From patchwork Thu Nov 17 16:24:13 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: 13047014 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 2D357C4332F for ; Thu, 17 Nov 2022 16:26:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240472AbiKQQ0m (ORCPT ); Thu, 17 Nov 2022 11:26:42 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35064 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240462AbiKQQ0X (ORCPT ); Thu, 17 Nov 2022 11:26:23 -0500 Received: from mail-pl1-x641.google.com (mail-pl1-x641.google.com [IPv6:2607:f8b0:4864:20::641]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E7D797C441 for ; Thu, 17 Nov 2022 08:25:00 -0800 (PST) Received: by mail-pl1-x641.google.com with SMTP id io19so2070634plb.8 for ; Thu, 17 Nov 2022 08:25:00 -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=PWEXkOCkwXXMGqCPYq1KccYYNIXFmgDqg+Pvxcs/nb0=; b=K3XM6StXg30BTtPAfiWC0GTDIAebVGeEWI0M8OGb+NAv0YgZMqCk/gpOro7BkrvKyf U0OFg8fsMHOje7K4PlGp2cLuRkaq59FwD/z02c8YuygTd10ztbvazMrxPm9NDQYhN1IW cpWZiAjJJc1wLYnlyvyuGZD9F9YdRu/I4K/q75Rd2Pk5BABj1dEJrdBuyl6g3ODldTjZ N0W1iUPI3318Gl1xjHSAhMzp+I1qwOXnDSsdmjhNUl1icFimaiM75q/fxS+hrVh4iqiZ Cyu5fdSmMa/dAnY940HCLaUvkEIHv7D3MzyFQVGcXoD9GuWY5BQyHuSd/o6pTlpfUrMq 3Yng== 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=PWEXkOCkwXXMGqCPYq1KccYYNIXFmgDqg+Pvxcs/nb0=; b=MI9N7tpejJXhkL/ftQWdrZP1SRaXfR6UYBgcNMF/gtlIFiTeRRQsv5KabSIUum2Hbg 1N2PSL/bwtsbkpRMVbb2/k1cS0bV7PAOTUkSa/1V90Kdb35CD4JfNQ4OTjBKJHPDtiqt haxj2wa7e56vlK3G4Qgps0cmaOYBTrzQCjlGm0ScPahUkvBw1d3D4mv9r/6Uf86FRQVJ QyB9nebgUbhdTpyK708B8Aa+WTaY/W3G0JNmemrM3J6MoBt9A0VdhG+N3KfwHuhqbwQD sHpkSJidTwnzRIEU1usKvMg0l3x9gGtmrygYyXkuCc/o3/3caeiOPaRBSMP3yCVcpIyZ P5UQ== X-Gm-Message-State: ANoB5pl6c63n9WTg84ZuoopIDN5QujVaHm503JczHVYzVKvxFXFjeIxa Buog18gtdlaU5Gr4CrAuC7wnD0glTbQ= X-Google-Smtp-Source: AA0mqf5zATWwnAsSk8GigNC5yrItIN9ZI98D95nKC1yf/S/n7jO/Jg0udee5KCKkeM6+NMHswV5z9Q== X-Received: by 2002:a17:902:f10c:b0:176:d217:7e68 with SMTP id e12-20020a170902f10c00b00176d2177e68mr3441360plb.63.1668702300055; Thu, 17 Nov 2022 08:25:00 -0800 (PST) Received: from localhost ([103.4.221.252]) by smtp.gmail.com with ESMTPSA id s184-20020a625ec1000000b0056ba7ce4d5asm1360283pfb.52.2022.11.17.08.24.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 17 Nov 2022 08:24:59 -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 05/22] bpf: Introduce allocated objects support Date: Thu, 17 Nov 2022 21:54:13 +0530 Message-Id: <20221117162430.1213770-6-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=4893; i=memxor@gmail.com; h=from:subject; bh=CH78Zd/IJvjHgHBfOoFLama9Di30yIFuK7q41JG0EwY=; b=owEBbQKS/ZANAwAIAUzgyIZIvxHKAcsmYgBjdl7+vyj8qoLXn8SBnLP6GEcvcJHFXCZz8PQsm62f aOxmK1KJAjMEAAEIAB0WIQRLvip+Buz51YI8YRFM4MiGSL8RygUCY3Ze/gAKCRBM4MiGSL8RysjHD/ 429vc8a7oiiz4vlvJbcVv1xsY3wLTt1iBRzD8uMRS69pE34ENNzFHM2DrxfDRmsoOdw/FANUSm5qSJ i+kjSK6dat/G1JRTFRQC8yEgCSUI6gzfpD4j0n49n7x+9pG5wkrUVcjS7pvARojmn5+HUM/RJk4TQU Fa3rUIR8cVBBkb+HTlBcAxbaFbB/HuefsA64lcaHQXTjfKbI6kMwSkeZTqTvUAAU7oxDWh74oKNl+5 2eGLyHSaza34sQneGYTRviHkNLz+JhP6WCuXfjnmSWHGFlVvBuun+vBf2pnZHmAD1vx4pHHICczMo8 zJyZUJUalND4/rMsJdHPJCzdN3mUuYvEZzJZhE1RGcYf+rUo2tsnns0pPY4mc9OXmCzgpZUngFCDIY P8qn4/MXCQdzxexymWC4CBhz0/gFg0FIRoZo3EVf+eZpdN9RCi4545kX+Ml5wLiUzmrTTSRd5w3Xm6 jgXIkOUzVCf1U2YkscH7jztZgERz1b0rdQw+4PstO4y63Pid2nsNtJa54kN80DXFodRX3mKpZ8F6Y2 1AlezhU+iuUzDkwi7mDLv6KtWN1VGjAmNMBO6dASZCGLkBvHD9B4BP9naxAhPywRrUEc3yprUDI3Vo o/q6yIH3YJHMg4GzGAfelFSZ8ukORaiJ90J7KvG9w2ct1PPEo+muX5FPktmg== 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 Introduce support for representing pointers to objects allocated by the BPF program, i.e. PTR_TO_BTF_ID that point to a type in program BTF. This is indicated by the presence of MEM_ALLOC type flag in reg->type to avoid having to check btf_is_kernel when trying to match argument types in helpers. Whenever walking such types, any pointers being walked will always yield a SCALAR instead of pointer. In the future we might permit kptr inside such allocated objects (either kernel or program allocated), and it will then form a PTR_TO_BTF_ID of the respective type. For now, such allocated objects will always be referenced in verifier context, hence ref_obj_id == 0 for them is a bug. It is allowed to write to such objects, as long fields that are special are not touched (support for which will be added in subsequent patches). Note that once such a pointer is marked PTR_UNTRUSTED, it is no longer allowed to write to it. No PROBE_MEM handling is therefore done for loads into this type unless PTR_UNTRUSTED is part of the register type, since they can never be in an undefined state, and their lifetime will always be valid. Signed-off-by: Kumar Kartikeya Dwivedi --- include/linux/bpf.h | 11 +++++++++++ kernel/bpf/btf.c | 5 +++++ kernel/bpf/verifier.c | 25 +++++++++++++++++++++++-- 3 files changed, 39 insertions(+), 2 deletions(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 54462dd28824..53c47c8c6230 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -524,6 +524,11 @@ enum bpf_type_flag { /* Size is known at compile time. */ MEM_FIXED_SIZE = BIT(10 + BPF_BASE_TYPE_BITS), + /* MEM is of an allocated object of type in program BTF. This is used to + * tag PTR_TO_BTF_ID allocated using bpf_obj_new. + */ + MEM_ALLOC = BIT(11 + BPF_BASE_TYPE_BITS), + __BPF_TYPE_FLAG_MAX, __BPF_TYPE_LAST_FLAG = __BPF_TYPE_FLAG_MAX - 1, }; @@ -2791,4 +2796,10 @@ struct bpf_key { bool has_ref; }; #endif /* CONFIG_KEYS */ + +static inline bool type_is_alloc(u32 type) +{ + return type & MEM_ALLOC; +} + #endif /* _LINUX_BPF_H */ diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 875355ff3718..9a596f430558 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -6034,6 +6034,11 @@ int btf_struct_access(struct bpf_verifier_log *log, switch (err) { case WALK_PTR: + /* For local types, the destination register cannot + * become a pointer again. + */ + if (type_is_alloc(reg->type)) + return SCALAR_VALUE; /* If we found the pointer or scalar on t+off, * we're done. */ diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 0312d9ce292f..49e08c1c2c61 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -4687,14 +4687,27 @@ static int check_ptr_to_btf_access(struct bpf_verifier_env *env, return -EACCES; } - if (env->ops->btf_struct_access) { + if (env->ops->btf_struct_access && !type_is_alloc(reg->type)) { + if (!btf_is_kernel(reg->btf)) { + verbose(env, "verifier internal error: reg->btf must be kernel btf\n"); + return -EFAULT; + } ret = env->ops->btf_struct_access(&env->log, reg, off, size, atype, &btf_id, &flag); } else { - if (atype != BPF_READ) { + /* Writes are permitted with default btf_struct_access for + * program allocated objects (which always have ref_obj_id > 0), + * but not for untrusted PTR_TO_BTF_ID | MEM_ALLOC. + */ + if (atype != BPF_READ && reg->type != (PTR_TO_BTF_ID | MEM_ALLOC)) { verbose(env, "only read is supported\n"); return -EACCES; } + if (type_is_alloc(reg->type) && !reg->ref_obj_id) { + verbose(env, "verifier internal error: ref_obj_id for allocated object must be non-zero\n"); + return -EFAULT; + } + ret = btf_struct_access(&env->log, reg, off, size, atype, &btf_id, &flag); } @@ -5973,6 +5986,7 @@ int check_func_arg_reg_off(struct bpf_verifier_env *env, * fixed offset. */ case PTR_TO_BTF_ID: + case PTR_TO_BTF_ID | MEM_ALLOC: /* When referenced PTR_TO_BTF_ID is passed to release function, * it's fixed offset must be 0. In the other cases, fixed offset * can be non-zero. @@ -13690,6 +13704,13 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env) break; case PTR_TO_BTF_ID: case PTR_TO_BTF_ID | PTR_UNTRUSTED: + /* PTR_TO_BTF_ID | MEM_ALLOC always has a valid lifetime, unlike + * PTR_TO_BTF_ID, and an active ref_obj_id, but the same cannot + * be said once it is marked PTR_UNTRUSTED, hence we must handle + * any faults for loads into such types. BPF_WRITE is disallowed + * for this case. + */ + case PTR_TO_BTF_ID | MEM_ALLOC | PTR_UNTRUSTED: if (type == BPF_READ) { insn->code = BPF_LDX | BPF_PROBE_MEM | BPF_SIZE((insn)->code);