From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from metis.whiteo.stw.pengutronix.de (metis.whiteo.stw.pengutronix.de [185.203.201.7]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0E73D30FF06 for ; Tue, 23 Sep 2025 07:42:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.203.201.7 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758613379; cv=none; b=q5X6BqodgAGcmYlAhCa5fk1m6+DihyJ9scfrKRFOCfnaaquGMKRDzvsrnlZwdGJNDdtvyoSiDCD9S/hMPFfbiJvLVYx6LxYFPMtE0t2PYxmC2xVZyJAO1BnvUy5gah3OdAW5Z1xTzgPpTKtcNU2u53f06MA/qOeM1JHlEXmC7L4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758613379; c=relaxed/simple; bh=rd32eBhFiAAJLcDnvaafjRB6AVqo9CCTAgAfyMBrfAM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=dFosL3nAIT1SE7Er31TKffrXP4jXZGZ1ydIw2oo5rtNiAIPVQm4ZUX0XlyXxbIYNsyz+KSRcUNjPLWT90VMf+fguZEgHF1n3Pj4I87UEnPke8imIyCbnQGxWXCo+GJbilpdLeZEittfNDy4ieXNQ/qKLwIDAIIRRyJ6TqCdffVA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=pengutronix.de; spf=pass smtp.mailfrom=pengutronix.de; arc=none smtp.client-ip=185.203.201.7 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=pengutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=pengutronix.de Received: from drehscheibe.grey.stw.pengutronix.de ([2a0a:edc0:0:c01:1d::a2]) by metis.whiteo.stw.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1v0xfg-0003cp-QY; Tue, 23 Sep 2025 09:42:44 +0200 Received: from moin.white.stw.pengutronix.de ([2a0a:edc0:0:b01:1d::7b] helo=bjornoya.blackshift.org) by drehscheibe.grey.stw.pengutronix.de with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.96) (envelope-from ) id 1v0xfg-0003Nh-0L; Tue, 23 Sep 2025 09:42:44 +0200 Received: from blackshift.org (p54b152ce.dip0.t-ipconnect.de [84.177.82.206]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange x25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) (Authenticated sender: mkl-all@blackshift.org) by smtp.blackshift.org (Postfix) with ESMTPSA id BDF36477A87; Tue, 23 Sep 2025 07:34:31 +0000 (UTC) From: Marc Kleine-Budde To: netdev@vger.kernel.org Cc: davem@davemloft.net, kuba@kernel.org, linux-can@vger.kernel.org, kernel@pengutronix.de, Vincent Mailhol , Marc Kleine-Budde Subject: [PATCH net 3/7] can: etas_es58x: populate ndo_change_mtu() to prevent buffer overflow Date: Tue, 23 Sep 2025 09:32:49 +0200 Message-ID: <20250923073427.493034-4-mkl@pengutronix.de> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20250923073427.493034-1-mkl@pengutronix.de> References: <20250923073427.493034-1-mkl@pengutronix.de> Precedence: bulk X-Mailing-List: linux-can@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-SA-Exim-Connect-IP: 2a0a:edc0:0:c01:1d::a2 X-SA-Exim-Mail-From: mkl@pengutronix.de X-SA-Exim-Scanned: No (on metis.whiteo.stw.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-can@vger.kernel.org From: Vincent Mailhol Sending an PF_PACKET allows to bypass the CAN framework logic and to directly reach the xmit() function of a CAN driver. The only check which is performed by the PF_PACKET framework is to make sure that skb->len fits the interface's MTU. Unfortunately, because the etas_es58x driver does not populate its net_device_ops->ndo_change_mtu(), it is possible for an attacker to configure an invalid MTU by doing, for example: $ ip link set can0 mtu 9999 After doing so, the attacker could open a PF_PACKET socket using the ETH_P_CANXL protocol: socket(PF_PACKET, SOCK_RAW, htons(ETH_P_CANXL)); to inject a malicious CAN XL frames. For example: struct canxl_frame frame = { .flags = 0xff, .len = 2048, }; The CAN drivers' xmit() function are calling can_dev_dropped_skb() to check that the skb is valid, unfortunately under above conditions, the malicious packet is able to go through can_dev_dropped_skb() checks: 1. the skb->protocol is set to ETH_P_CANXL which is valid (the function does not check the actual device capabilities). 2. the length is a valid CAN XL length. And so, es58x_start_xmit() receives a CAN XL frame which it is not able to correctly handle and will thus misinterpret it as a CAN(FD) frame. This can result in a buffer overflow. For example, using the es581.4 variant, the frame will be dispatched to es581_4_tx_can_msg(), go through the last check at the beginning of this function: if (can_is_canfd_skb(skb)) return -EMSGSIZE; and reach this line: memcpy(tx_can_msg->data, cf->data, cf->len); Here, cf->len corresponds to the flags field of the CAN XL frame. In our previous example, we set canxl_frame->flags to 0xff. Because the maximum expected length is 8, a buffer overflow of 247 bytes occurs! Populate net_device_ops->ndo_change_mtu() to ensure that the interface's MTU can not be set to anything bigger than CAN_MTU or CANFD_MTU (depending on the device capabilities). By fixing the root cause, this prevents the buffer overflow. Fixes: 8537257874e9 ("can: etas_es58x: add core support for ETAS ES58X CAN USB interfaces") Signed-off-by: Vincent Mailhol Link: https://patch.msgid.link/20250918-can-fix-mtu-v1-1-0d1cada9393b@kernel.org Signed-off-by: Marc Kleine-Budde --- drivers/net/can/usb/etas_es58x/es58x_core.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/net/can/usb/etas_es58x/es58x_core.c b/drivers/net/can/usb/etas_es58x/es58x_core.c index db1acf6d504c..adc91873c083 100644 --- a/drivers/net/can/usb/etas_es58x/es58x_core.c +++ b/drivers/net/can/usb/etas_es58x/es58x_core.c @@ -7,7 +7,7 @@ * * Copyright (c) 2019 Robert Bosch Engineering and Business Solutions. All rights reserved. * Copyright (c) 2020 ETAS K.K.. All rights reserved. - * Copyright (c) 2020-2022 Vincent Mailhol + * Copyright (c) 2020-2025 Vincent Mailhol */ #include @@ -1977,6 +1977,7 @@ static const struct net_device_ops es58x_netdev_ops = { .ndo_stop = es58x_stop, .ndo_start_xmit = es58x_start_xmit, .ndo_eth_ioctl = can_eth_ioctl_hwts, + .ndo_change_mtu = can_change_mtu, }; static const struct ethtool_ops es58x_ethtool_ops = { -- 2.51.0