Re: memory corruptor in .18rc1-git

Chuck Ebbert
2006-07-15T19:57:50Z

In-Reply-To: <20060714043112.GA20478@redhat.com>

On Fri, 14 Jul 2006 00:31:12 -0400, Dave Jones wrote:

> +/**
> + * list_add - add a new entry
> + * @new: new entry to be added
> + * @head: list head to add it after
> + *
> + * Insert a new entry after the specified head.
> + * This is good for implementing stacks.
> + */
> +void list_add(struct list_head *new, struct list_head *head)
> +{
> + if (head->next->prev != head) {
> + printk("List corruption. next->prev should be %p, but was %p\n",
> + head, head->next->prev);
> + BUG();
> + }
> + if (head->prev->next != head) {
> + printk("List corruption. prev->next should be %p, but was %p\n",
> + head, head->prev->next);
> + BUG();
> + }
> +
> + __list_add(new, head, head->next);
> +}
> +EXPORT_SYMBOL(list_add);
> +
> +/**
> + * list_del - deletes entry from list.
> + * @entry: the element to delete from the list.
> + * Note: list_empty on entry does not return true after this, the entry is
> + * in an undefined state.
> + */
> +void list_del(struct list_head *entry)
> +{
> + if (entry->prev->next != entry) {
> + printk("List corruption. prev->next should be %p, but was %p\n",
> + entry, entry->prev->next);
> + BUG();
> + }
> + if (entry->next->prev != entry) {
> + printk("List corruption. next->prev should be %p, but was %p\n",
> + entry, entry->next->prev);
> + BUG();
> + }
> + __list_del(entry->prev, entry->next);
> + entry->next = LIST_POISON1;
> + entry->prev = LIST_POISON2;
> +}
> +EXPORT_SYMBOL(list_del);
> +
>

Shouldn't those four 'if' statements use unlikely()? There's no sense
causing more slowdown than necessary, even in debug code.

And I'd change the messages slightly, e.g.:

"list_add: corruption: next->prev should be %p, was %p\n"

Some people build (accidentally?) without verbose debug info and
don't get line numbers.

--
Chuck
"You can't read a newspaper if you can't read." --George W. Bush