From: Eric Dumazet <edumazet@google.com>
Subject: ipv4: use siphash instead of Jenkins in fnhe_hashfun()
Git-commit: 6457378fe796815c973f631a1904e147d6ee33b1
Patch-mainline: v5.14
References: bsc#1191790, CVE-2021-20322
Acked-by: Jiri Bohac <jbohac@suse.cz>

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@google.com>
Reported-by: Keyu Man <kman001@ucr.edu>
Cc: Willy Tarreau <w@1wt.eu>
Signed-off-by: David S. Miller <davem@davemloft.net>

---
 net/ipv4/route.c |   12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -617,14 +617,14 @@ static struct fib_nh_exception *fnhe_old
 	return oldest;
 }
 
-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)