CVE-2024-42224 in Linux
Summary
by MITRE • 07/30/2024
In the Linux kernel, the following vulnerability has been resolved:
net: dsa: mv88e6xxx: Correct check for empty list
Since commit a3c53be55c95 ("net: dsa: mv88e6xxx: Support multiple MDIO busses") mv88e6xxx_default_mdio_bus() has checked that the return value of list_first_entry() is non-NULL.
This appears to be intended to guard against the list chip->mdios being empty. However, it is not the correct check as the implementation of list_first_entry is not designed to return NULL for empty lists.
Instead, use list_first_entry_or_null() which does return NULL if the list is empty.
Flagged by Smatch. Compile tested only.
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Analysis
by VulDB Data Team • 07/19/2025
The vulnerability CVE-2024-42224 affects the Linux kernel's DSA (Distributed Switch Architecture) subsystem, specifically within the mv88e6xxx driver that manages Marvell 88E6xxx series switch chips. This issue represents a subtle but critical flaw in how the driver handles MDIO (Media Independent Interface) bus management, which could potentially lead to system instability or unexpected behavior in network switch operations. The vulnerability was introduced in commit a3c53be55c95 which added support for multiple MDIO busses, indicating that this is a regression introduced during feature enhancement rather than an inherent design flaw.
The technical flaw stems from an incorrect validation approach in the mv88e6xxx_default_mdio_bus() function where the code attempts to check for empty lists using list_first_entry() return value validation. This approach is fundamentally flawed because list_first_entry() is not designed to return NULL when encountering empty lists, unlike list_first_entry_or_null() which was specifically created for this purpose. The incorrect implementation creates a scenario where the driver may proceed with operations on what it believes to be valid list entries, but which are actually non-existent, leading to potential null pointer dereferences or undefined behavior. The vulnerability was identified by the Smatch static analysis tool, which flagged this improper list handling pattern as a potential source of instability.
The operational impact of this vulnerability could manifest in various ways including system crashes, kernel oops, or network switch malfunction when the driver attempts to manage MDIO buses on switch chips. Since this affects the core networking infrastructure in the Linux kernel, systems utilizing Marvell 88E6xxx switches in DSA configurations could experience intermittent connectivity issues or complete network service disruption. The vulnerability is particularly concerning in enterprise network environments where switch reliability is critical for maintaining network infrastructure stability. The fact that this is a compile-time only test suggests the issue may not be immediately exploitable in all scenarios but represents a latent condition that could trigger under specific operational circumstances.
The recommended mitigation strategy involves updating to a kernel version that includes the fix, which replaces the incorrect list_first_entry() call with the proper list_first_entry_or_null() function. This change ensures that empty list conditions are properly handled and prevents the potential for null pointer dereferences. System administrators should prioritize applying this kernel update, particularly in production environments where network switch reliability is paramount. The fix aligns with CWE-476 which addresses null pointer dereference vulnerabilities, and follows ATT&CK technique T1547.001 related to system service modification where improper list handling could lead to service disruptions. Organizations should also conduct thorough testing of network switch functionality after applying the update to ensure no regressions in switch behavior or network performance occur.