From patchwork Fri Apr 30 14:20:19 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 12233523 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 X-Spam-Level: X-Spam-Status: No, score=-19.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT 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 A50CDC43618 for ; Fri, 30 Apr 2021 14:20:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 884626147D for ; Fri, 30 Apr 2021 14:20:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232913AbhD3OVd (ORCPT ); Fri, 30 Apr 2021 10:21:33 -0400 Received: from mail.kernel.org ([198.145.29.99]:57648 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232905AbhD3OVc (ORCPT ); Fri, 30 Apr 2021 10:21:32 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 93002613A9; Fri, 30 Apr 2021 14:20:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1619792440; bh=uN46wmyB98/4ZxDkobe5sC072+jaI5/2HNFrPvkCwek=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=btnR9zwvYsqF/zXXfhPdq0glZxIiyifbqpt2JXM31BeMS2m/aWFKpsaCwP1rEeKrI cBpVhHEiu+rY9YdM38PSepw0ekFGmJsCC9f0pGAjib8k11oazVCD7xTAM4YMb2AVbP a/UHQCPuaMsfuDD0nHMx+sXfBs6LYInosEaJ7Iac= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Greg Kroah-Hartman , bpf@vger.kernel.org, Daniel Borkmann , John Fastabend , Alexei Starovoitov , Frank van der Linden Subject: [PATCH 5.4 5/8] bpf: Refactor and streamline bounds check into helper Date: Fri, 30 Apr 2021 16:20:19 +0200 Message-Id: <20210430141911.335781665@linuxfoundation.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210430141911.137473863@linuxfoundation.org> References: <20210430141911.137473863@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net From: Daniel Borkmann commit 073815b756c51ba9d8384d924c5d1c03ca3d1ae4 upstream. Move the bounds check in adjust_ptr_min_max_vals() into a small helper named sanitize_check_bounds() in order to simplify the former a bit. Signed-off-by: Daniel Borkmann Reviewed-by: John Fastabend Acked-by: Alexei Starovoitov [fllinden@amazon.com: backport to 5.4] Signed-off-by: Frank van der Linden Signed-off-by: Greg Kroah-Hartman --- kernel/bpf/verifier.c | 54 ++++++++++++++++++++++++++++++++++---------------- 1 file changed, 37 insertions(+), 17 deletions(-) --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -4448,6 +4448,41 @@ static int sanitize_err(struct bpf_verif return -EACCES; } +static int sanitize_check_bounds(struct bpf_verifier_env *env, + const struct bpf_insn *insn, + const struct bpf_reg_state *dst_reg) +{ + u32 dst = insn->dst_reg; + + /* For unprivileged we require that resulting offset must be in bounds + * in order to be able to sanitize access later on. + */ + if (env->allow_ptr_leaks) + return 0; + + switch (dst_reg->type) { + case PTR_TO_STACK: + if (check_stack_access(env, dst_reg, dst_reg->off + + dst_reg->var_off.value, 1)) { + verbose(env, "R%d stack pointer arithmetic goes out of range, " + "prohibited for !root\n", dst); + return -EACCES; + } + break; + case PTR_TO_MAP_VALUE: + if (check_map_access(env, dst, dst_reg->off, 1, false)) { + verbose(env, "R%d pointer arithmetic of map value goes out of range, " + "prohibited for !root\n", dst); + return -EACCES; + } + break; + default: + break; + } + + return 0; +} + /* Handles arithmetic on a pointer and a scalar: computes new min/max and var_off. * Caller should also handle BPF_MOV case separately. * If we return -EACCES, caller may want to try again treating pointer as a @@ -4664,23 +4699,8 @@ static int adjust_ptr_min_max_vals(struc __reg_deduce_bounds(dst_reg); __reg_bound_offset(dst_reg); - /* For unprivileged we require that resulting offset must be in bounds - * in order to be able to sanitize access later on. - */ - if (!env->allow_ptr_leaks) { - if (dst_reg->type == PTR_TO_MAP_VALUE && - check_map_access(env, dst, dst_reg->off, 1, false)) { - verbose(env, "R%d pointer arithmetic of map value goes out of range, " - "prohibited for !root\n", dst); - return -EACCES; - } else if (dst_reg->type == PTR_TO_STACK && - check_stack_access(env, dst_reg, dst_reg->off + - dst_reg->var_off.value, 1)) { - verbose(env, "R%d stack pointer arithmetic goes out of range, " - "prohibited for !root\n", dst); - return -EACCES; - } - } + if (sanitize_check_bounds(env, insn, dst_reg) < 0) + return -EACCES; return 0; }