netdev - Re: [PATCH net-next 4/4] selinux: bpf: Add addtional check for bpf object file receive

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Message-ID: <59D57263.3080601@iogearbox.net>
Date:   Thu, 05 Oct 2017 01:44:35 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Chenbo Feng <chenbofeng.kernel@...il.com>, netdev@...r.kernel.org,
        SELinux <Selinux@...ho.nsa.gov>,
        linux-security-module@...r.kernel.org
CC:     Jeffrey Vander Stoep <jeffv@...gle.com>,
        Lorenzo Colitti <lorenzo@...gle.com>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Chenbo Feng <fengc@...gle.com>
Subject: Re: [PATCH net-next 4/4] selinux: bpf: Add addtional check for bpf
 object file receive

On 10/04/2017 08:29 PM, Chenbo Feng wrote:
> From: Chenbo Feng <fengc@...gle.com>
>
> Introduce a bpf object related check when sending and receiving files
> through unix domain socket as well as binder. It checks if the receiving
> process have privilege to read/write the bpf map or use the bpf program.
> This check is necessary because the bpf maps and programs are using a
> anonymous inode as their shared inode so the normal way of checking the
> files and sockets when passing between processes cannot work properly on
> eBPF object. This check only works when the BPF_SYSCALL is configured.

[...]
> +/* This function will check the file pass through unix socket or binder to see
> + * if it is a bpf related object. And apply correspinding checks on the bpf
> + * object based on the type. The bpf maps and programs, not like other files and
> + * socket, are using a shared anonymous inode inside the kernel as their inode.
> + * So checking that inode cannot identify if the process have privilege to
> + * access the bpf object and that's why we have to add this additional check in
> + * selinux_file_receive and selinux_binder_transfer_files.
> + */
[...]

If selinux/lsm folks have some input on this one in particular, would
be great. The issue is not really tied to bpf specifically, but to the
use of anon-inodes wrt fd passing. Maybe some generic resolution can
be found to tackle this ...