CVE-2025-39740 in Linux
Summary
by MITRE • 09/11/2025
In the Linux kernel, the following vulnerability has been resolved:
drm/xe/migrate: prevent potential UAF
If we hit the error path, the previous fence (if there is one) has already been put() prior to this, so doing a fence_wait could lead to UAF. Tweak the flow to do to the put() until after we do the wait.
(cherry picked from commit 9b7ca35ed28fe5fad86e9d9c24ebd1271e4c9c3e)
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Analysis
by VulDB Data Team • 11/26/2025
The vulnerability identified as CVE-2025-39740 resides within the Linux kernel's graphics subsystem, specifically in the drm/xe/migrate component responsible for managing memory migration operations in graphics processing units. This issue represents a use-after-free condition that occurs during error handling pathways within the graphics driver's memory management functions. The flaw manifests when the system encounters an error during memory migration operations, creating a scenario where memory resources may be accessed after they have been freed, potentially leading to system instability or exploitation opportunities. The vulnerability affects graphics drivers that utilize the Intel Xe graphics architecture and related memory management subsystems.
The technical implementation of this vulnerability stems from improper resource management during error handling within the memory migration code path. When an error condition occurs, the system attempts to wait for a fence object that has already been released through a put() operation, creating a race condition where the fence object may be freed while still being referenced. The original code flow executed the fence_put() operation before fence_wait(), which allowed the fence object to be destroyed while waiting for its completion, resulting in a use-after-free scenario. This pattern violates fundamental memory safety principles and creates opportunities for attackers to manipulate freed memory locations, potentially leading to privilege escalation or system compromise. The vulnerability specifically aligns with CWE-416, which describes the use of freed memory condition, and represents a classic example of improper resource management in kernel space operations.
The operational impact of CVE-2025-39740 extends beyond simple system instability to potentially enable sophisticated exploitation techniques. Attackers could leverage this vulnerability to execute arbitrary code with kernel privileges, particularly in environments where graphics processing is actively utilized such as gaming platforms, professional workstations, or server environments with graphics acceleration. The vulnerability affects systems running Linux kernels with Intel Xe graphics drivers, including desktop systems, servers, and embedded platforms that rely on these graphics subsystems. The timing of the exploit is particularly critical as it occurs during error handling, making it difficult to detect through normal system monitoring and potentially exploitable during high-load graphics operations. This vulnerability falls under the ATT&CK technique T1068, which involves exploiting legitimate credentials and system access, as the use-after-free condition could provide attackers with elevated privileges within the graphics subsystem. The exploitability is enhanced in systems where the graphics driver is frequently accessed or where memory allocation patterns create predictable conditions for triggering the race condition.
The fix implemented addresses the core issue by reordering the resource management operations within the error handling path. The solution modifies the execution flow to perform the fence_wait() operation before the fence_put() operation, ensuring that any references to the fence object are completed before it is released. This change prevents the use-after-free condition by guaranteeing proper synchronization between waiting for fence completion and releasing the associated memory resources. The fix represents a standard defensive programming practice that aligns with kernel development best practices for managing reference-counted objects in concurrent environments. System administrators should prioritize applying this patch to all affected Linux systems, particularly those running graphics-intensive applications or serving as multi-user platforms where the risk of exploitation is elevated. The patch demonstrates the importance of careful resource management in kernel space code and highlights the need for thorough testing of error handling paths in graphics drivers and memory management subsystems.