From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Graf Subject: Re: Where exactly will arch_fast_hash be used Date: Thu, 4 Dec 2014 15:39:38 +0000 Message-ID: <20141204153938.GC32140@casper.infradead.org> References: <20141204081147.GA19030@gondor.apana.org.au> <20141204152637.GA32140@casper.infradead.org> <20141204152929.GA22075@gondor.apana.org.au> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Daniel Borkmann , "David S. Miller" , Theodore Ts'o , netdev@vger.kernel.org, Linux Kernel Mailing List To: Herbert Xu Return-path: Content-Disposition: inline In-Reply-To: <20141204152929.GA22075@gondor.apana.org.au> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 12/04/14 at 11:29pm, Herbert Xu wrote: > On Thu, Dec 04, 2014 at 03:26:37PM +0000, Thomas Graf wrote: > > > > As Daniel pointed out, this work originated for the OVS edge use > > case where security is of less concern and the rehashing is > > sufficient. Identifying collisions is less of interest as the user > > space fall back provides a greater surface for an attack. > > Well in that case the current setup I think is very misleading. > It's inviting unsuspecting kernel developers to use it as a hash > function for general hash tables, which AFAICS is something that > it fails at miserably. Well, it's called fast hash and not secure hash ;-) but a clear hint definitely wouldn't hurt. I wasn't aware of the distribution weakness of the lower bits. Do you have a reference to more information?