6.12-stable review patch. If anyone has any objections, please let me know.
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From: Vincent Mailhol mailhol@kernel.org
[ Upstream commit 38c0abad45b190a30d8284a37264d2127a6ec303 ]
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 mailhol@kernel.org Link: https://patch.msgid.link/20250918-can-fix-mtu-v1-1-0d1cada9393b@kernel.org Signed-off-by: Marc Kleine-Budde mkl@pengutronix.de Signed-off-by: Sasha Levin sashal@kernel.org --- 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 71f24dc0a9271..4fc9bed0d2e1e 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 mailhol.vincent@wanadoo.fr + * Copyright (c) 2020-2025 Vincent Mailhol mailhol@kernel.org */
#include <linux/unaligned.h> @@ -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 = {