Re: [patch 2/16] list_head debugging

Bernd Jendrissek
2002-06-07T14:19:11Z

[sorry for the nonexistent In-Reply-To/whatever headers - cutting&pasting]

Andrew Morton wrote:
> A common and very subtle bug is to use list_heads which aren't on any
> lists. It causes kernel memory corruption which is observed long after
> the offending code has executed.
>
> The patch nulls out the dangling pointers so we get a nice oops at the
> site of the buggy code.

I'm not current with the kernel tree, but will one such oops occur in
netfilter? See

http://lists.samba.org/pipermail/netfilter-announce/2002/000010.html

Hmm, no. A DoS maybe?

> --- 2.5.19/include/linux/list.h~list-debug Sat Jun 1 01:18:05 2002
> +++ 2.5.19-akpm/include/linux/list.h Sat Jun 1 01:18:05 2002
> @@ -94,6 +94,11 @@ static __inline__ void __list_del(struct
> static __inline__ void list_del(struct list_head *entry)
> {
> __list_del(entry->prev, entry->next);
> + /*
> + * This is debug. Remove it when the kernel has no bugs ;)
> + */
> + entry->next = 0;
> + entry->prev = 0;
> }
>
> /**

Bernd Jendrissek