From patchwork Wed Jul 22 21:12:17 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jiri Olsa X-Patchwork-Id: 1334173 X-Patchwork-Delegate: bpf@iogearbox.net Return-Path: X-Original-To: patchwork-incoming-netdev@ozlabs.org Delivered-To: patchwork-incoming-netdev@ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org (client-ip=23.128.96.18; helo=vger.kernel.org; envelope-from=netdev-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=pass (p=none dis=none) header.from=kernel.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by ozlabs.org (Postfix) with ESMTP id 4BBp8Z745bz9sRR for ; Thu, 23 Jul 2020 07:13:02 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732944AbgGVVNC convert rfc822-to-8bit (ORCPT ); Wed, 22 Jul 2020 17:13:02 -0400 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:56052 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1732919AbgGVVNB (ORCPT ); Wed, 22 Jul 2020 17:13:01 -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-329-NJ2TPhdBO0KIYlch7ka9RA-1; Wed, 22 Jul 2020 17:12:54 -0400 X-MC-Unique: NJ2TPhdBO0KIYlch7ka9RA-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id D34C98015F3; Wed, 22 Jul 2020 21:12:52 +0000 (UTC) Received: from krava.redhat.com (unknown [10.40.194.40]) by smtp.corp.redhat.com (Postfix) with ESMTP id CEA0919C4F; Wed, 22 Jul 2020 21:12:49 +0000 (UTC) From: Jiri Olsa To: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko Cc: netdev@vger.kernel.org, bpf@vger.kernel.org, Song Liu , Yonghong Song , Martin KaFai Lau , David Miller , John Fastabend , Wenbo Zhang , KP Singh , Brendan Gregg , Florent Revest , Al Viro Subject: [PATCH v8 bpf-next 07/13] bpf: Add btf_struct_ids_match function Date: Wed, 22 Jul 2020 23:12:17 +0200 Message-Id: <20200722211223.1055107-8-jolsa@kernel.org> In-Reply-To: <20200722211223.1055107-1-jolsa@kernel.org> References: <20200722211223.1055107-1-jolsa@kernel.org> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: kernel.org Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Adding btf_struct_ids_match function to check if given address provided by BTF object + offset is also address of another nested BTF object. This allows to pass an argument to helper, which is defined via parent BTF object + offset, like for bpf_d_path (added in following changes): SEC("fentry/filp_close") int BPF_PROG(prog_close, struct file *file, void *id) { ... ret = bpf_d_path(&file->f_path, ... The first bpf_d_path argument is hold by verifier as BTF file object plus offset of f_path member. The btf_struct_ids_match function will walk the struct file object and check if there's nested struct path object on the given offset. Signed-off-by: Jiri Olsa --- include/linux/bpf.h | 2 ++ kernel/bpf/btf.c | 29 +++++++++++++++++++++++++++++ kernel/bpf/verifier.c | 18 ++++++++++++------ 3 files changed, 43 insertions(+), 6 deletions(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index bae557ff2da8..c981e258fed3 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -1306,6 +1306,8 @@ int btf_struct_access(struct bpf_verifier_log *log, const struct btf_type *t, int off, int size, enum bpf_access_type atype, u32 *next_btf_id); +bool btf_struct_ids_match(struct bpf_verifier_log *log, + int off, u32 id, u32 mid); 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 1ab5fd5bf992..562d4453fad3 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -4140,6 +4140,35 @@ int btf_struct_access(struct bpf_verifier_log *log, return -EINVAL; } +bool btf_struct_ids_match(struct bpf_verifier_log *log, + int off, u32 id, u32 mid) +{ + const struct btf_type *type; + u32 nid; + int err; + + do { + type = btf_type_by_id(btf_vmlinux, id); + if (!type) + return false; + err = btf_struct_walk(log, type, off, 1, &nid); + if (err < 0) + return false; + + /* We found nested struct object. If it matches + * the requested ID, we're done. Otherwise let's + * continue the search with offset 0 in the new + * type. + */ + if (err == walk_struct && mid == nid) + return true; + off = 0; + id = nid; + } while (err == walk_struct); + + return false; +} + 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 9a6703bc3f36..39922fa07154 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -3887,16 +3887,21 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg, goto err_type; } } else if (arg_type == ARG_PTR_TO_BTF_ID) { + bool ids_match = false; + expected_type = PTR_TO_BTF_ID; if (type != expected_type) goto err_type; if (!fn->check_btf_id) { 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; + ids_match = btf_struct_ids_match(&env->log, reg->off, reg->btf_id, + meta->btf_id); + if (!ids_match) { + 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; + } } } else if (!fn->check_btf_id(reg->btf_id, arg)) { verbose(env, "Helper does not support %s in R%d\n", @@ -3904,7 +3909,8 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg, return -EACCES; } - if (!tnum_is_const(reg->var_off) || reg->var_off.value || reg->off) { + if (!ids_match && + (!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;