CVE-2026-99144

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

sched ext: Fix use-after-free of a destroyed user DSQ by a deferred reenqueue

A deferred reenqueue can read a freed user DSQ. The request stays on its CPU's deferred list until run deferred() takes it, and the RCU callback that frees the DSQ assumes that the grace period has flushed it, so exit dsq() checks the per-CPU node without the deferred list lock. A grace period waits for readers in flight, not for a pending run deferred(). A run deferred() which starts after the grace period began can detach the request right before the callback looks and then read the freed DSQ's id.

Cancel the pending requests before the grace period instead. The irq work that frees the DSQ unlinks every CPU's request under the per-CPU deferred list lock, and schedule dsq reenq() ignores a new request under the same lock once the id is invalid. Only a run deferred() that started before the grace period can hold a request, and it runs with IRQs disabled, so the grace period waits for it and nothing touches the DSQ after the callback.