tpm_ftpm_tee: Free and unregister TEE shared memory during kexec

commit dfb703ad2a8d366b829818a558337be779746575 upstream.

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: 09e574831b27 ("tpm/tpm_ftpm_tee: A driver for firmware TPM running inside TEE")
Fixes: 1760eb689ed6 ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/char/tpm/tpm_ftpm_tee.c b/drivers/char/tpm/tpm_ftpm_tee.c
index 22bf553ccf9df35e61c411707a78373f4ea8aa38..69937be2032b1ca8c3604cef6839a216dbb00708 100644 (file)
--- a/drivers/char/tpm/tpm_ftpm_tee.c
+++ b/drivers/char/tpm/tpm_ftpm_tee.c
@@ -255,11 +255,11 @@ static int ftpm_tee_probe(struct platform_device *pdev)
        pvt_data->session = sess_arg.session;
 
        /* Allocate dynamic shared memory with fTPM TA */
-       pvt_data->shm = tee_shm_alloc(pvt_data->ctx,
-                                     MAX_COMMAND_SIZE + MAX_RESPONSE_SIZE,
-                                     TEE_SHM_MAPPED | TEE_SHM_DMA_BUF);
+       pvt_data->shm = tee_shm_alloc_kernel_buf(pvt_data->ctx,
+                                                MAX_COMMAND_SIZE +
+                                                MAX_RESPONSE_SIZE);
        if (IS_ERR(pvt_data->shm)) {
-               dev_err(dev, "%s: tee_shm_alloc failed\n", __func__);
+               dev_err(dev, "%s: tee_shm_alloc_kernel_buf failed\n", __func__);
                rc = -ENOMEM;
                goto out_shm_alloc;
        }