From patchwork Tue Apr 19 10:51:56 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 53032 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id AC5103857345 for ; Tue, 19 Apr 2022 10:53:56 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org AC5103857345 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1650365636; bh=53JAmCbbxwYYqlbiSRkvibAV4gBaVOyeZsHA1rz19Xg=; h=To:Subject:Date:In-Reply-To:References:List-Id:List-Unsubscribe: List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To:Cc: From; b=A1j5mRU+bETb1r3LULOx6V+nj/bSdDP7n9RrMqKc3SI3J2XcEPEoJVxCXb+F095IT +6A+IkLfdPJgjF1YQECCkF1CxIJZTUn/wEAA4Orcp08BsJ2+epPdojOK/cEIPET/s1 Rb9oF0PmS2kCCRf7nDcin/wbl8ppC8XZkyiIWmm4= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by sourceware.org (Postfix) with ESMTPS id 89BD03857349 for ; Tue, 19 Apr 2022 10:52:11 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 89BD03857349 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 5D6D3B81719; Tue, 19 Apr 2022 10:52:10 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9312DC385AC; Tue, 19 Apr 2022 10:52:06 +0000 (UTC) To: Catalin Marinas , Will Deacon Subject: [PATCH v13 2/2] arm64: Enable BTI for main executable as well as the interpreter Date: Tue, 19 Apr 2022 11:51:56 +0100 Message-Id: <20220419105156.347168-3-broonie@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20220419105156.347168-1-broonie@kernel.org> References: <20220419105156.347168-1-broonie@kernel.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3954; h=from:subject; bh=nM87AwZCcIUCsNfFiO7pQEUlSzAKS0CjflMvMdi3+ho=; b=owGbwMvMwMWocq27KDak/QLjabUkhqS4Kd5Sn7M1RMK5llsFhM0/US1Wd3JZqdWhaQpnY0TWB82W mafRyWjMwsDIxSArpsiy9lnGqvRwia3zH81/BTOIlQlkCgMXpwBMZEE0+39v/3zGe0e5ttmk+akFZb eZzfv4V/qXk26lc/N5pqOdslVPHsYlbdsxucO7JN6Sae55GZbZsjydXQmhB+q5fS/7iO6Z/XnFFANp tSMMM5MVrO/aG5laulz7mLU15WDuuiYd5rpT6q2HTPjX7Fqa7usgU8y9+YRZcqqGwtq9D3e72c07JJ vTf65Cy+NY7/ojxn6sBlHJ3KEBFu6cH98kbLWIn8CyNm3/ztpat6LWZKXiQ9x87U2533ekSMyacS9u 8csbViwSfcdq/n1RjWFyMhf6m9V+5EGT2ZcPGrddlbsjbJhuNqbOcKr9+jFaZJ+N0fnrconaO9q4e2 5mnLS46q7ppJmXrlxiznIq9hsA X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB X-Spam-Status: No, score=-11.4 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, SPF_HELO_NONE, SPF_PASS, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: Mark Brown via Libc-alpha From: Mark Brown Reply-To: Mark Brown Cc: linux-arch@vger.kernel.org, Yu-cheng Yu , libc-alpha@sourceware.org, Kees Cook , Szabolcs Nagy , Jeremy Linton , Mark Brown , linux-arm-kernel@lists.infradead.org Errors-To: libc-alpha-bounces+patchwork=sourceware.org@sourceware.org Sender: "Libc-alpha" 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 adding a sysctl abi.bti_main which causes the kernel to checking the BTI property for the main executable and enable BTI if it is present when doing the initial mapping. This sysctl is disabled by default. Signed-off-by: Mark Brown Reviewed-by: Catalin Marinas --- arch/arm64/include/asm/elf.h | 15 ++++++++--- arch/arm64/kernel/process.c | 52 +++++++++++++++++++++++++++--------- 2 files changed, 51 insertions(+), 16 deletions(-) diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h index 5cc002376abe..c4aa60db76a4 100644 --- a/arch/arm64/include/asm/elf.h +++ b/arch/arm64/include/asm/elf.h @@ -251,12 +251,21 @@ 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, \ } +static inline int arm64_elf_bti_flag(bool is_interp) +{ + if (is_interp) + return ARM64_ELF_INTERP_BTI; + else + return ARM64_ELF_EXEC_BTI; +} + static inline int arch_parse_elf_property(u32 type, const void *data, size_t datasz, bool compat, bool has_interp, bool is_interp, @@ -272,9 +281,9 @@ 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 && + if (system_supports_bti() && (*p & GNU_PROPERTY_AARCH64_FEATURE_1_BTI)) - arch->flags |= ARM64_ELF_BTI; + arch->flags |= arm64_elf_bti_flag(is_interp); } return 0; diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index 7fa97df55e3a..665d375cc3f1 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -702,23 +702,49 @@ core_initcall(tagged_addr_init); #endif /* CONFIG_ARM64_TAGGED_ADDR_ABI */ #ifdef CONFIG_BINFMT_ELF +static unsigned int bti_main; + int arch_elf_adjust_prot(int prot, const struct arch_elf_state *state, bool has_interp, 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 (!(state->flags & ARM64_ELF_BTI)) - return prot; - - if (prot & PROT_EXEC) + if ((prot & PROT_EXEC) && + (is_interp || !has_interp || bti_main) && + (state->flags & arm64_elf_bti_flag(is_interp))) prot |= PROT_BTI; return prot; } -#endif + +#ifdef CONFIG_ARM64_BTI +/* + * If this sysctl is enabled then we will apply PROT_BTI to the main + * executable as well as the dynamic linker if it has the appropriate + * ELF note. It is disabled by default, in which case we will only + * apply PROT_BTI to the dynamic linker or static binaries. + */ +static struct ctl_table bti_main_sysctl_table[] = { + { + .procname = "bti_main", + .mode = 0644, + .data = &bti_main, + .maxlen = sizeof(int), + .proc_handler = proc_dointvec_minmax, + .extra1 = SYSCTL_ZERO, + .extra2 = SYSCTL_ONE, + }, + { } +}; + +static int __init bti_main_init(void) +{ + if (!system_supports_bti()) + return 0; + + if (!register_sysctl("abi", bti_main_sysctl_table)) + return -EINVAL; + return 0; +} +core_initcall(bti_main_init); +#endif /* CONFIG_ARM64_BTI */ + +#endif /* CONFIG_BINFMT_ELF */