record(int audit_fd, const __u16 type, return err; } -static int __maybe_unused matches_log_domain_allocated(int audit_fd, +static int __maybe_unused matches_log_domain_allocated(int audit_fd, pid_t pid, __u64 *domain_id) { - return audit_match_record( - audit_fd, AUDIT_LANDLOCK_DOMAIN, - REGEX_LANDLOCK_PREFIX - " status=allocated mode=enforcing pid=[0-9]\\+ uid=[0-9]\\+" - " exe=\"[^\"]\\+\" comm=\".*_test\"$", - domain_id); + static const char log_template[] = REGEX_LANDLOCK_PREFIX + " status=allocated mode=enforcing pid=%d uid=[0-9]\\+" + " exe=\"[^\"]\\+\" comm=\".*_test\"$"; + char log_match[sizeof(log_template) + 10]; + int log_match_len; + + log_match_len = + snprintf(log_match, sizeof(log_match), log_template, pid); + if (log_match_len > sizeof(log_match)) + return -E2BIG; + + return audit_match_record(audit_fd, AUDIT_LANDLOCK_DOMAIN, log_match, + domain_id); } static int __maybe_unused matches_log_domain_deallocated( diff --git a/tools/testing/selftests/landlock/audit_test.c b/tools/testing/selftests/landlock/audit_test.c index 815c0f03e1fb..cfc571afd0eb 100644 --- a/tools/testing/selftests/landlock/audit_test.c +++ b/tools/testing/selftests/landlock/audit_test.c @@ -9,6 +9,7 @@ #include #include #include +#include #include #include #include @@ -104,7 +105,8 @@ TEST_F(audit, layers) matches_log_signal(_metadata, self->audit_fd, getppid(), &denial_dom)); EXPECT_EQ(0, matches_log_domain_allocated( - self->audit_fd, &allocated_dom)); + self->audit_fd, getpid(), + &allocated_dom)); EXPECT_NE(denial_dom, 1); EXPECT_NE(denial_dom, 0); EXPECT_EQ(denial_dom, allocated_dom); @@ -156,6 +158,126 @@ TEST_F(audit, layers) EXPECT_EQ(0, close(ruleset_fd)); } +struct thread_data { + pid_t parent_pid; + int ruleset_fd, pipe_child, pipe_parent; +}; + +static void *thread_audit_test(void *arg) +{ + const struct thread_data *data = (struct thread_data *)arg; + uintptr_t err = 0; + char buffer; + + /* TGID and TID are different for a second thread. */ + if (getpid() == gettid()) { + err = 1; + goto out; + } + + if (landlock_restrict_self(data->ruleset_fd, 0)) { + err = 2; + goto out; + } + + if (close(data->ruleset_fd)) { + err = 3; + goto out; + } + + /* Creates a denial to get the domain ID. */ + if (kill(data->parent_pid, 0) != -1) { + err = 4; + goto out; + } + + if (EPERM != errno) { + err = 5; + goto out; + } + + /* Signals the parent to read denial logs. */ + if (write(data->pipe_child, ".", 1) != 1) { + err = 6; + goto out; + } + + /* Waits for the parent to update audit filters. */ + if (read(data->pipe_parent, &buffer, 1) != 1) { + err = 7; + goto out; + } + +out: + close(data->pipe_child); + close(data->pipe_parent); + return (void *)err; +} + +/* Checks that the PID tied to a domain is not a TID but the TGID. */ +TEST_F(audit, thread) +{ + const struct landlock_ruleset_attr ruleset_attr = { + .scoped = LANDLOCK_SCOPE_SIGNAL, + }; + __u64 denial_dom = 1; + __u64 allocated_dom = 2; + __u64 deallocated_dom = 3; + pthread_t thread; + int pipe_child[2], pipe_parent[2]; + char buffer; + struct thread_data child_data; + + child_data.parent_pid = getppid(); + ASSERT_EQ(0, pipe2(pipe_child, O_CLOEXEC)); + child_data.pipe_child = pipe_child[1]; + ASSERT_EQ(0, pipe2(pipe_parent, O_CLOEXEC)); + child_data.pipe_parent = pipe_parent[0]; + child_data.ruleset_fd = + landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0); + ASSERT_LE(0, child_data.ruleset_fd); + + /* TGID and TID are the same for the initial thread . */ + EXPECT_EQ(getpid(), gettid()); + EXPECT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)); + ASSERT_EQ(0, pthread_create(&thread, NULL, thread_audit_test, + &child_data)); + + /* Waits for the child to generate a denial. */ + ASSERT_EQ(1, read(pipe_child[0], &buffer, 1)); + EXPECT_EQ(0, close(pipe_child[0])); + + /* Matches the signal log to get the domain ID. */ + EXPECT_EQ(0, matches_log_signal(_metadata, self->audit_fd, + child_data.parent_pid, &denial_dom)); + EXPECT_NE(denial_dom, 1); + EXPECT_NE(denial_dom, 0); + + EXPECT_EQ(0, matches_log_domain_allocated(self->audit_fd, getpid(), + &allocated_dom)); + EXPECT_EQ(denial_dom, allocated_dom); + + /* Updates filter rules to match the drop record. */ + set_cap(_metadata, CAP_AUDIT_CONTROL); + EXPECT_EQ(0, audit_filter_drop(self->audit_fd, AUDIT_ADD_RULE)); + EXPECT_EQ(0, audit_filter_exe(self->audit_fd, &self->audit_filter, + AUDIT_DEL_RULE)); + clear_cap(_metadata, CAP_AUDIT_CONTROL); + + /* Signals the thread to exit, which will generate a domain deallocation. */ + ASSERT_EQ(1, write(pipe_parent[1], ".", 1)); + EXPECT_EQ(0, close(pipe_parent[1])); + ASSERT_EQ(0, pthread_join(thread, NULL)); + + EXPECT_EQ(0, setsockopt(self->audit_fd, SOL_SOCKET, SO_RCVTIMEO, + &audit_tv_dom_drop, sizeof(audit_tv_dom_drop))); + EXPECT_EQ(0, matches_log_domain_deallocated(self->audit_fd, 1, + &deallocated_dom)); + EXPECT_EQ(denial_dom, deallocated_dom); + EXPECT_EQ(0, setsockopt(self->audit_fd, SOL_SOCKET, SO_RCVTIMEO, + &audit_tv_default, sizeof(audit_tv_default))); +} + FIXTURE(audit_flags) { struct audit_filter audit_filter; @@ -270,7 +392,8 @@ TEST_F(audit_flags, signal) /* Checks domain information records. */ EXPECT_EQ(0, matches_log_domain_allocated( - self->audit_fd, &allocated_dom)); + self->audit_fd, getpid(), + &allocated_dom)); EXPECT_NE(*self->domain_id, 1); EXPECT_NE(*self->domain_id, 0); EXPECT_EQ(*self->domain_id, allocated_dom); diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c index f819011a8798..73729382d40f 100644 --- a/tools/testing/selftests/landlock/fs_test.c +++ b/tools/testing/selftests/landlock/fs_test.c @@ -5964,7 +5964,8 @@ TEST_F(audit_layout1, refer_handled) EXPECT_EQ(EXDEV, errno); EXPECT_EQ(0, matches_log_fs(_metadata, self->audit_fd, "fs\\.refer", dir_s1d1)); - EXPECT_EQ(0, matches_log_domain_allocated(self->audit_fd, NULL)); + EXPECT_EQ(0, + matches_log_domain_allocated(self->audit_fd, getpid(), NULL)); EXPECT_EQ(0, matches_log_fs(_metadata, self->audit_fd, "fs\\.refer", dir_s1d3)); From 50492f942c281af4a48f8028f8409d7b8f2655d9 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= Date: Wed, 16 Apr 2025 17:47:11 +0200 Subject: [PATCH 5/7] landlock: Fix documentation for landlock_create_ruleset(2) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Move and fix the flags documentation, and improve formatting. It makes more sense and it eases maintenance to document syscall flags in landlock.h, where they are defined. This is already the case for landlock_restrict_self(2)'s flags. The flags are now rendered like the syscall's parameters and description. Cc: Günther Noack Cc: Paul Moore Link: https://lore.kernel.org/r/20250416154716.1799902-1-mic@digikod.net Signed-off-by: Mickaël Salaün --- include/uapi/linux/landlock.h | 14 +++++++++----- security/landlock/syscalls.c | 15 +++++++-------- 2 files changed, 16 insertions(+), 13 deletions(-) diff --git a/include/uapi/linux/landlock.h b/include/uapi/linux/landlock.h index d9d0cb827117..9a4b64be9869 100644 --- a/include/uapi/linux/landlock.h +++ b/include/uapi/linux/landlock.h @@ -53,12 +53,16 @@ struct landlock_ruleset_attr { __u64 scoped; }; -/* - * sys_landlock_create_ruleset() flags: +/** + * DOC: landlock_create_ruleset_flags * - * - %LANDLOCK_CREATE_RULESET_VERSION: Get the highest supported Landlock ABI - * version. - * - %LANDLOCK_CREATE_RULESET_ERRATA: Get a bitmask of fixed issues. + * **Flags** + * + * %LANDLOCK_CREATE_RULESET_VERSION + * Get the highest supported Landlock ABI version (starting at 1). + * + * %LANDLOCK_CREATE_RULESET_ERRATA + * Get a bitmask of fixed issues for the current Landlock ABI version. */ /* clang-format off */ #define LANDLOCK_CREATE_RULESET_VERSION (1U << 0) diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c index 54a9f29e6ebb..9515dc92b99f 100644 --- a/security/landlock/syscalls.c +++ b/security/landlock/syscalls.c @@ -169,20 +169,16 @@ const int landlock_abi_version = 7; * the new ruleset. * @size: Size of the pointed &struct landlock_ruleset_attr (needed for * backward and forward compatibility). - * @flags: Supported value: + * @flags: Supported values: + * * - %LANDLOCK_CREATE_RULESET_VERSION * - %LANDLOCK_CREATE_RULESET_ERRATA * * This system call enables to create a new Landlock ruleset, and returns the * related file descriptor on success. * - * If @flags is %LANDLOCK_CREATE_RULESET_VERSION and @attr is NULL and @size is - * 0, then the returned value is the highest supported Landlock ABI version - * (starting at 1). - * - * If @flags is %LANDLOCK_CREATE_RULESET_ERRATA and @attr is NULL and @size is - * 0, then the returned value is a bitmask of fixed issues for the current - * Landlock ABI version. + * If %LANDLOCK_CREATE_RULESET_VERSION or %LANDLOCK_CREATE_RULESET_ERRATA is + * set, then @attr must be NULL and @size must be 0. * * Possible returned errors are: * @@ -191,6 +187,9 @@ const int landlock_abi_version = 7; * - %E2BIG: @attr or @size inconsistencies; * - %EFAULT: @attr or @size inconsistencies; * - %ENOMSG: empty &landlock_ruleset_attr.handled_access_fs. + * + * .. kernel-doc:: include/uapi/linux/landlock.h + * :identifiers: landlock_create_ruleset_flags */ SYSCALL_DEFINE3(landlock_create_ruleset, const struct landlock_ruleset_attr __user *const, attr, From 25b1fc1cdc8931cf26e8d169f65ad07dfd653ca2 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= Date: Wed, 16 Apr 2025 17:47:12 +0200 Subject: [PATCH 6/7] landlock: Fix documentation for landlock_restrict_self(2) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Fix, deduplicate, and improve rendering of landlock_restrict_self(2)'s flags documentation. The flags are now rendered like the syscall's parameters and description. Cc: Günther Noack Cc: Paul Moore Link: https://lore.kernel.org/r/20250416154716.1799902-2-mic@digikod.net Signed-off-by: Mickaël Salaün --- include/uapi/linux/landlock.h | 59 +++++++++++++++++++++-------------- security/landlock/syscalls.c | 12 +++---- 2 files changed, 41 insertions(+), 30 deletions(-) diff --git a/include/uapi/linux/landlock.h b/include/uapi/linux/landlock.h index 9a4b64be9869..8b2a1dc5c70b 100644 --- a/include/uapi/linux/landlock.h +++ b/include/uapi/linux/landlock.h @@ -69,31 +69,42 @@ struct landlock_ruleset_attr { #define LANDLOCK_CREATE_RULESET_ERRATA (1U << 1) /* clang-format on */ -/* - * sys_landlock_restrict_self() flags: +/** + * DOC: landlock_restrict_self_flags + * + * **Flags** + * + * %LANDLOCK_RESTRICT_SELF_LOG_SAME_EXEC_OFF + * Do not create any log related to the enforced restrictions. This should + * only be set by tools launching unknown or untrusted programs (e.g. a + * sandbox tool, container runtime, system service manager). Because + * programs sandboxing themselves should fix any denied access, they should + * not set this flag to be aware of potential issues reported by system's + * logs (i.e. audit). + * + * %LANDLOCK_RESTRICT_SELF_LOG_NEW_EXEC_ON + * Explicitly ask to continue logging denied access requests even after an + * :manpage:`execve(2)` call. This flag should only be set if all the + * programs than can legitimately be executed will not try to request a + * denied access (which could spam audit logs). + * + * %LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF + * Do not create any log related to the enforced restrictions coming from + * future nested domains created by the caller or its descendants. This + * should only be set according to a runtime configuration (i.e. not + * hardcoded) by programs launching other unknown or untrusted programs that + * may create their own Landlock domains and spam logs. The main use case + * is for container runtimes to enable users to mute buggy sandboxed + * programs for a specific container image. Other use cases include + * sandboxer tools and init systems. Unlike + * ``LANDLOCK_RESTRICT_SELF_LOG_SAME_EXEC_OFF``, + * ``LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF`` does not impact the + * requested restriction (if any) but only the future nested domains. + * + * It is allowed to only pass the + * ``LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF`` flag with a @ruleset_fd + * value of -1. * - * - %LANDLOCK_RESTRICT_SELF_LOG_SAME_EXEC_OFF: Do not create any log related to the - * enforced restrictions. This should only be set by tools launching unknown - * or untrusted programs (e.g. a sandbox tool, container runtime, system - * service manager). Because programs sandboxing themselves should fix any - * denied access, they should not set this flag to be aware of potential - * issues reported by system's logs (i.e. audit). - * - %LANDLOCK_RESTRICT_SELF_LOG_NEW_EXEC_ON: Explicitly ask to continue - * logging denied access requests even after an :manpage:`execve(2)` call. - * This flag should only be set if all the programs than can legitimately be - * executed will not try to request a denied access (which could spam audit - * logs). - * - %LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF: Do not create any log related - * to the enforced restrictions coming from future nested domains created by - * the caller or its descendants. This should only be set according to a - * runtime configuration (i.e. not hardcoded) by programs launching other - * unknown or untrusted programs that may create their own Landlock domains - * and spam logs. The main use case is for container runtimes to enable users - * to mute buggy sandboxed programs for a specific container image. Other use - * cases include sandboxer tools and init systems. Unlike - * %LANDLOCK_RESTRICT_SELF_LOG_SAME_EXEC_OFF, - * %LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF does not impact the requested - * restriction (if any) but only the future nested domains. */ /* clang-format off */ #define LANDLOCK_RESTRICT_SELF_LOG_SAME_EXEC_OFF (1U << 0) diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c index 9515dc92b99f..b9561e3417ae 100644 --- a/security/landlock/syscalls.c +++ b/security/landlock/syscalls.c @@ -451,18 +451,15 @@ SYSCALL_DEFINE4(landlock_add_rule, const int, ruleset_fd, * @ruleset_fd: File descriptor tied to the ruleset to merge with the target. * @flags: Supported values: * - * - %LANDLOCK_RESTRICT_SELF_LOG_SAME_EXEC_OFF - * - %LANDLOCK_RESTRICT_SELF_LOG_NEW_EXEC_ON - * - %LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF + * - %LANDLOCK_RESTRICT_SELF_LOG_SAME_EXEC_OFF + * - %LANDLOCK_RESTRICT_SELF_LOG_NEW_EXEC_ON + * - %LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF * * This system call enables to enforce a Landlock ruleset on the current * thread. Enforcing a ruleset requires that the task has %CAP_SYS_ADMIN in its * namespace or is running with no_new_privs. This avoids scenarios where * unprivileged tasks can affect the behavior of privileged children. * - * It is allowed to only pass the %LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF - * flag with a @ruleset_fd value of -1. - * * Possible returned errors are: * * - %EOPNOTSUPP: Landlock is supported by the kernel but disabled at boot time; @@ -474,6 +471,9 @@ SYSCALL_DEFINE4(landlock_add_rule, const int, ruleset_fd, * %CAP_SYS_ADMIN in its namespace. * - %E2BIG: The maximum number of stacked rulesets is reached for the current * thread. + * + * .. kernel-doc:: include/uapi/linux/landlock.h + * :identifiers: landlock_restrict_self_flags */ SYSCALL_DEFINE2(landlock_restrict_self, const int, ruleset_fd, const __u32, flags) From 47ce2af848b7301d8571f0e01a0d7c7162d51e4a Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= Date: Wed, 16 Apr 2025 17:47:13 +0200 Subject: [PATCH 7/7] landlock: Update log documentation MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Fix and improve documentation related to landlock_restrict_self(2)'s flags. Update the LANDLOCK_RESTRICT_SELF_LOG_SAME_EXEC_OFF documentation according to the current semantic. Cc: Günther Noack Cc: Paul Moore Link: https://lore.kernel.org/r/20250416154716.1799902-3-mic@digikod.net Signed-off-by: Mickaël Salaün --- include/uapi/linux/landlock.h | 64 +++++++++++++++++++++-------------- 1 file changed, 38 insertions(+), 26 deletions(-) diff --git a/include/uapi/linux/landlock.h b/include/uapi/linux/landlock.h index 8b2a1dc5c70b..f030adc462ee 100644 --- a/include/uapi/linux/landlock.h +++ b/include/uapi/linux/landlock.h @@ -74,37 +74,49 @@ struct landlock_ruleset_attr { * * **Flags** * + * By default, denied accesses originating from programs that sandbox themselves + * are logged via the audit subsystem. Such events typically indicate unexpected + * behavior, such as bugs or exploitation attempts. However, to avoid excessive + * logging, access requests denied by a domain not created by the originating + * program are not logged by default. The rationale is that programs should know + * their own behavior, but not necessarily the behavior of other programs. This + * default configuration is suitable for most programs that sandbox themselves. + * For specific use cases, the following flags allow programs to modify this + * default logging behavior. + * + * The %LANDLOCK_RESTRICT_SELF_LOG_SAME_EXEC_OFF and + * %LANDLOCK_RESTRICT_SELF_LOG_NEW_EXEC_ON flags apply to the newly created + * Landlock domain. + * * %LANDLOCK_RESTRICT_SELF_LOG_SAME_EXEC_OFF - * Do not create any log related to the enforced restrictions. This should - * only be set by tools launching unknown or untrusted programs (e.g. a - * sandbox tool, container runtime, system service manager). Because - * programs sandboxing themselves should fix any denied access, they should - * not set this flag to be aware of potential issues reported by system's - * logs (i.e. audit). + * Disables logging of denied accesses originating from the thread creating + * the Landlock domain, as well as its children, as long as they continue + * running the same executable code (i.e., without an intervening + * :manpage:`execve(2)` call). This is intended for programs that execute + * unknown code without invoking :manpage:`execve(2)`, such as script + * interpreters. Programs that only sandbox themselves should not set this + * flag, so users can be notified of unauthorized access attempts via system + * logs. * * %LANDLOCK_RESTRICT_SELF_LOG_NEW_EXEC_ON - * Explicitly ask to continue logging denied access requests even after an - * :manpage:`execve(2)` call. This flag should only be set if all the - * programs than can legitimately be executed will not try to request a - * denied access (which could spam audit logs). + * Enables logging of denied accesses after an :manpage:`execve(2)` call, + * providing visibility into unauthorized access attempts by newly executed + * programs within the created Landlock domain. This flag is recommended + * only when all potential executables in the domain are expected to comply + * with the access restrictions, as excessive audit log entries could make + * it more difficult to identify critical events. * * %LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF - * Do not create any log related to the enforced restrictions coming from - * future nested domains created by the caller or its descendants. This - * should only be set according to a runtime configuration (i.e. not - * hardcoded) by programs launching other unknown or untrusted programs that - * may create their own Landlock domains and spam logs. The main use case - * is for container runtimes to enable users to mute buggy sandboxed - * programs for a specific container image. Other use cases include - * sandboxer tools and init systems. Unlike - * ``LANDLOCK_RESTRICT_SELF_LOG_SAME_EXEC_OFF``, - * ``LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF`` does not impact the - * requested restriction (if any) but only the future nested domains. - * - * It is allowed to only pass the - * ``LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF`` flag with a @ruleset_fd - * value of -1. - * + * Disables logging of denied accesses originating from nested Landlock + * domains created by the caller or its descendants. This flag should be set + * according to runtime configuration, not hardcoded, to avoid suppressing + * important security events. It is useful for container runtimes or + * sandboxing tools that may launch programs which themselves create + * Landlock domains and could otherwise generate excessive logs. Unlike + * ``LANDLOCK_RESTRICT_SELF_LOG_SAME_EXEC_OFF``, this flag only affects + * 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. */ /* clang-format off */ #define LANDLOCK_RESTRICT_SELF_LOG_SAME_EXEC_OFF (1U << 0)