From:   Anjali Kulkarni <anjali.k.kulkarni@oracle.com>
To:     Jakub Kicinski <kuba@kernel.org>
CC:     "davem@davemloft.net" <davem@davemloft.net>,
        "edumazet@google.com" <edumazet@google.com>,
        "pabeni@redhat.com" <pabeni@redhat.com>,
        "zbr@ioremap.net" <zbr@ioremap.net>,
        "brauner@kernel.org" <brauner@kernel.org>,
        "johannes@sipsolutions.net" <johannes@sipsolutions.net>,
        "ecree.xilinx@gmail.com" <ecree.xilinx@gmail.com>,
        "leon@kernel.org" <leon@kernel.org>,
        "keescook@chromium.org" <keescook@chromium.org>,
        "socketcan@hartkopp.net" <socketcan@hartkopp.net>,
        "petrm@nvidia.com" <petrm@nvidia.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>
Subject: Re: [PATCH v1 2/5] connector/cn_proc: Add filtering to fix some bugs
Thread-Topic: [PATCH v1 2/5] connector/cn_proc: Add filtering to fix some bugs
Thread-Index: AQHZU53jvr0f3jRxyk20sGUEtokB+a75b4CAgAAhVuA=
Date:   Tue, 14 Mar 2023 02:32:13 +0000
Message-ID: <BY5PR10MB41295AF42563F023651E109FC4BE9@BY5PR10MB4129.namprd10.prod.outlook.com>
References: <20230310221547.3656194-1-anjali.k.kulkarni@oracle.com>
        <20230310221547.3656194-3-anjali.k.kulkarni@oracle.com>
 <20230313172441.480c9ec7@kernel.org>
In-Reply-To: <20230313172441.480c9ec7@kernel.org>
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=0A=
> -int cn_netlink_send_mult(struct cn_msg *msg, u16 len, u32 portid, u32 gr=
oup, gfp_t gfp_mask);=0A=
> +int cn_netlink_send_mult(struct cn_msg *msg, u16 len, u32 portid,=0A=
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 u32 grou=
p, gfp_t gfp_mask,=0A=
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 int (*fi=
lter)(struct sock *dsk, struct sk_buff *skb,=0A=
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=
=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 void *data),=0A=
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 void *fi=
lter_data);=0A=
=0A=
kdoc needs to be extended=0A=
ANJALI> Thanks, will update in next revision.=0A=
=0A=
> -=0A=
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 if (sk->sk_protocol =3D=3D NETLINK_=
CONNECTOR) {=0A=
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 if (test_bi=
t(CN_IDX_PROC - 1, nlk->groups)) {=0A=
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=
=A0=A0=A0=A0 kfree(sk->sk_user_data);=0A=
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=
=A0=A0=A0=A0 sk->sk_user_data =3D NULL;=0A=
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 }=0A=
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 }=0A=
>=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 for (i =3D 0; i < nlk->ngrou=
ps; i++)=0A=
>=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 if (=
test_bit(i, nlk->groups))=0A=
>=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=
=A0=A0=A0=A0=A0=A0=A0 nlk->netlink_unbind(sock_net(sk), i + 1);=0A=
=0A=
This is clearly a layering violation, right?=0A=
Please don't add "if (family_x)" to the core netlink code.=0A=
ANJALI> Yes, it is, but there does not seem a very clean way to do it other=
wise and I saw a check for protocol NETLINK_GENERIC just below it, so used =
it for connector as well. There is no release or free callback in the netli=
nk_sock. Is it ok to add it? There was another bug (for which I have not ye=
t sent a patch) in which, we need to decrement proc_event_num_listeners, wh=
en client exits without calling IGNORE, else that count again gets out of s=
tatus of actual no of listeners. =0A=
The other option is to add a flag in netlink_sock, something like NETLINK_F=
_SK_USER_DATA_FREE, which will free the sk_user_data, if this flag is set. =
But it does not solve the above scenario.=0A=
.=