From patchwork Fri Nov 11 19:32:06 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: 13040737 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 BA779C433FE for ; Fri, 11 Nov 2022 19:33:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233865AbiKKTdh (ORCPT ); Fri, 11 Nov 2022 14:33:37 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35348 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233828AbiKKTdg (ORCPT ); Fri, 11 Nov 2022 14:33:36 -0500 Received: from mail-pg1-x542.google.com (mail-pg1-x542.google.com [IPv6:2607:f8b0:4864:20::542]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1107712AD4 for ; Fri, 11 Nov 2022 11:33:35 -0800 (PST) Received: by mail-pg1-x542.google.com with SMTP id b62so5160882pgc.0 for ; Fri, 11 Nov 2022 11:33:35 -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=EkCP4Dony/PsvTJnx7VXRtAY09Fp+elLOavyTVsL+mM=; b=O6EEv9Zn/QdYjXyJkambhe8De3lN2lBQmXNkhVlUtGVpGEPtGa0B42FatsfrrPub37 wjD1aqT63Oo4uZxK8+f8Ic3Fw9IIMFsvyiE572gkpMqLhZlg299ERvbROPvVVoiqQcXK POi2I4yY6gntkzYN5+Pgbb+vTzBe6XecXro/jcsmCre3JLlU9s0lTvajslftKZ89Uu+d LnWStP6z3r3Ne/bfpDA3OqKYcE9oEsibotezHOUa3ZiTm3ZlYW6joIkN9XuuTFullnxM GdFbj9gkj7KwR/s74b8KMwfhds5997fuwLKuuCHeJafnqupgglL7KvKHDdbdy1CL7i33 G1wQ== 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=EkCP4Dony/PsvTJnx7VXRtAY09Fp+elLOavyTVsL+mM=; b=pgH3zfJgVI4i3DWUP1ehSssa/DlYu/lv7phNNmTsS0P/W8Z/HokjxPrfaIsslJXpto K3ZsggYB7NPqr/7+j3Qh7x7lw1YKYkI+mSAxLTH5MPk10OeeZKS2868QobWRKL7izuvP XHWjf0L3bIVVrpF+SetxZF1143iWGddFZA6h0CA3jk0YqPh+pY2bFO5Mt8eG+xhGCWCg ixYqvPdv466gmwwHj0FMSYWnaWTydtdPfjTEjYl7c9hXhZ7qG7z/fk05DmoTGDmB+AkM Lx6q2uqH9yQ0IfhK6mDDmfHBhHI0LaQD9Q0VXOJNkVdczADasa/cy9hzj83dSD4aj/gA tyOQ== X-Gm-Message-State: ANoB5plwebz8lG8zWkxID6lSF/Z1o6QxqfT1sB7DdEJ4y75qUVYajBv5 XUTUqX0i2cof/OKEyUSRm4kJ2UclK6mZFg== X-Google-Smtp-Source: AA0mqf6jF0yHfS4VbGr42Dg87w+qb37XiIdNf3nmDXbtWnuF6xjenR+C9M2/J6v7TOfEdEXHoYn1uw== X-Received: by 2002:a63:1665:0:b0:426:9c23:9f94 with SMTP id 37-20020a631665000000b004269c239f94mr2929036pgw.105.1668195214260; Fri, 11 Nov 2022 11:33:34 -0800 (PST) Received: from localhost ([14.96.13.220]) by smtp.gmail.com with ESMTPSA id u3-20020a170902e80300b00172e19c5f8bsm2089877plg.168.2022.11.11.11.33.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 11 Nov 2022 11:33:33 -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 08/26] bpf: Introduce allocated objects support Date: Sat, 12 Nov 2022 01:02:06 +0530 Message-Id: <20221111193224.876706-9-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=4871; i=memxor@gmail.com; h=from:subject; bh=meS7gQZTEGq/DUEJpmd9jyqWTUThhVE5S28cbBs7iUA=; b=owEBbQKS/ZANAwAIAUzgyIZIvxHKAcsmYgBjbqIo0xyMZd3AtlXePT7oI/kJPUEhIBQ1Tl7N1l1f t0tz1JaJAjMEAAEIAB0WIQRLvip+Buz51YI8YRFM4MiGSL8RygUCY26iKAAKCRBM4MiGSL8Ryk17EA CZIAsithALdp/QdbU9kHEYOH1EgKJlh4WqdQ5Wecvz4eFTDOcfFtnXwCFwOzWKvYIsDaTuOGu60yXO NR5aDUaxVmFOyuhU/XCX7yMHKXl1qg4f7e7D28C1nl0uPiYN4Y8hgMpdNpPybQEbKm1aLlrJWm8QaX H+7IIZwewP844hw+sd8adNWMsDP0wKcKBrXzotf/aX6u+Qdgqke1jazmZdoJ2JlMPHm1aR3lEhINAe OPiz6ulKw0AtYzLGzLsWl7u0qqqu120KCvkIj9VeVvL1LBh9xwKHYwBawiA+04mlvkBJ2SZUaPfY9n XdAQf23GfT1kIWJOz4+O/5adfe8FKFtJGOc2+oDb4tTP37Ona3z0XH+KfeAISvrO3HuStEvtvQegaH sFeDadm+KXpYO4sMhgdOUi92D/sYWwm1WBXl+ofKu9PI/3WHfgqQVdTdJcDd810Xyp2ywZNoqNkFSr kyn4PBEJC750ltQi4XGtqdSzXzMTyGkNkK6X1OjPQxbvfwGbaXngNF1hStspqPovOZwWIpUB0sbK4B HHa2+UFNUywdpFuh7cOn/CVrYtXpgha1CPxCo6LmuDex0JBsbdAf5HghwBC3oPluFWCkPPo/8LhtWA YYPWmJNa+J/SNByItwugDIdOUz9I5/JyFY+HPlsD4zR1oYDqv0X4swBakfeQ== 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 local), 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 49f9d2bec401..3cab113b149e 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 a an allocated object of type from 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 bbbb0f27c7d1..5cf14c1391a5 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -4682,14 +4682,27 @@ 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 local + * kptrs (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); } @@ -5968,6 +5981,7 @@ 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. @@ -13650,6 +13664,13 @@ 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);