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    Subject[PATCH 5.4 366/434] tpm: fix invalid locking in NONBLOCKING mode
    Date
    From: Tadeusz Struk <tadeusz.struk@intel.com>

    commit d23d12484307b40eea549b8a858f5fffad913897 upstream.

    When an application sends TPM commands in NONBLOCKING mode
    the driver holds chip->tpm_mutex returning from write(),
    which triggers: "WARNING: lock held when returning to user space".
    To fix this issue the driver needs to release the mutex before
    returning and acquire it again in tpm_dev_async_work() before
    sending the command.

    Cc: stable@vger.kernel.org
    Fixes: 9e1b74a63f776 (tpm: add support for nonblocking operation)
    Reported-by: Jeffrin Jose T <jeffrin@rajagiritech.edu.in>
    Tested-by: Jeffrin Jose T <jeffrin@rajagiritech.edu.in>
    Signed-off-by: Tadeusz Struk <tadeusz.struk@intel.com>
    Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
    Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/char/tpm/tpm-dev-common.c | 8 ++++++++
    1 file changed, 8 insertions(+)

    --- a/drivers/char/tpm/tpm-dev-common.c
    +++ b/drivers/char/tpm/tpm-dev-common.c
    @@ -61,6 +61,12 @@ static void tpm_dev_async_work(struct wo

    mutex_lock(&priv->buffer_mutex);
    priv->command_enqueued = false;
    + ret = tpm_try_get_ops(priv->chip);
    + if (ret) {
    + priv->response_length = ret;
    + goto out;
    + }
    +
    ret = tpm_dev_transmit(priv->chip, priv->space, priv->data_buffer,
    sizeof(priv->data_buffer));
    tpm_put_ops(priv->chip);
    @@ -68,6 +74,7 @@ static void tpm_dev_async_work(struct wo
    priv->response_length = ret;
    mod_timer(&priv->user_read_timer, jiffies + (120 * HZ));
    }
    +out:
    mutex_unlock(&priv->buffer_mutex);
    wake_up_interruptible(&priv->async_wait);
    }
    @@ -204,6 +211,7 @@ ssize_t tpm_common_write(struct file *fi
    if (file->f_flags & O_NONBLOCK) {
    priv->command_enqueued = true;
    queue_work(tpm_dev_wq, &priv->async_work);
    + tpm_put_ops(priv->chip);
    mutex_unlock(&priv->buffer_mutex);
    return size;
    }

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