module: Clean up ro/nx after early module load failures

The commit

4982223e51e8 module: set nx before marking module MODULE_STATE_COMING.

introduced a regression: if a module fails to parse its arguments or
if mod_sysfs_setup fails, then the module's memory will be freed
while still read-only. Anything that reuses that memory will crash
as soon as it tries to write to it.

Cc: [e-mail] # v3.16
Cc: Rusty Russell <[e-mail]>
Signed-off-by: Andy Lutomirski <[e-mail]>
Signed-off-by: Rusty Russell <[e-mail]>

kernel/module.c

···
 	mutex_lock(&module_mutex);
 	module_bug_cleanup(mod);
 	mutex_unlock(&module_mutex);
+
+	/* we can't deallocate the module until we clear memory protection */
+	unset_module_init_ro_nx(mod);
+	unset_module_core_ro_nx(mod);
+
  ddebug_cleanup:
 	dynamic_debug_remove(info->debug);
 	synchronize_sched();