linux-kernel - Re: v5 of seccomp filter c/r patches

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Message-ID: <560F0BED.2070304@iogearbox.net>
Date:	Sat, 03 Oct 2015 00:57:49 +0200
From:	Daniel Borkmann <daniel@...earbox.net>
To:	Tycho Andersen <tycho.andersen@...onical.com>,
	Kees Cook <keescook@...omium.org>
CC:	Alexei Starovoitov <ast@...nel.org>,
	Will Drewry <wad@...omium.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Andy Lutomirski <luto@...capital.net>,
	Pavel Emelyanov <xemul@...allels.com>,
	"Serge E. Hallyn" <serge.hallyn@...ntu.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Network Development <netdev@...r.kernel.org>,
	Linux API <linux-api@...r.kernel.org>
Subject: Re: v5 of seccomp filter c/r patches

On 10/03/2015 12:44 AM, Tycho Andersen wrote:
> On Fri, Oct 02, 2015 at 02:10:24PM -0700, Kees Cook wrote:
...
> Ok, how about,
>
> struct sock_filter insns[BPF_MAXINSNS];
> insn_cnt = ptrace(PTRACE_SECCOMP_GET_FILTER, pid, insns, i);

Would also be good that when the storage buffer (insns) is NULL,
it just returns you the number of sock_filter insns (or 0 when
nothing attached).

That would be consistent with classic socket filters (see
sk_get_filter()), and user space could allocate a specific
size instead of always passing in max insns.

> when asking for the ith filter? It returns either the number of
> instructions, -EINVAL if something was wrong (i, pid,
> CONFIG_CHECKPOINT_RESTORE isn't enabled). While it would always
> succeed now, if/when the underlying filter was not created from a bpf
> classic filter, we can return -EMEDIUMTYPE? (Suggestions welcome, I
> picked this mostly based on what sounds nice.)
>
> Tycho
>

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