CVE-2026-93041 in Linux
Summary
by MITRE • 09/17/2026
In the Linux kernel, the following vulnerability has been resolved:
dmaengine: dw-edma: Serialize abort state updates
dw_edma_abort_interrupt() drops vc.lock before changing request and status. issue_pending() can acquire the lock in that small window, observe the old busy state, and skip starting queued descriptors. Then the abort handler overwrites the channel status as idle, leaving the new descriptors stranded for good.
Keep descriptor completion and the state transition in the same critical section.
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Analysis
by VulDB Data Team • 09/18/2026
The vulnerability identified within the Linux kernel's dw-edma driver represents a classic race condition arising from improper synchronization of shared hardware state during asynchronous operations. Specifically, the issue resides in the dw_edma_abort_interrupt function, which is responsible for handling interrupt signals related to DMA channel aborts. In the original implementation, this function releases the virtual channel lock before updating the internal request and status variables that track the operational state of the DMA engine. This sequence creates a critical timing window where the system's consistency guarantees are temporarily suspended, allowing other concurrent execution paths to interact with partially updated or stale data structures.
The core technical flaw involves the interaction between the abort handler and the issue_pending function. When dw_edma_abort_interrupt drops the vc.lock early in its execution flow, it leaves a gap during which another thread of control can acquire the same lock via issue_pending. This competing process observes the channel status as busy based on outdated information because the abort handler has not yet completed its state transition to idle. Consequently, issue_pending incorrectly determines that the channel is occupied and skips initiating any newly queued descriptors. Shortly after this erroneous check, the abort handler proceeds to overwrite the channel status with an idle state. This results in a scenario where new descriptors are left stranded without being processed, effectively causing them to be lost or ignored indefinitely until the next reset or manual intervention.
From an operational perspective, this race condition leads to significant reliability issues within systems relying on high-performance DMA transfers for data movement between memory and peripherals. The primary impact is the silent failure of queued operations, which can manifest as data corruption if subsequent processes expect specific buffers to be populated by these DMA transactions. In real-time or safety-critical applications such as automotive control units or industrial automation controllers, this behavior could lead to system instability, loss of sensor data, or unresponsive peripheral interfaces. The lack of explicit error reporting for the stranded descriptors makes debugging particularly challenging, as the symptoms may appear intermittently depending on timing variations in interrupt handling and scheduler preemption.
This vulnerability aligns with CWE-362, which describes concurrent execution using shared resources with insufficient synchronization. By releasing the lock before completing all necessary state updates, the code violates the atomicity principle required for safe multi-threaded access to hardware registers and driver internal states. Furthermore, this scenario can be mapped to MITRE ATT&CK techniques related to resource manipulation or denial of service through race conditions, although in this context it is primarily a stability issue rather than an exploitable attack vector for privilege escalation. The flaw highlights the importance of maintaining strict critical sections when modifying shared state that influences control flow decisions in other parts of the driver stack.
To mitigate this vulnerability and prevent future occurrences of similar synchronization errors, developers must ensure that all modifications to shared hardware status variables are performed within a single atomic operation protected by the appropriate mutex or spinlock. In this specific case, the fix involves keeping descriptor completion logic and state transitions inside the same critical section so that no other thread can observe an inconsistent intermediate state. Best practices for kernel development dictate that lock acquisition should occur as late as possible before accessing shared data and release only after all dependent updates are complete. Additionally, implementing rigorous code review processes focused on concurrency patterns and utilizing static analysis tools capable of detecting race conditions in multi-threaded environments can help identify such issues early in the software lifecycle. Regular testing under high-load scenarios with randomized timing variations is also recommended to expose latent synchronization bugs that may not manifest during standard functional verification.