From patchwork Wed May 6 13:29:41 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jiri Olsa X-Patchwork-Id: 219776 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 7569BC47256 for ; Wed, 6 May 2020 13:30:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4597D20575 for ; Wed, 6 May 2020 13:30:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588771821; bh=7ieu6Wy3OIv/IuQ2nZzXG92ko/1vesi/1A0bznDF78A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=RE20VaMGt8w/7vcFz2We2FZ/t2VFAD4/91VovGnfC+fdwigpNU7hyOFQK8hZRm149 Ju9r9ebpDp2a4UTCqKolAhYbDGUztm7PNzysSxl5x56RyZcX5P5ez+/cVRymnVpWvR oT2VQTUskomQMS3YxODNpsG8Y0qu7eZqjPGMtsag= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728665AbgEFNaU convert rfc822-to-8bit (ORCPT ); Wed, 6 May 2020 09:30:20 -0400 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:37191 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728483AbgEFNaU (ORCPT ); Wed, 6 May 2020 09:30:20 -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-459-w_mcWS0RPaiftR-2fN3aAQ-1; Wed, 06 May 2020 09:30:11 -0400 X-MC-Unique: w_mcWS0RPaiftR-2fN3aAQ-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 65FCC460; Wed, 6 May 2020 13:30:09 +0000 (UTC) Received: from krava.redhat.com (unknown [10.40.192.32]) by smtp.corp.redhat.com (Postfix) with ESMTP id 10A3F64430; Wed, 6 May 2020 13:30:02 +0000 (UTC) From: Jiri Olsa To: Alexei Starovoitov , Daniel Borkmann Cc: netdev@vger.kernel.org, bpf@vger.kernel.org, Yonghong Song , Martin KaFai Lau , David Miller , John Fastabend , Jesper Dangaard Brouer , Wenbo Zhang , KP Singh , Andrii Nakryiko , bgregg@netflix.com, Florent Revest , Al Viro Subject: [PATCH 4/9] bpf: Allow nested BTF object to be refferenced by BTF object + offset Date: Wed, 6 May 2020 15:29:41 +0200 Message-Id: <20200506132946.2164578-5-jolsa@kernel.org> In-Reply-To: <20200506132946.2164578-1-jolsa@kernel.org> References: <20200506132946.2164578-1-jolsa@kernel.org> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 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_address function that takes 2 BTF objects and offset as arguments and checks wether 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 | 69 +++++++++++++++++++++++++++++++++++++++++++ kernel/bpf/verifier.c | 32 +++++++++++++------- 3 files changed, 94 insertions(+), 10 deletions(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 1262ec460ab3..bc589cdd8c34 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -1213,6 +1213,9 @@ 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); +int btf_struct_address(struct bpf_verifier_log *log, + const struct btf_type *t, + u32 off, u32 exp_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 a2cfba89a8e1..07f22469acab 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -4004,6 +4004,75 @@ int btf_struct_access(struct bpf_verifier_log *log, return -EINVAL; } +int btf_struct_address(struct bpf_verifier_log *log, + const struct btf_type *t, + u32 off, u32 exp_id) +{ + u32 i, moff, mtrue_end, msize = 0; + const struct btf_member *member; + const struct btf_type *mtype; + const char *tname, *mname; + +again: + tname = __btf_name_by_offset(btf_vmlinux, t->name_off); + if (!btf_type_is_struct(t)) { + bpf_log(log, "Type '%s' is not a struct\n", tname); + return -EINVAL; + } + + if (off > t->size) { + bpf_log(log, "address beyond struct %s at off %u size %u\n", + tname, off, t->size); + return -EACCES; + } + + for_each_member(i, t, member) { + /* offset of the field in bytes */ + moff = btf_member_bit_offset(t, member) / 8; + if (off < moff) + /* won't find anything, field is already too far */ + break; + + /* we found the member */ + if (off == moff && member->type == exp_id) + return 0; + + /* type of the field */ + mtype = btf_type_by_id(btf_vmlinux, member->type); + mname = __btf_name_by_offset(btf_vmlinux, member->name_off); + + mtype = btf_resolve_size(btf_vmlinux, mtype, &msize, + NULL, NULL); + if (IS_ERR(mtype)) { + bpf_log(log, "field %s doesn't have size\n", mname); + return -EFAULT; + } + + mtrue_end = moff + msize; + if (off >= mtrue_end) + /* no overlap with member, keep iterating */ + continue; + + /* the 'off' we're looking for is either equal to start + * of this field or inside of this struct + */ + if (btf_type_is_struct(mtype)) { + /* our field must be inside that union or struct */ + t = mtype; + + /* adjust offset we're looking for */ + off -= moff; + goto again; + } + + bpf_log(log, "struct %s doesn't have struct field at offset %d\n", tname, off); + return -EACCES; + } + + bpf_log(log, "struct %s doesn't have field at offset %d\n", tname, off); + return -EACCES; +} + static int __btf_resolve_helper_id(struct bpf_verifier_log *log, void *fn, int arg) { diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 70ad009577f8..b988df5ada20 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -3665,6 +3665,7 @@ 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) @@ -3743,17 +3744,28 @@ 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); + 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; - } - 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; + 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) {