Executive brief
The Linux kernel's display driver for handling DisplayPort Multi-Stream Transport (MST) monitors had a race condition that could trigger spurious kernel warnings and compositor crashes when users connected or disconnected DP MST monitors. The issue occurred when the MST topology was torn down concurrently with a probe operation, causing the system to generate diagnostic warnings that crashed the graphics compositor rather than handling the situation gracefully.
Technical details
This is a race condition in the drm_dp_mst_topology_queue_probe() function in drivers/gpu/drm/display/drm_dp_mst_topology.c. A hotplug or link-loss event can tear down the MST topology (setting mgr->mst_state = false and mgr->mst_primary = NULL) concurrently with a caller invoking this function. The check is performed under mgr->lock, making this a valid race condition rather than a programming error—the topology was valid when the caller decided to call the function but was torn down before the lock was acquired. The fix replaces a drm_WARN_ON() macro with a graceful early return and debugging trace, eliminating spurious kernel warnings that were causing compositor crashes when connecting/disconnecting DP MST monitors. No authentication or network access is required; the condition occurs through normal device hotplug operations.
Affected products
- Linux Linux kernel multiple versions
Timeline
- 2026-05-03: other: Fix committed upstream
- 2026-06-22: patched: Patch included in stable kernel updates
- 2026-08-12: disclosed