[PATCH 5.4 19/68] mcb: fix error handling in mcb_alloc_bus()

[Greg Kroah-Hartman]

From: Dan Carpenter <dan.carpenter@xxxxxxxxxx>

commit 25a1433216489de4abc889910f744e952cb6dbae upstream.

There are two bugs:
1) If ida_simple_get() fails then this code calls put_device(carrier)
   but we haven't yet called get_device(carrier) and probably that
   leads to a use after free.
2) After device_initialize() then we need to use put_device() to
   release the bus.  This will free the internal resources tied to the
   device and call mcb_free_bus() which will free the rest.

Fixes: 5d9e2ab9fea4 ("mcb: Implement bus->dev.release callback")
Fixes: 18d288198099 ("mcb: Correctly initialize the bus's device")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Signed-off-by: Johannes Thumshirn <jth@xxxxxxxxxx>
Link: https://lore.kernel.org/r/32e160cf6864ce77f9d62948338e24db9fd8ead9.1630931319.git.johannes.thumshirn@xxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/mcb/mcb-core.c |   12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

--- a/drivers/mcb/mcb-core.c
+++ b/drivers/mcb/mcb-core.c
@@ -277,8 +277,8 @@ struct mcb_bus *mcb_alloc_bus(struct dev
 
 	bus_nr = ida_simple_get(&mcb_ida, 0, 0, GFP_KERNEL);
 	if (bus_nr < 0) {
-		rc = bus_nr;
-		goto err_free;
+		kfree(bus);
+		return ERR_PTR(bus_nr);
 	}
 
 	bus->bus_nr = bus_nr;
@@ -293,12 +293,12 @@ struct mcb_bus *mcb_alloc_bus(struct dev
 	dev_set_name(&bus->dev, "mcb:%d", bus_nr);
 	rc = device_add(&bus->dev);
 	if (rc)
-		goto err_free;
+		goto err_put;
 
 	return bus;
-err_free:
-	put_device(carrier);
-	kfree(bus);
+
+err_put:
+	put_device(&bus->dev);
 	return ERR_PTR(rc);
 }
 EXPORT_SYMBOL_GPL(mcb_alloc_bus);