From mboxrd@z Thu Jan 1 00:00:00 1970 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 68151226CF7; Tue, 30 Sep 2025 14:53:45 +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=1759244025; cv=none; b=ls4egpqtzwzPkToTyi+f0X4M37ERLtgd7UUP/e/T2GTo8K+7VqgRNbPP4LbE4ijKvhaOhC04l7/ueSMRK3R+swSmdjdUc5mPK+q7bVhjISjwj3E4vk8my0R7hRXCuj1VmBU9r3ggS5ut4RMUlqJT+RtnU1xwFDVO/CNUVTIpmUQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759244025; c=relaxed/simple; bh=3kaAMRTo48BXU5QL5pzA4Mhxcf59u1e4z8iw4I1JssY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=o5qq7TbNKRoKu6SfoaSZvb6zKaWXQ4wBLDkIIr8/31IqlmoLBOzvYgUHyLVEotAT1C106WWGFlCCPLRT+OpkbX7K8GTGcJttoLIGVq3W5+trmmWFa1mM0hB28UTEqR3lhkXdERZp6qIG8seqrrvnLp/d7kswhA5iKUlFZHkGF94= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=dlR/+ytU; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="dlR/+ytU" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 94826C4CEF0; Tue, 30 Sep 2025 14:53:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1759244025; bh=3kaAMRTo48BXU5QL5pzA4Mhxcf59u1e4z8iw4I1JssY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=dlR/+ytUOU4kgt/Okle0gx7WYsDyqPYIhLTRVVybYJuVp4q4+XK5OiYdi/O0eDN8o CKAu8wpJkV/6UKS3i3ssAP/JvKppARofCg/6BvtDGDG4iru9EhdaGcrA7Ez7QC43Oc BTLvPnPy5uL2jRZoIaxelUn6W5LBBVzbgyWM5TMs= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Vincent Mailhol , Marc Kleine-Budde , Sasha Levin Subject: [PATCH 5.4 67/81] can: mcba_usb: populate ndo_change_mtu() to prevent buffer overflow Date: Tue, 30 Sep 2025 16:47:09 +0200 Message-ID: <20250930143822.487170605@linuxfoundation.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20250930143819.654157320@linuxfoundation.org> References: <20250930143819.654157320@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Vincent Mailhol [ Upstream commit 17c8d794527f01def0d1c8b7dc2d7b8d34fed0e6 ] 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 mcba_usb 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, mcba_usb_start_xmit() receives a CAN XL frame which it is not able to correctly handle and will thus misinterpret it as a CAN frame. This can result in a buffer overflow. The driver will consume cf->len as-is with no further checks on these lines: usb_msg.dlc = cf->len; memcpy(usb_msg.data, cf->data, usb_msg.dlc); 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. By fixing the root cause, this prevents the buffer overflow. Fixes: 51f3baad7de9 ("can: mcba_usb: Add support for Microchip CAN BUS Analyzer") Signed-off-by: Vincent Mailhol Link: https://patch.msgid.link/20250918-can-fix-mtu-v1-4-0d1cada9393b@kernel.org Signed-off-by: Marc Kleine-Budde Signed-off-by: Sasha Levin --- drivers/net/can/usb/mcba_usb.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/net/can/usb/mcba_usb.c b/drivers/net/can/usb/mcba_usb.c index 16fb4fc265183..e43bd02401a24 100644 --- a/drivers/net/can/usb/mcba_usb.c +++ b/drivers/net/can/usb/mcba_usb.c @@ -769,6 +769,7 @@ static const struct net_device_ops mcba_netdev_ops = { .ndo_open = mcba_usb_open, .ndo_stop = mcba_usb_close, .ndo_start_xmit = mcba_usb_start_xmit, + .ndo_change_mtu = can_change_mtu, }; /* Microchip CANBUS has hardcoded bittiming values by default. -- 2.51.0