tpm_ftpm_tee: Free and unregister TEE shared memory during kexec
dma-buf backed shared memory cannot be reliably freed and unregistered during a kexec operation even when tee_shm_free() is called on the shm from a .shutdown hook. The problem occurs because dma_buf_put() calls fput() which then uses task_work_add(), with the TWA_RESUME parameter, to queue tee_shm_release() to be called before the current task returns to user mode. However, the current task never returns to user mode before the kexec completes so the memory is never freed nor unregistered. Use tee_shm_alloc_kernel_buf() to avoid dma-buf backed shared memory allocation so that tee_shm_free() can directly call tee_shm_release(). This will ensure that the shm can be freed and unregistered during a kexec operation. Fixes: 09e57483 ("tpm/tpm_ftpm_tee: A driver for firmware TPM running inside TEE") Fixes: 1760eb68 ("tpm/tpm_ftpm_tee: add shutdown call back") Cc: stable@vger.kernel.org Signed-off-by: Tyler Hicks <tyhicks@linux.microsoft.com> Reviewed-by: Sumit Garg <sumit.garg@linaro.org> Acked-by: Jarkko Sakkinen <jarkko@kernel.org> Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
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