netdev - Re: [RFC PATCH v1 1/2] landlock: Fix non-TCP sockets restriction

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Message-ID: <8f023c51-bac1-251e-0f40-24dbe2bba729@huawei-partners.com>
Date: Fri, 4 Oct 2024 00:30:02 +0300
From: Mikhail Ivanov <ivanov.mikhail1@...wei-partners.com>
To: Mickaël Salaün <mic@...ikod.net>
CC: <gnoack@...gle.com>, <willemdebruijn.kernel@...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>, Matthieu Buffet
	<matthieu@...fet.re>
Subject: Re: [RFC PATCH v1 1/2] landlock: Fix non-TCP sockets restriction

On 10/3/2024 8:45 PM, Mickaël Salaün wrote:
> Please also add Matthieu in Cc for the network patch series.
> 
> On Thu, Oct 03, 2024 at 10:39:31PM +0800, Mikhail Ivanov wrote:
>> Do not check TCP access right if socket protocol is not IPPROTO_TCP.
>> LANDLOCK_ACCESS_NET_BIND_TCP and LANDLOCK_ACCESS_NET_CONNECT_TCP
>> should not restrict bind(2) and connect(2) for non-TCP protocols
>> (SCTP, MPTCP, SMC).
>>
>> Closes: https://github.com/landlock-lsm/linux/issues/40
>> Fixes: fff69fb03dde ("landlock: Support network rules with TCP bind and connect")
>> Signed-off-by: Mikhail Ivanov <ivanov.mikhail1@...wei-partners.com>
>> ---
>>   security/landlock/net.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/security/landlock/net.c b/security/landlock/net.c
>> index bc3d943a7118..6f59dd98bb13 100644
>> --- a/security/landlock/net.c
>> +++ b/security/landlock/net.c
>> @@ -68,7 +68,7 @@ static int current_check_access_socket(struct socket *const sock,
>>   		return -EACCES;
>>   
>>   	/* Checks if it's a (potential) TCP socket. */
> 
> We can extend this comment to explain that we don't use sk_is_tcp()
> because we need to handle the AF_UNSPEC case.

Indeed, I'll do this.

> 
>> -	if (sock->type != SOCK_STREAM)
>> +	if (sock->type != SOCK_STREAM || sock->sk->sk_protocol != IPPROTO_TCP)
> 
> I think we should check sock->sk->sk_type instead of sock->type (even if
> it should be the same).  To make it simpler, we should only use sk in
> current_check_access_socket():
> struct sock *sk = sock->sk;

Agreed.

> 
> Could you please also do s/__sk_common\.skc_/sk_/g ?

Ofc

Btw, there is probably incorrect read of skc_family in this function
[1]. I'll add READ_ONCE for sk->sk_family.

[1] https://lore.kernel.org/all/20240202095404.183274-1-edumazet@google.com/

> 
>>   		return 0;
>>   
>>   	/* Checks for minimal header length to safely read sa_family. */
>> -- 
>> 2.34.1
>>
>>