netdev - Re: [PATCH bpf-next v2] Only run BPF cgroup unix sockaddr recvmsg() hooks on named sockets

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Message-ID: <20231012181142.60636-1-kuniyu@amazon.com>
Date: Thu, 12 Oct 2023 11:11:42 -0700
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: <daan.j.demeyer@...il.com>
CC: <bpf@...r.kernel.org>, <kernel-team@...a.com>, <martin.lau@...ux.dev>,
	<netdev@...r.kernel.org>, <kuniyu@...zon.com>
Subject: Re: [PATCH bpf-next v2] Only run BPF cgroup unix sockaddr recvmsg() hooks on named sockets

From: Daan De Meyer <daan.j.demeyer@...il.com>
Date: Thu, 12 Oct 2023 10:52:13 +0200
> Changes since v1:
> 
> * Added missing Signed-off-by tag

You can put these after --- so that it will disappear when merged.


> 
> We should not run the recvmsg() hooks on unnamed sockets as we do
> not run them on unnamed sockets in the other hooks either. We may
> look into relaxing this later but for now let's make sure we are
> consistent and not run the hooks on unnamed sockets anywhere.
> 
> Signed-off-by: Daan De Meyer <daan.j.demeyer@...il.com>
> ---
>  net/unix/af_unix.c | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
> index e10d07c76044..81fb8bddaff9 100644
> --- a/net/unix/af_unix.c
> +++ b/net/unix/af_unix.c
> @@ -2416,9 +2416,10 @@ int __unix_dgram_recvmsg(struct sock *sk, struct msghdr *msg, size_t size,
>  	if (msg->msg_name) {
>  		unix_copy_addr(msg, skb->sk);

How is an unnamed socket set to skb->sk ?


> 
> -		BPF_CGROUP_RUN_PROG_UNIX_RECVMSG_LOCK(sk,
> -						      msg->msg_name,
> -						      &msg->msg_namelen);
> +		if (msg->msg_namelen > 0)
> +			BPF_CGROUP_RUN_PROG_UNIX_RECVMSG_LOCK(sk,
> +							      msg->msg_name,
> +							      &msg->msg_namelen);
>  	}
> 
>  	if (size > skb->len - skip)
> @@ -2773,9 +2774,10 @@ static int unix_stream_read_generic(struct unix_stream_read_state *state,
>  					 state->msg->msg_name);
>  			unix_copy_addr(state->msg, skb->sk);
> 
> -			BPF_CGROUP_RUN_PROG_UNIX_RECVMSG_LOCK(sk,
> -							      state->msg->msg_name,
> -							      &state->msg->msg_namelen);
> +			if (state->msg->msg_namelen > 0)
> +				BPF_CGROUP_RUN_PROG_UNIX_RECVMSG_LOCK(sk,
> +								      state->msg->msg_name,
> +								      &state->msg->msg_namelen);
> 
>  			sunaddr = NULL;
>  		}
> --
> 2.41.0
>