netdev - Re: [PATCH RFC net-next 08/14] bpf: add eBPF verifier

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CA+ZOOTM9KkOYJ5Nf25_x1fT+f76xMsdJRkqjYaABiNK9y3FNXA@mail.gmail.com>
Date:	Wed, 2 Jul 2014 16:35:23 -0700
From:	Chema Gonzalez <chema@...gle.com>
To:	Alexei Starovoitov <ast@...mgrid.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Daniel Borkmann <dborkman@...hat.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Jiri Olsa <jolsa@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Kees Cook <keescook@...omium.org>,
	Linux API <linux-api@...r.kernel.org>,
	Network Development <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC net-next 08/14] bpf: add eBPF verifier

On Wed, Jul 2, 2014 at 4:04 PM, Alexei Starovoitov <ast@...mgrid.com> wrote:
>>> +       reg = regs + BPF_REG_1; /* 1st arg to a function */
>>> +       reg->ptr = PTR_TO_CTX;
>> Wait, doesn't this depend on doing "BPF_MOV64_REG(BPF_REG_CTX,
>> BPF_REG_ARG1)" (the bpf-to-ebpf prologue), which is only enforced on
>> filters converted from bpf? In fact, shouldn't this set
>> regs[BPF_REG_CTX] instead of regs[BPF_REG_1] ?
>
> nope. it's REG_1.
> as you said r6=r1 is only emitted by converted classic filters.
> Verifier will see this 'r6=r1' assignment and will copy the r1 type into r6.
You're right. I read BPF_MOV64_REG() AT&T-syntax-style.

BTW, check_stack_write() in kernel/bpf/verifier.c has a couple of
assignments of a slot->ptr to 0 (instead of INVALID_PTR). I assume
this is unintended.

-Chema
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html