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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_MUTT 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 12F0DC04EB8 for ; Fri, 30 Nov 2018 13:19:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CA7DC20867 for ; Fri, 30 Nov 2018 13:19:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CA7DC20867 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726666AbeLAA2m (ORCPT ); Fri, 30 Nov 2018 19:28:42 -0500 Received: from foss.arm.com ([217.140.101.70]:56156 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726070AbeLAA2m (ORCPT ); Fri, 30 Nov 2018 19:28:42 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id DDA47A78; Fri, 30 Nov 2018 05:19:25 -0800 (PST) Received: from edgewater-inn.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id A92EC3F5A0; Fri, 30 Nov 2018 05:19:25 -0800 (PST) Received: by edgewater-inn.cambridge.arm.com (Postfix, from userid 1000) id 737A11AE12D3; Fri, 30 Nov 2018 13:19:44 +0000 (GMT) Date: Fri, 30 Nov 2018 13:19:44 +0000 From: Will Deacon To: AKASHI Takahiro Cc: catalin.marinas@arm.com, dhowells@redhat.com, vgoyal@redhat.com, herbert@gondor.apana.org.au, davem@davemloft.net, dyoung@redhat.com, bhe@redhat.com, arnd@arndb.de, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, prudo@linux.ibm.com, ard.biesheuvel@linaro.org, james.morse@arm.com, bhsharma@redhat.com, kexec@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v16 16/16] arm64: kexec_file: add kaslr support Message-ID: <20181130131944.GA9000@arm.com> References: <20181115055254.2812-1-takahiro.akashi@linaro.org> <20181115055254.2812-17-takahiro.akashi@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181115055254.2812-17-takahiro.akashi@linaro.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 15, 2018 at 02:52:55PM +0900, AKASHI Takahiro wrote: > Adding "kaslr-seed" to dtb enables triggering kaslr, or kernel virtual > address randomization, at secondary kernel boot. We always do this as > it will have no harm on kaslr-incapable kernel. > > We don't have any "switch" to turn off this feature directly, but still > can suppress it by passing "nokaslr" as a kernel boot argument. > > Signed-off-by: AKASHI Takahiro > Cc: Catalin Marinas > Cc: Will Deacon > --- > arch/arm64/kernel/machine_kexec_file.c | 46 +++++++++++++++++++++++++- > 1 file changed, 45 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c > index ab296b98d633..a0a730bd9be6 100644 > --- a/arch/arm64/kernel/machine_kexec_file.c > +++ b/arch/arm64/kernel/machine_kexec_file.c > @@ -16,6 +16,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -28,6 +29,7 @@ > #define FDT_PSTR_INITRD_STA "linux,initrd-start" > #define FDT_PSTR_INITRD_END "linux,initrd-end" > #define FDT_PSTR_BOOTARGS "bootargs" > +#define FDT_PSTR_KASLR_SEED "kaslr-seed" > > const struct kexec_file_ops * const kexec_file_loaders[] = { > &kexec_image_ops, > @@ -46,11 +48,38 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image) > return kexec_image_post_load_cleanup_default(image); > } > > +/* crng needs to have been initialized for providing kaslr-seed */ > +static int random_ready; > + > +static void random_ready_notified(struct random_ready_callback *unused) > +{ > + random_ready = 1; > +} > + > +static struct random_ready_callback random_ready_cb = { > + .func = random_ready_notified, > +}; > + > +static __init int init_random_ready_cb(void) > +{ > + int ret; > + > + ret = add_random_ready_callback(&random_ready_cb); > + if (ret == -EALREADY) > + random_ready = 1; > + else if (ret) > + pr_warn("failed to add a callback for random_ready\n"); > + > + return 0; > +} > +late_initcall(init_random_ready_cb) Why can't we just call crng_ready()? > + > static int setup_dtb(struct kimage *image, > unsigned long initrd_load_addr, unsigned long initrd_len, > char *cmdline, void *dtb) > { > int nodeoffset; > + u64 value; > int ret; > > nodeoffset = fdt_path_offset(dtb, "/chosen"); > @@ -106,12 +135,27 @@ static int setup_dtb(struct kimage *image, > return -EINVAL; > } > > + /* add kaslr-seed */ > + ret = fdt_delprop(dtb, nodeoffset, FDT_PSTR_KASLR_SEED); > + if (ret && (ret != -FDT_ERR_NOTFOUND)) > + return -EINVAL; > + > + if (random_ready) { > + get_random_bytes(&value, sizeof(value)); get_random_u64() ? > + ret = fdt_setprop_u64(dtb, nodeoffset, FDT_PSTR_KASLR_SEED, > + value); > + if (ret) > + return (ret == -FDT_ERR_NOSPACE ? -ENOMEM : -EINVAL); > + } else { Wouldn't we be better off preserving the previous seed here, if it was present? > + pr_notice("kaslr-seed won't be fed\n"); "fed" is probably not the right word here. Will