CVE-2024-44932 in Linux
Summary
by MITRE • 08/26/2024
In the Linux kernel, the following vulnerability has been resolved:
idpf: fix UAFs when destroying the queues
The second tagged commit started sometimes (very rarely, but possible) throwing WARNs from net/core/page_pool.c:page_pool_disable_direct_recycling(). Turned out idpf frees interrupt vectors with embedded NAPIs *before* freeing the queues making page_pools' NAPI pointers lead to freed memory before these pools are destroyed by libeth. It's not clear whether there are other accesses to the freed vectors when destroying the queues, but anyway, we usually free queue/interrupt vectors only when the queues are destroyed and the NAPIs are guaranteed to not be referenced anywhere.
Invert the allocation and freeing logic making queue/interrupt vectors be allocated first and freed last. Vectors don't require queues to be present, so this is safe. Additionally, this change allows to remove that useless queue->q_vector pointer cleanup, as vectors are still valid when freeing the queues (+ both are freed within one function, so it's not clear why nullify the pointers at all).
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Analysis
by VulDB Data Team • 12/14/2024
The vulnerability identified as CVE-2024-44932 represents a use-after-free condition affecting the Linux kernel's implementation of the Intel Data Plane Framework (IDPF) driver. This flaw manifests specifically during the destruction of network queues within the driver's resource management lifecycle, creating a critical security risk that could potentially be exploited by malicious actors. The issue stems from an improper ordering of resource deallocation operations that leaves memory references in an invalid state.
The technical root cause of this vulnerability lies in the improper sequence of operations during queue destruction within the IDPF driver implementation. When the driver attempts to free interrupt vectors that contain embedded Network Application Programming Interface (NAPI) structures, it performs these operations before freeing the associated queues. This creates a scenario where page pool structures that reference these now-freed interrupt vectors can still be accessed, leading to the kernel warning messages generated from net/core/page_pool.c at the page_pool_disable_direct_recycling() function. The vulnerability is classified as a use-after-free condition under CWE-416, representing a classic memory safety issue where freed memory is accessed after deallocation.
The operational impact of this vulnerability extends beyond simple kernel warnings to potentially enable more serious security exploits. The improper resource management sequence creates a window where memory corruption can occur, potentially allowing attackers to execute arbitrary code with kernel privileges or cause system instability through denial-of-service conditions. This is particularly concerning in environments where the IDPF driver is actively used for high-performance network processing, as the timing of these race conditions can be leveraged for privilege escalation attacks. The vulnerability aligns with ATT&CK technique T1068 which covers exploit for privilege escalation and T1499 which covers endpoint denial of service.
The fix implemented addresses the core problem by inverting the allocation and deallocation logic for queue and interrupt vector resources. This modification ensures that interrupt vectors and their associated NAPI structures are allocated first and freed last, establishing proper resource lifetime management. The solution eliminates the problematic dependency where queues required interrupt vectors to be valid, instead making interrupt vectors independent of queue existence. This change removes the need for the previously required queue->q_vector pointer cleanup operations since the vectors remain valid during queue destruction. The fix also aligns with the principle of resource management best practices where resources should be freed in the reverse order of allocation, preventing the scenario where freed memory references are still accessible.
The remediation approach demonstrates a sound understanding of kernel memory management principles and resource lifecycle management. By ensuring that interrupt vectors are allocated before queues and freed after queues, the fix eliminates the race condition that led to the use-after-free scenario. This solution is architecturally sound as it maintains the independence of interrupt vectors from queue structures, allowing for cleaner resource management and eliminating the potential for memory corruption. The change also reduces code complexity by removing unnecessary pointer nullification operations that were previously required to prevent access to freed memory, thereby improving both maintainability and security posture of the kernel driver implementation.