In the Linux kernel, the following vulnerability has been resolved:
can: sun4i_can: populate ndo_change_mtu() to prevent buffer overflow
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 sun4i_can 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, sun4ican_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 this line:
dlc = 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 a
couple line below when doing:
for (i = 0; i < dlc; i++)
writel(cf->data[i], priv->base + (dreg + i * 4));
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.
Metrics
Affected Vendors & Products
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References
History
Wed, 15 Oct 2025 08:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: can: sun4i_can: populate ndo_change_mtu() to prevent buffer overflow 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 sun4i_can 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, sun4ican_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 this line: dlc = 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 a couple line below when doing: for (i = 0; i < dlc; i++) writel(cf->data[i], priv->base + (dreg + i * 4)); 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. | |
| Title | can: sun4i_can: populate ndo_change_mtu() to prevent buffer overflow | |
| References |
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MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2025-10-15T07:56:05.143Z
Reserved: 2025-04-16T07:20:57.150Z
Link: CVE-2025-39986
Vulnrichment
No data.
NVD
Status : Received
Published: 2025-10-15T08:15:36.653
Modified: 2025-10-15T08:15:36.653
Link: CVE-2025-39986
Redhat
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OpenCVE Enrichment
No data.