slimbus: core: fix device reference leak on report present

commit 9391380eb91ea5ac792aae9273535c8da5b9aa01 upstream.

Slimbus devices can be allocated dynamically upon reception of
report-present messages.

Make sure to drop the reference taken when looking up already registered
devices.

Note that this requires taking an extra reference in case the device has
not yet been registered and has to be allocated.

Fixes: 46a2bb5a7f ("slimbus: core: Add slim controllers support")
Cc: stable@vger.kernel.org	# 4.16
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://patch.msgid.link/20251126145329.5022-4-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ulrich Hecht <uli@kernel.org>

drivers/slimbus/core.c

@@ -351,6 +351,8 @@ struct slim_device *slim_get_device(struct slim_controller *ctrl,
 		sbdev = slim_alloc_device(ctrl, e_addr, NULL);
 		if (!sbdev)
 			return ERR_PTR(-ENOMEM);
+
+		get_device(&sbdev->dev);
 	}
 
 	return sbdev;
@@ -482,6 +484,7 @@ int slim_device_report_present(struct slim_controller *ctrl,
 		ret = slim_device_alloc_laddr(sbdev, true);
 	}
 
+	put_device(&sbdev->dev);
 out_put_rpm:
 	pm_runtime_mark_last_busy(ctrl->dev);
 	pm_runtime_put_autosuspend(ctrl->dev);