bus: fsl-mc: use generic driver_override infrastructure

When a driver is probed through __driver_attach(), the bus' match()
callback is called without the device lock held, thus accessing the
driver_override field without a lock, which can cause a UAF.

Fix this by using the driver-core driver_override infrastructure taking
care of proper locking internally.

Note that calling match() from __driver_attach() without the device lock
held is intentional. [1]

Tested-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Acked-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Acked-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>
Link: https://lore.kernel.org/driver-core/DGRGTIRHA62X.3RY09D9SOK77P@kernel.org/ [1]
Reported-by: Gui-Dong Han <hanguidong02@gmail.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220789
Fixes: 1f86a00c11 ("bus/fsl-mc: add support for 'driver_override' in the mc-bus")
Link: https://patch.msgid.link/20260324005919.2408620-3-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

drivers/vfio/fsl-mc/vfio_fsl_mc.c

@@ -424,9 +424,7 @@ static int vfio_fsl_mc_bus_notifier(struct notifier_block *nb,
 
 	if (action == BUS_NOTIFY_ADD_DEVICE &&
 	    vdev->mc_dev == mc_cont) {
-		mc_dev->driver_override = kasprintf(GFP_KERNEL, "%s",
-						    vfio_fsl_mc_ops.name);
-		if (!mc_dev->driver_override)
+		if (device_set_driver_override(dev, vfio_fsl_mc_ops.name))
 			dev_warn(dev, "VFIO_FSL_MC: Setting driver override for device in dprc %s failed\n",
 				 dev_name(&mc_cont->dev));
 		else