CVE-2026-68211 in Linux
Summary
by MITRE • 08/10/2026
In the Linux kernel, the following vulnerability has been resolved:
media: stm32-dcmipp: Return queued buffers on start_streaming() failure
The vb2 framework hands buffers to the driver via buf_queue() before calling start_streaming(). If start_streaming() returns an error without first returning those buffers via vb2_buffer_done(), vb2_start_streaming() fires WARN_ON(owned_by_drv_count) and the queued buffers leak.
dcmipp_bytecap_start_streaming() returned -EINVAL when the source subdevice could not be resolved from the media graph, before pm_runtime_resume_and_get() and media_pipeline_start() had been called. The remaining error paths already converge on the err_buffer_done label, which calls dcmipp_bytecap_all_buffers_done(..., VB2_BUF_STATE_QUEUED). Jump to that label directly: the intermediate err_pm_put / err_media_pipeline_stop labels are skipped, which is correct because nothing they would undo has happened yet.
This mirrors the uvcvideo fix in commit 4cf3b6fd54eb ("media: uvcvideo: Return queued buffers on start_streaming() failure").
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Analysis
by VulDB Data Team • 08/11/2026
The vulnerability resides within the Linux kernel's media subsystem, specifically affecting the stm32-dcmipp driver implementation. This issue manifests when the video buffer (vb2) framework attempts to initiate streaming operations but encounters a failure during the start_streaming() call execution. The fundamental problem occurs because the vb2 framework queues buffers to the driver through buf_queue() before invoking start_streaming(), creating a dependency where buffers must be properly managed throughout the entire process. When start_streaming() fails and does not explicitly return queued buffers via vb2_buffer_done(), the vb2_start_streaming() function triggers a WARN_ON(owned_by_drv_count) assertion, resulting in buffer leakage that can lead to resource exhaustion and system instability.
The technical flaw specifically exists in the dcmipp_bytecap_start_streaming() function which returns -EINVAL when it cannot resolve the source subdevice from the media graph. This occurs before critical initialization functions like pm_runtime_resume_and_get() and media_pipeline_start() are executed, creating an inconsistent state where buffers remain queued but are not properly accounted for. The error handling path demonstrates a code pattern that fails to maintain proper buffer state management, as it bypasses intermediate cleanup labels (err_pm_put and err_media_pipeline_stop) that would normally handle the necessary buffer return operations.
This vulnerability directly impacts system stability and resource management within embedded multimedia processing environments that rely on the stm32-dcmipp driver for image capture and processing. The buffer leak can accumulate over time, potentially leading to memory exhaustion, performance degradation, or complete system lockup when the driver cannot properly handle streaming failures. The operational impact extends beyond simple resource waste to include potential security implications through denial-of-service conditions that could affect critical embedded systems in automotive, industrial, or IoT applications.
The resolution implements a fix pattern consistent with established industry practices, specifically mirroring the uvcvideo driver fix referenced in commit 4cf3b6fd54eb. This approach ensures that all queued buffers are properly returned through the vb2_buffer_done() mechanism regardless of the error path taken during start_streaming() execution. The solution involves directly jumping to the err_buffer_done label which correctly calls dcmipp_bytecap_all_buffers_done(..., VB2_BUF_STATE_QUEUED) to ensure buffer state consistency. This fix aligns with common security best practices for buffer management and follows the CWE-459 principle of proper resource cleanup, while also addressing potential ATT&CK techniques related to privilege escalation through system stability compromise.
The mitigation strategy requires updating affected kernel versions to include this specific buffer management fix, ensuring that all error paths in start_streaming() execution properly account for previously queued buffers. System administrators should prioritize kernel updates for embedded devices using the stm32-dcmipp driver, particularly in mission-critical applications where resource exhaustion or system instability could have severe consequences. The fix represents a defensive programming approach that prevents resource leaks and maintains proper buffer state management throughout all possible execution paths, reducing attack surface and improving overall system robustness against denial-of-service conditions.