load_module: no BUG if module_subsys uninitialized

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

In my case, net-pf-1 is getting modprobed as a result of hotplug trying to
create a UNIX socket.  Calls to hotplug begin after the topology_init
initcall.

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

Signed-off-by: Adrian Bunk <bunk@stusta.de>

diff --git a/kernel/module.c b/kernel/module.c
index 5aad477ddc79c94567c02e9ee704f1eb71fa1b66..5e2e2c27931dd96cf51cac9c1c47320f58ee7b9d 100644 (file)
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -1109,6 +1109,12 @@ static int mod_sysfs_setup(struct module *mod,
 {
        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)