linux-kernel - [PATCH 5.4 2/2] ipv4: use siphash instead of Jenkins in fnhe

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Message-Id: <20211028174230.1800007-3-ovidiu.panait@windriver.com>
Date:   Thu, 28 Oct 2021 20:42:30 +0300
From:   Ovidiu Panait <ovidiu.panait@...driver.com>
To:     linux-kernel@...r.kernel.org
Cc:     edumazet@...gle.com, davem@...emloft.net, kman001@....edu,
        weiwan@...gle.com
Subject: [PATCH 5.4 2/2] ipv4: use siphash instead of Jenkins in fnhe_hashfun()

From: Eric Dumazet <edumazet@...gle.com>

commit 6457378fe796815c973f631a1904e147d6ee33b1 upstream.

A group of security researchers brought to our attention
the weakness of hash function used in fnhe_hashfun().

Lets use siphash instead of Jenkins Hash, to considerably
reduce security risks.

Also remove the inline keyword, this really is distracting.

Fixes: d546c621542d ("ipv4: harden fnhe_hashfun()")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Reported-by: Keyu Man <kman001@....edu>
Cc: Willy Tarreau <w@....eu>
Signed-off-by: David S. Miller <davem@...emloft.net>
[OP: adjusted context for 5.4 stable]
Signed-off-by: Ovidiu Panait <ovidiu.panait@...driver.com>
---
 net/ipv4/route.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 539492998864..d1feec97fa06 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -631,14 +631,14 @@ static void fnhe_remove_oldest(struct fnhe_hash_bucket *hash)
 	kfree_rcu(oldest, rcu);
 }
 
-static inline u32 fnhe_hashfun(__be32 daddr)
+static u32 fnhe_hashfun(__be32 daddr)
 {
-	static u32 fnhe_hashrnd __read_mostly;
-	u32 hval;
+	static siphash_key_t fnhe_hash_key __read_mostly;
+	u64 hval;
 
-	net_get_random_once(&fnhe_hashrnd, sizeof(fnhe_hashrnd));
-	hval = jhash_1word((__force u32) daddr, fnhe_hashrnd);
-	return hash_32(hval, FNHE_HASH_SHIFT);
+	net_get_random_once(&fnhe_hash_key, sizeof(fnhe_hash_key));
+	hval = siphash_1u32((__force u32)daddr, &fnhe_hash_key);
+	return hash_64(hval, FNHE_HASH_SHIFT);
 }
 
 static void fill_route_from_fnhe(struct rtable *rt, struct fib_nh_exception *fnhe)
-- 
2.25.1