Re: [PATCH net 1/2] ipv6: make exception cache less predictible

[David Ahern <dsahern@gmail.com>]

On 8/29/21 3:16 PM, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@google.com>
> 
> Even after commit 4785305c05b2 ("ipv6: use siphash in rt6_exception_hash()"),
> an attacker can still use brute force to learn some secrets from a victim
> linux host.
> 
> One way to defeat these attacks is to make the max depth of the hash
> table bucket a random value.
> 
> Before this patch, each bucket of the hash table used to store exceptions
> could contain 6 items under attack.
> 
> After the patch, each bucket would contains a random number of items,
> between 6 and 10. The attacker can no longer infer secrets.
> 
> This is slightly increasing memory size used by the hash table,
> we do not expect this to be a problem.
> 
> Following patch is dealing with the same issue in IPv4.
> 
> Fixes: 35732d01fe31 ("ipv6: introduce a hash table to store dst cache")
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Reported-by: Keyu Man <kman001@ucr.edu>
> Cc: Wei Wang <weiwan@google.com>
> Cc: Martin KaFai Lau <kafai@fb.com>
> ---
>  net/ipv6/route.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 

Reviewed-by: David Ahern <dsahern@kernel.org>