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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 autolearn=no 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 6985EC3F2CF for ; Fri, 28 Feb 2020 06:32:55 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id DEE472468E for ; Fri, 28 Feb 2020 06:32:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DEE472468E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=buserror.net Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 48TKTt2F64zDrMC for ; Fri, 28 Feb 2020 17:32:50 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=none (no SPF record) smtp.mailfrom=buserror.net (client-ip=165.227.176.147; helo=baldur.buserror.net; envelope-from=oss@buserror.net; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=buserror.net X-Greylist: delayed 2008 seconds by postgrey-1.36 at bilbo; Fri, 28 Feb 2020 17:31:15 AEDT Received: from baldur.buserror.net (baldur.buserror.net [165.227.176.147]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 48TKS33sXhzDr6l for ; Fri, 28 Feb 2020 17:31:15 +1100 (AEDT) Received: from [2601:449:8480:af0:12bf:48ff:fe84:c9a0] by baldur.buserror.net with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1j7YaJ-0001Y7-1g; Thu, 27 Feb 2020 23:53:15 -0600 Message-ID: From: Scott Wood To: Jason Yan , Daniel Axtens , mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org, diana.craciun@nxp.com, christophe.leroy@c-s.fr, benh@kernel.crashing.org, paulus@samba.org, npiggin@gmail.com, keescook@chromium.org, kernel-hardening@lists.openwall.com Date: Thu, 27 Feb 2020 23:53:13 -0600 In-Reply-To: <8171d326-5138-4f5c-cff6-ad3ee606f0c2@huawei.com> References: <20200206025825.22934-1-yanaijie@huawei.com> <87tv3drf79.fsf@dja-thinkpad.axtens.net> <8171d326-5138-4f5c-cff6-ad3ee606f0c2@huawei.com> Organization: Red Hat Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.28.5-0ubuntu0.18.04.1 Mime-Version: 1.0 Content-Transfer-Encoding: 8bit X-SA-Exim-Connect-IP: 2601:449:8480:af0:12bf:48ff:fe84:c9a0 X-SA-Exim-Rcpt-To: yanaijie@huawei.com, dja@axtens.net, mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org, diana.craciun@nxp.com, christophe.leroy@c-s.fr, benh@kernel.crashing.org, paulus@samba.org, npiggin@gmail.com, keescook@chromium.org, kernel-hardening@lists.openwall.com, linux-kernel@vger.kernel.org, zhaohongjiang@huawei.com X-SA-Exim-Mail-From: oss@buserror.net Subject: Re: [PATCH v3 0/6] implement KASLR for powerpc/fsl_booke/64 X-SA-Exim-Version: 4.2.1 (built Tue, 02 Aug 2016 21:08:31 +0000) X-SA-Exim-Scanned: Yes (on baldur.buserror.net) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-kernel@vger.kernel.org, zhaohongjiang@huawei.com Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Wed, 2020-02-26 at 16:18 +0800, Jason Yan wrote: > Hi Daniel, > > 在 2020/2/26 15:16, Daniel Axtens 写道: > > Hi Jason, > > > > > This is a try to implement KASLR for Freescale BookE64 which is based on > > > my earlier implementation for Freescale BookE32: > > > https://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=131718 > > > > > > The implementation for Freescale BookE64 is similar as BookE32. One > > > difference is that Freescale BookE64 set up a TLB mapping of 1G during > > > booting. Another difference is that ppc64 needs the kernel to be > > > 64K-aligned. So we can randomize the kernel in this 1G mapping and make > > > it 64K-aligned. This can save some code to creat another TLB map at > > > early boot. The disadvantage is that we only have about 1G/64K = 16384 > > > slots to put the kernel in. > > > > > > KERNELBASE > > > > > > 64K |--> kernel <--| > > > | | | > > > +--+--+--+ +--+--+--+--+--+--+--+--+--+ +--+--+ > > > | | | |....| | | | | | | | | |....| | | > > > +--+--+--+ +--+--+--+--+--+--+--+--+--+ +--+--+ > > > | | 1G > > > |-----> offset <-----| > > > > > > kernstart_virt_addr > > > > > > I'm not sure if the slot numbers is enough or the design has any > > > defects. If you have some better ideas, I would be happy to hear that. > > > > > > Thank you all. > > > > > > > Are you making any attempt to hide kernel address leaks in this series? > > Yes. > > > I've just been looking at the stackdump code just now, and it directly > > prints link registers and stack pointers, which is probably enough to > > determine the kernel base address: > > > > SPs: LRs: %pS pointer > > [ 0.424506] [c0000000de403970] [c000000001fc0458] dump_stack+0xfc/0x154 > > (unreliable) > > [ 0.424593] [c0000000de4039c0] [c000000000267eec] panic+0x258/0x5ac > > [ 0.424659] [c0000000de403a60] [c0000000024d7a00] > > mount_block_root+0x634/0x7c0 > > [ 0.424734] [c0000000de403be0] [c0000000024d8100] > > prepare_namespace+0x1ec/0x23c > > [ 0.424811] [c0000000de403c60] [c0000000024d7010] > > kernel_init_freeable+0x804/0x880 > > > > git grep \\\"REG\\\" arch/powerpc shows a few other uses like this, all > > in process.c or in xmon. > > > > Thanks for reminding this. > > > Maybe replacing the REG format string in KASLR mode would be sufficient? > > > > Most archs have removed the address printing when dumping stack. Do we > really have to print this? > > If we have to do this, maybe we can use "%pK" so that they will be > hidden from unprivileged users. I've found the addresses to be useful, especially if I had a way to dump the stack data itself. Wouldn't the register dump also be likely to give away the addresses? I don't see any debug setting for %pK (or %p) to always print the actual address (closest is kptr_restrict=1 but that only works in certain contexts)... from looking at the code it seems it hashes even if kaslr is entirely disabled? Or am I missing something? -Scott