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=-13.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 3528AC54FCB for ; Wed, 22 Apr 2020 14:35:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E4FC8206D4 for ; Wed, 22 Apr 2020 14:35:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727872AbgDVOfc (ORCPT ); Wed, 22 Apr 2020 10:35:32 -0400 Received: from foss.arm.com ([217.140.110.172]:50868 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726573AbgDVOfb (ORCPT ); Wed, 22 Apr 2020 10:35:31 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id CDCF230E; Wed, 22 Apr 2020 07:35:30 -0700 (PDT) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 240433F68F; Wed, 22 Apr 2020 07:35:29 -0700 (PDT) Date: Wed, 22 Apr 2020 15:35:27 +0100 From: Mark Rutland To: Phong Tran Cc: steve.capper@arm.com, steven.price@arm.com, will@kernel.org, keescook@chromium.org, greg@kroah.com, akpm@linux-foundation.org, alexios.zavras@intel.com, broonie@kernel.org, kernel-hardening@lists.openwall.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, tglx@linutronix.de Subject: Re: [PATCH v2] arm64: add check_wx_pages debugfs for CHECK_WX Message-ID: <20200422143526.GD54796@lakrids.cambridge.arm.com> References: <20200307093926.27145-1-tranmanphong@gmail.com> <20200421173557.10817-1-tranmanphong@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200421173557.10817-1-tranmanphong@gmail.com> User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 22, 2020 at 12:35:58AM +0700, Phong Tran wrote: > follow the suggestion from > https://github.com/KSPP/linux/issues/35 > > Signed-off-by: Phong Tran > --- > Change since v1: > - Update the Kconfig help text > - Don't check the return value of debugfs_create_file() > - Tested on QEMU aarch64 As on v1, I think that this should be generic across all architectures with CONFIG_DEBUG_WX. Adding this only on arm64 under CONFIG_PTDUMP_DEBUGFS (which does not generally imply a WX check) doesn't seem right. Maybe we need a new ARCH_HAS_CHECK_WX config to make that simpler, but that seems simple to me. Thanks, Marm. > root@qemuarm64:~# zcat /proc/config.gz | grep PTDUMP > CONFIG_GENERIC_PTDUMP=y > CONFIG_PTDUMP_CORE=y > CONFIG_PTDUMP_DEBUGFS=y > root@qemuarm64:~# uname -a > Linux qemuarm64 5.7.0-rc2-00001-g20ddb383c313 #3 SMP PREEMPT Tue Apr 21 23:18:56 +07 2020 aarch64 GNU/Linux > root@qemuarm64:~# echo 1 > /sys/kernel/debug/check_wx_pages > [ 63.261868] Checked W+X mappings: passed, no W+X pages found > --- > arch/arm64/Kconfig.debug | 5 ++++- > arch/arm64/include/asm/ptdump.h | 2 ++ > arch/arm64/mm/dump.c | 1 + > arch/arm64/mm/ptdump_debugfs.c | 18 ++++++++++++++++++ > 4 files changed, 25 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/Kconfig.debug b/arch/arm64/Kconfig.debug > index a1efa246c9ed..cd82c9d3664a 100644 > --- a/arch/arm64/Kconfig.debug > +++ b/arch/arm64/Kconfig.debug > @@ -48,7 +48,10 @@ config DEBUG_WX > of other unfixed kernel bugs easier. > > There is no runtime or memory usage effect of this option > - once the kernel has booted up - it's a one time check. > + once the kernel has booted up - it's a one time check at > + boot, and can also be triggered at runtime by echo "1" to > + "check_wx_pages". The "check_wx_pages" is available only with > + CONFIG_PTDUMP_DEBUGFS is enabled. > > If in doubt, say "Y". > > diff --git a/arch/arm64/include/asm/ptdump.h b/arch/arm64/include/asm/ptdump.h > index 38187f74e089..c90a6ec6f59b 100644 > --- a/arch/arm64/include/asm/ptdump.h > +++ b/arch/arm64/include/asm/ptdump.h > @@ -24,9 +24,11 @@ struct ptdump_info { > void ptdump_walk(struct seq_file *s, struct ptdump_info *info); > #ifdef CONFIG_PTDUMP_DEBUGFS > void ptdump_debugfs_register(struct ptdump_info *info, const char *name); > +void ptdump_check_wx_init(void); > #else > static inline void ptdump_debugfs_register(struct ptdump_info *info, > const char *name) { } > +static inline void ptdump_check_wx_init(void) { } > #endif > void ptdump_check_wx(void); > #endif /* CONFIG_PTDUMP_CORE */ > diff --git a/arch/arm64/mm/dump.c b/arch/arm64/mm/dump.c > index 860c00ec8bd3..60c99a047763 100644 > --- a/arch/arm64/mm/dump.c > +++ b/arch/arm64/mm/dump.c > @@ -378,6 +378,7 @@ static int ptdump_init(void) > #endif > ptdump_initialize(); > ptdump_debugfs_register(&kernel_ptdump_info, "kernel_page_tables"); > + ptdump_check_wx_init(); > return 0; > } > device_initcall(ptdump_init); > diff --git a/arch/arm64/mm/ptdump_debugfs.c b/arch/arm64/mm/ptdump_debugfs.c > index d29d722ec3ec..6b0aa16cb17b 100644 > --- a/arch/arm64/mm/ptdump_debugfs.c > +++ b/arch/arm64/mm/ptdump_debugfs.c > @@ -20,3 +20,21 @@ void ptdump_debugfs_register(struct ptdump_info *info, const char *name) > { > debugfs_create_file(name, 0400, NULL, info, &ptdump_fops); > } > + > +static int check_wx_debugfs_set(void *data, u64 val) > +{ > + if (val != 1ULL) > + return -EINVAL; > + > + ptdump_check_wx(); > + > + return 0; > +} > + > +DEFINE_SIMPLE_ATTRIBUTE(check_wx_fops, NULL, check_wx_debugfs_set, "%llu\n"); > + > +void ptdump_check_wx_init(void) > +{ > + debugfs_create_file("check_wx_pages", 0200, NULL, > + NULL, &check_wx_fops) ? 0 : -ENOMEM; > +} > -- > 2.20.1 >