From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0356AC433DF for ; Tue, 16 Jun 2020 10:06:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CD3FA20734 for ; Tue, 16 Jun 2020 10:06:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592301967; bh=136+XOOVraZ9FjGrfwW2i0WvsejAoXGO+zwRir+BXpo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=0kKO1eD7+jL1z5ZRfZnVvaEsi6VFbb2xwVcb6VVGZopHZIugCwv9ZOFkrl0KMNbK8 guy1QIphnEeLFPyVjvikhd8cadramBx2gYkARLVsIpwW8lt015xfIiphRSved07dpE mMmzvnJQwlrAMzthXHYQKEj6OzFgTZ8KbzkBeqeo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728395AbgFPKGF convert rfc822-to-8bit (ORCPT ); Tue, 16 Jun 2020 06:06:05 -0400 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:21457 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726805AbgFPKGD (ORCPT ); Tue, 16 Jun 2020 06:06:03 -0400 Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-333-tskNkK2nNAqO-yujiWa7jw-1; Tue, 16 Jun 2020 06:05:59 -0400 X-MC-Unique: tskNkK2nNAqO-yujiWa7jw-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id CD3888A636E; Tue, 16 Jun 2020 10:05:53 +0000 (UTC) Received: from krava.redhat.com (unknown [10.40.195.228]) by smtp.corp.redhat.com (Postfix) with ESMTP id A15FB5D9D5; Tue, 16 Jun 2020 10:05:49 +0000 (UTC) From: Jiri Olsa To: Alexei Starovoitov , Daniel Borkmann Cc: netdev@vger.kernel.org, bpf@vger.kernel.org, Song Liu , Yonghong Song , Martin KaFai Lau , David Miller , John Fastabend , Wenbo Zhang , KP Singh , Andrii Nakryiko , Brendan Gregg , Florent Revest , Al Viro Subject: [PATCH 07/11] bpf: Allow nested BTF object to be refferenced by BTF object + offset Date: Tue, 16 Jun 2020 12:05:08 +0200 Message-Id: <20200616100512.2168860-8-jolsa@kernel.org> In-Reply-To: <20200616100512.2168860-1-jolsa@kernel.org> References: <20200616100512.2168860-1-jolsa@kernel.org> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: kernel.org Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: 8BIT Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Adding btf_struct_address function that takes 2 BTF objects and offset as arguments and checks whether object A is nested in object B on given offset. This function is be used when checking the helper function PTR_TO_BTF_ID arguments. If the argument has an offset value, the btf_struct_address will check if the final address is the expected BTF ID. This way we can access nested BTF objects under PTR_TO_BTF_ID pointer type and pass them to helpers, while they still point to valid kernel BTF objects. Signed-off-by: Jiri Olsa --- include/linux/bpf.h | 3 +++ kernel/bpf/btf.c | 63 ++++++++++++++++++++++++++++++++++++++----- kernel/bpf/verifier.c | 32 ++++++++++++++-------- 3 files changed, 81 insertions(+), 17 deletions(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index b7d3b5f3dc09..e98c113a5d27 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -1283,6 +1283,9 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type, int btf_struct_access(struct bpf_verifier_log *log, const struct btf_type *t, int off, int size, u32 *next_btf_id); +int btf_struct_address(struct bpf_verifier_log *log, + const struct btf_type *t, + u32 off, u32 id); int btf_resolve_helper_id(struct bpf_verifier_log *log, const struct bpf_func_proto *fn, int); diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 304369a4c2e2..6924180a19c4 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -3829,9 +3829,22 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type, return true; } -int btf_struct_access(struct bpf_verifier_log *log, - const struct btf_type *t, int off, int size, - u32 *next_btf_id) +enum access_op { + ACCESS_NEXT, + ACCESS_EXPECT, +}; + +struct access_data { + enum access_op op; + union { + u32 *next_btf_id; + const struct btf_type *exp_type; + }; +}; + +static int struct_access(struct bpf_verifier_log *log, + const struct btf_type *t, int off, int size, + struct access_data *data) { u32 i, moff, mtrue_end, msize = 0, total_nelems = 0; const struct btf_type *mtype, *elem_type = NULL; @@ -3879,8 +3892,7 @@ int btf_struct_access(struct bpf_verifier_log *log, goto error; off = (off - moff) % elem_type->size; - return btf_struct_access(log, elem_type, off, size, - next_btf_id); + return struct_access(log, elem_type, off, size, data); error: bpf_log(log, "access beyond struct %s at off %u size %u\n", @@ -4008,9 +4020,21 @@ int btf_struct_access(struct bpf_verifier_log *log, /* adjust offset we're looking for */ off -= moff; + + /* We are nexting into another struct, + * check if we are crossing expected ID. + */ + if (data->op == ACCESS_EXPECT && !off && t == data->exp_type) + return 0; goto again; } + /* We are interested only in structs for expected ID, + * bail out. + */ + if (data->op == ACCESS_EXPECT) + return -EINVAL; + if (btf_type_is_ptr(mtype)) { const struct btf_type *stype; u32 id; @@ -4024,7 +4048,7 @@ int btf_struct_access(struct bpf_verifier_log *log, stype = btf_type_skip_modifiers(btf_vmlinux, mtype->type, &id); if (btf_type_is_struct(stype)) { - *next_btf_id = id; + *data->next_btf_id = id; return PTR_TO_BTF_ID; } } @@ -4048,6 +4072,33 @@ int btf_struct_access(struct bpf_verifier_log *log, return -EINVAL; } +int btf_struct_access(struct bpf_verifier_log *log, + const struct btf_type *t, int off, int size, + u32 *next_btf_id) +{ + struct access_data data = { + .op = ACCESS_NEXT, + .next_btf_id = next_btf_id, + }; + + return struct_access(log, t, off, size, &data); +} + +int btf_struct_address(struct bpf_verifier_log *log, + const struct btf_type *t, + u32 off, u32 id) +{ + struct access_data data = { .op = ACCESS_EXPECT }; + const struct btf_type *type; + + type = btf_type_by_id(btf_vmlinux, id); + if (!type) + return -EINVAL; + + data.exp_type = type; + return struct_access(log, t, off, 1, &data); +} + int btf_resolve_helper_id(struct bpf_verifier_log *log, const struct bpf_func_proto *fn, int arg) { diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index b553e4523bd3..bee3da2cd945 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -3741,6 +3741,7 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno, { struct bpf_reg_state *regs = cur_regs(env), *reg = ®s[regno]; enum bpf_reg_type expected_type, type = reg->type; + const struct btf_type *btf_type; int err = 0; if (arg_type == ARG_DONTCARE) @@ -3820,17 +3821,26 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno, expected_type = PTR_TO_BTF_ID; if (type != expected_type) goto err_type; - if (reg->btf_id != meta->btf_id) { - verbose(env, "Helper has type %s got %s in R%d\n", - kernel_type_name(meta->btf_id), - kernel_type_name(reg->btf_id), regno); - - return -EACCES; - } - if (!tnum_is_const(reg->var_off) || reg->var_off.value || reg->off) { - verbose(env, "R%d is a pointer to in-kernel struct with non-zero offset\n", - regno); - return -EACCES; + if (reg->off) { + btf_type = btf_type_by_id(btf_vmlinux, reg->btf_id); + if (btf_struct_address(&env->log, btf_type, reg->off, meta->btf_id)) { + verbose(env, "Helper has type %s got %s in R%d, off %d\n", + kernel_type_name(meta->btf_id), + kernel_type_name(reg->btf_id), regno, reg->off); + return -EACCES; + } + } else { + if (reg->btf_id != meta->btf_id) { + verbose(env, "Helper has type %s got %s in R%d\n", + kernel_type_name(meta->btf_id), + kernel_type_name(reg->btf_id), regno); + return -EACCES; + } + if (!tnum_is_const(reg->var_off) || reg->var_off.value) { + verbose(env, "R%d is a pointer to in-kernel struct with non-zero offset\n", + regno); + return -EACCES; + } } } else if (arg_type == ARG_PTR_TO_SPIN_LOCK) { if (meta->func_id == BPF_FUNC_spin_lock) { -- 2.25.4