From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752482AbdEHXbQ (ORCPT ); Mon, 8 May 2017 19:31:16 -0400 Received: from mail-io0-f169.google.com ([209.85.223.169]:32927 "EHLO mail-io0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752016AbdEHXbM (ORCPT ); Mon, 8 May 2017 19:31:12 -0400 MIME-Version: 1.0 In-Reply-To: <20170508225308.a6uznrhdm7pgyhcg@treble> References: <1494271972-140319-1-git-send-email-keescook@chromium.org> <1494271972-140319-3-git-send-email-keescook@chromium.org> <20170508225308.a6uznrhdm7pgyhcg@treble> From: Kees Cook Date: Mon, 8 May 2017 16:31:11 -0700 X-Google-Sender-Auth: pdcnCpW_FUv1ecfN81-GGuse-Pc Message-ID: Subject: Re: [PATCH v3 2/2] x86/refcount: Implement fast refcount overflow protection To: Josh Poimboeuf Cc: LKML , Peter Zijlstra , PaX Team , Jann Horn , Eric Biggers , Christoph Hellwig , "axboe@kernel.dk" , James Bottomley , Elena Reshetova , Hans Liljestrand , David Windsor , "x86@kernel.org" , Ingo Molnar , Arnd Bergmann , Greg Kroah-Hartman , "David S. Miller" , Rik van Riel , linux-arch , "kernel-hardening@lists.openwall.com" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 8, 2017 at 3:53 PM, Josh Poimboeuf wrote: > On Mon, May 08, 2017 at 12:32:52PM -0700, Kees Cook wrote: >> +#define REFCOUNT_EXCEPTION \ >> + "movl $0x7fffffff, %[counter]\n\t" \ >> + "int $"__stringify(X86_REFCOUNT_VECTOR)"\n" \ >> + "0:\n\t" \ >> + _ASM_EXTABLE(0b, 0b) > > Despite the objtool warnings going away, this still uses the exception > table in a new way, which will confuse objtool. I need to do some more > thinking about the best way to fix it, either as a change to your patch > or a change to objtool. In that it's not a "true" exception? >> diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h >> index 532372c6cf15..0590f384f234 100644 >> --- a/include/asm-generic/sections.h >> +++ b/include/asm-generic/sections.h >> @@ -20,6 +20,8 @@ >> * may be out of this range on some architectures. >> * [_sinittext, _einittext]: contains .init.text.* sections >> * [__bss_start, __bss_stop]: contains BSS sections >> + * [__refcount_overflow/underflow_start, ..._end]: contains .text sections >> + * for refcount error handling. >> * >> * Following global variables are optional and may be unavailable on some >> * architectures and/or kernel configurations. >> @@ -39,6 +41,8 @@ extern char __per_cpu_load[], __per_cpu_start[], __per_cpu_end[]; >> extern char __kprobes_text_start[], __kprobes_text_end[]; >> extern char __entry_text_start[], __entry_text_end[]; >> extern char __start_rodata[], __end_rodata[]; >> +extern char __refcount_overflow_start[], __refcount_overflow_end[]; >> +extern char __refcount_underflow_start[], __refcount_underflow_end[]; > > I think this part is no longer needed, since you got rid of the new > sections? Oh whoops, thanks. I thought I'd removed those, but clearly I didn't. :) Thanks! -Kees -- Kees Cook Pixel Security