Re: [Bugme-new] [Bug 33502] New: Caught 64-bit read from uninitialized memory in __alloc_skb

Eric Dumazet
2011-04-20T06:04:36Z

Le mercredi 20 avril 2011 à 08:56 +0300, Pekka Enberg a écrit :
> On 4/19/11 11:17 PM, Eric Dumazet wrote:
> > Le mardi 19 avril 2011 à 12:10 -0500, Christoph Lameter a écrit :
> >> On Tue, 19 Apr 2011, Eric Dumazet wrote:
> >>
> >>> }
> >>> }
> >>>
> >>> -#ifdef CONFIG_CMPXCHG_LOCAL
> >>> +#if defined(CONFIG_CMPXCHG_LOCAL)&& \
> >>> + !defined(CONFIG_KMEMCHECK)&& !defined(DEBUG_PAGEALLOC)
> >>> +#define SLUB_USE_CMPXCHG_DOUBLE
> >>> +#endif
> >>> +
> >>> +#ifdef SLUB_USE_CMPXCHG_DOUBLE
> >>> #ifdef CONFIG_PREEMPT
> >>> /*
> >> Ugg.. Isnt there some way to indicate to kmemcheck that a speculative
> >> access is occurring?
> > Yes, here is a totally untested patch (only compiled here), to keep
> > kmemcheck& cmpxchg_double together.
>
> Looks good to me! Can we get someone to test it as well?

I tested first patch, but was not able to trigger the fault anyway
without it. I'll try a bit more today if time permits...

It would be nice if Christian can reproduce the initial problem easily
and give us the steps...