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 932D6C2F3D5 for ; Mon, 21 Jan 2019 14:19:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 58C3820879 for ; Mon, 21 Jan 2019 14:19:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548080396; bh=a1LdWQc0p1Nku2Zvoxyw1OpfsyflpL9nUBPhMk2WZs8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Sl2Zai2r/J7J3kBFWwe4stzaySxpu8LK7B7+sMdPXwvOGypoZUKR4tRbyCSbT7i2Q jjeq38tSrJFKSqusaj7dPPT075NgCwMm18nOXRi13y89ZMFaa2By3JRecYWFBJdn7E eOnq6QnCNtsM9+T5EtFqfDLnu1s0lVAYsGH5LyXI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729921AbfAUNsX (ORCPT ); Mon, 21 Jan 2019 08:48:23 -0500 Received: from mail.kernel.org ([198.145.29.99]:58180 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729905AbfAUNsU (ORCPT ); Mon, 21 Jan 2019 08:48:20 -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 17E542063F; Mon, 21 Jan 2019 13:48:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548078499; bh=a1LdWQc0p1Nku2Zvoxyw1OpfsyflpL9nUBPhMk2WZs8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=WepoDPVi6bL6BdCCO+IhNGjSuRnRqh3UPOXOdflkJt0cJNABSRMTLZFwgi8AYS4ms QWBD327JW6x5mBF2eIBQrb+WSR0/5TXVfHO5ayatzG/SaNzxABIEncToEwqDROm7SR CVMOE2ErpbmG8V7xHcuqmGTo0k399odHQmTkgLzI= 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 4.20 005/111] can: gw: ensure DLC boundaries after CAN frame modification Date: Mon, 21 Jan 2019 14:41:59 +0100 Message-Id: <20190121122456.378732690@linuxfoundation.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190121122455.819406896@linuxfoundation.org> References: <20190121122455.819406896@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: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.20-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 @@ -416,13 +416,29 @@ 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 */ @@ -434,6 +450,14 @@ 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 net *net, struct cgw_job *gwj)