[PATCH v2] landlock: Improve bit operations in audit code
Mickaël Salaün
mic at digikod.net
Mon May 12 09:37:30 UTC 2025
Use the BIT() and BIT_ULL() macros in the new audit code instead of
explicit shifts to improve readability. Use bitmask instead of modulo
operation to simplify code.
Add test_range1_rand15() and test_range2_rand15() KUnit tests to improve
get_id_range() coverage.
Signed-off-by: Günther Noack <gnoack3000 at gmail.com>
Signed-off-by: Mickaël Salaün <mic at digikod.net>
---
Changes since v1:
https://lore.kernel.org/r/20250507185404.1029055-1-mic@digikod.net
- Use bitmask instead of modulo operation to simplify random value
truncation, suggested by Günther.
- Add KUnit tests.
---
security/landlock/audit.c | 2 +-
security/landlock/id.c | 33 +++++++++++++++++++++++++++++++--
security/landlock/syscalls.c | 3 ++-
3 files changed, 34 insertions(+), 4 deletions(-)
diff --git a/security/landlock/audit.c b/security/landlock/audit.c
index 58d5c40d4d0e..c52d079cdb77 100644
--- a/security/landlock/audit.c
+++ b/security/landlock/audit.c
@@ -437,7 +437,7 @@ void landlock_log_denial(const struct landlock_cred_security *const subject,
return;
/* Checks if the current exec was restricting itself. */
- if (subject->domain_exec & (1 << youngest_layer)) {
+ if (subject->domain_exec & BIT(youngest_layer)) {
/* Ignores denials for the same execution. */
if (!youngest_denied->log_same_exec)
return;
diff --git a/security/landlock/id.c b/security/landlock/id.c
index 11fab9259c15..56f7cc0fc744 100644
--- a/security/landlock/id.c
+++ b/security/landlock/id.c
@@ -7,6 +7,7 @@
#include <kunit/test.h>
#include <linux/atomic.h>
+#include <linux/bitops.h>
#include <linux/random.h>
#include <linux/spinlock.h>
@@ -25,7 +26,7 @@ static void __init init_id(atomic64_t *const counter, const u32 random_32bits)
* Ensures sure 64-bit values are always used by user space (or may
* fail with -EOVERFLOW), and makes this testable.
*/
- init = 1ULL << 32;
+ init = BIT_ULL(32);
/*
* Makes a large (2^32) boot-time value to limit ID collision in logs
@@ -105,7 +106,7 @@ static u64 get_id_range(size_t number_of_ids, atomic64_t *const counter,
* to get a new ID (e.g. a full landlock_restrict_self() call), and the
* cost of draining all available IDs during the system's uptime.
*/
- random_4bits = random_4bits % (1 << 4);
+ random_4bits &= 0b1111;
step = number_of_ids + random_4bits;
/* It is safe to cast a signed atomic to an unsigned value. */
@@ -144,6 +145,19 @@ static void test_range1_rand1(struct kunit *const test)
init + 2);
}
+static void test_range1_rand15(struct kunit *const test)
+{
+ atomic64_t counter;
+ u64 init;
+
+ init = get_random_u32();
+ atomic64_set(&counter, init);
+ KUNIT_EXPECT_EQ(test, get_id_range(1, &counter, 15), init);
+ KUNIT_EXPECT_EQ(
+ test, get_id_range(get_random_u8(), &counter, get_random_u8()),
+ init + 16);
+}
+
static void test_range1_rand16(struct kunit *const test)
{
atomic64_t counter;
@@ -196,6 +210,19 @@ static void test_range2_rand2(struct kunit *const test)
init + 4);
}
+static void test_range2_rand15(struct kunit *const test)
+{
+ atomic64_t counter;
+ u64 init;
+
+ init = get_random_u32();
+ atomic64_set(&counter, init);
+ KUNIT_EXPECT_EQ(test, get_id_range(2, &counter, 15), init);
+ KUNIT_EXPECT_EQ(
+ test, get_id_range(get_random_u8(), &counter, get_random_u8()),
+ init + 17);
+}
+
static void test_range2_rand16(struct kunit *const test)
{
atomic64_t counter;
@@ -232,10 +259,12 @@ static struct kunit_case __refdata test_cases[] = {
KUNIT_CASE(test_init_once),
KUNIT_CASE(test_range1_rand0),
KUNIT_CASE(test_range1_rand1),
+ KUNIT_CASE(test_range1_rand15),
KUNIT_CASE(test_range1_rand16),
KUNIT_CASE(test_range2_rand0),
KUNIT_CASE(test_range2_rand1),
KUNIT_CASE(test_range2_rand2),
+ KUNIT_CASE(test_range2_rand15),
KUNIT_CASE(test_range2_rand16),
{}
/* clang-format on */
diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
index b9561e3417ae..33eafb71e4f3 100644
--- a/security/landlock/syscalls.c
+++ b/security/landlock/syscalls.c
@@ -9,6 +9,7 @@
#include <asm/current.h>
#include <linux/anon_inodes.h>
+#include <linux/bitops.h>
#include <linux/build_bug.h>
#include <linux/capability.h>
#include <linux/cleanup.h>
@@ -563,7 +564,7 @@ SYSCALL_DEFINE2(landlock_restrict_self, const int, ruleset_fd, const __u32,
new_llcred->domain = new_dom;
#ifdef CONFIG_AUDIT
- new_llcred->domain_exec |= 1 << (new_dom->num_layers - 1);
+ new_llcred->domain_exec |= BIT(new_dom->num_layers - 1);
#endif /* CONFIG_AUDIT */
return commit_creds(new_cred);
--
2.49.0
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