CVE-2026-68429: drm/dp_mst: Handle torn-down topology gracefully in drm_dp_mst_topology_queue_probe()

Severity: unknown
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-08-12 · updated 2026-08-17

Description

In the Linux kernel, the following vulnerability has been resolved: drm/dp_mst: Handle torn-down topology gracefully in drm_dp_mst_topology_queue_probe() 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 drm_dp_mst_topology_queue_probe(). Since the check is already performed under mgr->lock, the condition is not a programming error but a valid race -- the topology was valid when the caller decided to call this function, but was torn down before the lock was acquired. Replace the drm_WARN_ON() with a graceful early return. This eliminates spurious kernel warnings and the resulting compositor crashes observed when connecting/disconnecting DP MST monitors, while keeping the correct behavior of doing nothing when MST is not active. A drm_dbg_mst() trace is added so the skipped probe remains observable under MST debug logging. The existing WARN_ON(mgr->mst_primary) in drm_dp_mst_topology_mgr_set_mst() already catches the case where the topology is initialized twice, so no diagnostic coverage is lost.

Affected products

Linux kernel: from 6.6.86 before 6.6.148; 6.12 — fixed in 6.6.148, 7.2

How to fix

Upgrade to a fixed version: Linux kernel 6.6.148, 7.2. Check the vendor advisory for mitigations.

References

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