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

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Date:	Mon, 26 Oct 2015 15:46:58 +0900
From:	Kees Cook <keescook@...omium.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Tycho Andersen <tycho.andersen@...onical.com>,
	Alexei Starovoitov <ast@...nel.org>,
	Will Drewry <wad@...omium.org>,
	Andy Lutomirski <luto@...capital.net>,
	Pavel Emelyanov <xemul@...allels.com>,
	"Serge E. Hallyn" <serge.hallyn@...ntu.com>,
	Daniel Borkmann <daniel@...earbox.net>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux API <linux-api@...r.kernel.org>
Subject: Re: [PATCH v8] seccomp, ptrace: add support for dumping seccomp filters

On Mon, Oct 26, 2015 at 12:39 AM, Oleg Nesterov <oleg@...hat.com> wrote:
> 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.

Cool, thanks. I'll get this into my tree after kernel summit. Thanks
for suffering through all this Tycho!

-Kees

-- 
Kees Cook
Chrome OS Security
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