netns: provide pure entropy for net_hash_mix()
[ Upstream commit 355b98553789b646ed97ad801a619ff898471b92 ] net_hash_mix() currently uses kernel address of a struct net, and is used in many places that could be used to reveal this address to a patient attacker, thus defeating KASLR, for the typical case (initial net namespace, &init_net is not dynamically allocated) I believe the original implementation tried to avoid spending too many cycles in this function, but security comes first. Also provide entropy regardless of CONFIG_NET_NS. Fixes: 0b441916 ("netns: introduce the net_hash_mix "salt" for hashes") Signed-off-by: NEric Dumazet <edumazet@google.com> Reported-by: NAmit Klein <aksecurity@gmail.com> Reported-by: NBenny Pinkas <benny@pinkas.net> Cc: Pavel Emelyanov <xemul@openvz.org> Signed-off-by: NDavid S. Miller <davem@davemloft.net> Signed-off-by: NSasha Levin <sashal@kernel.org>
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