CVE-2022-48934 in Linux
Summary
by MITRE • 08/22/2024
In the Linux kernel, the following vulnerability has been resolved:
nfp: flower: Fix a potential leak in nfp_tunnel_add_shared_mac()
ida_simple_get() returns an id between min (0) and max (NFP_MAX_MAC_INDEX) inclusive. So NFP_MAX_MAC_INDEX (0xff) is a valid id.
In order for the error handling path to work correctly, the 'invalid' value for 'ida_idx' should not be in the 0..NFP_MAX_MAC_INDEX range, inclusive.
So set it to -1.
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Analysis
by VulDB Data Team • 08/23/2024
The vulnerability identified as CVE-2022-48934 resides within the Linux kernel's network filtering platform implementation, specifically affecting the nfp (Netronome Flow Processor) driver component. This flaw manifests in the nfp_tunnel_add_shared_mac() function where improper handling of identifier allocation creates a potential memory leak scenario. The nfp driver operates within the context of network virtualization and flow steering, processing packets through hardware-accelerated network processing units that require precise management of shared MAC addresses for tunneling operations. The vulnerability stems from a fundamental misunderstanding of how the ida_simple_get() function operates within the kernel's identifier allocation framework, creating a dangerous condition where valid identifiers are incorrectly treated as invalid.
The technical flaw occurs due to improper initialization of the ida_idx variable within the error handling path of the nfp_tunnel_add_shared_mac() function. The ida_simple_get() function returns identifiers within the inclusive range of 0 to NFP_MAX_MAC_INDEX, where NFP_MAX_MAC_INDEX is defined as 0xff or 255 decimal. This means that 0xff represents a legitimate valid identifier that can be returned by the allocation function. However, the original implementation incorrectly set the invalid value for ida_idx to a value that falls within this valid range, specifically 0xff, which creates a logical inconsistency in the error handling mechanism. When the error path executes, it attempts to check if ida_idx represents an invalid state, but because 0xff is a valid return value from ida_simple_get(), the system fails to properly handle the error condition, leading to potential resource leakage.
The operational impact of this vulnerability extends beyond simple memory consumption issues, as it represents a potential denial of service condition within network processing environments that rely on the nfp driver. The memory leak occurs when the error handling path fails to properly release allocated resources, particularly in scenarios involving shared MAC address management for network tunneling operations. This vulnerability affects systems using Netronome network adapters that implement the nfp driver, potentially compromising system stability and performance in high-throughput network environments. The flaw is particularly concerning in cloud and virtualized environments where network tunneling is extensively used, as it could lead to progressive resource exhaustion and system instability over time.
The mitigation strategy for CVE-2022-48934 involves a straightforward fix to the ida_idx initialization within the nfp_tunnel_add_shared_mac() function, specifically setting the invalid value to -1 instead of 0xff. This change ensures that the error handling path correctly identifies when allocation has failed, as -1 is outside the valid range of identifiers that ida_simple_get() can return. This fix aligns with standard kernel development practices for identifier management and error handling, where negative values are conventionally used to indicate error conditions. The resolution addresses the core issue by ensuring proper resource cleanup in error scenarios, preventing the leak of allocated identifiers and associated resources. This vulnerability demonstrates the importance of proper error handling in kernel space code and aligns with CWE-704 (Incorrect Type Conversion or Cast) and CWE-705 (Incorrect Control Flow Implementation) categories, while potentially mapping to ATT&CK technique T1499.004 (Endpoint Denial of Service) through its potential for resource exhaustion. Organizations should apply the kernel patch that implements this fix to protect against potential exploitation and ensure stable operation of network processing functions that depend on the nfp driver's tunneling capabilities.