From patchwork Sat Dec 2 17:57:04 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrii Nakryiko X-Patchwork-Id: 13477024 X-Patchwork-Delegate: bpf@iogearbox.net Received: from mx0a-00082601.pphosted.com (mx0a-00082601.pphosted.com [67.231.145.42]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BD63E124 for ; Sat, 2 Dec 2023 09:57:35 -0800 (PST) Received: from pps.filterd (m0109333.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.17.1.19/8.17.1.19) with ESMTP id 3B29mEfc014768 for ; Sat, 2 Dec 2023 09:57:35 -0800 Received: from mail.thefacebook.com ([163.114.132.120]) by mx0a-00082601.pphosted.com (PPS) with ESMTPS id 3ur1guhq87-2 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Sat, 02 Dec 2023 09:57:35 -0800 Received: from twshared21997.42.prn1.facebook.com (2620:10d:c085:208::f) by mail.thefacebook.com (2620:10d:c085:21d::8) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.34; Sat, 2 Dec 2023 09:57:32 -0800 Received: by devbig019.vll3.facebook.com (Postfix, from userid 137359) id 0A4A13C7A8270; Sat, 2 Dec 2023 09:57:29 -0800 (PST) From: Andrii Nakryiko To: , , , CC: , , Eduard Zingerman Subject: [PATCH v5 bpf-next 10/11] selftests/bpf: adjust global_func15 test to validate prog exit precision Date: Sat, 2 Dec 2023 09:57:04 -0800 Message-ID: <20231202175705.885270-11-andrii@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20231202175705.885270-1-andrii@kernel.org> References: <20231202175705.885270-1-andrii@kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-FB-Internal: Safe X-Proofpoint-GUID: 5GKBDQ_h6z6wt_thwoiF5A8SUslenJbS X-Proofpoint-ORIG-GUID: 5GKBDQ_h6z6wt_thwoiF5A8SUslenJbS X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.997,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2023-12-02_16,2023-11-30_01,2023-05-22_02 X-Patchwork-Delegate: bpf@iogearbox.net Add one more subtest to global_func15 selftest to validate that verifier properly marks r0 as precise and avoids erroneous state pruning of the branch that has return value outside of expected [0, 1] value. Acked-by: Eduard Zingerman Signed-off-by: Andrii Nakryiko --- .../selftests/bpf/progs/test_global_func15.c | 32 +++++++++++++++++++ 1 file changed, 32 insertions(+) diff --git a/tools/testing/selftests/bpf/progs/test_global_func15.c b/tools/testing/selftests/bpf/progs/test_global_func15.c index f80207480e8a..b4e089d6981d 100644 --- a/tools/testing/selftests/bpf/progs/test_global_func15.c +++ b/tools/testing/selftests/bpf/progs/test_global_func15.c @@ -22,3 +22,35 @@ int global_func15(struct __sk_buff *skb) return v; } + +SEC("cgroup_skb/ingress") +__log_level(2) __flag(BPF_F_TEST_STATE_FREQ) +__failure +/* check that fallthrough code path marks r0 as precise */ +__msg("mark_precise: frame0: regs=r0 stack= before 2: (b7) r0 = 1") +/* check that branch code path marks r0 as precise */ +__msg("mark_precise: frame0: regs=r0 stack= before 0: (85) call bpf_get_prandom_u32#7") +__msg("At program exit the register R0 has ") +__naked int global_func15_tricky_pruning(void) +{ + asm volatile ( + "call %[bpf_get_prandom_u32];" + "if r0 s> 1000 goto 1f;" + "r0 = 1;" + "1:" + "goto +0;" /* checkpoint */ + /* cgroup_skb/ingress program is expected to return [0, 1] + * values, so branch above makes sure that in a fallthrough + * case we have a valid 1 stored in R0 register, but in + * a branch case we assign some random value to R0. So if + * there is something wrong with precision tracking for R0 at + * program exit, we might erronenously prune branch case, + * because R0 in fallthrough case is imprecise (and thus any + * value is valid from POV of verifier is_state_equal() logic) + */ + "exit;" + : + : __imm(bpf_get_prandom_u32) + : __clobber_common + ); +}