From patchwork Thu Nov 17 22:54:52 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: 13047430 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 BBEF9C433FE for ; Thu, 17 Nov 2022 22:55:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234802AbiKQWzj (ORCPT ); Thu, 17 Nov 2022 17:55:39 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53078 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234954AbiKQWzh (ORCPT ); Thu, 17 Nov 2022 17:55:37 -0500 Received: from mail-pl1-x644.google.com (mail-pl1-x644.google.com [IPv6:2607:f8b0:4864:20::644]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 72CF862CE for ; Thu, 17 Nov 2022 14:55:36 -0800 (PST) Received: by mail-pl1-x644.google.com with SMTP id y10so1802528plp.3 for ; Thu, 17 Nov 2022 14:55:36 -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=/dEo1al8fIigkT4udLYOJzh2efBnOQsqXleDSugVnjg=; b=dT4mH/aISJwAAmAGzhZjNFy4ouoCf63hy6duiDZCR1XlVHOFA2D6DmzE55dIBjyXBQ e4BvQKZ7t4z7kBMgO+B7ZKq7MA8TOmBXxE1korCsByO0YjA6y6mIG2+ELj1NMgCSZLsg d7W7UMT8wxkUKCVeZgZxJJSpcomEuwiBaatGO+Ek363x15JOvejuKT6AhUDoLuOi7jZ/ hUo8e2oCAs8kMUmQcjEHjqdPGiDf4NFET8SA5ybklP/zyhsyb2acILhJ6BFGQQaRoKu6 hqCIfexpTEKqI6E/oFPJPnElZATG37uY7wu/ojxQa/31n+wdz3q1ACSzHqf4j7ZaJgPH /gGQ== 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=/dEo1al8fIigkT4udLYOJzh2efBnOQsqXleDSugVnjg=; b=ZM2u0jp+14pOqLqjdp4lH9Bth6Kpt/Ev8iZpqhF0Bnt806vGgMCJcxg/t8elZKkhv0 5xu2MuaRYqi34b1dicjp8KhjtTp5ZXKxTP4qgh59D+FXmO0k3DgVH5udCr4lzEwOIYVe ke3YBpPKC2m97nszszzPcHDB3icq2WrVHN4eeN/kbVRTtODqUiCMaFoC4k055o/GdINg 8Tbjc9yrsUHCO6n9AdmYrxuXNimu+2xGykTGskvak5FKoA2r7PK1Fp2Kf8w9zDvci8ic rlcGzHtlbkDfltryU92CLKLhh8LftQWkN9p5iGSmOWzLRboDvD9Av+rSTkV5r2WgAmjX 4Qxw== X-Gm-Message-State: ANoB5pm3wLvqdbf/yH3bw0mP9eOEocKdZouWIXb0tuEMUrb5w8g+ZYFA RWo0vh4V4JBumDX8/AMlfJ3Rj9HWwe0= X-Google-Smtp-Source: AA0mqf7x/HMmU9y1c/0rMCouwiVCeyEOEvSUJ4MzFqNKn9UX0CreS5jwCy+/qRezEfB6K2f9BMMMAg== X-Received: by 2002:a17:90a:5607:b0:218:7d9e:f8ed with SMTP id r7-20020a17090a560700b002187d9ef8edmr1998465pjf.160.1668725735753; Thu, 17 Nov 2022 14:55:35 -0800 (PST) Received: from localhost ([2409:40f4:8:955c:5484:8048:c08:7b3]) by smtp.gmail.com with ESMTPSA id g28-20020aa79f1c000000b0056da2bf607csm1624238pfr.214.2022.11.17.14.55.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 17 Nov 2022 14:55:34 -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 v9 05/23] bpf: Introduce allocated objects support Date: Fri, 18 Nov 2022 04:24:52 +0530 Message-Id: <20221117225510.1676785-6-memxor@gmail.com> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221117225510.1676785-1-memxor@gmail.com> References: <20221117225510.1676785-1-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=bHOSzfm0SbGE8NR+y0cBZt0ThH4SH0n2SmsrPhxvaV8=; b=owEBbQKS/ZANAwAIAUzgyIZIvxHKAcsmYgBjdrkbKMre9cC5HaqcRxm4o8C4RgWVPDo7F/cJZ0b4 oQX18jiJAjMEAAEIAB0WIQRLvip+Buz51YI8YRFM4MiGSL8RygUCY3a5GwAKCRBM4MiGSL8RysrzD/ 4j1CjfwmwzVoHfRmJAAtn3p22t2JFXytPdaEhT0957reUeOVTI8ezvXG65J+q90sV62QAk7TXxmsvn /ZubeevxUN/pdKRF3REgDNrWgegJuRalsvmtwtx5Gf/95oNnblOLxIfElRND/W3Jt4u63z9Isu3RJS zFUEDEkLOe9QUOUCfrCbZrrZNJ4yn5Hqr83EYbvrVlKlccaGCFBa+oFxSaTGh3u+tZn1PsxVKjPk2O yceXO4OuU4n0QENIjVD5bZUQcB55p8/DC/vDNKjH5w/DQT2Cg/Xf8RfOlH8ON6NsMX83TrM7/iU/Wj NKAJryv0+060X84UUgE821cJqL1mY9tuOtB+y/2UYlqeb14VtHhjCnhAvAebL4ILJvOyWMM3AzvcJ8 OKDfWGo6lfNSi1Ea4cDHuTMroYkBCJZJE1cW3G4aKtZWJl03bFfE/v6LSHEiYjcoTP74UNcwUqczOB CZICp3Vv4fyfMLwELzH3dHGRVxt7hNDyPnDYAhhaqFrlrFY7urcyZ8jT4N2W5J1CnZMDpDtLkVq1QO IhKeDqEuJJRju6wJFdiNx0ZVGecezVLYBYf1t3NPjL7FpYiuXtjnR+DPx4dhIClDcKgITkRwgOdqiC riglKinTgqDRO6NB2wJVay0Q8jgN5gsRPMFRsGdzO0ujlol91s75ZJwRiUJw== 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 e60a5c052473..7440c20c4192 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -525,6 +525,11 @@ 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, }; @@ -2792,4 +2797,10 @@ 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);