[IA64] adding parameter check to module_free()

    module_free() refers the first parameter before checking.
    But it is called like below(in kernel/kprobes). The first parameter is always NULL.
This happens when many probe points(>1024) are set by kprobes.
I encountered this with using SystemTap. It can set many probes easily.

static int __kprobes collect_one_slot(struct kprobe_insn_page *kip, int idx)
{
...
    if (kip->nused == 0) {
	    hlist_del(&kip->hlist);
	    if (hlist_empty(&kprobe_insn_pages)) {
		...
	    } else {
		    module_free(NULL, kip->insns); //<<< 1st param always NULL
		    kfree(kip);
	    }
	    return 1;
    }
    return 0;
}
Signed-off-by: Akiyama, Nobuyuki <akiyama.nobuyuk@jp.fujitsu.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/kernel/module.c

@@ -321,7 +321,8 @@ module_alloc (unsigned long size)
 void
 module_free (struct module *mod, void *module_region)
 {
-	if (mod->arch.init_unw_table && module_region == mod->module_init) {
+	if (mod && mod->arch.init_unw_table &&
+	    module_region == mod->module_init) {
 		unw_remove_unwind_table(mod->arch.init_unw_table);
 		mod->arch.init_unw_table = NULL;
 	}