netdev - Re: [PATCH net-next 12/14] mlx4: use netdev_rss_key

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Date:	Sun, 23 Nov 2014 04:07:31 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Eric Dumazet <edumazet@...gle.com>,
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	Thomas Lendacky <Thomas.Lendacky@....com>,
	Ariel Elior <ariel.elior@...gic.com>,
	Michael Chan <mchan@...adcom.com>,
	Prashant Sreedharan <prashant@...adcom.com>,
	Rasesh Mody <rasesh.mody@...gic.com>,
	Sathya Perla <sathya.perla@...lex.com>,
	Subbu Seetharaman <subbu.seetharaman@...lex.com>,
	Ajit Khaparde <ajit.khaparde@...lex.com>,
	Jesse Brandeburg <jesse.brandeburg@...el.com>,
	Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
	Amir Vadai <amirv@...lanox.com>,
	Shradha Shah <sshah@...arflare.com>,
	Shreyas Bhatewara <sbhatewara@...are.com>
Subject: Re: [PATCH net-next 12/14] mlx4: use netdev_rss_key_fill() helper

On Sat, 2014-11-22 at 15:58 -0800, Eric Dumazet wrote:
> On Sat, 2014-11-22 at 21:49 +0000, Ben Hutchings wrote:
> > On Sun, 2014-11-16 at 06:23 -0800, Eric Dumazet wrote:
> > > Use of well known RSS key increases attack surface.
> > > Switch to a random one, using generic helper so that all
> > > ports share a common key.
> > > 
> > > Also provide ethtool -x support to fetch RSS key
> > [...]
> > > @@ -1799,6 +1805,7 @@ const struct ethtool_ops mlx4_en_ethtool_ops = {
> > >  	.get_rxnfc = mlx4_en_get_rxnfc,
> > >  	.set_rxnfc = mlx4_en_set_rxnfc,
> > >  	.get_rxfh_indir_size = mlx4_en_get_rxfh_indir_size,
> > > +	.get_rxfh_key_size = mlx4_en_get_rxfh_key_size,
> > >  	.get_rxfh = mlx4_en_get_rxfh,
> > >  	.set_rxfh = mlx4_en_set_rxfh,
> > [...]
> > 
> > A driver that implements get_rxfh_key_size() and set_rxfh() is assumed
> > to support setting the RSS key (and only the key).  However,
> > mlx4_en_set_rxfh() will currently crash if a new indirection table is
> > not provided.
> 
> Hi Ben.
> 
> Is this a net-next only concern, or is it an existing problem in net
> tree ?

It's introduced by the above patch, as you seem to have worked out.
Drivers not implementing ethtool_ops::get_rxfh_key_size will always get
a non-null indir pointer (see commit 61d88c6811f2).

Ben.

-- 
Ben Hutchings
Never put off till tomorrow what you can avoid all together.

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