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SubjectRe: [PATCH v2] tpm: fix an invalid condition in tpm_common_poll
On Tue, Mar 19, 2019 at 10:31 PM Tadeusz Struk <tadeusz.struk@intel.com> wrote:
>
> The poll condition should only check response_length,
> because reads should only be issued if there is data to read.
> The response_read flag only prevents double writes.
> The problem was that the write set the response_read to false,
> enqued a tpm job, and returned. Then application called poll
> which checked the response_read flag and returned EPOLLIN.
> Then the application called read, but got nothing.
> After all that the async_work kicked in.
> Added also mutex_lock around the poll check to prevent
> other possible race conditions.
>
> Fixes: 9488585b21bef0df12 ("tpm: add support for partial reads")
> Reported-by: Mantas Mikulėnas <grawity@gmail.com>
> Signed-off-by: Tadeusz Struk <tadeusz.struk@intel.com>
> ---
> drivers/char/tpm/tpm-dev-common.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/char/tpm/tpm-dev-common.c b/drivers/char/tpm/tpm-dev-common.c
> index 5eecad233ea1..7312d3214381 100644
> --- a/drivers/char/tpm/tpm-dev-common.c
> +++ b/drivers/char/tpm/tpm-dev-common.c
> @@ -203,12 +203,14 @@ __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)
> + if (priv->response_length)
> mask = EPOLLIN | EPOLLRDNORM;
> else
> mask = EPOLLOUT | EPOLLWRNORM;
>
> + mutex_unlock(&priv->buffer_mutex);
> return mask;
> }

Thanks, this patch seems to work, and I apologize for not responding
to test the patches earlier.

Any chance it'll be submitted for stable 5.0.x as well?

--
Mantas Mikulėnas

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