From patchwork Fri Nov 11 19:32:08 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: 13040739 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 8C2EEC4332F for ; Fri, 11 Nov 2022 19:33:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233870AbiKKTdp (ORCPT ); Fri, 11 Nov 2022 14:33:45 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35436 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233828AbiKKTdo (ORCPT ); Fri, 11 Nov 2022 14:33:44 -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 A9373FCD0 for ; Fri, 11 Nov 2022 11:33:43 -0800 (PST) Received: by mail-pf1-x441.google.com with SMTP id y13so5693119pfp.7 for ; Fri, 11 Nov 2022 11:33:43 -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=HJoDj6xrXZktYRxgvC1zzU8QhhM+z5Xg3gZS3dvgLB4=; b=enPQg/Zx6GAniJGD4re64/imcXgUX3pKLjBjOK8YotWPe65MKWjBtF+KLwp9jO45Lf SC2luCJTFU3BXq/DjkaNpevfCstfcl6gvzsdKvJtcja0Z9y6L82o0PzWx4HZ9SVz5/Z7 tGSivYpzerSAJ9T3tSFOW4HlPKMRUkeBbb7nCOFufb931Z3eaIRIHqzW7KauKspfou82 nNv4fMz3LusjSDxknYpyvbLYqHetwlXhV7UzEv7HLnA4wL5Ww872VWd2k2R2d5y2IpW1 LMcfeyLj2uZ+Z2auoJX8LI7Cl6QKZYSTyv6pfnWp0CFa4DpN/kG8hEMd7cnCSaX9+2G5 hOhg== 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=HJoDj6xrXZktYRxgvC1zzU8QhhM+z5Xg3gZS3dvgLB4=; b=Fh4fbC2bf664JMdKEM3/OsAzA18dQG+fuFUgntDdwGp8SA0tMP3FKg4BCKSnYkOxFu gXy0HlrXrVZWqMjFK6lUZ7yCOGG5REDUe12G+/gIPPw2UiS9e4uDl/kYTyaJYHsJ8WMO NayCIhVsKzJ2auTrPnutsZGjRzk/TJjfgp0hpDkILOLdx4FQULRXMu/sWB66pxRpyaJu KHsOFa4FqGyTLhHtJ+bd+aS1UZpJraZd3iiyoXq4iZ4CvLu9tlQ+QdIDOqwnx2w010X6 2frEwlZXQr2LT3MS0+TSpd8wZMJwA9rd8bwzKrei492xJGFDazFWyMEOYwncLcEz7AL4 WRxw== X-Gm-Message-State: ANoB5pl8+UwwNjsdqXTzNSYyzIvymPSk8Dx3We+9gutn3QTto2/r31n9 03yor3eU+xNVirULUxzBYAmhLX8aXrHt5Q== X-Google-Smtp-Source: AA0mqf5zZWtrJzgT0Iyn6JZC+TPeuSYtNsOKHs+Jh6X+yUap44YjsA2ZGuStkCuKKZ34dOFQquDBWA== X-Received: by 2002:a05:6a00:2487:b0:56c:afe:e8bf with SMTP id c7-20020a056a00248700b0056c0afee8bfmr4149122pfv.51.1668195222900; Fri, 11 Nov 2022 11:33:42 -0800 (PST) Received: from localhost ([14.96.13.220]) by smtp.gmail.com with ESMTPSA id x12-20020aa79acc000000b0056ddd2b5e9bsm1941489pfp.41.2022.11.11.11.33.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 11 Nov 2022 11:33:42 -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 v6 10/26] bpf: Verify ownership relationships for user BTF types Date: Sat, 12 Nov 2022 01:02:08 +0530 Message-Id: <20221111193224.876706-11-memxor@gmail.com> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221111193224.876706-1-memxor@gmail.com> References: <20221111193224.876706-1-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=ixmYvmiPkP0VLegCTd0JqLgG+KhMlzR4IX850VHvYng=; b=owEBbQKS/ZANAwAIAUzgyIZIvxHKAcsmYgBjbqIoVisz7aF7uHg3UxnNyEgFFhl7I1JfrCtmfRj+ zl7HHfKJAjMEAAEIAB0WIQRLvip+Buz51YI8YRFM4MiGSL8RygUCY26iKAAKCRBM4MiGSL8Ryu6KD/ 4rW+dxhYQYDMVOFHGn3aBHRDFeBJ+SXJKDJRoY0gGVIBb9UDa89BYxLKu8yQlLGPejQTzKEKDSr3e1 Dxg9N5iI4GMr3qEUH9uDdNJbAXgcAjzEybOFk+dHCAV0Y86wN+h8aUTI+UuFMQoggakmDEqH11i0kJ lg83GXm8MzcUhQD8WlMEZn/O1Yf4JxUCZVr8vO8wL+BJ60viHNknkjci7xsBYmLFtmFlgr0HplJJat SMg1DJnMfEE62uKIpbc5fCez1L59g4tn4DF0Cxe+Vxsnjtcap3gxA/qUKYZktypdaBJ0Y6IFTadKpc wHFPROre67jzcvboWiyS1+LHZhBCV6MPajERYwcNZnEeUa0I0Vl8Ixyjjsh+gEX3TGF7Oag4Yg5maD TZ1jABjWotmhtRoCWG011jSprZHVkDLXft/BLm4rdDL1Pr2XYkGQ/BAVgPfy/D5kzL0uJpTM1DneTH NyPA6RxHTtXmOGH/COpI/CVfUC/xVmjb2fHzPBVrSULp/3FF4lPOgr250J55kCWEnblh4+VWGxaUbj cIGxi0DeV38jqeAJ7uGV0SOBYhrDEnwOWKF+wDFysCwLWgSrKCSlOcP/b8N2/pCz1HQIgAvYX1GJH3 8hQjl5Q2NaTpGBpwfECVisOOrRYuUjbJ7zaqOAk25rCvPKkBySmW78o12k8Q== 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 4cd3c9e6f50b..c88f75a68893 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 fbcb846188e2..ef8710fab997 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; @@ -5412,6 +5473,16 @@ 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)