From patchwork Tue Oct 11 01:22:27 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: 13003529 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 D08D9C433F5 for ; Tue, 11 Oct 2022 01:26:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229494AbiJKB0Y (ORCPT ); Mon, 10 Oct 2022 21:26:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49584 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230015AbiJKB0E (ORCPT ); Mon, 10 Oct 2022 21:26:04 -0400 Received: from mail-pj1-x1042.google.com (mail-pj1-x1042.google.com [IPv6:2607:f8b0:4864:20::1042]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 17FB31839D for ; Mon, 10 Oct 2022 18:25:47 -0700 (PDT) Received: by mail-pj1-x1042.google.com with SMTP id v10-20020a17090a634a00b00205e48cf845so14541141pjs.4 for ; Mon, 10 Oct 2022 18:25:47 -0700 (PDT) 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=P6HfjkzrwKt+imTfngBptJXj/x6023U8OdWhlwfcr9w=; b=SpCLD7dlZRJx1CAzSnqdaxQmK9SUMzRZbTOAo/d2Cphdjpt08gWK8AIbVnm3+GgshU S6pjWXes6qfO44acRHyoYG1WNH7Y9rRbz4l/qGpiiOF3O8XCoY8MpH9oyP/51GAyvOKy h3WkecFYxNZjzdPlAJQnp7uw/GMhTSgah9nq5/Ka3khnD1S8TtZgOyXGTWbxTRgC/KvK +6+rg+UuR0S4NLHCQHYhEf4uoxRhm0XWB37xhUEg1nJMPmsfGK1LClIF6YYLGkh8BG4u VCVi/07QimUGt9hc/R6iZfP+wd029fd3QhKzYuiDNVAW2jBOb1MZu48dOlt5lQ7aY1KM s62g== 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=P6HfjkzrwKt+imTfngBptJXj/x6023U8OdWhlwfcr9w=; b=fmkI0cd97BhcPKFF0kNGNKU6p/RDXJPauJvTbdjv/pqKhLquhB35MroEKYnXkVryZv /CTHWZD6bpuP0cjkvNZesfkKBz/1lha+gK3fO4dcrq2YyBXCNcTDLttKCI8S3cK0LLXk 7G0+vZt271MgkEqddKNsou/KahVJ0Cs7ra4SawhbP5hVzQkWkp9tnmitFxTHYLnyttg5 ysvLKcFwBLZ7aY0CJs0Kd2wtopVWsG6a4fe22m0w1fVwCZ4sEbnebQ8TaIx8VGokhBvF ym/i5wcWem/eoHjnmfBqw09772rJtF0yuws1QGlR0E9p9spuIC0HqSYZhFBC81VuUBdF 5xcw== X-Gm-Message-State: ACrzQf0o1RTS3cSUUUGNtxapUw/D5/rFYyULHTZJOXDyxs7M0N/8SvnC f2dmb+SId3hqCVFCAjyuO3L40V9/332Akg== X-Google-Smtp-Source: AMsMyM5ykeNvnQXa1lrkOmVDHSAGKlVtv9uT8sS4y7VcfWn50RCOnai1wBTFEro9Ir5z5LuSGhrpHA== X-Received: by 2002:a17:902:cf42:b0:180:d75e:6792 with SMTP id e2-20020a170902cf4200b00180d75e6792mr15973845plg.130.1665451546262; Mon, 10 Oct 2022 18:25:46 -0700 (PDT) Received: from localhost ([103.4.221.252]) by smtp.gmail.com with ESMTPSA id u9-20020a17090341c900b0017f7bef8cfasm7314421ple.281.2022.10.10.18.25.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 10 Oct 2022 18:25:45 -0700 (PDT) From: Kumar Kartikeya Dwivedi To: bpf@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Dave Marchevsky , Delyan Kratunov Subject: [PATCH bpf-next v1 12/25] bpf: Verify ownership relationships for owning types Date: Tue, 11 Oct 2022 06:52:27 +0530 Message-Id: <20221011012240.3149-13-memxor@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20221011012240.3149-1-memxor@gmail.com> References: <20221011012240.3149-1-memxor@gmail.com> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=5464; i=memxor@gmail.com; h=from:subject; bh=FrGg0KDeqbB2+UcZWL9WxngGeePdYddRTyn7rJKLARo=; b=owEBbQKS/ZANAwAKAUzgyIZIvxHKAcsmYgBjRMUamM5QFADqUX2q0Sn4zf5uNvOKhsLuXmg3gmzv EJTCMBuJAjMEAAEKAB0WIQRLvip+Buz51YI8YRFM4MiGSL8RygUCY0TFGgAKCRBM4MiGSL8Ryv1aD/ 4yNAhqHD9fS8FOJGWH99ocRie+ZzSQme7RF/XjaWeb7b4v55PADqM4AeVIbKkaPtdaDDr57KYiIKh9 QRFd611OA9tguxpiz+SUPL+0i9ZUgYbw2iMz7iodXTWgMiN6aWGzaXgOGhqvkd1gdB0Qha7juBU0WP 0NiotQ4PwPGycF+YYKYAN2sOC2G/QNP9NSPm+81cSoqBYMoE9GKvMnlYwbr5XG5iV7OoZ2tUk/SNjT mcUhK8+qtax5aMK8tAvzj1ZDeLJX2drsEeBQjjEMMvrYIY/Hctdi2E9ixO5ANF3I9NI/RNlsQDhsqo GD8TmY2mZyBDxb2b3YOaMKUfyjApE5DaOkRiL8Rk8W98yw5DDhXTDrs20/0yN4h5gRXrzNbxBnd6Bg aoIeqcDo29ghXLp6rw7aRsn6AfpSwefaUAwH3bOrJFd/0oE4RjGSVl9y7GqE1axH4NqRcqS9nX14ix A++qs9NzxXm1TiaKlgK2rU41BRX6CUgYlC/FFASt3tXKPMvozdWKGt9+sHkD2Gy2gMBQqHL89uxLQk +tRKXNeUHDcyBWwnSkt6ZVtu1PTInq8vO2IZhOFyo1TOBQxV+w8qxW8PtBNBZZQ8vsJA4KAA3/FsT9 eDs2NTDYwbI+Ig/G7Tx9WcLuB8W6q6IPAmD3JB30A5BpldXfvuBkOk4r6Ncw== 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 local kptrs, 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. 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 76548a9d57db..b2419752542a 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -192,6 +192,7 @@ struct btf_field_list_head { struct btf *btf; u32 value_btf_id; u32 node_offset; + struct btf_type_fields *value_tab; }; struct btf_field { diff --git a/include/linux/btf.h b/include/linux/btf.h index b63c88de3135..4492636c3571 100644 --- a/include/linux/btf.h +++ b/include/linux/btf.h @@ -179,6 +179,7 @@ int btf_find_timer(const struct btf *btf, const struct btf_type *t); struct btf_type_fields *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_type_fields *tab); struct btf_type_fields_off *btf_parse_fields_off(struct btf_type_fields *tab); 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 d6aeb0a4d4b7..c038ba873ba4 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -3730,6 +3730,67 @@ struct btf_type_fields *btf_parse_fields(const struct btf *btf, return ERR_PTR(ret); } +int btf_check_and_fixup_fields(const struct btf *btf, struct btf_type_fields *tab) +{ + 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(tab) || !(tab->field_mask & BPF_LIST_HEAD)) + return 0; + for (i = 0; i < tab->cnt; i++) { + struct btf_struct_meta *meta; + u32 btf_id; + + if (!(tab->fields[i].type & BPF_LIST_HEAD)) + continue; + btf_id = tab->fields[i].list_head.value_btf_id; + meta = btf_find_struct_meta(btf, btf_id); + if (!meta) + return -EFAULT; + tab->fields[i].list_head.value_tab = meta->fields_tab; + + if (!(tab->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->fields_tab->field_mask & BPF_LIST_HEAD) + return -ELOOP; + } + return 0; +} + static int btf_type_fields_off_cmp(const void *_a, const void *_b, const void *priv) { const u32 a = *(const u32 *)_a; @@ -5414,6 +5475,16 @@ 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].fields_tab); + 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 c60bf641301d..c8e1bdcbc205 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -1043,6 +1043,10 @@ static int map_check_btf(struct bpf_map *map, const struct btf *btf, } } + ret = btf_check_and_fixup_fields(btf, map->fields_tab); + 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)