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=-6.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_PASS 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 3B30CC43387 for ; Wed, 9 Jan 2019 22:02:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 08EE0206B7 for ; Wed, 9 Jan 2019 22:02:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727307AbfAIWCF (ORCPT ); Wed, 9 Jan 2019 17:02:05 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:60326 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725775AbfAIWCE (ORCPT ); Wed, 9 Jan 2019 17:02:04 -0500 Received: from akpm3.svl.corp.google.com (unknown [104.133.8.65]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id 8FDC1B55; Wed, 9 Jan 2019 22:02:03 +0000 (UTC) Date: Wed, 9 Jan 2019 14:02:01 -0800 From: Andrew Morton To: Qian Cai Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RESEND PATCH] x86_64: increase stack size for KASAN_EXTRA Message-Id: <20190109140201.4434ff87880ee29bdedb37cc@linux-foundation.org> In-Reply-To: <20190109215209.2903-1-cai@lca.pw> References: <20181228020639.80425-1-cai@lca.pw> <20190109215209.2903-1-cai@lca.pw> X-Mailer: Sylpheed 3.6.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 9 Jan 2019 16:52:09 -0500 Qian Cai wrote: > If the kernel is configured with KASAN_EXTRA, the stack size is > increasted significantly due to enable this option will set > "-fstack-reuse" to "none" in GCC [1]. As the results, it could trigger > stack overrun quite often with 32k stack size compiled using GCC 8. For > example, this reproducer > > https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/\ > syscalls/madvise/madvise06.c > > could trigger a "corrupted stack end detected inside scheduler" very > reliably with CONFIG_SCHED_STACK_END_CHECK enabled. > > There are just too many functions that could have a large stack with > KASAN_EXTRA due to large local variables that have been called over and > over again without being able to reuse the stacks. Some noticiable ones > are, > > size > 7648 shrink_page_list > 3584 xfs_rmap_convert > 3312 migrate_page_move_mapping > 3312 dev_ethtool > 3200 migrate_misplaced_transhuge_page > 3168 copy_process > > There are other 49 functions are over 2k in size while compiling kernel > with "-Wframe-larger-than=" even with a related minimal config on this > machine. Hence, it is too much work to change Makefiles for each object > to compile without "-fsanitize-address-use-after-scope" individually. > > [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81715#c23 > > Although there is a patch in GCC 9 to help the situation, GCC 9 probably > won't be released in a few months and then it probably take another > 6-month to 1-year for all major distros to include it as a default. > Hence, the stack usage with KASAN_EXTRA can be revisited again in 2020 > when GCC 9 is everywhere. Until then, this patch will help users avoid > stack overrun. > > This has already been fixed for arm64 for the same reason via > 6e8830674ea (arm64: kasan: Increase stack size for KASAN_EXTRA). Sounds good. > --- a/arch/x86/include/asm/page_64_types.h > +++ b/arch/x86/include/asm/page_64_types.h > @@ -7,7 +7,11 @@ > #endif > > #ifdef CONFIG_KASAN > +#ifdef CONFIG_KASAN_EXTRA > +#define KASAN_STACK_ORDER 2 > +#else > #define KASAN_STACK_ORDER 1 > +#endif > #else > #define KASAN_STACK_ORDER 0 > #endif I'm suspecting this logic could be performed in Kconfig, for all architectures. Add a new always-defined CONFIG_KASAN_STACK_ORDER?