CVE-2026-68228 in Linux
Summary
by MITRE • 08/10/2026
In the Linux kernel, the following vulnerability has been resolved:
media: chips-media: wave5: Move src_buf Removal to finish_encode
During encoder processing, there is a case where the IRQ response could return the buffer back to userspace via v4l2_m2m_buf_done call. In this time, userspace could queue up this same buffer before start_encode removes the index from the ready queue. This would then lead to a case where the buffer in the ready queue could be a self loop due to the WRITE_ONCE(prev->next, new) call in __list_add.
When __list_del is finally called, the loop is already made so nothing points back to ready queue list head and pointers are poisoned.
A buffer should not be marked as DONE before the buffer is removed from m2m ready queue. Move removal entirely to finish_encode.
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Analysis
by VulDB Data Team • 08/11/2026
This vulnerability exists within the linux kernel's media subsystem, specifically in the chips-media wave5 encoder driver implementation. The issue stems from a race condition in the buffer management workflow during encoder processing where the timing of buffer state transitions creates potential for memory corruption through list manipulation. The flaw occurs when an interrupt response returns a buffer back to userspace via the v4l2_m2m_buf_done call while userspace simultaneously queues the same buffer before the start_encode function removes it from the ready queue. This temporal mismatch creates a scenario where the buffer reference in the ready queue becomes self-referential due to the WRITE_ONCE(prev->next, new) operation within the __list_add function, effectively creating a circular list structure that violates normal queue semantics.
The technical execution of this vulnerability involves a complex interplay between hardware interrupt handling and software buffer management within the v4l2 memory-to-memory framework. When the encoder processes buffers, it maintains a ready queue to track which buffers are available for processing, but the current implementation fails to properly synchronize the buffer state transitions between the hardware completion path and the software queue management. The WRITE_ONCE macro used in __list_add creates an atomic update that can result in corrupted list structures when concurrent access occurs, particularly when the same buffer reference is processed through multiple code paths simultaneously. This memory corruption manifests as a circular reference where a buffer's next pointer points back to itself rather than to the proper queue structure.
The operational impact of this vulnerability extends beyond simple buffer corruption to potentially enable arbitrary code execution or system instability within media processing applications. Attackers could exploit this race condition by carefully orchestrating buffer queuing operations to force the creation of circular lists that would cause kernel memory corruption during list traversal operations, particularly when __list_del is eventually called on the corrupted structure. The poisoning of pointers during cleanup operations indicates that the kernel's memory management systems detect and mark corrupted data structures, but the damage has already been done through the malformed list references that bypass normal queue integrity checks. This vulnerability affects any system utilizing the wave5 encoder driver within the v4l2 framework, particularly those running multimedia applications that rely on hardware-accelerated video encoding.
The root cause of this vulnerability aligns with CWE-367 weakness category, specifically focusing on Time-of-Check to Time-of-Use (TOCTOU) race conditions in kernel memory management operations. The issue also maps to ATT&CK technique T1068 which involves exploiting local privilege escalation through kernel vulnerabilities. The solution requires reorganizing the buffer management workflow by moving the buffer removal operation entirely to the finish_encode function, ensuring that buffers are only marked as DONE after they have been completely removed from the m2m ready queue. This approach prevents the race condition by eliminating the temporal window where userspace operations could interfere with the kernel's internal queue management, thereby maintaining list integrity throughout the entire processing lifecycle and preventing the creation of self-referential buffer structures that could lead to memory corruption or system instability.
This vulnerability demonstrates a classic example of improper synchronization in kernel space memory management where concurrent access patterns create conditions for data structure corruption. The fix implementation involves restructuring the buffer state transition logic to ensure proper ordering between the completion signaling and queue removal operations, thereby preventing the race condition that allows circular list references to form. The solution directly addresses the temporal mismatch between hardware interrupt processing and software queue management by ensuring that all buffer cleanup operations occur within a single atomic sequence that maintains data structure integrity throughout the entire encoder processing workflow, eliminating the potential for userspace interference with kernel-managed lists that could otherwise lead to memory corruption or system crashes during normal operation.