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=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,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 4CE50C07E9B for ; Mon, 19 Jul 2021 10:06:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 34D296113A for ; Mon, 19 Jul 2021 10:06:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235676AbhGSJZq (ORCPT ); Mon, 19 Jul 2021 05:25:46 -0400 Received: from foss.arm.com ([217.140.110.172]:54428 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235609AbhGSJZq (ORCPT ); Mon, 19 Jul 2021 05:25:46 -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 1DE0E6D; Mon, 19 Jul 2021 03:06:26 -0700 (PDT) Received: from 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 C15763F73D; Mon, 19 Jul 2021 03:06:24 -0700 (PDT) Date: Mon, 19 Jul 2021 11:05:08 +0100 From: Dave Martin To: Mark Brown Cc: Catalin Marinas , Will Deacon , Szabolcs Nagy , Jeremy Linton , "H . J . Lu" , Yu-cheng Yu , linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, libc-alpha@sourceware.org Subject: Re: [PATCH v4 2/4] arm64: Enable BTI for main executable as well as the interpreter Message-ID: <20210719100507.GU4187@arm.com> References: <20210712115259.29547-1-broonie@kernel.org> <20210712115259.29547-3-broonie@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210712115259.29547-3-broonie@kernel.org> User-Agent: Mutt/1.5.23 (2014-03-12) Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org On Mon, Jul 12, 2021 at 12:52:57PM +0100, Mark Brown wrote: > Currently for dynamically linked ELF executables we only enable BTI for > the interpreter, expecting the interpreter to do this for the main > executable. This is a bit inconsistent since we do map main executable and > is causing issues with systemd's MemoryDenyWriteExecute feature which is > implemented using a seccomp filter which prevents setting PROT_EXEC on > already mapped memory and lacks the context to be able to detect that > memory is already mapped with PROT_EXEC. > > Resolve this by checking the BTI property for the main executable and > enabling BTI if it is present when doing the initial mapping. This does > mean that we may get more code with BTI enabled if running on a system > without BTI support in the dynamic linker, this is expected to be a safe > configuration and testing seems to confirm that. It also reduces the > flexibility userspace has to disable BTI but it is expected that for cases > where there are problems which require BTI to be disabled it is more likely > that it will need to be disabled on a system level. > > Signed-off-by: Mark Brown > Reviewed-by: Dave Martin > Tested-by: Jeremy Linton > --- > arch/arm64/include/asm/elf.h | 14 ++++++++++---- > arch/arm64/kernel/process.c | 23 +++++++++++------------ > 2 files changed, 21 insertions(+), 16 deletions(-) > > diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h > index a488a1329b16..9f86dbce2680 100644 > --- a/arch/arm64/include/asm/elf.h > +++ b/arch/arm64/include/asm/elf.h > @@ -253,7 +253,8 @@ struct arch_elf_state { > int flags; > }; > > -#define ARM64_ELF_BTI (1 << 0) > +#define ARM64_ELF_INTERP_BTI (1 << 0) > +#define ARM64_ELF_EXEC_BTI (1 << 1) > > #define INIT_ARCH_ELF_STATE { \ > .flags = 0, \ > @@ -274,9 +275,14 @@ static inline int arch_parse_elf_property(u32 type, const void *data, > if (datasz != sizeof(*p)) > return -ENOEXEC; > > - if (system_supports_bti() && has_interp == is_interp && > - (*p & GNU_PROPERTY_AARCH64_FEATURE_1_BTI)) > - arch->flags |= ARM64_ELF_BTI; > + if (system_supports_bti() && > + (*p & GNU_PROPERTY_AARCH64_FEATURE_1_BTI)) { > + if (is_interp) { > + arch->flags |= ARM64_ELF_INTERP_BTI; > + } else { > + arch->flags |= ARM64_ELF_EXEC_BTI; > + } Can this just be arch->flags |= arm64_elf_bti_flag(is_interp); if the helper is moved to this header? > + } > } > > return 0; > diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c > index c8989b999250..5a6c3b198bd3 100644 > --- a/arch/arm64/kernel/process.c > +++ b/arch/arm64/kernel/process.c > @@ -683,21 +683,20 @@ core_initcall(tagged_addr_init); > #endif /* CONFIG_ARM64_TAGGED_ADDR_ABI */ > > #ifdef CONFIG_BINFMT_ELF > -int arch_elf_adjust_prot(int prot, const struct arch_elf_state *state, > - bool has_interp, bool is_interp) > +static inline int arm64_elf_bti_flag(bool is_interp) > { > - /* > - * For dynamically linked executables the interpreter is > - * responsible for setting PROT_BTI on everything except > - * itself. > - */ > - if (is_interp != has_interp) > - return prot; > + if (is_interp) > + return ARM64_ELF_INTERP_BTI; > + else > + return ARM64_ELF_EXEC_BTI; > +} > > - if (!(state->flags & ARM64_ELF_BTI)) > - return prot; > > - if (prot & PROT_EXEC) > +int arch_elf_adjust_prot(int prot, const struct arch_elf_state *state, > + bool has_interp, bool is_interp) > +{ > + if ((prot & PROT_EXEC) && > + (state->flags & arm64_elf_bti_flag(is_interp))) Preferably with the above change (but if not, I'll live without): Reviewed-by: Dave Martin > prot |= PROT_BTI; > > return prot; > -- 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=-16.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 690C4C07E9B for ; Mon, 19 Jul 2021 10:08:51 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 368B5610FB for ; Mon, 19 Jul 2021 10:08:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 368B5610FB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=NLY9FGawysMZXnxhcD/hMwmfUfY4FzawxDmAkPplSI4=; b=nOf6FY+Mmn9pFg QEVtZc0k2ZN0HJdjUCLP4t73qzQamn00rK3U48o+igKQqnzz4kohvrzpdN6/KbyYN4L/q52MTNAs5 Dz1xB8QiJZzWAOW+Gmh+D4T7VkDEJ/V8A9P5aq2OyRQs3Q9cn3EFx53fNxNTj0RzahS3YZQNvJbt9 9r62+/7idt9bkIcMs4BKGirtrfKW0BsL/9+MlY5GLkDIrqbCHEgEeIzyF8bqhh4rCwyIJDBiq/tfF NsyOZ7YebGbOFX2cAyI4SukGBtbBl5NdVlTqqdklG+lF4CTX9iAVHHGYDvFUhH1J3FjbbEsH9qivv q5jQBObrG5qC1SSph+qQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1m5QAb-009C4G-UA; Mon, 19 Jul 2021 10:06:42 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1m5QAN-009Bzm-Ql for linux-arm-kernel@lists.infradead.org; Mon, 19 Jul 2021 10:06:29 +0000 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 1DE0E6D; Mon, 19 Jul 2021 03:06:26 -0700 (PDT) Received: from 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 C15763F73D; Mon, 19 Jul 2021 03:06:24 -0700 (PDT) Date: Mon, 19 Jul 2021 11:05:08 +0100 From: Dave Martin To: Mark Brown Cc: Catalin Marinas , Will Deacon , Szabolcs Nagy , Jeremy Linton , "H . J . Lu" , Yu-cheng Yu , linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, libc-alpha@sourceware.org Subject: Re: [PATCH v4 2/4] arm64: Enable BTI for main executable as well as the interpreter Message-ID: <20210719100507.GU4187@arm.com> References: <20210712115259.29547-1-broonie@kernel.org> <20210712115259.29547-3-broonie@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210712115259.29547-3-broonie@kernel.org> User-Agent: Mutt/1.5.23 (2014-03-12) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210719_030628_053575_F320352D X-CRM114-Status: GOOD ( 34.98 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Jul 12, 2021 at 12:52:57PM +0100, Mark Brown wrote: > Currently for dynamically linked ELF executables we only enable BTI for > the interpreter, expecting the interpreter to do this for the main > executable. This is a bit inconsistent since we do map main executable and > is causing issues with systemd's MemoryDenyWriteExecute feature which is > implemented using a seccomp filter which prevents setting PROT_EXEC on > already mapped memory and lacks the context to be able to detect that > memory is already mapped with PROT_EXEC. > > Resolve this by checking the BTI property for the main executable and > enabling BTI if it is present when doing the initial mapping. This does > mean that we may get more code with BTI enabled if running on a system > without BTI support in the dynamic linker, this is expected to be a safe > configuration and testing seems to confirm that. It also reduces the > flexibility userspace has to disable BTI but it is expected that for cases > where there are problems which require BTI to be disabled it is more likely > that it will need to be disabled on a system level. > > Signed-off-by: Mark Brown > Reviewed-by: Dave Martin > Tested-by: Jeremy Linton > --- > arch/arm64/include/asm/elf.h | 14 ++++++++++---- > arch/arm64/kernel/process.c | 23 +++++++++++------------ > 2 files changed, 21 insertions(+), 16 deletions(-) > > diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h > index a488a1329b16..9f86dbce2680 100644 > --- a/arch/arm64/include/asm/elf.h > +++ b/arch/arm64/include/asm/elf.h > @@ -253,7 +253,8 @@ struct arch_elf_state { > int flags; > }; > > -#define ARM64_ELF_BTI (1 << 0) > +#define ARM64_ELF_INTERP_BTI (1 << 0) > +#define ARM64_ELF_EXEC_BTI (1 << 1) > > #define INIT_ARCH_ELF_STATE { \ > .flags = 0, \ > @@ -274,9 +275,14 @@ static inline int arch_parse_elf_property(u32 type, const void *data, > if (datasz != sizeof(*p)) > return -ENOEXEC; > > - if (system_supports_bti() && has_interp == is_interp && > - (*p & GNU_PROPERTY_AARCH64_FEATURE_1_BTI)) > - arch->flags |= ARM64_ELF_BTI; > + if (system_supports_bti() && > + (*p & GNU_PROPERTY_AARCH64_FEATURE_1_BTI)) { > + if (is_interp) { > + arch->flags |= ARM64_ELF_INTERP_BTI; > + } else { > + arch->flags |= ARM64_ELF_EXEC_BTI; > + } Can this just be arch->flags |= arm64_elf_bti_flag(is_interp); if the helper is moved to this header? > + } > } > > return 0; > diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c > index c8989b999250..5a6c3b198bd3 100644 > --- a/arch/arm64/kernel/process.c > +++ b/arch/arm64/kernel/process.c > @@ -683,21 +683,20 @@ core_initcall(tagged_addr_init); > #endif /* CONFIG_ARM64_TAGGED_ADDR_ABI */ > > #ifdef CONFIG_BINFMT_ELF > -int arch_elf_adjust_prot(int prot, const struct arch_elf_state *state, > - bool has_interp, bool is_interp) > +static inline int arm64_elf_bti_flag(bool is_interp) > { > - /* > - * For dynamically linked executables the interpreter is > - * responsible for setting PROT_BTI on everything except > - * itself. > - */ > - if (is_interp != has_interp) > - return prot; > + if (is_interp) > + return ARM64_ELF_INTERP_BTI; > + else > + return ARM64_ELF_EXEC_BTI; > +} > > - if (!(state->flags & ARM64_ELF_BTI)) > - return prot; > > - if (prot & PROT_EXEC) > +int arch_elf_adjust_prot(int prot, const struct arch_elf_state *state, > + bool has_interp, bool is_interp) > +{ > + if ((prot & PROT_EXEC) && > + (state->flags & arm64_elf_bti_flag(is_interp))) Preferably with the above change (but if not, I'll live without): Reviewed-by: Dave Martin > prot |= PROT_BTI; > > return prot; > -- _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel