netdev - Re: [PATCH bpf-next v5 4/9] bpf: Implement cgroup sockaddr hooks for unix sockets

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Message-ID: <20230925221241.2345534-1-jrife@google.com>
Date: Mon, 25 Sep 2023 17:12:41 -0500
From: Jordan Rife <jrife@...gle.com>
To: daan.j.demeyer@...il.com
Cc: bpf@...r.kernel.org, kernel-team@...a.com, martin.lau@...ux.dev, 
	netdev@...r.kernel.org, Jordan Rife <jrife@...gle.com>
Subject: Re: [PATCH bpf-next v5 4/9] bpf: Implement cgroup sockaddr hooks for
 unix sockets

> @@ -1919,6 +1936,13 @@ static int unix_dgram_sendmsg(struct socket *sock, struct msghdr *msg,
>  		goto out;
>
>  	if (msg->msg_namelen) {
> +		err = BPF_CGROUP_RUN_PROG_UNIX_SENDMSG_LOCK(sk,
> +							    msg->msg_name,
> +							    &msg->msg_namelen,
> +							    NULL);
> +		if (err)
> +			goto out;
> +
>  		err = unix_validate_addr(sunaddr, msg->msg_namelen);
>  		if (err)
>  			goto out;

Just an FYI, I /think/ this is going to introduce a bug similar to the one I'm
addressing in my patch here:

- https://lore.kernel.org/netdev/20230921234642.1111903-2-jrife@google.com/

With this change, callers to sock_sendmsg() in kernel space would see their
value of msg->msg_namelen change if they are using Unix sockets. While it's
unclear if there are any real systems that would be impacted, it can't hurt to
insulate callers from these kind of side-effects. I can update my my patch to
account for possible changes to msg_namelen.

Also, with this patch series is it possible for AF_INET BPF hooks (connect4,
sendmsg4, connect6, etc.) to modify the address length?