From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752135AbdHCQPo (ORCPT ); Thu, 3 Aug 2017 12:15:44 -0400 Received: from dispatch1-us1.ppe-hosted.com ([67.231.154.164]:39570 "EHLO dispatch1-us1.ppe-hosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751131AbdHCQPl (ORCPT ); Thu, 3 Aug 2017 12:15:41 -0400 From: Edward Cree Subject: [PATCH v4 net-next 11/13] selftests/bpf: variable offset negative tests To: , Alexei Starovoitov , Alexei Starovoitov , Daniel Borkmann References: <22441d84-0a11-5c00-2d2a-25e7dbafa6c2@solarflare.com> CC: , , iovisor-dev Message-ID: Date: Thu, 3 Aug 2017 17:15:31 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.1.0 MIME-Version: 1.0 In-Reply-To: <22441d84-0a11-5c00-2d2a-25e7dbafa6c2@solarflare.com> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.17.20.45] X-ClientProxiedBy: ocex03.SolarFlarecom.com (10.20.40.36) To ukex01.SolarFlarecom.com (10.17.10.4) X-TM-AS-Product-Ver: SMEX-11.0.0.1191-8.100.1062-23234.003 X-TM-AS-Result: No--3.275100-0.000000-31 X-TM-AS-User-Approved-Sender: Yes X-TM-AS-User-Blocked-Sender: No X-MDID: 1501776941-nEgHtGKXWrbC Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Variable ctx accesses and stack accesses aren't allowed, because we can't determine what type of value will be read. Signed-off-by: Edward Cree --- tools/testing/selftests/bpf/test_verifier.c | 41 +++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+) diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c index 876b878..65aa562 100644 --- a/tools/testing/selftests/bpf/test_verifier.c +++ b/tools/testing/selftests/bpf/test_verifier.c @@ -5980,6 +5980,47 @@ static struct bpf_test tests[] = { .errstr = "R0 min value is negative, either use unsigned index or do a if (index >=0) check.", .result = REJECT, }, + { + "variable-offset ctx access", + .insns = { + /* Get an unknown value */ + BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, 0), + /* Make it small and 4-byte aligned */ + BPF_ALU64_IMM(BPF_AND, BPF_REG_2, 4), + /* add it to skb. We now have either &skb->len or + * &skb->pkt_type, but we don't know which + */ + BPF_ALU64_REG(BPF_ADD, BPF_REG_1, BPF_REG_2), + /* dereference it */ + BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1, 0), + BPF_EXIT_INSN(), + }, + .errstr = "variable ctx access var_off=(0x0; 0x4)", + .result = REJECT, + .prog_type = BPF_PROG_TYPE_LWT_IN, + }, + { + "variable-offset stack access", + .insns = { + /* Fill the top 8 bytes of the stack */ + BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0), + /* Get an unknown value */ + BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, 0), + /* Make it small and 4-byte aligned */ + BPF_ALU64_IMM(BPF_AND, BPF_REG_2, 4), + BPF_ALU64_IMM(BPF_SUB, BPF_REG_2, 8), + /* add it to fp. We now have either fp-4 or fp-8, but + * we don't know which + */ + BPF_ALU64_REG(BPF_ADD, BPF_REG_2, BPF_REG_10), + /* dereference it */ + BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_2, 0), + BPF_EXIT_INSN(), + }, + .errstr = "variable stack access var_off=(0xfffffffffffffff8; 0x4)", + .result = REJECT, + .prog_type = BPF_PROG_TYPE_LWT_IN, + }, }; static int probe_filter_length(const struct bpf_insn *fp)