From nobody Thu Oct 2 10:38:50 2025 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 BA3CB2F60DB; Thu, 18 Sep 2025 09:01:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758186109; cv=none; b=qjp1h7sR+egoEbwz1MD4uTOo14U493OPyDExj76G8mEb/xRcckuocJ2cnArn+efMigrGhwXZCmcJ4y/w2p5hvZ7SAuSuQ5OUydSgmUCpIUPJZNCm+AjuREG5QrBQHBjNZIbS4swaeqxpYCm2kmH7AhK1eLN/GuF7FiwW8gxdV8I= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758186109; c=relaxed/simple; bh=99bx0qqju2UEGVzQhTUbxA8T28JN+IzFGx/ISmPcSf4=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=AYqO7DXrVnNYap4cc0EhfFX/YodLsBMBG+pxqpzEcWA3DG7ywJah1qQ2ox/qHgD3zhJU2aUduDya1RIGm89l82msm3y8TrkM0Xv7P4eUz8UeycIa1aWYVhd6TdQctm7m2hSmeO2/CDNqFl8YJHNJ8LrvzhxhCNpWY1J/KJN0kgs= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=kH+ibA9R; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="kH+ibA9R" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 25FDEC4CEFB; Thu, 18 Sep 2025 09:01:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1758186109; bh=99bx0qqju2UEGVzQhTUbxA8T28JN+IzFGx/ISmPcSf4=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=kH+ibA9RimkNjlWOzcnxzqAitYkbqRM5/CJfNWkcORvEWN9WrfPs8ShwdVZHY0ET3 DLo1QhJc6/oze4/74DjYNN8TRgrCK/l3COjFnV8n7+Cb0C76nbjjg5bLHij0GzSZ2h 3TzKGnZ4WY4B3caZ7HLMNfTyU7WWFBW+sgPjl4rbvLNu3hQ7JEyvZH3WeEu3UqQGUC +lVV80yrpLw0iCThDxCePzELPZvmE9Qt7Qv1kzE1/HvHhjdShe+zyG+BCfqghLPFHg kCnA4lxvwsVx2dBT2BfC2qB6iPC/ajxONhI0ZVxe0xS4pkQ+TxtzURGaqrSW9DlEEr R0u3OoKCTs/pw== From: Vincent Mailhol Date: Thu, 18 Sep 2025 18:00:24 +0900 Subject: [PATCH 1/4] can: etas_es58x: populate ndo_change_mtu() to prevent buffer overflow Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20250918-can-fix-mtu-v1-1-0d1cada9393b@kernel.org> References: <20250918-can-fix-mtu-v1-0-0d1cada9393b@kernel.org> In-Reply-To: <20250918-can-fix-mtu-v1-0-0d1cada9393b@kernel.org> To: Marc Kleine-Budde , Oliver Hartkopp Cc: Arunachalam Santhanam , Akshay Bhat , Wolfgang Grandegger , Chen-Yu Tsai , Jernej Skrabec , Samuel Holland , Maxime Ripard , Gerhard Bertelsmann , Yasushi SHOJI , =?utf-8?q?Remigiusz_Ko=C5=82=C5=82=C4=85taj?= , linux-can@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-sunxi@lists.linux.dev, Vincent Mailhol X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=3267; i=mailhol@kernel.org; h=from:subject:message-id; bh=99bx0qqju2UEGVzQhTUbxA8T28JN+IzFGx/ISmPcSf4=; b=owGbwMvMwCV2McXO4Xp97WbG02pJDBmnT+U6it09XHjp1J2k1U/PXLpx2WKK4Pf+wt9vFizWt tKrNly6rKOUhUGMi0FWTJFlWTknt0JHoXfYob+WMHNYmUCGMHBxCsBEinsZ/keu99z6r3fH53Xz J7b6aCTJxvsI/W2Yd9en/DqfW7nGEWGG36xXD6w/bl9nMtfX9BXD1goJ7rAF0u+3Lwn/m6bGmn2 cjQMA X-Developer-Key: i=mailhol@kernel.org; a=openpgp; fpr=ED8F700574E67F20E574E8E2AB5FEB886DBB99C2 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 =3D { .flags =3D 0xff, .len =3D 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 --- 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 db1acf6d504cf37cec724d392c9f7fee2d1f6045..adc91873c083f968ff7571a5b0d= b5747988482c5 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 */ =20 #include @@ -1977,6 +1977,7 @@ static const struct net_device_ops es58x_netdev_ops = =3D { .ndo_stop =3D es58x_stop, .ndo_start_xmit =3D es58x_start_xmit, .ndo_eth_ioctl =3D can_eth_ioctl_hwts, + .ndo_change_mtu =3D can_change_mtu, }; =20 static const struct ethtool_ops es58x_ethtool_ops =3D { --=20 2.49.1