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From patchwork Thu Mar 21 23:02:12 2019
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X-Patchwork-Submitter: Tadeusz Struk <tadeusz.struk@intel.com>
X-Patchwork-Id: 10864497
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Subject: [PATCH v3] tpm: fix an invalid condition in tpm_common_poll
From: Tadeusz Struk <tadeusz.struk@intel.com>
To: jarkko.sakkinen@linux.intel.com
Cc: grawity@gmail.com, James.Bottomley@HansenPartnership.com,
linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org,
stable@vger.kernel.org, tadeusz.struk@intel.com
Date: Thu, 21 Mar 2019 16:02:12 -0700
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<155320933278.5015.1752135965699928631.stgit@tstruk-mobl1.jf.intel.com>
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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>
Tested-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;
}
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