mcb: remove is_added flag from mcb_device struct

When calling mcb_bus_add_devices(), both mcb devices and the mcb
bus will attempt to attach a device to a driver because they share
the same bus_type. This causes an issue when trying to cast the
container of the device to mcb_device struct using to_mcb_device(),
leading to a wrong cast when the mcb_bus is added. A crash occurs
when freing the ida resources as the bus numbering of mcb_bus gets
confused with the is_added flag on the mcb_device struct.

The only reason for this cast was to keep an is_added flag on the
mcb_device struct that does not seem necessary. The function
device_attach() handles already bound devices and the mcb subsystem
does nothing special with this is_added flag so remove it completely.

Fixes: 18d2881 ("mcb: Correctly initialize the bus's device")
Cc: stable <stable@kernel.org>
Signed-off-by: Jorge Sanjuan Garcia <jorge.sanjuangarcia@duagon.com>
Co-developed-by: Jose Javier Rodriguez Barbarin <JoseJavier.Rodriguez@duagon.com>
Signed-off-by: Jose Javier Rodriguez Barbarin <JoseJavier.Rodriguez@duagon.com>
Link: https://lore.kernel.org/r/20230906114901.63174-2-JoseJavier.Rodriguez@duagon.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: mad-jsanjuan

drivers/mcb/mcb-core.c

@@ -387,17 +387,13 @@ EXPORT_SYMBOL_NS_GPL(mcb_free_dev, MCB);
 
 static int __mcb_bus_add_devices(struct device *dev, void *data)
 {
-	struct mcb_device *mdev = to_mcb_device(dev);
 	int retval;
 
-	if (mdev->is_added)
-		return 0;
-
 	retval = device_attach(dev);
-	if (retval < 0)
+	if (retval < 0) {
 		dev_err(dev, "Error adding device (%d)\n", retval);
-
-	mdev->is_added = true;
+		return retval;
+	}
 
 	return 0;
 }

drivers/mcb/mcb-parse.c

@@ -99,8 +99,6 @@ static int chameleon_parse_gdd(struct mcb_bus *bus,
 	mdev->mem.end = mdev->mem.start + size - 1;
 	mdev->mem.flags = IORESOURCE_MEM;
 
-	mdev->is_added = false;
-
 	ret = mcb_device_register(bus, mdev);
 	if (ret < 0)
 		goto err;

include/linux/mcb.h

@@ -63,7 +63,6 @@ static inline struct mcb_bus *to_mcb_bus(struct device *dev)
 struct mcb_device {
 	struct device dev;
 	struct mcb_bus *bus;
-	bool is_added;
 	struct mcb_driver *driver;
 	u16 id;
 	int inst;