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authorTadeusz Struk <tadeusz.struk@intel.com>2019-03-27 11:32:38 -0700
committerJames Morris <james.morris@microsoft.com>2019-04-08 15:58:53 -0700
commit7110629263469b4664d00b38ef80a656eddf3637 (patch)
tree37d9040e8ac9e3fcd3644d85a2960172ee510413
parente891db1a18bf11e02533ec2386b796cfd8d60666 (diff)
download96b-common-7110629263469b4664d00b38ef80a656eddf3637.tar.gz
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: 9488585b21bef0df12 ("tpm: add support for partial reads") Reported-by: Mantas Mikul─Śnas <grawity@gmail.com> Tested-by: Mantas Mikul─Śnas <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>
-rw-r--r--drivers/char/tpm/tpm-dev-common.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/drivers/char/tpm/tpm-dev-common.c b/drivers/char/tpm/tpm-dev-common.c
index 8856cce5a23b..817ae09a369e 100644
--- a/drivers/char/tpm/tpm-dev-common.c
+++ b/drivers/char/tpm/tpm-dev-common.c
@@ -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;
}