netdev - Re: [PATCH net-next] ipv6: switch inet6_addr

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Message-ID: <20241008162105.94440-1-kuniyu@amazon.com>
Date: Tue, 8 Oct 2024 09:21:05 -0700
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: <edumazet@...gle.com>
CC: <davem@...emloft.net>, <dsahern@...nel.org>, <eric.dumazet@...il.com>,
	<kuba@...nel.org>, <kuniyu@...zon.com>, <netdev@...r.kernel.org>,
	<pabeni@...hat.com>
Subject: Re: [PATCH net-next] ipv6: switch inet6_addr_hash() to less predictable hash

From: Eric Dumazet <edumazet@...gle.com>
Date: Tue,  8 Oct 2024 12:01:01 +0000
> In commit 3f27fb23219e ("ipv6: addrconf: add per netns perturbation
> in inet6_addr_hash()"), I added net_hash_mix() in inet6_addr_hash()
> to get better hash dispersion, at a time all netns were sharing the
> hash table.
> 
> Since then, commit 21a216a8fc63 ("ipv6/addrconf: allocate a per
> netns hash table") made the hash table per netns.
> 
> We could remove the net_hash_mix() from inet6_addr_hash(), but
> there is still an issue with ipv6_addr_hash().
> 
> It is highly predictable and a malicious user can easily create
> thousands of IPv6 addresses all stored in the same hash bucket.
> 
> Switch to __ipv6_addr_jhash(). We could use a dedicated
> secret, or reuse net_hash_mix() as I did in this patch.
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Reviewed-by: Kuniyuki Iwashima <kuniyu@...zon.com>