netdev - [PATCH net-next] ipv6: switch inet6_acaddr

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Message-ID: <20241008121307.800040-1-edumazet@google.com>
Date: Tue,  8 Oct 2024 12:13:07 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: David Ahern <dsahern@...nel.org>, Kuniyuki Iwashima <kuniyu@...zon.com>, netdev@...r.kernel.org, 
	eric.dumazet@...il.com, Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next] ipv6: switch inet6_acaddr_hash() to less predictable hash

commit 2384d02520ff ("net/ipv6: Add anycast addresses to a global hashtable")
added inet6_acaddr_hash(), using ipv6_addr_hash() and net_hash_mix()
to get hash spreading for typical users.

However ipv6_addr_hash() is highly predictable and a malicious user
could abuse a specific 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>
---
 net/ipv6/anycast.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/ipv6/anycast.c b/net/ipv6/anycast.c
index 0627c4c18d1a5067a668da778ad444855194cbeb..562cace50ca9ae635dd0762e147b452be44c729c 100644
--- a/net/ipv6/anycast.c
+++ b/net/ipv6/anycast.c
@@ -49,9 +49,10 @@ static DEFINE_SPINLOCK(acaddr_hash_lock);
 
 static int ipv6_dev_ac_dec(struct net_device *dev, const struct in6_addr *addr);
 
-static u32 inet6_acaddr_hash(struct net *net, const struct in6_addr *addr)
+static u32 inet6_acaddr_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);
 }
-- 
2.47.0.rc0.187.ge670bccf7e-goog