CVE-2026-68256 in Linux
Summary
by MITRE • 08/10/2026
In the Linux kernel, the following vulnerability has been resolved:
drm/amd/display: detect_link_and_local_sink: DP alt mode timeout path leaks prev_sink reference
prev_sink is unconditionally retained via dc_sink_retain at function entry, but the DP alt mode timeout path inside SIGNAL_TYPE_DISPLAY_PORT returns false without releasing prev_sink. All other return paths in the function correctly call dc_sink_release(prev_sink), making this the only missing cleanup.
(cherry picked from commit 45510cf662dcf46b5d8926d454f338809f107b9d)
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Analysis
by VulDB Data Team • 08/10/2026
This vulnerability exists in the AMD display driver component of the Linux kernel within the drm/amd/display subsystem where a reference counting issue occurs during display port alternate mode detection. The flaw manifests in the detect_link_and_local_sink function which manages the lifecycle of display sink references during connection establishment. The function begins by unconditionally retaining the previous sink reference through dc_sink_retain at entry, establishing a reference count that should be properly managed throughout execution.
The technical flaw occurs specifically within the DP alt mode timeout path when handling SIGNAL_TYPE_DISPLAY_PORT conditions. When this particular timeout scenario is encountered, the function returns false without executing the necessary cleanup routine that would normally call dc_sink_release(prev_sink). This creates a memory leak where the previous sink reference remains unreleased despite the function completing its execution. All other code paths within the same function properly release the prev_sink reference through dc_sink_release calls, making this the sole oversight in the reference management logic.
The operational impact of this vulnerability represents a memory leak that gradually consumes system resources over time, particularly affecting systems with frequent display connection changes or those running extended periods without rebooting. The leak occurs each time the specific timeout path is triggered during display port alternate mode detection, potentially leading to progressive memory exhaustion that could affect system performance and stability. While not immediately catastrophic, this leak accumulates over repeated operations and may eventually contribute to system resource constraints.
This vulnerability aligns with CWE-401: Improper Release of Memory Before Removing Last Reference, which specifically addresses memory management issues where resources are not properly deallocated despite being no longer needed. The flaw also relates to ATT&CK technique T1070.004: Indicator Removal on Host - File Deletion, as it represents an improper resource cleanup that leaves references in an inconsistent state. The fix implemented through the cherry-picked commit ensures that the timeout path properly releases the retained reference by adding the missing dc_sink_release(prev_sink) call, maintaining consistent reference counting behavior across all execution paths within the function.
The resolution addresses a fundamental issue in kernel memory management where proper resource cleanup is essential for system stability and performance. This fix demonstrates the importance of comprehensive testing of all code paths within functions that manage reference-counted objects, particularly in kernel drivers where resource leaks can have long-term operational consequences. The vulnerability highlights the need for careful attention to resource management patterns in concurrent systems where multiple execution paths must maintain consistent state management.
This memory leak scenario represents a common class of issues in kernel development where defensive programming practices fail to account for all possible code execution paths, particularly in complex driver subsystems that handle various hardware states and error conditions. The fix ensures proper adherence to reference counting principles that are fundamental to maintaining system stability in kernel-space memory management operations.