From patchwork Fri Mar 19 12:18:43 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "gregkh@linuxfoundation.org" X-Patchwork-Id: 405411 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=ham 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 D7B8EC4332E for ; Fri, 19 Mar 2021 12:20:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AB4E564F75 for ; Fri, 19 Mar 2021 12:20:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230204AbhCSMTk (ORCPT ); Fri, 19 Mar 2021 08:19:40 -0400 Received: from mail.kernel.org ([198.145.29.99]:56938 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230153AbhCSMTP (ORCPT ); Fri, 19 Mar 2021 08:19:15 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 820B964F6C; Fri, 19 Mar 2021 12:19:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1616156355; bh=xdqez2M8PZhhoNJcWin0B4KUfGQky0l/PGiEm4W2sqo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=OYrVU1m9ZCmHQZ6xlOl9weJIlXiRQZfhLiA9FsEVakNTBOYd/Jij6uaLOg8CUoCvk ru6uIyVomvlakeD5+LIXAyEcsYoUrOj5CKXPAtKn0u/oIhRpixkCeh67UQRpJ/TE+8 bq1Zny/Zqckj1/5x0apQXnZZfUkmRVFkb8z1bWKU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Piotr Krysiuk , Daniel Borkmann , Alexei Starovoitov Subject: [PATCH 5.4 05/18] bpf: Add sanity check for upper ptr_limit Date: Fri, 19 Mar 2021 13:18:43 +0100 Message-Id: <20210319121745.633988469@linuxfoundation.org> X-Mailer: git-send-email 2.31.0 In-Reply-To: <20210319121745.449875976@linuxfoundation.org> References: <20210319121745.449875976@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Piotr Krysiuk commit 1b1597e64e1a610c7a96710fc4717158e98a08b3 upstream. Given we know the max possible value of ptr_limit at the time of retrieving the latter, add basic assertions, so that the verifier can bail out if anything looks odd and reject the program. Nothing triggered this so far, but it also does not hurt to have these. Signed-off-by: Piotr Krysiuk Co-developed-by: Daniel Borkmann Signed-off-by: Daniel Borkmann Acked-by: Alexei Starovoitov Signed-off-by: Greg Kroah-Hartman --- kernel/bpf/verifier.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -4268,10 +4268,14 @@ static int retrieve_ptr_limit(const stru { bool mask_to_left = (opcode == BPF_ADD && off_is_neg) || (opcode == BPF_SUB && !off_is_neg); - u32 off; + u32 off, max; switch (ptr_reg->type) { case PTR_TO_STACK: + /* Offset 0 is out-of-bounds, but acceptable start for the + * left direction, see BPF_REG_FP. + */ + max = MAX_BPF_STACK + mask_to_left; /* Indirect variable offset stack access is prohibited in * unprivileged mode so it's not handled here. */ @@ -4280,15 +4284,16 @@ static int retrieve_ptr_limit(const stru *ptr_limit = MAX_BPF_STACK + off; else *ptr_limit = -off - 1; - return 0; + return *ptr_limit >= max ? -ERANGE : 0; case PTR_TO_MAP_VALUE: + max = ptr_reg->map_ptr->value_size; if (mask_to_left) { *ptr_limit = ptr_reg->umax_value + ptr_reg->off; } else { off = ptr_reg->smin_value + ptr_reg->off; *ptr_limit = ptr_reg->map_ptr->value_size - off - 1; } - return 0; + return *ptr_limit >= max ? -ERANGE : 0; default: return -EINVAL; }