[PATCH V4 04/14] i3c: master: Fix use-after-free of master->this

[Adrian Hunter <adrian.hunter@intel.com>]

sysfs attribute callbacks for the master controller device dereference
master->this.  However, master->this is freed in
i3c_master_detach_free_devs() before the master device itself is
released.

As a result, sysfs accesses can dereference a freed master->this
pointer, leading to a use-after-free.

Keep master->this alive until i3c_masterdev_release(), which is called
after the master device and its sysfs state are being torn down. Do not
free master->this as part of the normal device detach path.

On the error path in i3c_master_set_info(), reset master->this and
bus.cur_master to NULL before freeing the allocated device.

Fixes: 3a379bbcea0a ("i3c: Add core I3C infrastructure")
Cc: stable@vger.kernel.org
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
---


Changes in V4:

	Also reset master->this and bus.cur_master to NULL on the
	i3c_master_set_info() error path before freeing the allocated
	device.  Tidied up the commit message wording.

Changes in V3:

	New patch


 drivers/i3c/master.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
index abb582645a2e..2357874bb9d6 100644
--- a/drivers/i3c/master.c
+++ b/drivers/i3c/master.c
@@ -842,6 +842,11 @@ static struct attribute *i3c_masterdev_attrs[] = {
 };
 ATTRIBUTE_GROUPS(i3c_masterdev);
 
+static void i3c_master_free_i3c_dev(struct i3c_dev_desc *dev)
+{
+	kfree(dev);
+}
+
 static void i3c_masterdev_release(struct device *dev)
 {
 	struct i3c_master_controller *master = dev_to_i3cmaster(dev);
@@ -854,6 +859,8 @@ static void i3c_masterdev_release(struct device *dev)
 	i3c_bus_cleanup(bus);
 
 	fwnode_handle_put(dev->fwnode);
+
+	i3c_master_free_i3c_dev(master->this);
 }
 
 static const struct device_type i3c_masterdev_type = {
@@ -1125,11 +1132,6 @@ static void i3c_device_release(struct device *dev)
 	kfree(i3cdev);
 }
 
-static void i3c_master_free_i3c_dev(struct i3c_dev_desc *dev)
-{
-	kfree(dev);
-}
-
 static struct i3c_dev_desc *
 i3c_master_alloc_i3c_dev(struct i3c_master_controller *master,
 			 const struct i3c_device_info *info)
@@ -2266,6 +2268,8 @@ int i3c_master_set_info(struct i3c_master_controller *master,
 	return 0;
 
 err_free_dev:
+	master->bus.cur_master = NULL;
+	master->this = NULL;
 	i3c_master_free_i3c_dev(i3cdev);
 
 	return ret;
@@ -2286,7 +2290,8 @@ static void i3c_master_detach_free_devs(struct i3c_master_controller *master)
 					i3cdev->boardinfo->init_dyn_addr,
 					I3C_ADDR_SLOT_FREE);
 
-		i3c_master_free_i3c_dev(i3cdev);
+		if (i3cdev != master->this)
+			i3c_master_free_i3c_dev(i3cdev);
 	}
 
 	list_for_each_entry_safe(i2cdev, i2ctmp, &master->bus.devs.i2c,
-- 
2.53.0