From 4a0ec2aa0704c8271fde33a0f7bb92d09c066c17 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 8 Oct 2024 12:01:01 +0000 Subject: [PATCH] ipv6: switch inet6_addr_hash() to less predictable hash 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 Reviewed-by: David Ahern Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20241008120101.734521-1-edumazet@google.com Signed-off-by: Jakub Kicinski --- net/ipv6/addrconf.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c index 94dceac52884..f31528d4f694 100644 --- a/net/ipv6/addrconf.c +++ b/net/ipv6/addrconf.c @@ -1016,7 +1016,7 @@ ipv6_link_dev_addr(struct inet6_dev *idev, struct inet6_ifaddr *ifp) static u32 inet6_addr_hash(const struct net *net, const struct in6_addr *addr) { - u32 val = ipv6_addr_hash(addr) ^ net_hash_mix(net); + u32 val = __ipv6_addr_jhash(addr, net_hash_mix(net)); return hash_32(val, IN6_ADDR_HSIZE_SHIFT); }