[PATCH] Don't oops when unregistering unknown kprobes

[Frederik Deweerdt <frederik.deweerdt@laposte.net>]

Hi Prasanna,

Here's a patch that handles gracefully attempts to unregister
unregistered kprobes (ie. a warning message instead of an oops).
Patch is against 2.6.12-rc3

Signed-off-by: Frederik Deweerdt <frederik.deweerdt@laposte.net>

Regards,
Frederik

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--- linux-2.6.12-rc3/kernel/kprobes.c	2005-04-26 16:35:22.000000000 +0200
+++ linux-2.6.12-rc3-devel/kernel/kprobes.c	2005-04-26 16:44:57.000000000 +0200
@@ -107,6 +107,13 @@ rm_kprobe:
 void unregister_kprobe(struct kprobe *p)
 {
 	unsigned long flags;
+
+	if (!get_kprobe(p)) {
+		printk(KERN_WARNING "Warning: Attempt to unregister "
+					"unknown kprobe (addr:0x%lx)\n",
+					(unsigned long) p);
+		return;
+	}
 	arch_remove_kprobe(p);
 	spin_lock_irqsave(&kprobe_lock, flags);
 	*p->addr = p->opcode;