From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Borkmann Subject: [PATCH net] netlink: use jhash as hashfn for rhashtable Date: Mon, 8 Dec 2014 17:30:30 +0100 Message-ID: <1418056230-8700-1-git-send-email-dborkman@redhat.com> Cc: netdev@vger.kernel.org, Herbert Xu , Thomas Graf , Hannes Frederic Sowa To: davem@davemloft.net Return-path: Received: from mx1.redhat.com ([209.132.183.28]:33734 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751132AbaLHQdW (ORCPT ); Mon, 8 Dec 2014 11:33:22 -0500 Sender: netdev-owner@vger.kernel.org List-ID: For netlink, we shouldn't be using arch_fast_hash() as a hashing discipline, but rather jhash() instead. Since netlink sockets can be opened by any user, a local attacker would be able to easily create collisions with the DPDK-derived arch_fast_hash(), which trades off performance for security by using crc32 CPU instructions on x86_64. While it might have a legimite use case in other places, it should be avoided in netlink context, though. As rhashtable's API is very flexible, we could later on still decide on other hashing disciplines, if legitimate. Reference: http://thread.gmane.org/gmane.linux.kernel/1844123 Fixes: e341694e3eb5 ("netlink: Convert netlink_lookup() to use RCU protected hash table") Cc: Herbert Xu Cc: Thomas Graf Cc: Hannes Frederic Sowa Signed-off-by: Daniel Borkmann --- net/netlink/af_netlink.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c index 0007b81..b6bf8e8 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -3130,7 +3130,7 @@ static int __init netlink_proto_init(void) .head_offset = offsetof(struct netlink_sock, node), .key_offset = offsetof(struct netlink_sock, portid), .key_len = sizeof(u32), /* portid */ - .hashfn = arch_fast_hash, + .hashfn = jhash, .max_shift = 16, /* 64K */ .grow_decision = rht_grow_above_75, .shrink_decision = rht_shrink_below_30, -- 1.7.11.7