CVE-2024-47739 in Linux
Summary
by MITRE • 10/21/2024
In the Linux kernel, the following vulnerability has been resolved:
padata: use integer wrap around to prevent deadlock on seq_nr overflow
When submitting more than 2^32 padata objects to padata_do_serial, the current sorting implementation incorrectly sorts padata objects with overflowed seq_nr, causing them to be placed before existing objects in the reorder list. This leads to a deadlock in the serialization process as padata_find_next cannot match padata->seq_nr and pd->processed because the padata instance with overflowed seq_nr will be selected next.
To fix this, we use an unsigned integer wrap around to correctly sort padata objects in scenarios with integer overflow.
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Analysis
by VulDB Data Team • 01/19/2026
The vulnerability described in CVE-2024-47739 represents a critical flaw in the Linux kernel's padata subsystem that can lead to system deadlock under specific conditions. This issue affects the parallel data processing framework used by the kernel to handle concurrent operations across multiple CPUs. The padata subsystem is designed to serialize and reorder data processing tasks to maintain consistency, but the implementation contains a fundamental flaw in how it handles sequence number overflow. The vulnerability manifests when the system processes more than 2^32 padata objects, causing the sequence number counter to overflow and trigger incorrect sorting behavior. This flaw falls under the CWE-191 Integer Underflow/Overflow category, specifically involving unsigned integer wraparound behavior that is not properly accounted for in the sorting logic.
The technical implementation of this vulnerability stems from the improper handling of sequence number comparisons within the padata_do_serial function. When sequence numbers exceed the 32-bit unsigned integer limit and wrap around, the sorting algorithm fails to correctly position these overflowed objects within the reorder list. This misordering causes the padata_find_next function to enter an infinite loop or deadlock situation because it cannot properly match the sequence numbers against processed items. The root cause lies in the assumption that sequence numbers will always be in ascending order, without accounting for the wraparound behavior that occurs with unsigned integer arithmetic. This type of vulnerability demonstrates poor understanding of integer arithmetic properties and their implications in concurrent systems, making it a classic example of a logic flaw that can be exploited to cause system-wide service disruption.
The operational impact of this vulnerability is significant as it can lead to complete system deadlock where the kernel becomes unresponsive to further padata processing requests. This affects systems that rely heavily on parallel data processing, including high-performance computing environments, database servers, and network infrastructure that utilize the padata subsystem for efficient task distribution. The vulnerability can be triggered through legitimate system operations that generate large volumes of padata objects, making it particularly dangerous in production environments where such workloads are common. Attackers could potentially exploit this by crafting specific workloads that force the sequence number to overflow, thereby causing denial of service conditions that may require system reboot to resolve. The issue demonstrates how seemingly minor implementation details in kernel code can have catastrophic effects on system reliability and availability.
Mitigation strategies for this vulnerability focus on updating to patched kernel versions that implement proper unsigned integer wraparound handling in the padata sorting logic. System administrators should prioritize kernel updates and verify that the specific patch addressing CVE-2024-47739 is applied to all affected systems. Monitoring for unusual patterns in padata processing or system performance degradation could serve as early indicators of potential exploitation attempts. Additionally, implementing workload limits or rate limiting on padata operations can reduce the likelihood of triggering the overflow condition. Organizations should also consider implementing automated patch management systems to ensure timely deployment of security fixes. The fix implemented in the kernel addresses the core issue by ensuring that sequence number comparisons correctly handle unsigned integer wraparound, aligning with best practices for concurrent system design and integer arithmetic in kernel space operations. This vulnerability highlights the importance of thorough testing of integer overflow scenarios in kernel code and adherence to security standards such as those outlined in the CERT/CC Secure Coding Standards for kernel-level programming.