CVE-2022-48812 in Linux
Summary
by MITRE • 07/16/2024
In the Linux kernel, the following vulnerability has been resolved:
net: dsa: lantiq_gswip: don't use devres for mdiobus
As explained in commits: 74b6d7d13307 ("net: dsa: realtek: register the MDIO bus under devres") 5135e96a3dd2 ("net: dsa: don't allocate the slave_mii_bus using devres")
mdiobus_free() will panic when called from devm_mdiobus_free() <- devres_release_all() <- __device_release_driver(), and that mdiobus was not previously unregistered.
The GSWIP switch is a platform device, so the initial set of constraints that I thought would cause this (I2C or SPI buses which call ->remove on ->shutdown) do not apply. But there is one more which applies here.
If the DSA master itself is on a bus that calls ->remove from ->shutdown (like dpaa2-eth, which is on the fsl-mc bus), there is a device link between the switch and the DSA master, and device_links_unbind_consumers() will unbind the GSWIP switch driver on shutdown.
So the same treatment must be applied to all DSA switch drivers, which is: either use devres for both the mdiobus allocation and registration, or don't use devres at all.
The gswip driver has the code structure in place for orderly mdiobus removal, so just replace devm_mdiobus_alloc() with the non-devres variant, and add manual free where necessary, to ensure that we don't let devres free a still-registered bus.
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Analysis
by VulDB Data Team • 10/03/2025
The vulnerability described in CVE-2022-48812 represents a critical issue within the Linux kernel's DSA (Distributed Switch Architecture) subsystem, specifically affecting the Lantiq GSWIP switch driver. This flaw manifests as a potential system panic during device shutdown sequences, stemming from improper management of MDIO (Management Data Input/Output) bus resources within the device resource management framework. The vulnerability occurs when the kernel attempts to free an MDIO bus that has not been properly unregistered, leading to a kernel panic condition that can compromise system stability and availability.
The technical root cause of this vulnerability lies in the inconsistent application of device resource management patterns within the DSA switch driver implementation. The issue specifically affects the interaction between devm_mdiobus_alloc() and devm_mdiobus_free() functions, where the automatic resource cleanup mechanism conflicts with the manual device shutdown sequence. When the DSA master device resides on a bus that invokes the ->remove callback during ->shutdown operations, such as the dpaa2-eth driver on the fsl-mc bus, the device link mechanism triggers device_links_unbind_consumers() which unbinds the GSWIP switch driver. This sequence creates a race condition where the device resource manager attempts to free an MDIO bus that is still actively registered, resulting in a kernel panic.
The vulnerability demonstrates a pattern that was previously addressed in other DSA switch drivers through commits 74b6d7d13307 and 5135e96a3dd2, which established consistent resource management practices for MDIO bus allocation and registration. However, the GSWIP driver implementation failed to adopt these established patterns, creating an inconsistency in the kernel's device resource management approach. This inconsistency particularly affects platform devices like the GSWIP switch, where the traditional constraints that would cause such issues on I2C or SPI buses do not apply, but the shutdown sequence still triggers the problematic device link unbinding behavior.
The operational impact of this vulnerability extends beyond simple system crashes to potentially compromise network connectivity and overall system reliability in embedded networking environments. When the kernel panics due to this condition, it can result in complete system downtime, requiring manual intervention to restore normal operation. This is particularly concerning in production environments where network infrastructure devices must maintain high availability and cannot afford unexpected shutdowns or crashes. The vulnerability affects systems using Lantiq GSWIP switches within DSA configurations, particularly those employing buses that trigger shutdown removal sequences, making it relevant to a broad range of networking hardware implementations.
The recommended mitigation strategy involves modifying the GSWIP driver to maintain consistency with other DSA switch drivers by replacing devm_mdiobus_alloc() with the non-device resource variant and implementing manual cleanup procedures. This approach ensures that MDIO bus resources are properly managed throughout the device lifecycle, preventing the kernel from attempting to free a still-registered bus during device shutdown sequences. The solution aligns with established best practices in device driver development and follows the patterns already implemented in other successful DSA switch driver implementations, thereby reducing the risk of similar issues occurring in other drivers within the same subsystem. This remediation addresses the fundamental resource management inconsistency and ensures proper device lifecycle handling across all DSA switch drivers.
This vulnerability maps to CWE-415: Double Free and CWE-755: Improper Handling of Exceptional Conditions within the Common Weakness Enumeration framework, as it involves improper resource management leading to system instability. From an ATT&CK perspective, this vulnerability could be leveraged in supply chain attacks targeting embedded networking devices or in denial-of-service scenarios against network infrastructure, potentially affecting the network availability and integrity of systems relying on affected hardware platforms. The vulnerability's impact is particularly severe in environments where network reliability is critical, such as data centers, telecommunications infrastructure, or industrial control systems where unexpected network outages can have significant operational consequences.