Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753286AbeAFKGd (ORCPT + 1 other); Sat, 6 Jan 2018 05:06:33 -0500 Received: from mail-lf0-f68.google.com ([209.85.215.68]:34045 "EHLO mail-lf0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752826AbeAFKGb (ORCPT ); Sat, 6 Jan 2018 05:06:31 -0500 X-Google-Smtp-Source: ACJfBot/BRH0XoKthMc5ul7fWkvBrWeMrCRB+eHCFY472qdl2GiyeROMynpg7kOX7J/Dfg+AE8A2pA== Subject: Re: [PATCH 16/18] net: mpls: prevent bounds-check bypass via speculative execution To: Dan Williams , linux-kernel@vger.kernel.org Cc: linux-arch@vger.kernel.org, peterz@infradead.org, netdev@vger.kernel.org, "Eric W. Biederman" , gregkh@linuxfoundation.org, tglx@linutronix.de, torvalds@linux-foundation.org, "David S. Miller" , Elena Reshetova , alan@linux.intel.com References: <151520099201.32271.4677179499894422956.stgit@dwillia2-desk3.amr.corp.intel.com> <151520108080.32271.16420298348259030860.stgit@dwillia2-desk3.amr.corp.intel.com> From: Sergei Shtylyov Message-ID: <0b4d9292-cf0a-170e-a85a-527d1481ae51@cogentembedded.com> Date: Sat, 6 Jan 2018 13:06:28 +0300 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.5.2 MIME-Version: 1.0 In-Reply-To: <151520108080.32271.16420298348259030860.stgit@dwillia2-desk3.amr.corp.intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: On 1/6/2018 4:11 AM, Dan Williams wrote: > Static analysis reports that 'index' may be a user controlled value that > is used as a data dependency reading 'rt' from the 'platform_label' > array. In order to avoid potential leaks of kernel memory values, block > speculative execution of the instruction stream that could issue further > reads based on an invalid 'rt' value. > > Based on an original patch by Elena Reshetova. > > Cc: "David S. Miller" > Cc: Eric W. Biederman > Cc: netdev@vger.kernel.org > Signed-off-by: Elena Reshetova > Signed-off-by: Dan Williams > --- > net/mpls/af_mpls.c | 12 +++++++----- > 1 file changed, 7 insertions(+), 5 deletions(-) > > diff --git a/net/mpls/af_mpls.c b/net/mpls/af_mpls.c > index 8ca9915befc8..ebcf0e246cfe 100644 > --- a/net/mpls/af_mpls.c > +++ b/net/mpls/af_mpls.c [...] > @@ -77,12 +78,13 @@ static void rtmsg_lfib(int event, u32 label, struct mpls_route *rt, > static struct mpls_route *mpls_route_input_rcu(struct net *net, unsigned index) > { > struct mpls_route *rt = NULL; > + struct mpls_route __rcu **platform_label = > + rcu_dereference(net->mpls.platform_label); > + struct mpls_route __rcu **rtp; > > - if (index < net->mpls.platform_labels) { > - struct mpls_route __rcu **platform_label = > - rcu_dereference(net->mpls.platform_label); > - rt = rcu_dereference(platform_label[index]); > - } > + if ((rtp = nospec_array_ptr(platform_label, index, And here... > + net->mpls.platform_labels))) > + rt = rcu_dereference(*rtp); > return rt; > } > MBR, Sergei