linux-kernel - [PATCH 5.4 366/434] tpm: fix invalid locking in NONBLOCKING mode

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Date:   Sun, 29 Dec 2019 18:26:59 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Jeffrin Jose T <jeffrin@...agiritech.edu.in>,
        Tadeusz Struk <tadeusz.struk@...el.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Subject: [PATCH 5.4 366/434] tpm: fix invalid locking in NONBLOCKING mode

From: Tadeusz Struk <tadeusz.struk@...el.com>

commit d23d12484307b40eea549b8a858f5fffad913897 upstream.

When an application sends TPM commands in NONBLOCKING mode
the driver holds chip->tpm_mutex returning from write(),
which triggers: "WARNING: lock held when returning to user space".
To fix this issue the driver needs to release the mutex before
returning and acquire it again in tpm_dev_async_work() before
sending the command.

Cc: stable@...r.kernel.org
Fixes: 9e1b74a63f776 (tpm: add support for nonblocking operation)
Reported-by: Jeffrin Jose T <jeffrin@...agiritech.edu.in>
Tested-by: Jeffrin Jose T <jeffrin@...agiritech.edu.in>
Signed-off-by: Tadeusz Struk <tadeusz.struk@...el.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/char/tpm/tpm-dev-common.c |    8 ++++++++
 1 file changed, 8 insertions(+)

--- a/drivers/char/tpm/tpm-dev-common.c
+++ b/drivers/char/tpm/tpm-dev-common.c
@@ -61,6 +61,12 @@ static void tpm_dev_async_work(struct wo
 
 	mutex_lock(&priv->buffer_mutex);
 	priv->command_enqueued = false;
+	ret = tpm_try_get_ops(priv->chip);
+	if (ret) {
+		priv->response_length = ret;
+		goto out;
+	}
+
 	ret = tpm_dev_transmit(priv->chip, priv->space, priv->data_buffer,
 			       sizeof(priv->data_buffer));
 	tpm_put_ops(priv->chip);
@@ -68,6 +74,7 @@ static void tpm_dev_async_work(struct wo
 		priv->response_length = ret;
 		mod_timer(&priv->user_read_timer, jiffies + (120 * HZ));
 	}
+out:
 	mutex_unlock(&priv->buffer_mutex);
 	wake_up_interruptible(&priv->async_wait);
 }
@@ -204,6 +211,7 @@ ssize_t tpm_common_write(struct file *fi
 	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;
 	}