netdev - Re: [PATCH net] netlink: use jhash as hashfn for rhashtable

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Message-ID: <20141208163802.GC9831@casper.infradead.org>
Date:	Mon, 8 Dec 2014 16:38:02 +0000
From:	Thomas Graf <tgraf@...g.ch>
To:	Daniel Borkmann <dborkman@...hat.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Hannes Frederic Sowa <hannes@...essinduktion.org>
Subject: Re: [PATCH net] netlink: use jhash as hashfn for rhashtable

On 12/08/14 at 05:30pm, Daniel Borkmann wrote:
> For netlink, we shouldn't be using arch_fast_hash() as a hashing
> discipline, but rather jhash() instead.
> 
> Since netlink sockets can be opened by any user, a local attacker
> would be able to easily create collisions with the DPDK-derived
> arch_fast_hash(), which trades off performance for security by
> using crc32 CPU instructions on x86_64.
> 
> While it might have a legimite use case in other places, it should
> be avoided in netlink context, though. As rhashtable's API is very
> flexible, we could later on still decide on other hashing disciplines,
> if legitimate.
> 
> Reference: http://thread.gmane.org/gmane.linux.kernel/1844123
> Fixes: e341694e3eb5 ("netlink: Convert netlink_lookup() to use RCU protected hash table")
> Cc: Herbert Xu <herbert@...dor.apana.org.au>
> Cc: Thomas Graf <tgraf@...g.ch>
> Cc: Hannes Frederic Sowa <hannes@...essinduktion.org>
> Signed-off-by: Daniel Borkmann <dborkman@...hat.com>

Acked-by: Thomas Graf <tgraf@...g.ch>
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