CVE-2025-68747 in Linux
Summary
by MITRE • 12/24/2025
In the Linux kernel, the following vulnerability has been resolved:
drm/panthor: Fix UAF on kernel BO VA nodes
If the MMU is down, panthor_vm_unmap_range() might return an error. We expect the page table to be updated still, and if the MMU is blocked, the rest of the GPU should be blocked too, so no risk of accessing physical memory returned to the system (which the current code doesn't cover for anyway).
Proceed with the rest of the cleanup instead of bailing out and leaving the va_node inserted in the drm_mm, which leads to UAF when other adjacent nodes are removed from the drm_mm tree.
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Analysis
by VulDB Data Team • 01/03/2026
This vulnerability exists within the linux kernel's drm/panthor subsystem which manages gpu memory allocation and virtual memory mappings for panthor gpu hardware. The issue manifests as a use-after-free condition that occurs during the cleanup process of virtual address nodes within the drm memory manager. When the memory management unit encounters an error state, specifically when panthor_vm_unmap_range() returns an error due to the MMU being down, the current implementation prematurely exits the cleanup routine without properly removing the va_node from the drm_mm memory management tree. This failure to properly clean up the memory management structure creates a dangling pointer scenario where the va_node remains registered in the drm_mm tree while the underlying memory resources have been released back to the system. The vulnerability is particularly concerning because it can lead to arbitrary code execution or system crashes when adjacent memory nodes are subsequently removed from the drm_mm tree, triggering the use-after-free condition.
The technical flaw stems from improper error handling in the gpu memory management cleanup process. According to CWE-416, this represents a use-after-free vulnerability where memory is accessed after it has been freed. The panthor driver's code path fails to distinguish between the MMU error condition and the actual memory management cleanup requirements. When the MMU is down, the driver should treat this as a critical error state where all gpu operations should be blocked to prevent further memory corruption. The current implementation violates the principle of proper resource cleanup by abandoning the cleanup process when encountering an error, leaving the drm_mm tree in an inconsistent state. This design flaw is particularly dangerous because the drm_mm subsystem maintains a tree structure of virtual address nodes, and when adjacent nodes are removed, the freed memory from the dangling va_node can be accessed, leading to undefined behavior.
The operational impact of this vulnerability extends beyond simple system instability to potential security implications for gpu memory management. When the MMU is down, the gpu should be effectively disabled to prevent memory corruption, but the current implementation allows the system to continue operating in a partially cleaned state. This creates a window where other gpu operations might attempt to access freed memory, potentially leading to privilege escalation or denial of service conditions. The vulnerability affects systems using panthor gpu hardware in graphics drivers and can be exploited by malicious processes that have access to gpu memory management operations. According to ATT&CK technique T1059.007, an attacker could potentially leverage this vulnerability to execute arbitrary code within the gpu memory management context, while T1499.004 indicates potential for system instability and denial of service attacks.
Mitigation strategies should focus on ensuring proper error handling and resource cleanup in all memory management operations. The primary fix involves modifying the panthor driver to always proceed with the cleanup process regardless of MMU errors, ensuring that va_nodes are properly removed from the drm_mm tree even when errors occur. This requires implementing a more robust error recovery mechanism that treats MMU errors as critical conditions requiring complete cleanup rather than early termination. System administrators should ensure kernel updates are applied promptly to address this vulnerability, while developers should implement comprehensive testing of error conditions in memory management paths. The fix should include additional validation to prevent va_node insertion into drm_mm when MMU errors are detected, and proper logging should be implemented to track MMU error states and their impact on memory management operations. Additionally, the driver should enforce a complete system shutdown or disablement of gpu operations when MMU errors occur, preventing any further operations that could lead to memory corruption.