CVE-2026-98689: thunderbolt: Don't access a DP tunnel after its DPRX read was canceled

In the Linux kernel, the following vulnerability has been resolved:

thunderbolt: Don't access a DP tunnel after its DPRX read was canceled

tbdpdprxwork() checks ->dprxcanceled before it takes tb->lock so it misses a tbdpdprxstop() that could not cancel the already running work. It then polls the DPRX capabilities and runs the callback for a tunnel that has already been torn down while the domain is suspending or going away.

This can be hit by cancelling the DPRX read from outside the ordered tb->wq: During suspend tbdisconnectandreleasedp() does just this and with a later patch tbstop() will do it as well. The latter in combination with the Apple NHI where the DPRX read never completed is how I hit this.

Check the flag with tb->lock held instead and check it again in tbdptunnelactive() because the callback runs after the lock has been dropped again.

Also clear the flag in tbdpdprxstart() so that it only ever describes the work that is currently in flight.