netdev - Re: [v1 PATCH 7/14] netfilter: Use rhashtable_lookup instead of lookup

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20150320215612.GA566@casper.infradead.org>
Date:	Fri, 20 Mar 2015 21:56:12 +0000
From:	Thomas Graf <tgraf@...g.ch>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	Patrick McHardy <kaber@...sh.net>,
	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [v1 PATCH 7/14] netfilter: Use rhashtable_lookup instead of
 lookup_compare

On 03/21/15 at 08:47am, Herbert Xu wrote:
> On Fri, Mar 20, 2015 at 10:27:01AM +0000, Patrick McHardy wrote:
> > On 20.03, Herbert Xu wrote:
> >
> > > Any hash function can be attacked.  That's why we need to be able
> > > to rehash it.  And the best way to decide when to rehash is based
> > > on chain length (otherwise you'd waste time rehashing periodically
> > > like we used to do).  With name spaces these days anyone could be
> > > an adversary.
> > 
> > We already had this discussion. I strongly do not believe this is
> > the right way to fix namespace problems. There are millions of ways
> > of creating CPU intensive workloads. You need to be able to put
> > bounds on the entire namespace. Fixing individual spots will not
> > solve that problem.
> 
> A CPU intensive workload that can be rescheduled is completely
> different from one that is running under spin lock with BH disabled.

Just make the chain length based growth function configurable
and nft_hash can disable it. nft_hash entries are not created by
unprivileged users so attacking the table is out of the question.
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html