CVE-2026-98693: thunderbolt: Hold a router reference for each allocated HopID
In the Linux kernel, the following vulnerability has been resolved:
thunderbolt: Hold a router reference for each allocated HopID
tbstop() drops the reference to all DP tunnels but does not deactivate them, thus nothing cancels a dprxwork still in flight (which holds its own tunnel reference) and the tunnel can outlive tbswitchremove(). The HopID releases in tbpathfree() then operate on freed IDAs and trigger warnings like
idafree called for id=8 which is not allocated.
This can be triggered by unbinding the driver while a DP tunnel is still waiting for the DPRX capabilities read to finish. On the Apple NHI unplugging the cable runs into just that reliably because the read can never finish right now and because the unplug powers down the entire USB4 complex and removes the NHI device.
Take a router reference whenever an input or output HopID is allocated and drop it again after the HopID is released. This keeps the ports and their HopID IDAs alive for as long as they are used.
The KUnit tests allocate routers without ever registering their devices so initialize the embedded struct device there as well and drop its initial reference when the test is finished.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Compensating control
Hold a router reference whenever an input or output HopID is allocated, and drop the reference after the HopID is released so the router and its HopID IDA remain alive while in use.
- Operational
For KUnit tests, initialize the embedded struct device for each test router and drop its initial reference when the test finishes.