From patchwork Thu Nov 17 16:24:15 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: 13047017 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 DFA6EC433FE for ; Thu, 17 Nov 2022 16:26:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239727AbiKQQ0q (ORCPT ); Thu, 17 Nov 2022 11:26:46 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35088 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240476AbiKQQ0Y (ORCPT ); Thu, 17 Nov 2022 11:26:24 -0500 Received: from mail-pj1-x1043.google.com (mail-pj1-x1043.google.com [IPv6:2607:f8b0:4864:20::1043]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 55B3073B8A for ; Thu, 17 Nov 2022 08:25:09 -0800 (PST) Received: by mail-pj1-x1043.google.com with SMTP id b11so2098909pjp.2 for ; Thu, 17 Nov 2022 08:25:09 -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=i4mZ6hP9ObJ5uQf5JqTcbQKElLyiJzgs0Cf81+J0nCQ=; b=Il+JEOK5Do3cP8ik4X+B5lEK0GFItcbrQl1vf/Z1USIHDpTtnz/r14MrSdND1CfsHo SecF6f17JGP78t3uUgC9ZDiy/l0tDRol+xUQLihKx7AheoZTOly2jFB3Okr+LnZz8R+3 mS8t7VGdIadKAuL52gZ/KfpciiOB4KpGoCfJmC+abu3snBKghSNaPalPmfxJSK+UCKlb +Z5g+LlSwIHnJzA496uaN/uLy+EPy5QAthk80bywhcjRLrp4IEfUkhft9ggiyr/uyBsS T9h9umyVA8HrmBRp+/6oAmJ4+VV//fIzGdFL1GonXcPTMNt6LUUxnH410351tSaykqxh l2tw== 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=i4mZ6hP9ObJ5uQf5JqTcbQKElLyiJzgs0Cf81+J0nCQ=; b=qnExRVGg97UwLI8op7p+oMEzzIFQfS2DgrRP+HDERR88tfxdkQffvjKF8AnMhjT/x5 A3Z46r82axVUS37h1xQhs0QewTX+dznd9G5iAR/KFXMcEjqJtyMXml/Jh7RSyUAjOudz LQyaDhAqmkOd1tLxPiblNDCKT/1g2DrdTm9mjyUkqTUJEohCmh0G4yYB03+yItLMvaPy 1yeX677DbnneUGpgFyBJpfl3c63D6a/u6UYpoR055tcy+8Wv36vBLQQTG6nSVIrGaqig 2KtqVHOU4F1XWk7HCk9JR9HNBp3C9HH96o65TOZ1uT/hxsxGdEbfNO7vDkuZThLJBTmp 8TmQ== X-Gm-Message-State: ANoB5pkd8xyzLI3Wa4rK9jnKi4oZ7LD0VFycdSIJZWhGCBLb8Wi64u2H QgdSrMiXupC7D/Ki13TKdJ4V8zXXNLA= X-Google-Smtp-Source: AA0mqf4/+0mq5v39qdXDVHKdJaoIxznG5yu8cgos8jLt5c+vEhV0M4kd7eeijemYS2aPZNbvrcHR5w== X-Received: by 2002:a17:902:e807:b0:17e:539:c405 with SMTP id u7-20020a170902e80700b0017e0539c405mr3475369plg.53.1668702308531; Thu, 17 Nov 2022 08:25:08 -0800 (PST) Received: from localhost ([103.4.221.252]) by smtp.gmail.com with ESMTPSA id y15-20020a17090264cf00b00188f9534a3esm221456pli.87.2022.11.17.08.25.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 17 Nov 2022 08:25:08 -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 v8 07/22] bpf: Verify ownership relationships for user BTF types Date: Thu, 17 Nov 2022 21:54:15 +0530 Message-Id: <20221117162430.1213770-8-memxor@gmail.com> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221117162430.1213770-1-memxor@gmail.com> References: <20221117162430.1213770-1-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=4XpdADs4wUXZzYe4sFC8jTKjE7hThtzyMgL0BDjwri0=; b=owEBbQKS/ZANAwAIAUzgyIZIvxHKAcsmYgBjdl7+n/f/lYI7oMalgTVkux/lqAAyehT2pCDt/UlU ZUWi01GJAjMEAAEIAB0WIQRLvip+Buz51YI8YRFM4MiGSL8RygUCY3Ze/gAKCRBM4MiGSL8RyuGeD/ wNmp/DPN6Jv/SZb0vKayGNxzxNyNp1HhOpk4C/uUrhgbeycVZ2ICz/ZYYhrklGhPucUbaRFgGU55BV ohFGY2fu+VeUWC6AaOURGRCjrr91lTipXDIqiaTK/pQTHjfEBEF8o8tBTtjFWZ+9cDKN8RfZ5Ow0lm 5sNZpQBXDemp4WKH5Lfz7F4em8kLbWpwFvRAUr0k6rLpUQFn0e7iCcpoUZZITcWP+4gxhDm3GciZYi 0MLAECoa+KJHDdM1pFsUo8WTAOKL/le++sKEGIH0tAInZfbKH1PBxYQfa6cdwvWOovdcfqi7GgGAxO wAGI9a3HSTkGHsb2lHlo8XvbgH5J5bsZMve9vWGbOfhcQQ7KKn6bR+0iHpqH6FMyozIH7m1eBRQPgZ +qSWErlgyWJfkxJdvwTlv3WhKoT4SlhKJC42mD1m2w+2e+KRthlqwG/R7RNcVp4gQcb4uZMXTwEJLX u/n/n0rYpOC501mjTp8zATVYKFsf/ELs3wukxUlOa26OxOiVLA5iyqDIF95UVu28qPFjxzqssnV9R4 Qd/uPWJbRi0UszHWLmghGGKBGDwvXykkKEjqpcxl0cUyiXuuXRm7ioeD++sUy4pnjn8df2206NtHow DXRiLgVTjBL7QyLxLWhx9z8CMASkl7GdX7sJFhnjgjFTQyfV/iLZjMu73Mkw== 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 45d9323d44ba..7994222f1058 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -190,6 +190,7 @@ 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 75f86e621058..fcf17ef42d56 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -1045,6 +1045,10 @@ 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)