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Subject[PATCH] tpm: fix a race between poll and write in tpm-dev-common
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Date
Since the poll returns EPOLLIN base on the state of two
variables, the response_read being false and the
response_length > 0 the poll needs to take the buffer_mutex
after it is woken up.

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 | 2 ++
1 file changed, 2 insertions(+)

diff --git a/drivers/char/tpm/tpm-dev-common.c b/drivers/char/tpm/tpm-dev-common.c
index 5eecad233ea1..61e458d6f652 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)
mask = EPOLLIN | EPOLLRDNORM;
else
mask = EPOLLOUT | EPOLLWRNORM;

+ mutex_unlock(&priv->buffer_mutex);
return mask;
}

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