[PATCH] load_module: no BUG if module_subsys uninitialized

[Ed Swierk]

Invoking load_module() before param_sysfs_init() is called crashes in
mod_sysfs_setup(), since the kset in module_subsys is not initialized
yet.

Another patch for the same symptom
(module_subsys-initialize-earlier.patch) moves param_sysfs_init() to
the subsys initcalls, but this is still not early enough in the boot
process in some cases. In particular, topology_init() causes
/sbin/hotplug to run, which requests net-pf-1 (the UNIX socket
protocol) which can be compiled as a module. Moving param_sysfs_init()
to the postcore initcalls fixes this particular race, but there might
well be other cases where a usermodehelper causes a module to load
earlier still.

The patch below makes load_module() return an error rather than
crashing the kernel if invoked before module_subsys is initialized.

--- linux-2.6.17.11.orig/kernel/module.c        2006-08-23
21:16:33.000000000 +0000
+++ linux-2.6.17.11/kernel/module.c     2006-09-22 05:19:03.000000000 +0000
@@ -998,6 +998,12 @@
{
       int err;

+       if (!module_subsys.kset.subsys) {
+               printk(KERN_ERR "%s: module_subsys not initialized\n",
+                      mod->name);
+               err = -EINVAL;
+               goto out;
+       }
       memset(&mod->mkobj.kobj, 0, sizeof(mod->mkobj.kobj));
       err = kobject_set_name(&mod->mkobj.kobj, "%s", mod->name);
       if (err)
-
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