From patchwork Thu Sep 8 23:07:16 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dave Marchevsky X-Patchwork-Id: 12970775 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 F04B1C54EE9 for ; Thu, 8 Sep 2022 23:07:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229459AbiIHXH2 (ORCPT ); Thu, 8 Sep 2022 19:07:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36672 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229449AbiIHXH1 (ORCPT ); Thu, 8 Sep 2022 19:07:27 -0400 Received: from mx0a-00082601.pphosted.com (mx0a-00082601.pphosted.com [67.231.145.42]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B8F498F95D for ; Thu, 8 Sep 2022 16:07:26 -0700 (PDT) Received: from pps.filterd (m0044012.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.17.1.5/8.17.1.5) with ESMTP id 288Ml7Na026795 for ; Thu, 8 Sep 2022 16:07:26 -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=Ha6ExWTWMfhOASyGilTuffSe7jIPqtH7U4eRfyEcK74=; b=jPg3rLSiIzYea+xq/sHHk1Xkp+xO+RWxipY2Rlk/OUUDOShbtHSwKSvoGlM8IfDmEmbh BMofS7VI8dRuKfZpK2WaQh73zDY6HiyOMLA0u3exif1CXuH3gwnzwYWKbTGOCsO1+VHf /tOTwRS3KaUCzJJONP/JL3eMnTFAiYL9vs8= Received: from maileast.thefacebook.com ([163.114.130.16]) by mx0a-00082601.pphosted.com (PPS) with ESMTPS id 3jffdxcs9f-4 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Thu, 08 Sep 2022 16:07:26 -0700 Received: from twshared7509.08.ash8.facebook.com (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:82::c) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Thu, 8 Sep 2022 16:07:23 -0700 Received: by devbig077.ldc1.facebook.com (Postfix, from userid 158236) id E2985D2A734C; Thu, 8 Sep 2022 16:07:19 -0700 (PDT) From: Dave Marchevsky To: CC: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Kernel Team , Joanne Koong , Dave Marchevsky Subject: [PATCH bpf-next] bpf: Add verifier support for custom callback return range Date: Thu, 8 Sep 2022 16:07:16 -0700 Message-ID: <20220908230716.2751723-1-davemarchevsky@fb.com> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 X-FB-Internal: Safe X-Proofpoint-GUID: N6XbxTZ64K0HJdocsUOHSMtJ8KejfaqR X-Proofpoint-ORIG-GUID: N6XbxTZ64K0HJdocsUOHSMtJ8KejfaqR X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.895,Hydra:6.0.528,FMLib:17.11.122.1 definitions=2022-09-08_12,2022-09-08_01,2022-06-22_01 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net Verifier logic to confirm that a callback function returns 0 or 1 was added in commit 69c087ba6225b ("bpf: Add bpf_for_each_map_elem() helper"). At the time, callback return value was only used to continue or stop iteration. In order to support callbacks with a broader return value range, such as those added in rbtree series[0] and others, add a callback_ret_range to bpf_func_state. Verifier's helpers which set in_callback_fn will also set the new field, which the verifier will later use to check return value bounds. Default to tnum_range(0, 0) instead of using tnum_unknown as a sentinel value as the latter would prevent the valid range (0, U64_MAX) being used. Previous global default tnum_range(0, 1) is explicitly set for extant callback helpers. The change to global default was made after discussion around this patch in rbtree series [1], goal here is to make it more obvious that callback_ret_range should be explicitly set. [0]: lore.kernel.org/bpf/20220830172759.4069786-1-davemarchevsky@fb.com/ [1]: lore.kernel.org/bpf/20220830172759.4069786-2-davemarchevsky@fb.com/ Signed-off-by: Dave Marchevsky Reviewed-by: Stanislav Fomichev --- Sending this separately from rbtree patchset as Joanne also needs this change for her usecase. include/linux/bpf_verifier.h | 1 + kernel/bpf/verifier.c | 7 ++++++- 2 files changed, 7 insertions(+), 1 deletion(-) diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h index b49a349cc6ae..e197f8fb27e2 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h @@ -248,6 +248,7 @@ struct bpf_func_state { */ u32 async_entry_cnt; bool in_callback_fn; + struct tnum callback_ret_range; bool in_async_callback_fn; /* The following fields should be last. See copy_func_state() */ diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index c0f175ac187a..ac0cb88e452a 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -1749,6 +1749,7 @@ static void init_func_state(struct bpf_verifier_env *env, state->callsite = callsite; state->frameno = frameno; state->subprogno = subprogno; + state->callback_ret_range = tnum_range(0, 0); init_reg_state(env, state); mark_verifier_state_scratched(env); } @@ -6789,6 +6790,7 @@ static int set_map_elem_callback_state(struct bpf_verifier_env *env, return err; callee->in_callback_fn = true; + callee->callback_ret_range = tnum_range(0, 1); return 0; } @@ -6810,6 +6812,7 @@ static int set_loop_callback_state(struct bpf_verifier_env *env, __mark_reg_not_init(env, &callee->regs[BPF_REG_5]); callee->in_callback_fn = true; + callee->callback_ret_range = tnum_range(0, 1); return 0; } @@ -6839,6 +6842,7 @@ static int set_timer_callback_state(struct bpf_verifier_env *env, __mark_reg_not_init(env, &callee->regs[BPF_REG_4]); __mark_reg_not_init(env, &callee->regs[BPF_REG_5]); callee->in_async_callback_fn = true; + callee->callback_ret_range = tnum_range(0, 1); return 0; } @@ -6866,6 +6870,7 @@ static int set_find_vma_callback_state(struct bpf_verifier_env *env, __mark_reg_not_init(env, &callee->regs[BPF_REG_4]); __mark_reg_not_init(env, &callee->regs[BPF_REG_5]); callee->in_callback_fn = true; + callee->callback_ret_range = tnum_range(0, 1); return 0; } @@ -6893,7 +6898,7 @@ static int prepare_func_exit(struct bpf_verifier_env *env, int *insn_idx) caller = state->frame[state->curframe]; if (callee->in_callback_fn) { /* enforce R0 return value range [0, 1]. */ - struct tnum range = tnum_range(0, 1); + struct tnum range = callee->callback_ret_range; if (r0->type != SCALAR_VALUE) { verbose(env, "R0 not a scalar value\n");