CVE-2026-53265

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

dm cache policy smq: check allocation under invalidate lock

commit 2d1f7b65f5de ("dm cache policy smq: fix missing locks in

invalidating cache blocks") added mq->lock around the destructive part of

smq_invalidate_mapping(), but left the e->allocated check outside the

critical section.

That leaves a check-then-act race. Two concurrent invalidators can both

observe e->allocated as true before either of them takes mq->lock. The

first invalidator that acquires the lock removes the entry from the

queues and hash table and then calls free_entry(), which clears

e->allocated and puts the entry back on the free list. The second

invalidator can then acquire mq->lock and continue with the stale result

of the unlocked check.

This can corrupt the SMQ queues or hash table by deleting an entry that

is no longer on those structures. It can also hit the allocation check in

free_entry() when the same entry is freed again.

Move the allocation check under mq->lock so the predicate and the

destructive operations are serialized by the same lock.