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

Official 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 packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/b1d05cc61dfa6c4bd5e67855bec6a03e955f512d
• https://git.kernel.org/stable/c/4ed6d08c4a59ee6a8cb806347f6d9873de5d229e
• https://git.kernel.org/stable/c/8c6d84a54823cd839e6ce22af559925f1320c310
• https://git.kernel.org/stable/c/afdff9103818656627920c21822e48a6dae2906f
• https://git.kernel.org/stable/c/613059875958e7b217b250ed14c3b189f9488421