From patchwork Mon Aug 8 17:15:59 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dave Marchevsky X-Patchwork-Id: 12938914 X-Patchwork-Delegate: bpf@iogearbox.net Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1DBBCC00140 for ; Mon, 8 Aug 2022 17:16:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230103AbiHHRQL (ORCPT ); Mon, 8 Aug 2022 13:16:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57212 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229516AbiHHRQK (ORCPT ); Mon, 8 Aug 2022 13:16:10 -0400 Received: from mx0a-00082601.pphosted.com (mx0a-00082601.pphosted.com [67.231.145.42]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BD93E2BE6 for ; Mon, 8 Aug 2022 10:16:08 -0700 (PDT) Received: from pps.filterd (m0109333.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.17.1.5/8.17.1.5) with ESMTP id 278Cl6uE029098 for ; Mon, 8 Aug 2022 10:16:08 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : mime-version : content-transfer-encoding : content-type; s=facebook; bh=OMhitxhiCrdCYjAawdD5p5ob8YTo5TfSP71fCVY0j6U=; b=h7DB0Fpq9tzhKJZvH4y2xwCCu58nWsmszCeZcWUCt47KmZs9Qt+nFu3ZS5pl/D2/ldRz 8WJ1jsWe4yO3bWdc60CVWeH6yYGwSJ8GSqPSAM/6+YrAH3UeXsCYq6SYQLiqeScTaJp1 yRBqMGJeHTvOiTdhf2b69iA8vupxT3OJNYY= Received: from maileast.thefacebook.com ([163.114.130.16]) by mx0a-00082601.pphosted.com (PPS) with ESMTPS id 3htxr4k6ku-3 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Mon, 08 Aug 2022 10:16:08 -0700 Received: from twshared33626.07.ash9.facebook.com (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:83::4) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.28; Mon, 8 Aug 2022 10:16:05 -0700 Received: by devbig077.ldc1.facebook.com (Postfix, from userid 158236) id 92307B909132; Mon, 8 Aug 2022 10:16:00 -0700 (PDT) From: Dave Marchevsky To: CC: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Kernel Team , Kumar Kartikeya Dwivedi , Joanne Koong , Martin KaFai Lau , Dave Marchevsky Subject: [RESEND PATCH v2 bpf-next] bpf: Cleanup check_refcount_ok Date: Mon, 8 Aug 2022 10:15:59 -0700 Message-ID: <20220808171559.3251090-1-davemarchevsky@fb.com> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 X-FB-Internal: Safe X-Proofpoint-ORIG-GUID: WXrnc7LIUtq-S2mOX0x3cJpGKXXWmUb3 X-Proofpoint-GUID: WXrnc7LIUtq-S2mOX0x3cJpGKXXWmUb3 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.883,Hydra:6.0.517,FMLib:17.11.122.1 definitions=2022-08-08_11,2022-08-08_01,2022-06-22_01 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net Discussion around a recently-submitted patch provided historical context for check_refcount_ok [0]. Specifically, the function and its helpers - may_be_acquire_function and arg_type_may_be_refcounted - predate the OBJ_RELEASE type flag and the addition of many more helpers with acquire/release semantics. The purpose of check_refcount_ok is to ensure: 1) Helper doesn't have multiple uses of return reg's ref_obj_id 2) Helper with release semantics only has one arg needing to be released, since that's tracked using meta->ref_obj_id With current verifier, it's safe to remove check_refcount_ok and its helpers. Since addition of OBJ_RELEASE type flag, case 2) has been handled by the arg_type_is_release check in check_func_arg. To ensure case 1) won't result in verifier silently prioritizing one use of ref_obj_id, this patch adds a helper_multiple_ref_obj_use check which fails loudly if a helper passes > 1 test for use of ref_obj_id. [0]: lore.kernel.org/bpf/20220713234529.4154673-1-davemarchevsky@fb.com Signed-off-by: Dave Marchevsky Acked-by: Martin KaFai Lau Acked-by: Joanne Koong Acked-by: Kumar Kartikeya Dwivedi --- No extant helpers fail the helper_multiple_ref_obj_use check (as expected). I validated this by adding BPF_FUNC_dynptr_data to is_acquire_function check and observing that dynptr selftests failed with expected error, then doing the same for is_ptr_cast_function. v2 -> v2 Resend: lore.kernel.org/bpf/20220719215536.2787530-1-davemarchevsky@fb.com * Add Joanne ack * Rebase v1 -> v2: lore.kernel.org/bpf/20220719185853.1650806-1-davemarchevsky@fb.com * EFAULT instead of EINVAL, minor edit to dynptr acquire comment (Joanne) * Add Martin Acked-by kernel/bpf/verifier.c | 74 +++++++++++++++++-------------------------- 1 file changed, 29 insertions(+), 45 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 843a966cd02b..01e7f48b4d8c 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -467,25 +467,11 @@ static bool type_is_rdonly_mem(u32 type) return type & MEM_RDONLY; } -static bool arg_type_may_be_refcounted(enum bpf_arg_type type) -{ - return type == ARG_PTR_TO_SOCK_COMMON; -} - static bool type_may_be_null(u32 type) { return type & PTR_MAYBE_NULL; } -static bool may_be_acquire_function(enum bpf_func_id func_id) -{ - return func_id == BPF_FUNC_sk_lookup_tcp || - func_id == BPF_FUNC_sk_lookup_udp || - func_id == BPF_FUNC_skc_lookup_tcp || - func_id == BPF_FUNC_map_lookup_elem || - func_id == BPF_FUNC_ringbuf_reserve; -} - static bool is_acquire_function(enum bpf_func_id func_id, const struct bpf_map *map) { @@ -518,6 +504,26 @@ static bool is_ptr_cast_function(enum bpf_func_id func_id) func_id == BPF_FUNC_skc_to_tcp_request_sock; } +static bool is_dynptr_acquire_function(enum bpf_func_id func_id) +{ + return func_id == BPF_FUNC_dynptr_data; +} + +static bool helper_multiple_ref_obj_use(enum bpf_func_id func_id, + const struct bpf_map *map) +{ + int ref_obj_uses = 0; + + if (is_ptr_cast_function(func_id)) + ref_obj_uses++; + if (is_acquire_function(func_id, map)) + ref_obj_uses++; + if (is_dynptr_acquire_function(func_id)) + ref_obj_uses++; + + return ref_obj_uses > 1; +} + static bool is_cmpxchg_insn(const struct bpf_insn *insn) { return BPF_CLASS(insn->code) == BPF_STX && @@ -6453,33 +6459,6 @@ static bool check_arg_pair_ok(const struct bpf_func_proto *fn) return true; } -static bool check_refcount_ok(const struct bpf_func_proto *fn, int func_id) -{ - int count = 0; - - if (arg_type_may_be_refcounted(fn->arg1_type)) - count++; - if (arg_type_may_be_refcounted(fn->arg2_type)) - count++; - if (arg_type_may_be_refcounted(fn->arg3_type)) - count++; - if (arg_type_may_be_refcounted(fn->arg4_type)) - count++; - if (arg_type_may_be_refcounted(fn->arg5_type)) - count++; - - /* A reference acquiring function cannot acquire - * another refcounted ptr. - */ - if (may_be_acquire_function(func_id) && count) - return false; - - /* We only support one arg being unreferenced at the moment, - * which is sufficient for the helper functions we have right now. - */ - return count <= 1; -} - static bool check_btf_id_ok(const struct bpf_func_proto *fn) { int i; @@ -6502,8 +6481,7 @@ static int check_func_proto(const struct bpf_func_proto *fn, int func_id) { return check_raw_mode_ok(fn) && check_arg_pair_ok(fn) && - check_btf_id_ok(fn) && - check_refcount_ok(fn, func_id) ? 0 : -EINVAL; + check_btf_id_ok(fn) ? 0 : -EINVAL; } /* Packet data might have moved, any old PTR_TO_PACKET[_META,_END] @@ -7473,6 +7451,12 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn if (type_may_be_null(regs[BPF_REG_0].type)) regs[BPF_REG_0].id = ++env->id_gen; + if (helper_multiple_ref_obj_use(func_id, meta.map_ptr)) { + verbose(env, "verifier internal error: func %s#%d sets ref_obj_id more than once\n", + func_id_name(func_id), func_id); + return -EFAULT; + } + if (is_ptr_cast_function(func_id)) { /* For release_reference() */ regs[BPF_REG_0].ref_obj_id = meta.ref_obj_id; @@ -7485,10 +7469,10 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn regs[BPF_REG_0].id = id; /* For release_reference() */ regs[BPF_REG_0].ref_obj_id = id; - } else if (func_id == BPF_FUNC_dynptr_data) { + } else if (is_dynptr_acquire_function(func_id)) { int dynptr_id = 0, i; - /* Find the id of the dynptr we're acquiring a reference to */ + /* Find the id of the dynptr we're tracking the reference of */ for (i = 0; i < MAX_BPF_FUNC_REG_ARGS; i++) { if (arg_type_is_dynptr(fn->arg_type[i])) { if (dynptr_id) {