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,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,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 28134C2F3A0 for ; Mon, 21 Jan 2019 13:57:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EADE120879 for ; Mon, 21 Jan 2019 13:57:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548079035; bh=Ewe9QbfyG+Lq24Fb9cccT3hHP+2oZJbqCDgErkU0nxw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Q7e1j/3b2VsYz0YI0o7zk4Wi8D3vWByYmBv9wduZwIFgP9dpsP2Ow1Ds4VMViI4Zx GYT6gZ3zpqfMA0jPQSIwKXjNN/Jy241V5IThRKwYaGkQ0b9ZerLTgd9TETEc7ENoAg Ik9pC6suDBSKKwENyvRzrFb9uZthWcljijzebDWc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731971AbfAUN4h (ORCPT ); Mon, 21 Jan 2019 08:56:37 -0500 Received: from mail.kernel.org ([198.145.29.99]:40298 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731746AbfAUNze (ORCPT ); Mon, 21 Jan 2019 08:55:34 -0500 Received: from localhost (5356596B.cm-6-7b.dynamic.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2E7C92087F; Mon, 21 Jan 2019 13:55:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548078933; bh=Ewe9QbfyG+Lq24Fb9cccT3hHP+2oZJbqCDgErkU0nxw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=u7twAyYCtB5DAnXbs3M+1NEbMtXFJ8DpmepXBqo4Vwhqp7iAMRkrThVojahr89zJj rhYHl8usWbtvnFQV1R14qySSLG3mgD/tZJdYpIOzpli6EVvM5Aaxhp2Csmk9bSyWMu Mh6ThcI5iD5rqbcB5/OPLqarGU3dBjQT5PStXO08= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Muyu Yu , Marcus Meissner , Michal Kubecek , Oliver Hartkopp , Marc Kleine-Budde , "David S. Miller" Subject: [PATCH 4.9 05/51] can: gw: ensure DLC boundaries after CAN frame modification Date: Mon, 21 Jan 2019 14:44:01 +0100 Message-Id: <20190121122454.024021655@linuxfoundation.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190121122453.700446926@linuxfoundation.org> References: <20190121122453.700446926@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Oliver Hartkopp commit 0aaa81377c5a01f686bcdb8c7a6929a7bf330c68 upstream. Muyu Yu provided a POC where user root with CAP_NET_ADMIN can create a CAN frame modification rule that makes the data length code a higher value than the available CAN frame data size. In combination with a configured checksum calculation where the result is stored relatively to the end of the data (e.g. cgw_csum_xor_rel) the tail of the skb (e.g. frag_list pointer in skb_shared_info) can be rewritten which finally can cause a system crash. Michael Kubecek suggested to drop frames that have a DLC exceeding the available space after the modification process and provided a patch that can handle CAN FD frames too. Within this patch we also limit the length for the checksum calculations to the maximum of Classic CAN data length (8). CAN frames that are dropped by these additional checks are counted with the CGW_DELETED counter which indicates misconfigurations in can-gw rules. This fixes CVE-2019-3701. Reported-by: Muyu Yu Reported-by: Marcus Meissner Suggested-by: Michal Kubecek Tested-by: Muyu Yu Tested-by: Oliver Hartkopp Signed-off-by: Oliver Hartkopp Cc: linux-stable # >= v3.2 Signed-off-by: Marc Kleine-Budde Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/can/gw.c | 30 +++++++++++++++++++++++++++--- 1 file changed, 27 insertions(+), 3 deletions(-) --- a/net/can/gw.c +++ b/net/can/gw.c @@ -418,13 +418,29 @@ static void can_can_gw_rcv(struct sk_buf while (modidx < MAX_MODFUNCTIONS && gwj->mod.modfunc[modidx]) (*gwj->mod.modfunc[modidx++])(cf, &gwj->mod); - /* check for checksum updates when the CAN frame has been modified */ + /* Has the CAN frame been modified? */ if (modidx) { - if (gwj->mod.csumfunc.crc8) + /* get available space for the processed CAN frame type */ + int max_len = nskb->len - offsetof(struct can_frame, data); + + /* dlc may have changed, make sure it fits to the CAN frame */ + if (cf->can_dlc > max_len) + goto out_delete; + + /* check for checksum updates in classic CAN length only */ + if (gwj->mod.csumfunc.crc8) { + if (cf->can_dlc > 8) + goto out_delete; + (*gwj->mod.csumfunc.crc8)(cf, &gwj->mod.csum.crc8); + } + + if (gwj->mod.csumfunc.xor) { + if (cf->can_dlc > 8) + goto out_delete; - if (gwj->mod.csumfunc.xor) (*gwj->mod.csumfunc.xor)(cf, &gwj->mod.csum.xor); + } } /* clear the skb timestamp if not configured the other way */ @@ -436,6 +452,14 @@ static void can_can_gw_rcv(struct sk_buf gwj->dropped_frames++; else gwj->handled_frames++; + + return; + + out_delete: + /* delete frame due to misconfiguration */ + gwj->deleted_frames++; + kfree_skb(nskb); + return; } static inline int cgw_register_filter(struct cgw_job *gwj)