KEYS: trusted: dcp: fix NULL dereference in AEAD crypto operation

When sealing or unsealing a key blob we currently do not wait for
the AEAD cipher operation to finish and simply return after submitting
the request. If there is some load on the system we can exit before
the cipher operation is done and the buffer we read from/write to
is already removed from the stack. This will e.g. result in NULL
pointer dereference errors in the DCP driver during blob creation.

Fix this by waiting for the AEAD cipher operation to finish before
resuming the seal and unseal calls.

Cc: stable@vger.kernel.org # v6.10+
Fixes: 0e28bf61 ("KEYS: trusted: dcp: fix leak of blob encryption key")
Reported-by: Parthiban N <parthiban@linumiz.com>
Closes: https://lore.kernel.org/keyrings/254d3bb1-6dbc-48b4-9c08-77df04baee2f@linumiz.com/


Signed-off-by: David Gstir <david@sigma-star.at>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>