Re: debug: nt_conntrack and KVM crash

From: Eric Dumazet
Date: Sat Jan 30 2010 - 03:34:00 EST

Le samedi 30 janvier 2010 Ã 02:36 -0500, Jon Masters a Ãcrit :

> I'll play later. Right now, I'm looking over every iptables/ip call
> libvirt makes - it explicitly plays with the netns for the loopback,
> which looks interesting. Supposing it does cause the hashtables to get
> unintentionally zereod or the sizing to get wiped out, we should also
> nonetheless catch the case that the hash function generates a whacko
> number or that the hash size is set to zero when we want to use it.

I asked you if you had multiple namespaces, because I was not sure
conntracking hash was global (shared by all namespaces), or local.

If it is local, then we have a bug, because nf_conntrack_cachep
is still shared.

Because of SLAB_DESTROY_BY_RCU constraint, we must use a distinct
cachep, or an object can be freed from a namespace and immediatly reused
into another namespace, without lookups being able to notice.

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