CVE-2026-98688

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

thunderbolt: Fix NULL dereference in tb remove work()

There is a slight race between tb remove work() and tb domain remove() which leads to dereferencing a NULL tb->root switch pointer inside tb free unplugged xdomains():

Thread A              Thread B

tb remove work() tb domain remove() mutex lock(&tb->lock) tb stop() /* doesn't cancel a running callback / cancel delayed work(&tcm->remove work) ... tb switch remove(tb->root switch) tb->root switch = NULL mutex unlock(&tb->lock) mutex lock(&tb->lock) ... / without checking ->root switch */ tb free unplugged xdomains(tb->root switch) mutex unlock(&tb->lock)

Commit a8937f35cf39 ("thunderbolt: Remove XDomain from the bus without holding tb->lock") doesn't seem right to move tb free unplugged xdomains() out of the &tb->lock section and the check for tb->root switch, in particular. It states:

For this reason separate removing the XDomain from the topology data structures (where we need the lock) from unregistering the device from the bus (where remove callbacks of the drivers are being called).

tb free unplugged xdomains() belongs to the former group of functions requiring the lock. And it also calls tb xdomain remove() which should only be called with &tb->lock held.

Found by Linux Verification Center (linuxtesting.org) with Svace static analysis tool.