Miscdevice now supports revocable fops replacement. Use it to secure the cros_ec_device.
Signed-off-by: Tzung-Bi Shih <[email protected]> --- PoC patch. v5: - No primary changes but modify the API usage accordingly. v4: https://lore.kernel.org/chrome-platform/[email protected] - New in the series. drivers/platform/chrome/cros_ec_chardev.c | 22 +++++++++++++++++++++- 1 file changed, 21 insertions(+), 1 deletion(-) diff --git a/drivers/platform/chrome/cros_ec_chardev.c b/drivers/platform/chrome/cros_ec_chardev.c index c9d80ad5b57e..01691b023d7e 100644 --- a/drivers/platform/chrome/cros_ec_chardev.c +++ b/drivers/platform/chrome/cros_ec_chardev.c @@ -13,6 +13,7 @@ #include <linux/init.h> #include <linux/device.h> #include <linux/fs.h> +#include <linux/fs_revocable.h> #include <linux/miscdevice.h> #include <linux/mod_devicetable.h> #include <linux/module.h> @@ -166,7 +167,6 @@ 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 +370,19 @@ static const struct file_operations chardev_fops = { #endif }; +static int cros_ec_chardev_rev_try_access(struct revocable **revs, + size_t num_revs, void *data) +{ + struct chardev_priv *priv = data; + + priv->ec_dev = revocable_try_access(revs[0]); + return priv->ec_dev ? 0 : -ENODEV; +} + +static const struct fs_revocable_operations cros_ec_chardev_frops = { + .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); @@ -386,6 +399,13 @@ static int cros_ec_chardev_probe(struct platform_device *pdev) misc->name = ec_platform->ec_name; misc->parent = pdev->dev.parent; + misc->rps = devm_kcalloc(&pdev->dev, 1, sizeof(*misc->rps), GFP_KERNEL); + if (!misc->rps) + return -ENOMEM; + misc->rps[0] = ec->ec_dev->revocable_provider; + misc->num_rps = 1; + misc->frops = &cros_ec_chardev_frops; + dev_set_drvdata(&pdev->dev, misc); return misc_register(misc); -- 2.51.0.788.g6d19910ace-goog
