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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 66BABC433F5 for ; Mon, 22 Nov 2021 11:23:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238499AbhKVL0F (ORCPT ); Mon, 22 Nov 2021 06:26:05 -0500 Received: from relay5-d.mail.gandi.net ([217.70.183.197]:32935 "EHLO relay5-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238574AbhKVLZ6 (ORCPT ); Mon, 22 Nov 2021 06:25:58 -0500 Received: (Authenticated sender: alex@ghiti.fr) by relay5-d.mail.gandi.net (Postfix) with ESMTPSA id 732BD1C000F; Mon, 22 Nov 2021 11:22:47 +0000 (UTC) Message-ID: <325663a5-d9a1-a8b8-7f16-c2985c319864@ghiti.fr> Date: Mon, 22 Nov 2021 12:22:46 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.3.0 Subject: Re: [PATCH 6/8] mm: Allow arch specific arch_randomize_brk() with CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT Content-Language: fr To: Christophe Leroy , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org References: From: Alex Ghiti In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Christophe, Le 22/11/2021 à 09:48, Christophe Leroy a écrit : > Commit e7142bf5d231 ("arm64, mm: make randomization selected by > generic topdown mmap layout") introduced a default version of > arch_randomize_brk() provided when > CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT is selected. > > powerpc could select CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT > but needs to provide its own arch_randomize_brk(). > > In order to allow that, don't make > CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT select > CONFIG_ARCH_HAS_ELF_RANDOMIZE. Instead, ensure that > selecting CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT and > selecting CONFIG_ARCH_HAS_ELF_RANDOMIZE has the same effect. This feels weird to me since if CONFIG_ARCH_HAS_ELF_RANDOMIZE is used somewhere else at some point, it is not natural to add CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT: can't we use a __weak function or a new CONFIG_ARCH_HAS_RANDOMIZE_BRK? Thanks, Alex > > Then only provide the default arch_randomize_brk() when the > architecture has not selected CONFIG_ARCH_HAS_ELF_RANDOMIZE. > > Cc: Alexandre Ghiti > Signed-off-by: Christophe Leroy > --- > arch/Kconfig | 1 - > fs/binfmt_elf.c | 3 ++- > include/linux/elf-randomize.h | 3 ++- > mm/util.c | 2 ++ > 4 files changed, 6 insertions(+), 3 deletions(-) > > diff --git a/arch/Kconfig b/arch/Kconfig > index 26b8ed11639d..ef3ce947b7a1 100644 > --- a/arch/Kconfig > +++ b/arch/Kconfig > @@ -1000,7 +1000,6 @@ config HAVE_ARCH_COMPAT_MMAP_BASES > config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT > bool > depends on MMU > - select ARCH_HAS_ELF_RANDOMIZE > > config HAVE_STACK_VALIDATION > bool > diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c > index f8c7f26f1fbb..28968a189a91 100644 > --- a/fs/binfmt_elf.c > +++ b/fs/binfmt_elf.c > @@ -1287,7 +1287,8 @@ static int load_elf_binary(struct linux_binprm *bprm) > * (since it grows up, and may collide early with the stack > * growing down), and into the unused ELF_ET_DYN_BASE region. > */ > - if (IS_ENABLED(CONFIG_ARCH_HAS_ELF_RANDOMIZE) && > + if ((IS_ENABLED(CONFIG_ARCH_HAS_ELF_RANDOMIZE) || > + IS_ENABLED(CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT)) && > elf_ex->e_type == ET_DYN && !interpreter) { > mm->brk = mm->start_brk = ELF_ET_DYN_BASE; > } > diff --git a/include/linux/elf-randomize.h b/include/linux/elf-randomize.h > index da0dbb7b6be3..1e471ca7caaf 100644 > --- a/include/linux/elf-randomize.h > +++ b/include/linux/elf-randomize.h > @@ -4,7 +4,8 @@ > > struct mm_struct; > > -#ifndef CONFIG_ARCH_HAS_ELF_RANDOMIZE > +#if !defined(CONFIG_ARCH_HAS_ELF_RANDOMIZE) && \ > + !defined(CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT) > static inline unsigned long arch_mmap_rnd(void) { return 0; } > # if defined(arch_randomize_brk) && defined(CONFIG_COMPAT_BRK) > # define compat_brk_randomized > diff --git a/mm/util.c b/mm/util.c > index e58151a61255..edb9e94cceb5 100644 > --- a/mm/util.c > +++ b/mm/util.c > @@ -344,6 +344,7 @@ unsigned long randomize_stack_top(unsigned long stack_top) > } > > #ifdef CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT > +#ifndef CONFIG_ARCH_HAS_ELF_RANDOMIZE > unsigned long arch_randomize_brk(struct mm_struct *mm) > { > /* Is the current task 32bit ? */ > @@ -352,6 +353,7 @@ unsigned long arch_randomize_brk(struct mm_struct *mm) > > return randomize_page(mm->brk, SZ_1G); > } > +#endif > > unsigned long arch_mmap_rnd(void) > { > 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 Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 8B753C433F5 for ; Mon, 22 Nov 2021 11:23:48 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4HyPzQ4zbnz2ypK for ; Mon, 22 Nov 2021 22:23:46 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=none (no SPF record) smtp.mailfrom=ghiti.fr (client-ip=217.70.178.240; helo=mslow1.mail.gandi.net; envelope-from=alex@ghiti.fr; receiver=) Received: from mslow1.mail.gandi.net (mslow1.mail.gandi.net [217.70.178.240]) (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 4HyPyx54Rsz2yPm for ; Mon, 22 Nov 2021 22:23:21 +1100 (AEDT) Received: from relay5-d.mail.gandi.net (unknown [217.70.183.197]) by mslow1.mail.gandi.net (Postfix) with ESMTP id 03088D222E for ; Mon, 22 Nov 2021 11:23:16 +0000 (UTC) Received: (Authenticated sender: alex@ghiti.fr) by relay5-d.mail.gandi.net (Postfix) with ESMTPSA id 732BD1C000F; Mon, 22 Nov 2021 11:22:47 +0000 (UTC) Message-ID: <325663a5-d9a1-a8b8-7f16-c2985c319864@ghiti.fr> Date: Mon, 22 Nov 2021 12:22:46 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.3.0 Subject: Re: [PATCH 6/8] mm: Allow arch specific arch_randomize_brk() with CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT Content-Language: fr To: Christophe Leroy , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman References: From: Alex Ghiti In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit 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-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Hi Christophe, Le 22/11/2021 à 09:48, Christophe Leroy a écrit : > Commit e7142bf5d231 ("arm64, mm: make randomization selected by > generic topdown mmap layout") introduced a default version of > arch_randomize_brk() provided when > CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT is selected. > > powerpc could select CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT > but needs to provide its own arch_randomize_brk(). > > In order to allow that, don't make > CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT select > CONFIG_ARCH_HAS_ELF_RANDOMIZE. Instead, ensure that > selecting CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT and > selecting CONFIG_ARCH_HAS_ELF_RANDOMIZE has the same effect. This feels weird to me since if CONFIG_ARCH_HAS_ELF_RANDOMIZE is used somewhere else at some point, it is not natural to add CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT: can't we use a __weak function or a new CONFIG_ARCH_HAS_RANDOMIZE_BRK? Thanks, Alex > > Then only provide the default arch_randomize_brk() when the > architecture has not selected CONFIG_ARCH_HAS_ELF_RANDOMIZE. > > Cc: Alexandre Ghiti > Signed-off-by: Christophe Leroy > --- > arch/Kconfig | 1 - > fs/binfmt_elf.c | 3 ++- > include/linux/elf-randomize.h | 3 ++- > mm/util.c | 2 ++ > 4 files changed, 6 insertions(+), 3 deletions(-) > > diff --git a/arch/Kconfig b/arch/Kconfig > index 26b8ed11639d..ef3ce947b7a1 100644 > --- a/arch/Kconfig > +++ b/arch/Kconfig > @@ -1000,7 +1000,6 @@ config HAVE_ARCH_COMPAT_MMAP_BASES > config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT > bool > depends on MMU > - select ARCH_HAS_ELF_RANDOMIZE > > config HAVE_STACK_VALIDATION > bool > diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c > index f8c7f26f1fbb..28968a189a91 100644 > --- a/fs/binfmt_elf.c > +++ b/fs/binfmt_elf.c > @@ -1287,7 +1287,8 @@ static int load_elf_binary(struct linux_binprm *bprm) > * (since it grows up, and may collide early with the stack > * growing down), and into the unused ELF_ET_DYN_BASE region. > */ > - if (IS_ENABLED(CONFIG_ARCH_HAS_ELF_RANDOMIZE) && > + if ((IS_ENABLED(CONFIG_ARCH_HAS_ELF_RANDOMIZE) || > + IS_ENABLED(CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT)) && > elf_ex->e_type == ET_DYN && !interpreter) { > mm->brk = mm->start_brk = ELF_ET_DYN_BASE; > } > diff --git a/include/linux/elf-randomize.h b/include/linux/elf-randomize.h > index da0dbb7b6be3..1e471ca7caaf 100644 > --- a/include/linux/elf-randomize.h > +++ b/include/linux/elf-randomize.h > @@ -4,7 +4,8 @@ > > struct mm_struct; > > -#ifndef CONFIG_ARCH_HAS_ELF_RANDOMIZE > +#if !defined(CONFIG_ARCH_HAS_ELF_RANDOMIZE) && \ > + !defined(CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT) > static inline unsigned long arch_mmap_rnd(void) { return 0; } > # if defined(arch_randomize_brk) && defined(CONFIG_COMPAT_BRK) > # define compat_brk_randomized > diff --git a/mm/util.c b/mm/util.c > index e58151a61255..edb9e94cceb5 100644 > --- a/mm/util.c > +++ b/mm/util.c > @@ -344,6 +344,7 @@ unsigned long randomize_stack_top(unsigned long stack_top) > } > > #ifdef CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT > +#ifndef CONFIG_ARCH_HAS_ELF_RANDOMIZE > unsigned long arch_randomize_brk(struct mm_struct *mm) > { > /* Is the current task 32bit ? */ > @@ -352,6 +353,7 @@ unsigned long arch_randomize_brk(struct mm_struct *mm) > > return randomize_page(mm->brk, SZ_1G); > } > +#endif > > unsigned long arch_mmap_rnd(void) > { >