From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-19.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CB39CC433EF for ; Mon, 13 Sep 2021 13:29:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B6D2B613D5 for ; Mon, 13 Sep 2021 13:29:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241507AbhIMNaZ (ORCPT ); Mon, 13 Sep 2021 09:30:25 -0400 Received: from mail.kernel.org ([198.145.29.99]:34850 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241486AbhIMNYR (ORCPT ); Mon, 13 Sep 2021 09:24:17 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 80297610CF; Mon, 13 Sep 2021 13:21:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1631539314; bh=tThF4jZpKU2xHOEdviRgq2hF+Xvdn5VgoSe98/GUQD8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=nHz0Jlyi1Arekm3243w4JaEOC/ZnEp0kzUL4njK8hSwBML0UXoquP3OWn9WKhv5Ut jEy46/G9MsSRslIm3IXYQQMhI708CujNr+x3R1sQhkrWAst0tp066s7iuMURa5p081 i9u+QBN+Bx6yRiVmVEDbXZ4gZ15A22mDz/DZ+RSA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Dumazet , Keyu Man , Wei Wang , Martin KaFai Lau , David Ahern , "David S. Miller" , Sasha Levin Subject: [PATCH 5.4 121/144] ipv6: make exception cache less predictible Date: Mon, 13 Sep 2021 15:15:02 +0200 Message-Id: <20210913131051.969454176@linuxfoundation.org> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20210913131047.974309396@linuxfoundation.org> References: <20210913131047.974309396@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Eric Dumazet [ Upstream commit a00df2caffed3883c341d5685f830434312e4a43 ] Even after commit 4785305c05b2 ("ipv6: use siphash in rt6_exception_hash()"), an attacker can still use brute force to learn some secrets from a victim linux host. One way to defeat these attacks is to make the max depth of the hash table bucket a random value. Before this patch, each bucket of the hash table used to store exceptions could contain 6 items under attack. After the patch, each bucket would contains a random number of items, between 6 and 10. The attacker can no longer infer secrets. This is slightly increasing memory size used by the hash table, we do not expect this to be a problem. Following patch is dealing with the same issue in IPv4. Fixes: 35732d01fe31 ("ipv6: introduce a hash table to store dst cache") Signed-off-by: Eric Dumazet Reported-by: Keyu Man Cc: Wei Wang Cc: Martin KaFai Lau Reviewed-by: David Ahern Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- net/ipv6/route.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/net/ipv6/route.c b/net/ipv6/route.c index d6fc22f7d7a6..575bd0f1b008 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -1667,6 +1667,7 @@ static int rt6_insert_exception(struct rt6_info *nrt, struct in6_addr *src_key = NULL; struct rt6_exception *rt6_ex; struct fib6_nh *nh = res->nh; + int max_depth; int err = 0; spin_lock_bh(&rt6_exception_lock); @@ -1721,7 +1722,9 @@ static int rt6_insert_exception(struct rt6_info *nrt, bucket->depth++; net->ipv6.rt6_stats->fib_rt_cache++; - if (bucket->depth > FIB6_MAX_DEPTH) + /* Randomize max depth to avoid some side channels attacks. */ + max_depth = FIB6_MAX_DEPTH + prandom_u32_max(FIB6_MAX_DEPTH); + while (bucket->depth > max_depth) rt6_exception_remove_oldest(bucket); out: -- 2.30.2