[PATCH] Kprobes: Oops! in unregister_kprobe()

kernel oops!  when unregister_kprobe() is called on a non-registered
kprobe.  This patch fixes the above problem by checking if the probe exists
before unregistering.
Signed-off-by: NPrasanna S Panchamukhi <prasanna@in.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

kernel/kprobes.c

@@ -107,13 +107,17 @@ int register_kprobe(struct kprobe *p)
 void unregister_kprobe(struct kprobe *p)
 {
 	unsigned long flags;
-	arch_remove_kprobe(p);
 	spin_lock_irqsave(&kprobe_lock, flags);
+	if (!get_kprobe(p->addr)) {
+		spin_unlock_irqrestore(&kprobe_lock, flags);
+		return;
+	}
 	*p->addr = p->opcode;
 	hlist_del(&p->hlist);
 	flush_icache_range((unsigned long) p->addr,
 			   (unsigned long) p->addr + sizeof(kprobe_opcode_t));
 	spin_unlock_irqrestore(&kprobe_lock, flags);
+	arch_remove_kprobe(p);
 }
 
 static struct notifier_block kprobe_exceptions_nb = {