CVE-2025-21871: Loop with Unreachable Exit Condition

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

tee: optee: Fix supplicant wait loop

OP-TEE supplicant is a user-space daemon and it's possible for it be hung or crashed or killed in the middle of processing an OP-TEE RPC call. It becomes more complicated when there is incorrect shutdown ordering of the supplicant process vs the OP-TEE client application which can eventually lead to system hang-up waiting for the closure of the client application.

Allow the client process waiting in kernel for supplicant response to be killed rather than indefinitely waiting in an unkillable state. Also, a normal uninterruptible wait should not have resulted in the hung-task watchdog getting triggered, but the endless loop would.

This fixes issues observed during system reboot/shutdown when supplicant got hung for some reason or gets crashed/killed which lead to client getting hung in an unkillable state. It in turn lead to system being in hung up state requiring hard power off/on to recover.