From patchwork Mon Nov 7 23:09:33 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: 13035450 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 9839AC4332F for ; Mon, 7 Nov 2022 23:10:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232506AbiKGXK0 (ORCPT ); Mon, 7 Nov 2022 18:10:26 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47096 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232448AbiKGXKZ (ORCPT ); Mon, 7 Nov 2022 18:10:25 -0500 Received: from mail-pf1-x441.google.com (mail-pf1-x441.google.com [IPv6:2607:f8b0:4864:20::441]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C01651FCD6 for ; Mon, 7 Nov 2022 15:10:23 -0800 (PST) Received: by mail-pf1-x441.google.com with SMTP id 130so12199086pfu.8 for ; Mon, 07 Nov 2022 15:10:23 -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=rhA06fQZ2maF9obKz7l2Sp1w6d7RA8pXSzWK85L2jyU=; b=QHGMYFjzwmEXWDVZenwE6xV/M/K0Ia7iFZ7ESbsfqOK6dys0IsF6duGwz8j7BpwFdb xWNzYkWeeTjjR09/0gQsIT+gJJLdZsDmoxJOlv+AC3B0GuW8Ls9yFy2dhylWUOa2ASVA LjTSkIKxy08/eo94UmZg33gRIFPPYHusOdzlFP0omhWdAFdlwxxlnC30L0NXEymq7cyh qx1MFp1Vflm2FWwf34Cs7bCZYGACFHirEhHWk/+8ADSWFWbPENCARsGlfmjqKg3QbkKL donisfv63b3HBhFA/YQqpO2roi/axPOQPnJbPhcUa5aKGhK/L4Vst47UurQLnVxM9CZu tIsQ== 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=rhA06fQZ2maF9obKz7l2Sp1w6d7RA8pXSzWK85L2jyU=; b=LhDHfg2g7rKYSdiQ//PKgDfpgxIfQT4/DKhV6+gRG5OQI6y2aqGlyQOsNXxSP+Fw7v KI61h3EXNbQyIngtOrewI9+HD1oMYN+4LhwR3ugcDNeYLschKWia9eLAjHbK9qjOrtn+ t+fqQMI/QolktD9/vKeVrBhaEE39ufl+rHYNBqyvsGWEDNHwU84OoQjj4LOxHjir7FXs GANYvlCUBNLX1ywWMq40n/08QtYSY+tsudlLR2RjC91HixeR6S1W8h1ZiO7F8gEpMss/ +MsfOTaa8Y8qKFQClRSKtFiZ8apNpZs98vCb/YnBkWIsuDljps7CPsiS0CK6JV/3njay OfYg== X-Gm-Message-State: ACrzQf1CwQ2IvA5kvpKcWRs8NcqlLc3c/ryu1ssMFguE50c6QygJ+NG6 y0TnJb+JN50ON2J1DVsbdjCcT6zrNHdd5w== X-Google-Smtp-Source: AMsMyM43P9h+kn2wkFYqwdr9GQl3GPUEWXiL7VouQ+L70gpFg3vPwyNtPToMpzzSonYWo7hd+o+Urg== X-Received: by 2002:a63:dd16:0:b0:46f:9c0b:7f82 with SMTP id t22-20020a63dd16000000b0046f9c0b7f82mr40185810pgg.161.1667862622968; Mon, 07 Nov 2022 15:10:22 -0800 (PST) Received: from localhost ([14.96.13.220]) by smtp.gmail.com with ESMTPSA id f7-20020a170902ce8700b0018691ce1696sm5532564plg.131.2022.11.07.15.10.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 07 Nov 2022 15:10:22 -0800 (PST) From: Kumar Kartikeya Dwivedi To: bpf@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Martin KaFai Lau , Dave Marchevsky , Delyan Kratunov Subject: [PATCH bpf-next v5 08/25] bpf: Verify ownership relationships for user BTF types Date: Tue, 8 Nov 2022 04:39:33 +0530 Message-Id: <20221107230950.7117-9-memxor@gmail.com> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221107230950.7117-1-memxor@gmail.com> References: <20221107230950.7117-1-memxor@gmail.com> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=5565; i=memxor@gmail.com; h=from:subject; bh=dbxNcx/sah2xoNQU8s4VBd7QRq4f8gXikWmJQ28jzUY=; b=owEBbQKS/ZANAwAIAUzgyIZIvxHKAcsmYgBjaY+24y7s5OT1ntUl2PXNooZ2kqLUPBbzeUAc6Lkh x+6Q19uJAjMEAAEIAB0WIQRLvip+Buz51YI8YRFM4MiGSL8RygUCY2mPtgAKCRBM4MiGSL8RytW/D/ 99RP7Dit8WDiTaWhaGOmos1rAdxrXm1TAeduRVHzlbFdKW/crNcffKTmgAvi6RTwlJ0rUyANCe4OhQ L37UCinnkjLIjjFu91p8750n/2/ZorPVPpH59hRpM3Xbc9STxjbaDXFA7hoyaRG4pKrl1s5lEMONO2 GOklBPDv1mqaSjGw4gNSNrYAtjdypUBvbDyu1F19tnImQUqiawPS0rDeieqbfQKcSJPGxi61pLyIve uFtNa3Ujr17x69JQK0K9HAlwES8s1PGH0L4xJOipwjsSLRZkAxhtlGBAit9RBcQ8o9oXDWEvaXvqbp 0dSkMjn2hQX6iTdv7q+lUzljA3cHfQQ/Vuq0mRzJXh7oD8kK6z7Cx1td21mIITzRZir6U9IOxRtD3f jVLxVZiB1w/iEzcxqABJW7lkloCkqCEfAK48WRa6YKWZqdABexTEO9WtgErcQvTzeYGruaqpWRyPe8 vlrlpLQhVgPFhkF8ULCcsDs2MUISl2UsagJNpmWoED5TqOQvlv+RNqOMVgZTVnmRnCYuMOWM4XfBAh 0YWwSwvGjqLnuZC+gdEXf0etzW26gwzX1kNduClOmnC7smqW1ynRHxbPlAMsiMl9fnnn46ZnDoD0IY kmZMMUvEOgGG9GslBLZ4aA8OpPJ59wqzcE4vXfLj9QsPNQKltLBFPgE+3Fmw== 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. 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 dfcd34e36025..88ac4c12bab0 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 5e3cffe4bc37..685a6998432b 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -3721,6 +3721,67 @@ 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; @@ -5410,6 +5471,16 @@ 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 c96039a4e57f..4669020bb47d 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -1044,6 +1044,10 @@ 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)