CVE-2022-49472 in Linux
Summary
by MITRE • 02/26/2025
In the Linux kernel, the following vulnerability has been resolved:
net: phy: micrel: Allow probing without .driver_data
Currently, if the .probe element is present in the phy_driver structure and the .driver_data is not, a NULL pointer dereference happens.
Allow passing .probe without .driver_data by inserting NULL checks for priv->type.
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Analysis
by VulDB Data Team • 04/17/2025
This vulnerability exists within the Linux kernel's phy driver subsystem, specifically affecting the Micrel PHY driver implementation. The issue stems from a design flaw in how the kernel handles PHY driver probing operations when certain structure elements are omitted. The phy_driver structure contains a probe function pointer that can be defined independently of driver_data, creating a scenario where the probe function may be called without proper initialization of the associated driver data structure. This represents a classic null pointer dereference vulnerability that can lead to system instability and potential denial of service conditions.
The technical flaw manifests when the kernel attempts to access the priv->type member without first validating whether the driver_data field has been properly initialized. The probe function executes in a context where the driver_data field might be NULL, causing the kernel to attempt dereferencing a null pointer when accessing priv->type. This type of vulnerability falls under the CWE-476 category of Null Pointer Dereference, which is a common weakness in kernel space programming where developers fail to validate pointer references before use. The vulnerability specifically affects the network PHY subsystem, which handles physical layer communication for network interfaces, making it particularly concerning for network stability and availability.
The operational impact of this vulnerability extends beyond simple system crashes, as it can affect network connectivity and overall system reliability. When a NULL pointer dereference occurs during PHY probing, the kernel may experience a kernel oops or panic, leading to system instability and potential service disruption. Network interfaces that rely on Micrel PHY drivers could become unavailable, causing network outages for systems running affected kernel versions. This vulnerability particularly impacts embedded systems, servers, and network equipment that depend on the Linux kernel's PHY subsystem for network communication. The issue is especially problematic in production environments where network reliability is critical, as it could lead to unexpected downtime and service degradation.
Mitigation strategies for this vulnerability involve implementing proper null pointer validation within the kernel's PHY driver framework. The fix requires adding NULL checks for the priv->type member before attempting to access it, ensuring that the probe function can safely execute even when driver_data is not provided. System administrators should prioritize kernel updates to versions that contain the patched implementation, as this vulnerability affects multiple kernel versions and can be exploited by attackers who can trigger PHY probing operations. The fix aligns with ATT&CK technique T1068 by addressing a kernel-level privilege escalation vector, though this particular vulnerability primarily results in denial of service rather than privilege escalation. Organizations should also implement monitoring for kernel oops messages and system crashes related to PHY driver operations, as these could indicate exploitation attempts or unpatched systems. Regular kernel updates and security assessments of network infrastructure components are essential to prevent exploitation of similar vulnerabilities in the broader kernel subsystem.