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tpm: fix an invalid condition in tpm_common_poll 

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: 9488585b21 ("tpm: add support for partial reads")
Reported-by: Mantas Mikulėnas <grawity@gmail.com>
Tested-by: Mantas Mikulėnas <grawity@gmail.com>
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: James Morris <james.morris@microsoft.com>
This commit is contained in:
Tadeusz Struk 2019-03-27 11:32:38 -07:00 committed by James Morris
parent e891db1a18
commit 7110629263
1 changed files with 8 additions and 1 deletions
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9
drivers/char/tpm/tpm-dev-common.c
View File

@ -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;
}