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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, "Jason A. Donenfeld" <Jason@zx2c4.com>,
        Moshe Kol <moshe.kol@mail.huji.ac.il>,
        Yossi Gilad <yossi.gilad@mail.huji.ac.il>,
        Amit Klein <aksecurity@gmail.com>,
        Eric Dumazet <edumazet@google.com>, Willy Tarreau <w@1wt.eu>,
        Jakub Kicinski <kuba@kernel.org>,
        Ben Hutchings <ben@decadent.org.uk>
Subject: [PATCH 4.19 229/234] tcp: use different parts of the port_offset for index and offset
Date:   Thu, 23 Jun 2022 18:44:56 +0200
Message-Id: <20220623164349.529541203@linuxfoundation.org>
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From: Willy Tarreau <w@1wt.eu>

commit 9e9b70ae923baf2b5e8a0ea4fd0c8451801ac526 upstream.

Amit Klein suggests that we use different parts of port_offset for the
table's index and the port offset so that there is no direct relation
between them.

Cc: Jason A. Donenfeld <Jason@zx2c4.com>
Cc: Moshe Kol <moshe.kol@mail.huji.ac.il>
Cc: Yossi Gilad <yossi.gilad@mail.huji.ac.il>
Cc: Amit Klein <aksecurity@gmail.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/ipv4/inet_hashtables.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -766,7 +766,7 @@ int __inet_hash_connect(struct inet_time
 	net_get_random_once(table_perturb, sizeof(table_perturb));
 	index = hash_32(port_offset, INET_TABLE_PERTURB_SHIFT);
 
-	offset = READ_ONCE(table_perturb[index]) + port_offset;
+	offset = READ_ONCE(table_perturb[index]) + (port_offset >> 32);
 	offset %= remaining;
 
 	/* In first pass we try ports of @low parity.