tpm: fix an invalid condition in tpm_common_poll

[linux.git] / drivers / char / tpm / tpm-dev-common.c

diff --git a/drivers/char/tpm/tpm-dev-common.c b/drivers/char/tpm/tpm-dev-common.c
index 8856cce5a23b2858b58b69373f4cd89e2f898abb..817ae09a369ec2ba192a68f302205eaef7aadeb5 100644 (file)
--- a/drivers/char/tpm/tpm-dev-common.c
+++ b/drivers/char/tpm/tpm-dev-common.c
@@ -233,12 +233,19 @@ __poll_t tpm_common_poll(struct file *file, poll_table *wait)
        __poll_t mask = 0;
 
        poll_wait(file, &priv->async_wait, wait);
+       mutex_lock(&priv->buffer_mutex);
 
-       if (!priv->response_read || priv->response_length)
+       /*
+        * The response_length indicates if there is still response
+        * (or part of it) to be consumed. Partial reads decrease it
+        * by the number of bytes read, and write resets it the zero.
+        */
+       if (priv->response_length)
                mask = EPOLLIN | EPOLLRDNORM;
        else
                mask = EPOLLOUT | EPOLLWRNORM;
 
+       mutex_unlock(&priv->buffer_mutex);
        return mask;
 }