CVE-2026-90056 in Linux
Summary
by MITRE • 09/17/2026
In the Linux kernel, the following vulnerability has been resolved:
net: fec: only stop PTP if it was initialized
fec_ptp_init() is only called when fep->bufdesc_ex is available. However, fec_probe() unconditionally calls fec_ptp_stop() on the failed_init path, and fec_drv_remove() unconditionally calls fec_ptp_stop() during device removal.
Check fep->bufdesc_ex before calling fec_ptp_stop() in both paths to avoid stopping PTP when it was not initialized.
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Analysis
by VulDB Data Team • 09/17/2026
The identified vulnerability resides within the Linux kernel network driver for Freescale Ethernet controllers, specifically affecting the Precision Time Protocol implementation. This issue stems from a logical error in the initialization and removal sequences where the code fails to verify whether the hardware features required by PTP are actually present before attempting to manage them. The root cause is traced to two specific functions: fec_probe during device initialization and fec_drv_remove during driver unloading. In both scenarios, the kernel attempts to stop or clean up the PTP subsystem without first confirming that it was successfully initialized in the first place.
The technical flaw arises from an unconditional call to fec_ptp_stop() on error paths within fec_probe and during normal removal operations. The initialization function fec_ptp_init is designed to run only when a specific hardware capability flag, represented by fep->bufdesc_ex, indicates that extended buffer descriptors are available. This flag serves as the primary indicator of whether the underlying Ethernet controller supports the advanced features necessary for PTP operation. However, if the probe process fails before this initialization can occur, or if the device is removed without having been fully initialized due to earlier errors, the subsequent unconditional call to fec_ptp_stop() executes on uninitialized data structures. This mismatch between the assumption of availability and the actual state leads to undefined behavior.
The operational impact of this vulnerability includes potential kernel crashes, such as null pointer dereferences or use-after-free conditions, which can result in system instability or a complete denial of service for the host machine. By attempting to access memory regions or hardware registers associated with PTP that were never allocated or configured, the driver violates safe programming practices and exposes the system to critical runtime errors. This is particularly dangerous during device removal sequences where error handling paths are frequently exercised under varying state conditions, increasing the likelihood of triggering these faults in real-world deployment scenarios involving hot-plugging or dynamic module loading.
From a classification perspective, this vulnerability aligns with CWE-916, which describes using incorrect control flow statements leading to unintended execution paths, and specifically relates to improper initialization checks before resource cleanup. In terms of the MITRE ATT&CK framework, while not directly exploitable for remote code execution by an external attacker without local access or physical interaction, it represents a weakness in robustness that could be leveraged in localized denial-of-service attacks if triggered repeatedly through device manipulation. The failure to validate preconditions before performing state-dependent operations is a classic example of insufficient input validation regarding internal system states rather than just user-supplied data.
To mitigate this vulnerability, the recommended approach involves modifying both fec_probe and fec_drv_remove functions to include explicit checks for fep->bufdesc_ex prior invoking fec_ptp_stop(). This ensures that PTP cleanup routines are only executed when the hardware features have been successfully initialized. Developers should implement conditional logic that verifies the availability of extended buffer descriptors before proceeding with any PTP-related teardown operations. Additionally, rigorous code review processes and static analysis tools configured to detect uninitialized variable usage or improper resource management patterns can help identify similar issues in other parts of the network subsystem. Ensuring strict adherence to initialization state checks during both setup and teardown phases is critical for maintaining kernel stability and preventing crashes associated with premature resource deallocation.