[PATCH 1/1][SRU][D] tpm: fix an invalid condition in tpm_common_poll
ivan.hu at canonical.com
Mon Jun 24 08:10:13 UTC 2019
From: Tadeusz Struk <tadeusz.struk at intel.com>
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 at gmail.com>
Tested-by: Mantas Mikulėnas <grawity at gmail.com>
Signed-off-by: Tadeusz Struk <tadeusz.struk at intel.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen at linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen at linux.intel.com>
Signed-off-by: James Morris <james.morris at microsoft.com>
(cherry picked from commit 7110629263469b4664d00b38ef80a656eddf3637)
Signed-off-by: Ivan Hu <ivan.hu at canonical.com>
drivers/char/tpm/tpm-dev-common.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/drivers/char/tpm/tpm-dev-common.c b/drivers/char/tpm/tpm-dev-common.c
index 5eecad233ea1..744b0237300a 100644
@@ -203,12 +203,19 @@ __poll_t tpm_common_poll(struct file *file, poll_table *wait)
__poll_t mask = 0;
poll_wait(file, &priv->async_wait, wait);
- 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;
mask = EPOLLOUT | EPOLLWRNORM;
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