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

Eric Dumazet
2011-04-20T15:34:31Z

Le mercredi 20 avril 2011 à 17:15 +0200, Vegard Nossum a écrit :

> Thanks, guys. I wonder: Is it possible to make a reproducible test-case
> (e.g. loadable module) for this?
>

Not easy to code a specific test-case, but just use regular workload,
(and network trafic to get interrupts). Use CONFIG_PREEMPT to trigger
preemptions.

> Also, pardon my ignorance, but can you explain why this is a bug with
> kmemcheck/page-alloc debug and not without them?

Without them, we can read object->next without trigerring a fault.
We can read garbage data (if object is in use, it was overwritten with
user data), but this doesnt matter because cmpxchg_double() wont perform
its work (since tid will have change)