CVE-2026-53273

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

tee: optee: prevent use-after-free when the client exits before the supplicant

Commit 70b0d6b0a199 ("tee: optee: Fix supplicant wait loop") made the

client wait as killable so it can be interrupted during shutdown or

after a supplicant crash. This changes the original lifetime expectations:

the client task can now terminate while the supplicant is still processing

its request.

If the client exits first it removes the request from its queue and

kfree()s it, while the request ID remains in supp->idr. A subsequent

lookup on the supplicant path then dereferences freed memory, leading to

a use-after-free.

Serialise access to the request with supp->mutex:

* Hold supp->mutex in optee_supp_recv() and optee_supp_send() while

looking up and touching the request.

* Let optee_supp_thrd_req() notice that the client has terminated and

signal optee_supp_send() accordingly.

With these changes the request cannot be freed while the supplicant still

has a reference, eliminating the race.