From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934430AbcIOOHg (ORCPT ); Thu, 15 Sep 2016 10:07:36 -0400 Received: from merlin.infradead.org ([205.233.59.134]:52164 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754667AbcIOOH3 (ORCPT ); Thu, 15 Sep 2016 10:07:29 -0400 Date: Thu, 15 Sep 2016 16:07:23 +0200 From: Peter Zijlstra To: Alexander Shishkin Cc: Ingo Molnar , linux-kernel@vger.kernel.org, vince@deater.net, eranian@google.com, Arnaldo Carvalho de Melo , stable@vger.kernel.org Subject: Re: [PATCH 2/3] perf/x86: Tighten up the kernel_ip() check Message-ID: <20160915140723.GG5020@twins.programming.kicks-ass.net> References: <20160915132944.10331-1-alexander.shishkin@linux.intel.com> <20160915132944.10331-3-alexander.shishkin@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160915132944.10331-3-alexander.shishkin@linux.intel.com> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 15, 2016 at 04:29:43PM +0300, Alexander Shishkin wrote: > The kernel_ip() filter is used mostly by the DS/LBR code to look at the > branch addresses, but Intel PT also uses it to validate the address > filter offsets for kernel addresses, for which it is not sufficient: > supplying something in bits 64:48 that's not a sign extension of the lower > address bits (like 0xf00d000000000000) throws a #GP. > > In the interest of improving everybody's kernel address checks, this > patch adds address validation to kernel_ip(). > > Cc: stable@vger.kernel.org # 4.7 > Reported-by: Adrian Hunter > Signed-off-by: Alexander Shishkin > --- > arch/x86/events/perf_event.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h > index 5874d8de1f..88fb389356 100644 > --- a/arch/x86/events/perf_event.h > +++ b/arch/x86/events/perf_event.h > @@ -783,7 +783,7 @@ static inline bool kernel_ip(unsigned long ip) > #ifdef CONFIG_X86_32 > return ip > PAGE_OFFSET; > #else > - return (long)ip < 0; > + return (long)ip < 0 && virt_addr_valid(ip); > #endif > } I have a slight performance worry, this ends up being called a _lot_ on older machines that have to do the PEBS LBR-fixup.