• Cyrille Pitchen's avatar
    crypto: atmel-sha - fix a race between the 'done' tasklet and the crypto client · f56809c3
    Cyrille Pitchen authored
    The 'done' tasklet handler used to check the 'BUSY' flag to either
    finalize the processing of a crypto request which had just completed or
    manage the crypto queue to start the next crypto request.
    
    On request R1 completion, the driver calls atmel_sha_finish_req(), which:
    1 - clears the 'BUSY' flag since the hardware is no longer used and is
        ready again to process new crypto requests.
    2 - notifies the above layer (the client) about the completion of the
        asynchronous crypto request R1 by calling its base.complete()
        callback.
    3 - schedules the 'done' task to check the crypto queue and start to
        process the next crypto request (the 'BUSY' flag is supposed to be
        cleared at that moment) if such a pending request exists.
    
    However step 2 might wake the client up so it can now ask our driver to
    process a new crypto request R2. This request is enqueued by calling the
    atmel_sha_handle_queue() function, which sets the 'BUSY' flags then
    starts to process R2.
    
    If the 'done' tasklet, scheduled by step 3, runs just after, it would see
    that the 'BUSY' flag is set then understand that R2 has just completed,
    which is wrong!
    
    So the state of 'BUSY' flag is not a proper way to detect and handle
    crypto request completion.
    
    This patch fixes this race condition by using two different tasklets, one
    to handle the crypto request completion events, the other to manage the
    crypto queue if needed.
    Signed-off-by: default avatarCyrille Pitchen <cyrille.pitchen@atmel.com>
    Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
    f56809c3
atmel-sha.c 36.5 KB