From patchwork Tue Jan 1 23:20:41 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Daniel Borkmann X-Patchwork-Id: 1019819 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 43TqtR21NHz9s9G for ; Wed, 2 Jan 2019 10:21:03 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727197AbfAAXVB (ORCPT ); Tue, 1 Jan 2019 18:21:01 -0500 Received: from www62.your-server.de ([213.133.104.62]:58454 "EHLO www62.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727135AbfAAXVA (ORCPT ); Tue, 1 Jan 2019 18:21:00 -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 1geTLG-00071Q-Th; Wed, 02 Jan 2019 00:20:59 +0100 From: Daniel Borkmann To: ast@kernel.org Cc: jannh@google.com, davem@davemloft.net, netdev@vger.kernel.org, Daniel Borkmann Subject: [PATCH bpf v2 4/9] bpf: restrict map value pointer arithmetic for unprivileged Date: Wed, 2 Jan 2019 00:20:41 +0100 Message-Id: <20190101232046.2880-5-daniel@iogearbox.net> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20190101232046.2880-1-daniel@iogearbox.net> References: <20190101232046.2880-1-daniel@iogearbox.net> X-Authenticated-Sender: daniel@iogearbox.net X-Virus-Scanned: Clear (ClamAV 0.100.2/25260/Tue Jan 1 23:18:57 2019) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Restrict map value pointer arithmetic for unprivileged users in that arithmetic itself must not go out of bounds as opposed to the actual access later on. Therefore after each adjust_ptr_min_max_vals() with a map value pointer as a destination it will simulate a check_map_access() of 1 byte on the destination and once that fails the program is rejected for unprivileged program loads. We use this later on for masking any pointer arithmetic with the remainder of the map value space. The likelihood of breaking any existing real-world unprivileged eBPF program is very small for this corner case. Signed-off-by: Daniel Borkmann Acked-by: Alexei Starovoitov --- kernel/bpf/verifier.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index afa8515..4da8c73 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -3249,6 +3249,17 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env, __update_reg_bounds(dst_reg); __reg_deduce_bounds(dst_reg); __reg_bound_offset(dst_reg); + + /* For unprivileged we require that resulting offset must be in bounds + * in order to be able to sanitize access later on. + */ + if (!env->allow_ptr_leaks && dst_reg->type == PTR_TO_MAP_VALUE && + check_map_access(env, dst, dst_reg->off, 1, false)) { + verbose(env, "R%d pointer arithmetic of map value goes out of range, prohibited for !root\n", + dst); + return -EACCES; + } + return 0; }