| Message ID | 20241008120101.734521-1-edumazet@google.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 4a0ec2aa0704c8271fde33a0f7bb92d09c066c17 |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net-next] ipv6: switch inet6_addr_hash() to less predictable hash | expand |
On 10/8/24 6:01 AM, Eric Dumazet wrote: > 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@google.com> > --- > net/ipv6/addrconf.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > Reviewed-by: David Ahern <dsahern@kernel.org>
From: Eric Dumazet <edumazet@google.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@google.com> Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Hello: This patch was applied to netdev/net-next.git (main) by Jakub Kicinski <kuba@kernel.org>: On Tue, 8 Oct 2024 12:01:01 +0000 you wrote: > 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. > > [...] Here is the summary with links: - [net-next] ipv6: switch inet6_addr_hash() to less predictable hash https://git.kernel.org/netdev/net-next/c/4a0ec2aa0704 You are awesome, thank you!
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c index 94dceac528842c47c18e71ad75e9d16ae373b4f2..f31528d4f694e42032276ddd6230b23911c480b5 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); }
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@google.com> --- net/ipv6/addrconf.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)