netdev - Re: [RFC PATCH v2 5/9] selftests/landlock: Test listen on connected socket

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Message-ID: <79d21a08-ec8c-14e7-7040-38dd9c7d441f@huawei-partners.com>
Date: Tue, 20 Aug 2024 16:42:16 +0300
From: Mikhail Ivanov <ivanov.mikhail1@...wei-partners.com>
To: Günther Noack <gnoack@...gle.com>
CC: <mic@...ikod.net>, <willemdebruijn.kernel@...il.com>,
	<gnoack3000@...il.com>, <linux-security-module@...r.kernel.org>,
	<netdev@...r.kernel.org>, <netfilter-devel@...r.kernel.org>,
	<yusongping@...wei.com>, <artem.kuzin@...wei.com>,
	<konstantin.meskhidze@...wei.com>
Subject: Re: [RFC PATCH v2 5/9] selftests/landlock: Test listen on connected
 socket

8/20/2024 4:01 PM, Günther Noack wrote:
> On Wed, Aug 14, 2024 at 11:01:47AM +0800, Mikhail Ivanov wrote:
>> Test checks that listen(2) doesn't wrongfully return -EACCES instead
>> of -EINVAL when trying to listen for an incorrect socket state.
>>
>> Signed-off-by: Mikhail Ivanov <ivanov.mikhail1@...wei-partners.com>
>> ---
>>
>> Changes since v1:
>> * Uses 'protocol' fixture instead of 'ipv4_tcp'.
>> * Minor fixes.
>> ---
>>   tools/testing/selftests/landlock/net_test.c | 74 +++++++++++++++++++++
>>   1 file changed, 74 insertions(+)
>>
>> diff --git a/tools/testing/selftests/landlock/net_test.c b/tools/testing/selftests/landlock/net_test.c
>> index b6fe9bde205f..551891b18b7a 100644
>> --- a/tools/testing/selftests/landlock/net_test.c
>> +++ b/tools/testing/selftests/landlock/net_test.c
>> @@ -926,6 +926,80 @@ TEST_F(protocol, connect_unspec)
>>   	EXPECT_EQ(0, close(bind_fd));
>>   }
>>   
>> +TEST_F(protocol, listen_on_connected)
>> +{
>> +	int bind_fd, status;
>> +	pid_t child;
>> +
>> +	if (variant->sandbox == TCP_SANDBOX) {
>> +		const struct landlock_ruleset_attr ruleset_attr = {
>> +			.handled_access_net = ACCESS_ALL,
>> +		};
>> +		const struct landlock_net_port_attr tcp_not_restricted_p0 = {
>> +			.allowed_access = ACCESS_ALL,
>> +			.port = self->srv0.port,
>> +		};
>> +		const struct landlock_net_port_attr tcp_denied_listen_p1 = {
>> +			.allowed_access = ACCESS_ALL &
>> +					  ~LANDLOCK_ACCESS_NET_LISTEN_TCP,
>> +			.port = self->srv1.port,
>> +		};
>> +		int ruleset_fd;
>> +
>> +		ruleset_fd = landlock_create_ruleset(&ruleset_attr,
>> +						     sizeof(ruleset_attr), 0);
>> +		ASSERT_LE(0, ruleset_fd);
>> +
>> +		/* Allows all actions for the first port. */
>> +		ASSERT_EQ(0,
>> +			  landlock_add_rule(ruleset_fd, LANDLOCK_RULE_NET_PORT,
>> +					    &tcp_not_restricted_p0, 0));
>> +
>> +		/* Denies listening for the second port. */
>> +		ASSERT_EQ(0,
>> +			  landlock_add_rule(ruleset_fd, LANDLOCK_RULE_NET_PORT,
>> +					    &tcp_denied_listen_p1, 0));
>> +
>> +		enforce_ruleset(_metadata, ruleset_fd);
>> +		EXPECT_EQ(0, close(ruleset_fd));
>> +	}
> 
> Same remarks as in the previous commit apply here as well:
> 
>    - The if condition does the same thing, can maybe be deduplicated.
>    - Can merge ruleset_fd declaration and assignment into one line.
>      (This happens in a few more tests in later commits as well,
>      please double check these as well.)

Thanks for mentioning! You can check my reply in the previous commit
discussion.

> 
>> +
>> +	if (variant->prot.type != SOCK_STREAM)
>> +		SKIP(return, "listen(2) is supported only on stream sockets");
>> +
>> +	/* Initializes listening socket. */
>> +	bind_fd = socket_variant(&self->srv0);
>> +	ASSERT_LE(0, bind_fd);
>> +	EXPECT_EQ(0, bind_variant(bind_fd, &self->srv0));
>> +	EXPECT_EQ(0, listen_variant(bind_fd, backlog));
> 
> I believe if bind() or listen() fail here, it does not make sense to continue
> the test execution, so ASSERT_EQ would be more appropriate than EXPECT_EQ.

Will be fixed, thanks.

> 
> 
>> +
>> +	child = fork();
>> +	ASSERT_LE(0, child);
>> +	if (child == 0) {
>> +		int connect_fd;
>> +
>> +		/* Closes listening socket for the child. */
>> +		EXPECT_EQ(0, close(bind_fd));
> 
> You don't need to do this from a child process, you can just connect() from the
> same process to the listening port.  (Since you are not calling accept(), the
> server won't pick up the phone on the other end, but that is still enough to
> connect successfully.)  It would simplify the story of correctly propagating
> test exit statuses as well.

Thanks, I'll fix this.

> 
>> +
>> +		connect_fd = socket_variant(&self->srv1);
>> +		ASSERT_LE(0, connect_fd);
>> +		EXPECT_EQ(0, connect_variant(connect_fd, &self->srv0));
>> +
>> +		/* Tries to listen on connected socket. */
>> +		EXPECT_EQ(-EINVAL, listen_variant(connect_fd, backlog));
> 
> Since this assertion is the actual point of the test,
> maybe we could emphasize it a bit more with a comment here?
> 
> e.g:
> 
> /*
>   * Checks that we always return EINVAL
>   * and never accidentally return EACCES, if listen(2) fails.
>   */

You're right.. current description doesn't give an understanding of why
this test is needed at all. I'll change it.

> 
>> +
>> +		EXPECT_EQ(0, close(connect_fd));
>> +		_exit(_metadata->exit_code);
>> +		return;
>> +	}
>> +
>> +	EXPECT_EQ(child, waitpid(child, &status, 0));
>> +	EXPECT_EQ(1, WIFEXITED(status));
>> +	EXPECT_EQ(EXIT_SUCCESS, WEXITSTATUS(status));
>> +
>> +	EXPECT_EQ(0, close(bind_fd));
>> +}
>> +
>>   FIXTURE(ipv4)
>>   {
>>   	struct service_fixture srv0, srv1;
>> -- 
>> 2.34.1
>>