From patchwork Mon Jan 24 15:07:02 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 50404 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 7B411385800B for ; Mon, 24 Jan 2022 15:09:31 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 7B411385800B DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1643036971; bh=n2Kwa8UNxFnXIihqG2geFnRgdoqMP/MkI4oIymry0Wo=; 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=Amn67SXZxeDqHf8N6JT+55OUHskgveG6Il4oE9eCTUMfCMu60VirM9kwRI0UvhJV/ AYx/dpw+E0y3VfrvgZ/8vyWUPGLQ/8To5msd+IfPJEyO1ICiCpzOsYk73D/2D1r16C HiJCtv7re3zDUzHI6P0lhupLYY4hwP7dcNlg0ck8= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from sin.source.kernel.org (sin.source.kernel.org [145.40.73.55]) by sourceware.org (Postfix) with ESMTPS id 553AD3858016 for ; Mon, 24 Jan 2022 15:07:53 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 553AD3858016 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 sin.source.kernel.org (Postfix) with ESMTPS id C42A2CE119A; Mon, 24 Jan 2022 15:07:50 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 181F3C340EB; Mon, 24 Jan 2022 15:07:47 +0000 (UTC) To: Catalin Marinas , Will Deacon Subject: [PATCH v8 2/4] arm64: Enable BTI for main executable as well as the interpreter Date: Mon, 24 Jan 2022 15:07:02 +0000 Message-Id: <20220124150704.2559523-3-broonie@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20220124150704.2559523-1-broonie@kernel.org> References: <20220124150704.2559523-1-broonie@kernel.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3271; h=from:subject; bh=RP8vWe5V4SiwPaYUzNl2BKIfhh0nf3pGQ2yDgyzXenU=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBh7sCTXTHFIvz3vMiH916XxroI4hhVUGMITuiztmGl U9C4yR2JATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCYe7AkwAKCRAk1otyXVSH0AkGB/ wKz/RwlSB6VP7EZkkgneZMez6bIBqh9oMLf5JntkyryFk0HBLW+zZ8rMZoIVPy7GJT/FFmX3Vwq5Qr qkUUKTSnMjqvSBxkCt/GTBw1CEnpedWGdAKX4P/4/e78QyhqtxaC2hf3M9KcnbfGjZjMH3mxrXrqHZ bU3hmIQ4N2Uxarzog62y/qNyUQhBswbnJSRXO1mStmwXMH9jUKtiL9fG9hfdmeSlvcAAJZIpFYwz1x jmvkphO/0Mqxb6unqIgwFpMBKk4hg3v1ezQ97oGKirJ08Du2TzN3Lo3YRXO0H0YtID688qpPsVhGPP 0miy4Mb8HKzkASYyvaVbmFcq3jpxp1 X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB X-Spam-Status: No, score=-11.7 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 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, Szabolcs Nagy , Jeremy Linton , Mark Brown , Dave Martin , 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 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 Reviewed-by: Catalin Marinas --- arch/arm64/include/asm/elf.h | 15 ++++++++++++--- arch/arm64/kernel/process.c | 14 ++------------ 2 files changed, 14 insertions(+), 15 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 5369e649fa79..8157910a4181 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -704,18 +704,8 @@ core_initcall(tagged_addr_init); 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) && + (state->flags & arm64_elf_bti_flag(is_interp))) prot |= PROT_BTI; return prot;