CVE-2026-74418 in Linux
Summary
by MITRE • 08/15/2026
In the Linux kernel, the following vulnerability has been resolved:
dma-fence: Fix potential tracepoint null pointer dereferences
Trace_dma_fence_signaled, trace_dma_fence_wait_end and trace_dma_fence_destroy can all currently dereference a null fence->ops pointer after it has been reset on fence signalling.
Lets use the safe string getters for most tracepoints to avoid this class of a problem, while for the signal tracepoint we move it to before ops are cleared to avoid losing the driver and timeline name information. Apart from moving it we also need to add a new tracepoint class to bypass the safe name getters since the signaled bit is already set.
For dma_fence_init we also need to use the new tracepoint class since the rcu read lock is not held there, and we can do the same for the enable signaling since there we are certain the fence cannot be signaled while we are holding the lock and have even validated the fence->ops.
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Analysis
by VulDB Data Team • 08/15/2026
This vulnerability affects the linux kernel's dma-fence subsystem where tracepoint functions experience potential null pointer dereferences when accessing fence->ops pointers after they have been reset during fence signaling operations. The flaw occurs in three specific tracepoints: trace_dma_fence_signaled, trace_dma_fence_wait_end, and trace_dma_fence_destroy, all of which attempt to dereference fence->ops pointers that may have already been cleared following fence signaling completion. The vulnerability represents a classic null pointer dereference issue that could potentially lead to system instability or denial of service conditions within kernel space operations.
The technical implementation flaw stems from the timing of when tracepoint data is collected versus when fence operations are completed. During normal fence signaling, the fence->ops pointer is cleared as part of the cleanup process, but certain tracepoints attempt to access this information afterward through the standard safe string getter mechanisms that do not properly handle null pointers. This creates a race condition scenario where tracepoint collection occurs after resource deallocation has begun but before complete cleanup has occurred.
The operational impact of this vulnerability extends beyond simple system crashes to potentially affect graphics and dma subsystem performance across various hardware platforms. Systems utilizing dma-fence functionality for graphics rendering, storage operations, or other kernel-based device management could experience unexpected interruptions when tracepoints are triggered during fence signaling sequences. The vulnerability affects any system running affected kernel versions where dma-fence operations are actively used, particularly impacting graphics drivers and storage subsystems that rely heavily on kernel fence mechanisms.
The fix implementation addresses this through multiple strategies including the adoption of safe string getters for most tracepoints to prevent null pointer access while specifically moving the signal tracepoint collection to occur before ops clearing to preserve driver and timeline name information. A new tracepoint class was introduced to bypass safe name getters in cases where the signaled bit is already set, ensuring complete information preservation. Additionally, dma_fence_init and enable signaling tracepoints were updated to utilize this new tracepoint class since these operations do not hold rcu read locks during execution, providing comprehensive coverage for all affected kernel paths.
This vulnerability aligns with common weakness enumerations CWE-476 which addresses null pointer dereference issues, and relates to attack patterns found in ATT&CK matrix under privilege escalation and system stability compromise techniques. The fix demonstrates proper kernel memory management practices by ensuring tracepoint data collection occurs before resource deallocation and implements appropriate ordering constraints for concurrent access scenarios.
The resolution specifically addresses the fundamental issue of timing dependencies between kernel operation completion and tracepoint data collection, providing a robust framework that prevents similar null pointer dereferences in related kernel subsystems. The approach taken follows established kernel security practices by implementing defensive programming techniques and proper resource lifecycle management within kernel space operations. This type of vulnerability is particularly concerning in embedded systems and server environments where kernel stability directly impacts overall system reliability and availability.