CVE-2026-99024: optee: register TEE devices only once fully initialized
In the Linux kernel, the following vulnerability has been resolved:
optee: register TEE devices only once fully initialized
opteeprobe() called teedeviceregister() on both the client and the supplicant device before the rest of struct optee had been initialized.
teedeviceregister() calls cdevdeviceadd(), which does two things at once: it creates /dev/tee0 and /dev/teepriv0, and it links the device into the tee class so that classfinddevice() can find it. From that moment on the device is reachable both from user space via teeopen() and from kernel space via teeclientopencontext(). The only gate in teedevopen() is teedeviceget(), which merely checks that teedev->desc is non-NULL, which was already set by teedevicealloc(). Therefore, there is effectively no gate at all.
A context opened in that window can run against a struct optee where
- optee->callqueue.mutex is not initialized by opteecqinit() - optee->supp mutex and completions is not initialized by opteesuppinit() - optee->rpmbdevmutex is not initialized yet, - the message argument cache is not initialized by opteeshmargcacheinit() - optee->ctx is still NULL
Any open session or invoke during this window takes uninitialized mutexes and dereferences a NULL pointer.
Fix it by moving both teedeviceregister() calls down to the point where all of struct optee is set up.
[JW: adding fixes and cc]
Affected Software
Remediation
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ubuntu/linux-realtimeto a version that resolves this vulnerability.Fixed in 7.0.0-43.43.1 - Compensating control
Move both tee_device_register() calls in optee_probe() to the point where all of struct optee is initialized, including optee_cq_init(), optee_supp_init(), RPMB device mutex initialization, optee_shm_arg_cache_init(), and optee->ctx setup.
Event History
Frequently Asked Questions
Which access paths can reach the device during the vulnerable initialization window?
The device can be reached from user space through /dev/tee0 and /dev/teepriv0 via tee_open(), and from kernel space through tee_client_open_context(). The device is also discoverable through the TEE class after registration.
What does an attacker or triggering process need to do?
It must open a TEE context during the interval after the TEE devices are registered but before the OP-TEE structure has finished initialization, then perform an operation such as opening a session or invoking a command. The normal open-path check does not block this because it only checks that the device descriptor is non-NULL.
What incomplete state can operations encounter in that window?
Operations may run before the call-queue mutex, supplicant mutex and completions, RPMB mutex, and message-argument cache have been initialized. The OP-TEE context pointer may also still be NULL.