Re: [bug, netconsole, SLUB] BUG skbuff_head_cache: Poison overwritten

Pekka Enberg
2008-07-18T09:15:42Z

Hi Ingo,

On Fri, Jul 18, 2008 at 12:09 PM, Ingo Molnar <mingo@elte.hu> wrote:
> yeah, we want to check use-after free at the next allocation point -
> i.e. as late as possible to gather all corruptions that happened
> meanwhile.
>
> We could in theory have a SLUB debug mode where a SCHED_IDLE kernel
> thread would periodically check all free objects (of that CPU) in the
> background to ensure their integrity. That would catch corruptions
> sooner, with a possibly still meaningful context to print out. [right
> after the IRQ or process that corrupts them finishes running]
>
> It could also be hooked into ftrace to print out the last few hundred
> kernel function calls executed prior any corruption. ftrace/slub-debug
> plugin perhaps?

Well, there's this Norwegian guy, Vegard, who has written a small
piece of code that can detect use-after-free _as it happens_. I think
he calls the thing kmemcheck :-).