From patchwork Thu Nov 17 22:54:54 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kumar Kartikeya Dwivedi X-Patchwork-Id: 13047432 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 95B45C4332F for ; Thu, 17 Nov 2022 22:55:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234786AbiKQWzs (ORCPT ); Thu, 17 Nov 2022 17:55:48 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53218 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234843AbiKQWzo (ORCPT ); Thu, 17 Nov 2022 17:55:44 -0500 Received: from mail-pj1-x1041.google.com (mail-pj1-x1041.google.com [IPv6:2607:f8b0:4864:20::1041]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D9F0762CE for ; Thu, 17 Nov 2022 14:55:43 -0800 (PST) Received: by mail-pj1-x1041.google.com with SMTP id b1-20020a17090a7ac100b00213fde52d49so3390615pjl.3 for ; Thu, 17 Nov 2022 14:55:43 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=59LPQzxnxExTrnm9z27ZdhRyWEMEvy8zkWsOH6jmk1I=; b=CiEbwjfJhTyyHuW28tXo+HFVt6J9/53Ftsl8aIOzPqrL8QPpPfm67CNSOOlvFNYjeP mmJRRuFDfdpatCB1dZitk8FgpqLX9nOs3SXFFMLce6ceFmjyUnCyTEeHqB7r5f9oX/Kd haRbSiBIN66+wLmPv7yv5WEHaDDlTV2QIcmC7qT+y4vbyKKQUJTjQBatifLj4BoIJl91 EmeHiewR49RNAzk16j0Oxf7Xsdy7Av+0r90FEwCW592kg6Zodql3wiLdgRCTG6yMaMxw y4hiQh/e0T0Ay3ekr2OBvUlWjFpa+G+7l/0gKpGZc6E31wNMD043aSXEVvR9wTxPnKQt wpFA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=59LPQzxnxExTrnm9z27ZdhRyWEMEvy8zkWsOH6jmk1I=; b=cN43JjWp7IG7YLT17He5KNNbl/IVRf6ExT8F+f/h0RlIXXYAYOPdqb6mdvZBD3EFMu LZHLjhUq/Mzrb0KyynJhClDExF+B5kuJd+CD3fDxh7jmXXB/040VJaw3Zv+jqWJ8hwM3 S+FSoBzXyxvEpuxTPN4xN1WzHYB5J0CDxLbyAG+zcsmkxWHWsuNvgOI3YaM54LEwi3Oz MEC6HTiFB2ElYQrkYzAtNZ5aT1/QK4lQodPV8mKLpj/WOI2PGVCYW2Rm1edu/UIJMZ8g dCqTf8/yx8HTCuxv6VSSriokOhpcSgSZiOAiFdYmQLMitKS6BkM39HH6TNpXxgLNBeVP J4vw== X-Gm-Message-State: ANoB5plwrau3HEx8FeFK5PaBggkjKEhsWkIt1qpymsAzhsgI7GTPo57X nT9qgk2B3fjwV6VBOvRarMQZQL1W0po= X-Google-Smtp-Source: AA0mqf58+zZjkH0CyzpyzMpEhKdOeF/cA58fRQRbasaL2bkoFS6iyDzPQclmry6gcUdbbZlGHMoBDA== X-Received: by 2002:a17:902:bd96:b0:181:b55a:f987 with SMTP id q22-20020a170902bd9600b00181b55af987mr4890823pls.67.1668725743129; Thu, 17 Nov 2022 14:55:43 -0800 (PST) Received: from localhost ([2409:40f4:8:955c:5484:8048:c08:7b3]) by smtp.gmail.com with ESMTPSA id iw20-20020a170903045400b00179f370dbe7sm1847384plb.287.2022.11.17.14.55.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 17 Nov 2022 14:55:42 -0800 (PST) From: Kumar Kartikeya Dwivedi To: bpf@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Martin KaFai Lau , Dave Marchevsky Subject: [PATCH bpf-next v9 07/23] bpf: Verify ownership relationships for user BTF types Date: Fri, 18 Nov 2022 04:24:54 +0530 Message-Id: <20221117225510.1676785-8-memxor@gmail.com> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221117225510.1676785-1-memxor@gmail.com> References: <20221117225510.1676785-1-memxor@gmail.com> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=5571; i=memxor@gmail.com; h=from:subject; bh=yjHfgHm/5+Ygd2drsc/Tti6WmbVZpvw5QJdLaHTdJrM=; b=owEBbQKS/ZANAwAIAUzgyIZIvxHKAcsmYgBjdrkbBmK1fKl3Ixaf3FLvq3rDvimWbGzprZ//M+bf XUHGe2OJAjMEAAEIAB0WIQRLvip+Buz51YI8YRFM4MiGSL8RygUCY3a5GwAKCRBM4MiGSL8RyvJbD/ 9HqaY4aL9pfovYru3Zm/u0O26mfjgbsbQSNsQqm3RW2hhcUzezEXheX5Zs5DIvfRQGqryYyzeTQeix flKSeG59S2FF0+WSIoK2+aLYmmK0ZBojePNsP3nQpIz4+rFoOeLlZaGijS9OrK6EGqVQhgEvdoMdTH tIl41ktxruvuk1W+eUUXSrQvbYiOc4CbXmAUj+VYHFCOr+g6w+inJEFYaiGImDKDAokNbW/NxuRkKD F6tczFfVuE7OaBuoi4v84PAxW8FY70dgmZyTFbfqt3hMr8nHLjxKn+u1T88KwaV6fmNaLDyzrpJgqM oRfInbft/CPMUSH+HIFgsAiCm/f+QWuQ1f6AIR/VIhU4T5PtXxFzbAY9F3QBASqYGLTLYZsAThGc5f AWlutjPTwImXlmB9vDyB082EcwkeHZOVpixv/nwUURhfqxR4GtLTTWN7kJmxLiuM6P5Loz+G7YMpDv kgOMDQF+Hp5ylwsKyh9Z11lfWUGXoAM8hKgiI9R+X+UvTFM5m53NzIp9nSXW2J34fazq0j9cCV/YTC CaV09sB0rQ/ZipHlNHwBBxa7UTDx6V/YLPN/NVq19Ibeqded72clj+QlHUDIS/VGn/1QdScModa12c lyGUJoNpRVWfW6ScEi6txJK0WcK2OhI6yf/R6eTO8vS4Eep7o8kGsgQCkruA== X-Developer-Key: i=memxor@gmail.com; a=openpgp; fpr=4BBE2A7E06ECF9D5823C61114CE0C88648BF11CA Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net Ensure that there can be no ownership cycles among different types by way of having owning objects that can hold some other type as their element. For instance, a map value can only hold allocated objects, but these are allowed to have another bpf_list_head. To prevent unbounded recursion while freeing resources, elements of bpf_list_head in local kptrs can never have a bpf_list_head which are part of list in a map value. Later patches will verify this by having dedicated BTF selftests. Also, to make runtime destruction easier, once btf_struct_metas is fully populated, we can stash the metadata of the value type directly in the metadata of the list_head fields, as that allows easier access to the value type's layout to destruct it at runtime from the btf_field entry of the list head itself. Signed-off-by: Kumar Kartikeya Dwivedi --- include/linux/bpf.h | 1 + include/linux/btf.h | 1 + kernel/bpf/btf.c | 71 ++++++++++++++++++++++++++++++++++++++++++++ kernel/bpf/syscall.c | 4 +++ 4 files changed, 77 insertions(+) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index eb6ea53fa5a2..323985a39ece 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -191,6 +191,7 @@ struct btf_field_list_head { struct btf *btf; u32 value_btf_id; u32 node_offset; + struct btf_record *value_rec; }; struct btf_field { diff --git a/include/linux/btf.h b/include/linux/btf.h index a01a8da20021..42d8f3730a8d 100644 --- a/include/linux/btf.h +++ b/include/linux/btf.h @@ -178,6 +178,7 @@ int btf_find_spin_lock(const struct btf *btf, const struct btf_type *t); int btf_find_timer(const struct btf *btf, const struct btf_type *t); struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type *t, u32 field_mask, u32 value_size); +int btf_check_and_fixup_fields(const struct btf *btf, struct btf_record *rec); struct btf_field_offs *btf_parse_field_offs(struct btf_record *rec); bool btf_type_is_void(const struct btf_type *t); s32 btf_find_by_name_kind(const struct btf *btf, const char *name, u8 kind); diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index a04e10477567..91aa9c96621f 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -3723,6 +3723,67 @@ struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type return ERR_PTR(ret); } +int btf_check_and_fixup_fields(const struct btf *btf, struct btf_record *rec) +{ + int i; + + /* There are two owning types, kptr_ref and bpf_list_head. The former + * only supports storing kernel types, which can never store references + * to program allocated local types, atleast not yet. Hence we only need + * to ensure that bpf_list_head ownership does not form cycles. + */ + if (IS_ERR_OR_NULL(rec) || !(rec->field_mask & BPF_LIST_HEAD)) + return 0; + for (i = 0; i < rec->cnt; i++) { + struct btf_struct_meta *meta; + u32 btf_id; + + if (!(rec->fields[i].type & BPF_LIST_HEAD)) + continue; + btf_id = rec->fields[i].list_head.value_btf_id; + meta = btf_find_struct_meta(btf, btf_id); + if (!meta) + return -EFAULT; + rec->fields[i].list_head.value_rec = meta->record; + + if (!(rec->field_mask & BPF_LIST_NODE)) + continue; + + /* We need to ensure ownership acyclicity among all types. The + * proper way to do it would be to topologically sort all BTF + * IDs based on the ownership edges, since there can be multiple + * bpf_list_head in a type. Instead, we use the following + * reasoning: + * + * - A type can only be owned by another type in user BTF if it + * has a bpf_list_node. + * - A type can only _own_ another type in user BTF if it has a + * bpf_list_head. + * + * We ensure that if a type has both bpf_list_head and + * bpf_list_node, its element types cannot be owning types. + * + * To ensure acyclicity: + * + * When A only has bpf_list_head, ownership chain can be: + * A -> B -> C + * Where: + * - B has both bpf_list_head and bpf_list_node. + * - C only has bpf_list_node. + * + * When A has both bpf_list_head and bpf_list_node, some other + * type already owns it in the BTF domain, hence it can not own + * another owning type through any of the bpf_list_head edges. + * A -> B + * Where: + * - B only has bpf_list_node. + */ + if (meta->record->field_mask & BPF_LIST_HEAD) + return -ELOOP; + } + return 0; +} + static int btf_field_offs_cmp(const void *_a, const void *_b, const void *priv) { const u32 a = *(const u32 *)_a; @@ -5413,6 +5474,16 @@ static struct btf *btf_parse(bpfptr_t btf_data, u32 btf_data_size, } btf->struct_meta_tab = struct_meta_tab; + if (struct_meta_tab) { + int i; + + for (i = 0; i < struct_meta_tab->cnt; i++) { + err = btf_check_and_fixup_fields(btf, struct_meta_tab->types[i].record); + if (err < 0) + goto errout_meta; + } + } + if (log->level && bpf_verifier_log_full(log)) { err = -ENOSPC; goto errout_meta; diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 56ae97d490f4..6140cbc3ed8a 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -1054,6 +1054,10 @@ static int map_check_btf(struct bpf_map *map, const struct btf *btf, } } + ret = btf_check_and_fixup_fields(btf, map->record); + if (ret < 0) + goto free_map_tab; + if (map->ops->map_check_btf) { ret = map->ops->map_check_btf(map, btf, key_type, value_type); if (ret < 0)