CVE-2025-40104

In the Linux kernel, the following vulnerability has been resolved:

ixgbevf: fix mailbox API compatibility by negotiating supported features

There was backward compatibility in the terms of mailbox API. Various drivers from various OSes supporting 10G adapters from Intel portfolio could easily negotiate mailbox API.

This convention has been broken since introducing API 1.4. Commit 0062e7cc955e ("ixgbevf: add VF IPsec offload code") added support for IPSec which is specific only for the kernel ixgbe driver. None of the rest of the Intel 10G PF/VF drivers supports it. And actually lack of support was not included in the IPSec implementation - there were no such code paths. No possibility to negotiate support for the feature was introduced along with introduction of the feature itself.

Commit 339f28964147 ("ixgbevf: Add support for new mailbox communication between PF and VF") increasing API version to 1.5 did the same - it introduced code supported specifically by the PF ESX driver. It altered API version for the VF driver in the same time not touching the version defined for the PF ixgbe driver. It led to additional discrepancies, as the code provided within API 1.6 cannot be supported for Linux ixgbe driver as it causes crashes.

The issue was noticed some time ago and mitigated by Jake within the commit d0725312adf5 ("ixgbevf: stop attempting IPSEC offload on Mailbox API 1.5"). As a result we have regression for IPsec support and after increasing API to version 1.6 ixgbevf driver stopped to support ESX MBX.

To fix this mess add new mailbox op asking PF driver about supported features. Basing on a response determine whether to set support for IPSec and ESX-specific enhanced mailbox.

New mailbox op, for compatibility purposes, must be added within new API revision, as API version of OOT PF & VF drivers is already increased to 1.6 and doesn't incorporate features negotiate op.

Features negotiation mechanism gives possibility to be extended with new features when needed in the future.

This vulnerability is rated with a Moderate impact because exploitation is constrained to environments utilizing Intel 10GbE SR-IOV virtual function devices, where an unprivileged local user can trigger mailbox API mismatches between virtual and physical function drivers. The issue specifically affects systems running the ixgbevf network driver when interacting with an incompatible host PF driver, resulting in a kernel crash and localized denial of service. Systems that do not utilize Intel virtual function network adapters are unaffected.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.