[PATCH 6.18.y] i3c: master: Fix use-after-free of master->this

[Sasha Levin <sashal@kernel.org>]

From: Adrian Hunter <adrian.hunter@intel.com>

[ Upstream commit feb0ed76601f3c2f91f08688c5a7d8b9d382f720 ]

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>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/20260807145638.168865-5-adrian.hunter@intel.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
[ retained of_node_put(dev->of_node) instead of upstream’s fwnode_handle_put(dev->fwnode). ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 41452a27262d6..c528b58970fdb 100644
--- a/drivers/i3c/master.c
+++ b/drivers/i3c/master.c
@@ -799,6 +799,11 @@ 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);
@@ -811,6 +816,8 @@ static void i3c_masterdev_release(struct device *dev)
 	i3c_bus_cleanup(bus);
 
 	of_node_put(dev->of_node);
+
+	i3c_master_free_i3c_dev(master->this);
 }
 
 static const struct device_type i3c_masterdev_type = {
@@ -1023,11 +1030,6 @@ 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)
@@ -2023,6 +2025,8 @@ 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;
@@ -2043,7 +2047,8 @@ 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