linux-kernel - [PATCH v4 7/7] platform/chrome: cros_ec_chardev: Secure cros_ec

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Message-ID: <20250923075302.591026-8-tzungbi@kernel.org>
Date: Tue, 23 Sep 2025 07:53:02 +0000
From: Tzung-Bi Shih <tzungbi@...nel.org>
To: Benson Leung <bleung@...omium.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J . Wysocki" <rafael@...nel.org>,
	Danilo Krummrich <dakr@...nel.org>
Cc: Jonathan Corbet <corbet@....net>,
	Shuah Khan <shuah@...nel.org>,
	Dawid Niedzwiecki <dawidn@...gle.com>,
	linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	chrome-platform@...ts.linux.dev,
	linux-kselftest@...r.kernel.org,
	tzungbi@...nel.org,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Bartosz Golaszewski <brgl@...ev.pl>,
	Wolfram Sang <wsa+renesas@...g-engineering.com>
Subject: [PATCH v4 7/7] platform/chrome: cros_ec_chardev: Secure cros_ec_device via revocable

Miscdevice now supports revocable fops replacement.  Use it to secure
the cros_ec_device.

Signed-off-by: Tzung-Bi Shih <tzungbi@...nel.org>
---
PoC patch.

v4:
- New in the series.

 drivers/platform/chrome/cros_ec_chardev.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/platform/chrome/cros_ec_chardev.c b/drivers/platform/chrome/cros_ec_chardev.c
index c9d80ad5b57e..cacc73635d6b 100644
--- a/drivers/platform/chrome/cros_ec_chardev.c
+++ b/drivers/platform/chrome/cros_ec_chardev.c
@@ -166,7 +166,6 @@ static int cros_ec_chardev_open(struct inode *inode, struct file *filp)
 	if (!priv)
 		return -ENOMEM;
 
-	priv->ec_dev = ec_dev;
 	priv->cmd_offset = ec->cmd_offset;
 	filp->private_data = priv;
 	INIT_LIST_HEAD(&priv->events);
@@ -370,6 +369,18 @@ static const struct file_operations chardev_fops = {
 #endif
 };
 
+static int cros_ec_chardev_rev_try_access(struct revocable *rev, void *data)
+{
+	struct chardev_priv *priv = data;
+
+	priv->ec_dev = revocable_try_access(rev);
+	return priv->ec_dev ? 0 : -ENODEV;
+}
+
+static const struct revocable_operations cros_ec_chardev_rops = {
+	.try_access = cros_ec_chardev_rev_try_access,
+};
+
 static int cros_ec_chardev_probe(struct platform_device *pdev)
 {
 	struct cros_ec_dev *ec = dev_get_drvdata(pdev->dev.parent);
@@ -385,6 +396,8 @@ static int cros_ec_chardev_probe(struct platform_device *pdev)
 	misc->fops = &chardev_fops;
 	misc->name = ec_platform->ec_name;
 	misc->parent = pdev->dev.parent;
+	misc->rp = ec->ec_dev->revocable_provider;
+	misc->rops = &cros_ec_chardev_rops;
 
 	dev_set_drvdata(&pdev->dev, misc);
 
-- 
2.51.0.534.gc79095c0ca-goog