Subject: Re: [RFC PATCH v3 12/19] selftests/landlock: Test that kernel space sockets are not restricted

From: "Günther Noack" <[email-masked]>
Date: Wed, 18 Sep 2024 15:00:48 +0200

This is a good way to test this, IMHO. Good find.
The comment at the bottom is really valuable. :)

Out of curiosity: I suspect that a selftest with NFS or another network-backed
filesystem might be too complicated?  Have you tried that manually, by any
chance?

On Wed, Sep 04, 2024 at 06:48:17PM +0800, Mikhail Ivanov wrote:
> Add test validating that Landlock provides restriction of user space
> sockets only.
> 
> Signed-off-by: Mikhail Ivanov <[email-masked]>
> ---
>  .../testing/selftests/landlock/socket_test.c  | 39 ++++++++++++++++++-
>  1 file changed, 38 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/landlock/socket_test.c b/tools/testing/selftests/landlock/socket_test.c
> index ff5ace711697..23698b8c2f4d 100644
> --- a/tools/testing/selftests/landlock/socket_test.c
> +++ b/tools/testing/selftests/landlock/socket_test.c
> @@ -7,7 +7,7 @@
>  
>  #define _GNU_SOURCE
>  
> -#include <linux/landlock.h>
> +#include "landlock.h"
>  #include <linux/pfkeyv2.h>
>  #include <linux/kcm.h>
>  #include <linux/can.h>
> @@ -628,4 +628,41 @@ TEST(unsupported_af_and_prot)
>  	EXPECT_EQ(ESOCKTNOSUPPORT, test_socket(AF_UNIX, SOCK_PACKET, 0));
>  }
>  
> +TEST(kernel_socket)
> +{
> +	const struct landlock_ruleset_attr ruleset_attr = {
> +		.handled_access_socket = LANDLOCK_ACCESS_SOCKET_CREATE,
> +	};
> +	struct landlock_socket_attr smc_socket_create = {
> +		.allowed_access = LANDLOCK_ACCESS_SOCKET_CREATE,
> +		.family = AF_SMC,
> +		.type = SOCK_STREAM,
> +	};
> +	int ruleset_fd;
> +
> +	/*
> +	 * Checks that SMC socket is created sucessfuly without

Typo nit: "successfully"
             ^^     ^^

> +	 * landlock restrictions.
> +	 */
> +	ASSERT_EQ(0, test_socket(AF_SMC, SOCK_STREAM, 0));
> +
> +	ruleset_fd =
> +		landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
> +	ASSERT_LE(0, ruleset_fd);
> +
> +	ASSERT_EQ(0, landlock_add_rule(ruleset_fd, LANDLOCK_RULE_SOCKET,
> +				       &smc_socket_create, 0));
> +	enforce_ruleset(_metadata, ruleset_fd);
> +	ASSERT_EQ(0, close(ruleset_fd));
> +
> +	/*
> +	 * During the creation of an SMC socket, an internal service TCP socket
> +	 * is also created (Cf. smc_create_clcsk).
> +	 *
> +	 * Checks that Landlock does not restrict creation of the kernel space
> +	 * socket.
> +	 */
> +	EXPECT_EQ(0, test_socket(AF_SMC, SOCK_STREAM, 0));
> +}
> +
>  TEST_HARNESS_MAIN
> -- 
> 2.34.1
> 

Reviewed-by: Günther Noack <[email-masked]>