linux-kernel - Re: [PATCH v2 2/3] lockdown/kunit: Introduce kunit tests

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Message-ID: <aIdx4Y/lRYKs/quV@mail.hallyn.com>
Date: Mon, 28 Jul 2025 07:49:37 -0500
From: "Serge E. Hallyn" <serge@...lyn.com>
To: Nikolay Borisov <nik.borisov@...e.com>
Cc: linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org,
	paul@...l-moore.com, serge@...lyn.com, jmorris@...ei.org,
	dan.j.williams@...el.com
Subject: Re: [PATCH v2 2/3] lockdown/kunit: Introduce kunit tests

On Mon, Jul 28, 2025 at 02:15:16PM +0300, Nikolay Borisov wrote:
> Add a bunch of tests to ensure lockdown's conversion to bitmap hasn't
> regressed it.
> 
> Signed-off-by: Nikolay Borisov <nik.borisov@...e.com>

Reviewed-by: Serge Hallyn <serge@...lyn.com>

(And I see this answers my question to patch 1, but still a comment
there would be nice :)

thanks,
-serge

> ---
>  security/lockdown/Kconfig         |  5 +++
>  security/lockdown/Makefile        |  1 +
>  security/lockdown/lockdown.c      |  5 ++-
>  security/lockdown/lockdown_test.c | 54 +++++++++++++++++++++++++++++++
>  4 files changed, 64 insertions(+), 1 deletion(-)
>  create mode 100644 security/lockdown/lockdown_test.c
> 
> diff --git a/security/lockdown/Kconfig b/security/lockdown/Kconfig
> index e84ddf484010..5fb750da1f8c 100644
> --- a/security/lockdown/Kconfig
> +++ b/security/lockdown/Kconfig
> @@ -6,6 +6,11 @@ config SECURITY_LOCKDOWN_LSM
>  	  Build support for an LSM that enforces a coarse kernel lockdown
>  	  behaviour.
>  
> +config SECURITY_LOCKDOWN_LSM_TEST
> +	tristate "Test lockdown functionality" if !KUNIT_ALL_TESTS
> +	depends on SECURITY_LOCKDOWN_LSM && KUNIT
> +	default KUNIT_ALL_TESTS
> +
>  config SECURITY_LOCKDOWN_LSM_EARLY
>  	bool "Enable lockdown LSM early in init"
>  	depends on SECURITY_LOCKDOWN_LSM
> diff --git a/security/lockdown/Makefile b/security/lockdown/Makefile
> index e3634b9017e7..f35d90e39f1c 100644
> --- a/security/lockdown/Makefile
> +++ b/security/lockdown/Makefile
> @@ -1 +1,2 @@
>  obj-$(CONFIG_SECURITY_LOCKDOWN_LSM) += lockdown.o
> +obj-$(CONFIG_SECURITY_LOCKDOWN_LSM_TEST) += lockdown_test.o
> diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c
> index 5014d18c423f..412184121279 100644
> --- a/security/lockdown/lockdown.c
> +++ b/security/lockdown/lockdown.c
> @@ -25,7 +25,10 @@ static const enum lockdown_reason lockdown_levels[] = {LOCKDOWN_NONE,
>  /*
>   * Put the kernel into lock-down mode.
>   */
> -static int lock_kernel_down(const char *where, enum lockdown_reason level)
> +#if !IS_ENABLED(CONFIG_KUNIT)
> +static
> +#endif
> +int lock_kernel_down(const char *where, enum lockdown_reason level)
>  {
>  
>  	if (level > LOCKDOWN_CONFIDENTIALITY_MAX)
> diff --git a/security/lockdown/lockdown_test.c b/security/lockdown/lockdown_test.c
> new file mode 100644
> index 000000000000..3a3c6db5b470
> --- /dev/null
> +++ b/security/lockdown/lockdown_test.c
> @@ -0,0 +1,54 @@
> +#include <linux/security.h>
> +#include <kunit/test.h>
> +
> +int lock_kernel_down(const char *where, enum lockdown_reason level);
> +
> +static void lockdown_test_invalid_level(struct kunit *test)
> +{
> +	KUNIT_EXPECT_EQ(test, -EINVAL, lock_kernel_down("TEST", LOCKDOWN_CONFIDENTIALITY_MAX+1));
> +}
> +
> +static void lockdown_test_depth_locking(struct kunit *test)
> +{
> +	KUNIT_EXPECT_EQ(test, 0, lock_kernel_down("TEST", LOCKDOWN_INTEGRITY_MAX));
> +	for (int i = 1; i < LOCKDOWN_INTEGRITY_MAX; i++)
> +		KUNIT_EXPECT_EQ_MSG(test, -EPERM, security_locked_down(i), "at i=%d", i);
> +
> +	KUNIT_EXPECT_EQ(test, -EPERM, security_locked_down(LOCKDOWN_INTEGRITY_MAX));
> +}
> +
> +static void lockdown_test_individual_level(struct kunit *test)
> +{
> +	KUNIT_EXPECT_EQ(test, 0, lock_kernel_down("TEST", LOCKDOWN_PERF));
> +	KUNIT_EXPECT_EQ(test, -EPERM, security_locked_down(LOCKDOWN_PERF));
> +	/* Ensure adjacent levels are untouched */
> +	KUNIT_EXPECT_EQ(test, 0, security_locked_down(LOCKDOWN_TRACEFS));
> +	KUNIT_EXPECT_EQ(test, 0, security_locked_down(LOCKDOWN_DBG_READ_KERNEL));
> +}
> +
> +static void lockdown_test_no_downgrade(struct kunit *test)
> +{
> +	KUNIT_EXPECT_EQ(test, 0, lock_kernel_down("TEST", LOCKDOWN_CONFIDENTIALITY_MAX));
> +	KUNIT_EXPECT_EQ(test, 0, lock_kernel_down("TEST", LOCKDOWN_INTEGRITY_MAX));
> +	/*
> +	 * Ensure having locked down to a lower leve after a higher level
> +	 * lockdown nothing is lost
> +	 */
> +	KUNIT_EXPECT_EQ(test, -EPERM, security_locked_down(LOCKDOWN_TRACEFS));
> +}
> +
> +static struct kunit_case lockdown_tests[] = {
> +	KUNIT_CASE(lockdown_test_invalid_level),
> +	KUNIT_CASE(lockdown_test_depth_locking),
> +	KUNIT_CASE(lockdown_test_individual_level),
> +	KUNIT_CASE(lockdown_test_no_downgrade),
> +	{}
> +};
> +
> +static struct kunit_suite lockdown_test_suite = {
> +	.name = "lockdown test",
> +	.test_cases = lockdown_tests,
> +};
> +kunit_test_suite(lockdown_test_suite);
> +
> +MODULE_LICENSE("GPL");
> -- 
> 2.34.1
>