Re: [PATCH v8] seccomp, ptrace: add support for dumping seccomp filters

From: Oleg Nesterov <oleg@redhat.com>
To: Tycho Andersen <tycho.andersen@canonical.com>
Cc: Kees Cook <keescook@chromium.org>,
	Alexei Starovoitov <ast@kernel.org>,
	Will Drewry <wad@chromium.org>,
	Andy Lutomirski <luto@amacapital.net>,
	Pavel Emelyanov <xemul@parallels.com>,
	"Serge E. Hallyn" <serge.hallyn@ubuntu.com>,
	Daniel Borkmann <daniel@iogearbox.net>,
	linux-kernel@vger.kernel.org, linux-api@vger.kernel.org
Subject: Re: [PATCH v8] seccomp, ptrace: add support for dumping seccomp filters
Date: Sun, 25 Oct 2015 16:39:43 +0100	[thread overview]
Message-ID: <20151025153943.GA1912@redhat.com> (raw)
In-Reply-To: <20151021213306.GF30729@hopstrocity>

On 10/21, Tycho Andersen wrote:
>
> > And this leads to another question... If we expect that this interface
> > can change later, then perhaps PTRACE_SECCOMP_GET_FILTER should also
> > dump some header before copy_to_user(fprog->filter) ? Say, just
> > "unsigned long version" == 0 for now. So that we can avoid
> > PTRACE_SECCOMP_GET_FILTER_V2 in future.
>
> So this is interesting. Like Kees mentioned, the bulk of the work
> would be done by the bpf syscall. We'd still need some way to get
> access to the fd itself, which we could (ab)use
> PTRACE_SECCOMP_GET_FILTER for, by returning the fd + BPF_MAXINSNS (so
> that it doesn't conflict with length) or something like that. Or add a
> _V2 as you say. If there is some change we can make to have a nicer
> interface than fd + BPF_MAXINSNS to future proof, I'm fine with making
> it.

Can't comment, this is up to you/Kees ;)

So, just in case, let me repeat I am fine with this patch.

Oleg.