CVE-2024-42142 in Linux
Summary
by MITRE • 07/30/2024
In the Linux kernel, the following vulnerability has been resolved:
net/mlx5: E-switch, Create ingress ACL when needed
Currently, ingress acl is used for three features. It is created only when vport metadata match and prio tag are enabled. But active-backup lag mode also uses it. It is independent of vport metadata match and prio tag. And vport metadata match can be disabled using the following devlink command:
# devlink dev param set pci/0000:08:00.0 name esw_port_metadata \ value false cmode runtime
If ingress acl is not created, will hit panic when creating drop rule for active-backup lag mode. If always create it, there will be about 5% performance degradation.
Fix it by creating ingress acl when needed. If esw_port_metadata is true, ingress acl exists, then create drop rule using existing ingress acl. If esw_port_metadata is false, create ingress acl and then create drop rule.
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Analysis
by VulDB Data Team • 07/19/2025
The vulnerability described in CVE-2024-42142 resides within the Linux kernel's Mellanox 5 (mlx5) network driver, specifically addressing an issue in the Ethernet switch (E-switch) functionality. This flaw manifests in the conditional creation of ingress access control lists (ACLs) that are essential for managing network traffic within the switch fabric. The vulnerability impacts systems utilizing Mellanox network adapters in configurations that employ active-backup link aggregation mode, where the ingress ACL creation logic fails to properly account for all use cases requiring such network filtering capabilities.
The technical root cause of this vulnerability stems from the conditional logic governing ingress ACL creation within the mlx5 driver's E-switch implementation. Currently, ingress ACLs are only instantiated when both vport metadata match and priority tag features are enabled, which is a restrictive approach that does not account for the independent usage requirements of active-backup link aggregation mode. This design oversight creates a scenario where the system can encounter a kernel panic when attempting to create drop rules for active-backup LAG mode, as the necessary ingress ACL structure has not been established. The vulnerability represents a classic case of incomplete conditional logic and resource allocation that fails to consider all operational modes within the network switch's feature set.
The operational impact of this vulnerability extends beyond simple system stability concerns to encompass potential network service disruption and denial of service conditions. When systems attempt to configure active-backup LAG mode with ingress ACLs disabled through the devlink command interface, the kernel panics occurs during drop rule creation, leading to complete system crashes or reboot cycles. This represents a significant security and reliability concern for enterprise networks relying on Mellanox adapters, particularly in high-availability environments where link aggregation is commonly deployed. The vulnerability affects systems where network administrators might have disabled vport metadata match for performance or configuration reasons, inadvertently creating a path to system instability.
The mitigation strategy for this vulnerability involves implementing a dynamic ingress ACL creation mechanism that evaluates the current configuration state before determining whether to create or utilize existing ingress ACL structures. When the esw_port_metadata parameter is set to true, the system should leverage the existing ingress ACL for drop rule creation, while maintaining backward compatibility with the existing behavior. When esw_port_metadata is set to false, the system must dynamically create the ingress ACL structure before proceeding with drop rule creation. This approach aligns with the principle of least privilege and conditional resource allocation while maintaining performance characteristics. The fix addresses the underlying issue by ensuring that ingress ACLs are created only when necessary, avoiding the 5% performance degradation that would occur from always creating them while preventing the kernel panic scenario. This vulnerability demonstrates the importance of considering all feature interactions in complex network driver implementations and highlights the need for comprehensive testing across all operational modes. The fix should be implemented in accordance with security best practices and validated through extensive regression testing to ensure that the dynamic ACL creation does not introduce new performance bottlenecks or security vulnerabilities. The solution represents a proper application of the principle that network security mechanisms must be robustly implemented across all operational configurations rather than assuming specific feature states. This vulnerability is classified as a software defect that can be addressed through proper conditional logic implementation and follows established patterns for kernel security patch development.