From: James Bottomley James.Bottomley@HansenPartnership.com

BugLink: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1881710

It has been reported that some TIS based TPMs are giving unexpected errors when using the O_NONBLOCK path of the TPM device. The problem is that some TPMs don't like it when you get and then relinquish a locality (as the tpm_try_get_ops()/tpm_put_ops() pair does) without sending a command. This currently happens all the time in the O_NONBLOCK write path. Fix this by moving the tpm_try_get_ops() further down the code to after the O_NONBLOCK determination is made. This is safe because the priv->buffer_mutex still protects the priv state being modified.

BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=206275 Fixes: d23d12484307 ("tpm: fix invalid locking in NONBLOCKING mode") Reported-by: Mario Limonciello Mario.Limonciello@dell.com Tested-by: Alex Guzman alex@guzman.io Cc: stable@vger.kernel.org Reviewed-by: Jerry Snitselaar jsnitsel@redhat.com Signed-off-by: James Bottomley James.Bottomley@HansenPartnership.com Reviewed-by: Jarkko Sakkinen jarkko.sakkinen@linux.intel.com Signed-off-by: Ivan Hu ivan.hu@canonical.com --- drivers/char/tpm/tpm-dev-common.c | 19 +++++++++---------- 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/drivers/char/tpm/tpm-dev-common.c b/drivers/char/tpm/tpm-dev-common.c index 10b9f63701e6..de55205d3a11 100644 --- a/drivers/char/tpm/tpm-dev-common.c +++ b/drivers/char/tpm/tpm-dev-common.c @@ -164,15 +164,6 @@ ssize_t tpm_common_write(struct file *file, const char __user *buf, goto out; }

- /* atomic tpm command send and result receive. We only hold the ops - * lock during this period so that the tpm can be unregistered even if - * the char dev is held open. - */ - if (tpm_try_get_ops(priv->chip)) { - ret = -EPIPE; - goto out; - } - priv->response_length = 0; priv->response_read = false; *off = 0; @@ -186,11 +177,19 @@ ssize_t tpm_common_write(struct file *file, const char __user *buf, if (file->f_flags & O_NONBLOCK) { priv->command_enqueued = true; queue_work(tpm_dev_wq, &priv->async_work); - tpm_put_ops(priv->chip); mutex_unlock(&priv->buffer_mutex); return size; }

+ /* atomic tpm command send and result receive. We only hold the ops + * lock during this period so that the tpm can be unregistered even if + * the char dev is held open. + */ + if (tpm_try_get_ops(priv->chip)) { + ret = -EPIPE; + goto out; + } + ret = tpm_transmit(priv->chip, priv->space, priv->data_buffer, sizeof(priv->data_buffer), 0); tpm_put_ops(priv->chip);