From patchwork Tue Jan 1 20:49:22 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Daniel Borkmann X-Patchwork-Id: 1019804 X-Patchwork-Delegate: bpf@iogearbox.net Return-Path: X-Original-To: patchwork-incoming-netdev@ozlabs.org Delivered-To: patchwork-incoming-netdev@ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=netdev-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=iogearbox.net Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 43TmXM2Zq0z9rxp for ; Wed, 2 Jan 2019 07:50:11 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727445AbfAAUtz (ORCPT ); Tue, 1 Jan 2019 15:49:55 -0500 Received: from www62.your-server.de ([213.133.104.62]:39122 "EHLO www62.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727373AbfAAUtx (ORCPT ); Tue, 1 Jan 2019 15:49:53 -0500 Received: from [83.9.249.248] (helo=localhost) by www62.your-server.de with esmtpsa (TLSv1.2:DHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89_1) (envelope-from ) id 1geQz1-0003sX-QP; Tue, 01 Jan 2019 21:49:52 +0100 From: Daniel Borkmann To: ast@kernel.org Cc: jannh@google.com, netdev@vger.kernel.org, Daniel Borkmann Subject: [PATCH bpf 6/9] bpf: restrict unknown scalars of mixed signed bounds for unpriviledged Date: Tue, 1 Jan 2019 21:49:22 +0100 Message-Id: <20190101204925.4584-7-daniel@iogearbox.net> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20190101204925.4584-1-daniel@iogearbox.net> References: <20190101204925.4584-1-daniel@iogearbox.net> X-Authenticated-Sender: daniel@iogearbox.net X-Virus-Scanned: Clear (ClamAV 0.100.2/25259/Tue Jan 1 15:32:04 2019) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org For unknown scalars of mixed signed bounds, meaning their smin_value is negative and their smax_value is positive, we need to reject arithmetic with pointer to map value. For unpriviledged the goal is to mask every map pointer arithmetic and this cannot reliably be done when it is unknown at verification time whether the scalar value is negative or positive. Given this is a corner case, the likelihood of breaking should be very small. Signed-off-by: Daniel Borkmann Acked-by: Alexei Starovoitov --- kernel/bpf/verifier.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 9ac205d..eebbc03 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -3081,8 +3081,8 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env, smin_ptr = ptr_reg->smin_value, smax_ptr = ptr_reg->smax_value; u64 umin_val = off_reg->umin_value, umax_val = off_reg->umax_value, umin_ptr = ptr_reg->umin_value, umax_ptr = ptr_reg->umax_value; + u32 dst = insn->dst_reg, src = insn->src_reg; u8 opcode = BPF_OP(insn->code); - u32 dst = insn->dst_reg; dst_reg = ®s[dst]; @@ -3115,6 +3115,13 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env, verbose(env, "R%d pointer arithmetic on %s prohibited\n", dst, reg_type_str[ptr_reg->type]); return -EACCES; + case PTR_TO_MAP_VALUE: + if (!env->allow_ptr_leaks && !known && (smin_val < 0) != (smax_val < 0)) { + verbose(env, "R%d has unknown scalar with mixed signed bounds, pointer arithmetic with it prohibited for !root\n", + off_reg == dst_reg ? dst : src); + return -EACCES; + } + /* fall-through */ default: break; }