blk-cgroup: Fix NULL deref caused by blkg_policy_data being installed before init

drivers/block/drbd/Makefile

@@ -3,6 +3,7 @@ drbd-y := drbd_buildtag.o drbd_bitmap.o drbd_proc.o
 drbd-y += drbd_worker.o drbd_receiver.o drbd_req.o drbd_actlog.o
 drbd-y += drbd_main.o drbd_strings.o drbd_nl.o
 drbd-y += drbd_interval.o drbd_state.o
+drbd-y += drbd_nl_gen.o
 drbd-$(CONFIG_DEBUG_FS) += drbd_debugfs.o
 
 obj-$(CONFIG_BLK_DEV_DRBD)     += drbd.o

drivers/block/drbd/drbd_buildtag.c

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0-only
-#include <linux/drbd_config.h>
+#include "drbd_config.h"
 #include <linux/module.h>
 
 const char *drbd_buildtag(void)

drivers/block/drbd/drbd_debugfs.c

@@ -844,7 +844,7 @@ static int drbd_version_show(struct seq_file *m, void *ignored)
 {
 	seq_printf(m, "# %s\n", drbd_buildtag());
 	seq_printf(m, "VERSION=%s\n", REL_VERSION);
-	seq_printf(m, "API_VERSION=%u\n", GENL_MAGIC_VERSION);
+	seq_printf(m, "API_VERSION=%u\n", DRBD_FAMILY_VERSION);
 	seq_printf(m, "PRO_VERSION_MIN=%u\n", PRO_VERSION_MIN);
 	seq_printf(m, "PRO_VERSION_MAX=%u\n", PRO_VERSION_MAX);
 	return 0;

drivers/block/drbd/drbd_int.h

@@ -32,14 +32,16 @@
 #include <net/tcp.h>
 #include <linux/lru_cache.h>
 #include <linux/prefetch.h>
-#include <linux/drbd_genl_api.h>
 #include <linux/drbd.h>
-#include <linux/drbd_config.h>
+#include "drbd_config.h"
+#include "drbd_nl_gen.h"
 #include "drbd_strings.h"
 #include "drbd_state.h"
 #include "drbd_protocol.h"
 #include "drbd_polymorph_printk.h"
 
+extern struct genl_family drbd_nl_family;
+
 /* shared module parameters, defined in drbd_main.c */
 #ifdef CONFIG_DRBD_FAULT_INJECTION
 extern int drbd_enable_faults;

drivers/block/drbd/drbd_main.c

@@ -2324,7 +2324,7 @@ static void drbd_cleanup(void)
 	if (retry.wq)
 		destroy_workqueue(retry.wq);
 
-	drbd_genl_unregister();
+	genl_unregister_family(&drbd_nl_family);
 
 	idr_for_each_entry(&drbd_devices, device, i)
 		drbd_delete_device(device);
@@ -2846,7 +2846,7 @@ static int __init drbd_init(void)
 	mutex_init(&resources_mutex);
 	INIT_LIST_HEAD(&drbd_resources);
 
-	err = drbd_genl_register();
+	err = genl_register_family(&drbd_nl_family);
 	if (err) {
 		pr_err("unable to register generic netlink family\n");
 		goto fail;
@@ -2876,7 +2876,7 @@ static int __init drbd_init(void)
 
 	pr_info("initialized. "
 	       "Version: " REL_VERSION " (api:%d/proto:%d-%d)\n",
-	       GENL_MAGIC_VERSION, PRO_VERSION_MIN, PRO_VERSION_MAX);
+	       DRBD_FAMILY_VERSION, PRO_VERSION_MIN, PRO_VERSION_MAX);
 	pr_info("%s\n", drbd_buildtag());
 	pr_info("registered as block device major %d\n", DRBD_MAJOR);
 	return 0; /* Success! */