CVE-2025-40332 in Linux
Summary
by MITRE • 12/09/2025
In the Linux kernel, the following vulnerability has been resolved:
drm/amdkfd: Fix mmap write lock not release
If mmap write lock is taken while draining retry fault, mmap write lock is not released because svm_range_restore_pages calls mmap_read_unlock then returns. This causes deadlock and system hangs later because mmap read or write lock cannot be taken.
Downgrade mmap write lock to read lock if draining retry fault fix this bug.
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Analysis
by VulDB Data Team • 07/09/2026
The vulnerability identified as CVE-2025-40332 resides within the Linux kernel's graphics subsystem, specifically affecting the amdkfd driver component that manages AMD GPU memory management. This issue manifests as a critical deadlock condition that can lead to complete system hangs, representing a significant threat to system stability and availability. The flaw occurs within the memory management subsystem where the kernel fails to properly release write locks during memory mapping operations, creating a cascading failure that prevents normal system operation.
The technical root cause involves improper lock management within the memory management subsystem when handling GPU memory faults and page restoration operations. Specifically, when the system encounters a retry fault during memory mapping operations, it takes a write lock on the memory mapping structure. However, during the subsequent svm_range_restore_pages function execution, the code incorrectly calls mmap_read_unlock instead of releasing the write lock, leaving the lock in a held state. This improper lock release creates a deadlock scenario where subsequent memory mapping operations cannot acquire the necessary locks to proceed, effectively halting system functionality.
The operational impact of this vulnerability extends beyond simple system hangs to potentially compromise the entire system's memory management capabilities. When the write lock remains unreleased, any attempt to perform memory mapping operations that require write access will block indefinitely, leading to complete system unresponsiveness. This affects systems running AMD GPU workloads where memory mapping operations are frequent and critical for proper system operation, particularly in server and workstation environments where GPU acceleration is heavily utilized.
The mitigation strategy implemented in the fix involves downgrading the write lock to a read lock when handling the specific scenario of draining retry faults. This approach addresses the fundamental lock management issue by ensuring that the appropriate lock type is maintained throughout the memory mapping operation lifecycle. The solution aligns with the principle of lock hierarchy management and proper resource cleanup, preventing the deadlock condition that would otherwise occur when transitioning between different lock states during fault handling operations.
This vulnerability demonstrates the critical importance of proper lock management in kernel space operations and relates to several cybersecurity principles including the prevention of deadlock conditions and resource exhaustion attacks. The flaw could potentially be exploited by malicious actors to create denial of service conditions or to gain unauthorized access to system resources through carefully crafted memory mapping operations. From a cybersecurity perspective, this represents a classic example of a resource management vulnerability that can lead to system compromise, making it particularly concerning for enterprise environments where system availability is paramount.
The fix implements a defensive programming approach that prevents the specific deadlock scenario by ensuring proper lock state transitions during memory management operations. This aligns with security best practices for kernel development and follows established patterns for managing shared resources in concurrent systems. The solution maintains system stability while preserving the intended functionality of the memory management subsystem, demonstrating the importance of careful lock management in preventing cascading failures that can compromise entire system operations. This vulnerability highlights the need for comprehensive testing of lock acquisition and release patterns in kernel space code, particularly in high-concurrency environments where memory management operations are frequent and critical for system performance.