CVE-2026-93052 in Linux
Summary
by MITRE • 09/17/2026
In the Linux kernel, the following vulnerability has been resolved:
misc: bcm-vk: Use acquire/release for msgq_inited
bcm_vk_sync_msgq() fills the message queue information and then sets msgq_inited. Readers call bcm_vk_drv_access_ok() before accessing the message queues and their cached queue information.
atomic_set()/atomic_read() do not order those accesses. A reader can see msgq_inited set while still seeing stale queue information. Use release when publishing the initialized queues and acquire when checking the gate.
Keep the clear in bcm_vk_blk_drv_access() as atomic_set(). It closes the gate and does not publish queue state to readers.
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Analysis
by VulDB Data Team • 09/17/2026
The vulnerability addressed involves a concurrency issue within the Broadcom VK driver of the Linux kernel, specifically concerning the synchronization mechanism used for message queues. The core flaw lies in the improper use of atomic operations that lack necessary memory ordering guarantees. In the bcm_vk_sync_msgq function, the code fills the message queue information structures and subsequently sets a flag named msgq_inited to indicate that the data is ready for consumption. However, the implementation relied on standard atomic_set and atomic_read functions which do not enforce strict memory barriers or orderings between these two operations. This oversight creates a race condition where reader threads may observe the msgq_inited flag as set while still accessing stale or partially initialized queue information cached in their local state.
This lack of proper synchronization can lead to significant operational instability and potential security implications. When a reader thread accesses the message queues based on an outdated view of initialization status, it may process corrupted data structures or encounter undefined behavior due to reading memory that has not been fully populated by the writer. Such scenarios typically manifest as kernel panics, data corruption within the driver's internal state machine, or unpredictable system crashes. In a broader security context, this type of race condition can potentially be exploited for denial-of-service attacks against systems running affected kernels and may serve as an entry point for further exploitation if the stale data leads to memory safety violations that are exploitable by local attackers.
The resolution implements proper acquire-release semantics to ensure correct ordering of memory accesses across CPU cores. Specifically, the code now uses atomic_release when publishing the initialized queues, which acts as a store-store and store-load barrier ensuring that all writes to the queue information occur before the flag is marked as ready. Conversely, readers utilize atomic_acquire when checking the msgq_inited gate, which functions as a load-load and load-store barrier guaranteeing that once the flag is observed as set, subsequent reads of the queue data will reflect the most recent updates made by the writer. This ensures that no reader can proceed with accessing the queues until all prior writes to those structures are globally visible.
The mitigation strategy aligns with industry standards for concurrent programming and kernel development best practices. The issue corresponds broadly to CWE-362, which covers race conditions involving shared resources without proper synchronization mechanisms like locks or memory barriers. From a threat modeling perspective using the MITRE ATT&CK framework, this vulnerability relates to techniques that exploit timing differences in multi-threaded applications, often categorized under resource competition flaws. By enforcing strict acquire-release ordering, the fix ensures data consistency and prevents the window of exposure where stale data could be processed.
Additionally, the patch maintains atomic_set for clearing the msgq_inited flag within bcm_vk_blk_drv_access. This decision is technically sound because closing the gate does not need to publish queue state changes to readers; it merely signals that no new valid data will be written until synchronization occurs again. Keeping this operation as a simple atomic set avoids unnecessary performance overhead from full memory barriers during teardown or reset operations, while still maintaining correctness since readers are blocked by other mechanisms when the flag is cleared. This balanced approach preserves system performance while eliminating the race condition inherent in the previous implementation.