From patchwork Mon Jul 12 11:52:57 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 44315 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 F11CF3888816 for ; Mon, 12 Jul 2021 11:58:55 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org F11CF3888816 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1626091136; bh=BLq+re303qqzBsTmldiqf7KdJbEksKntSbjqUYr9Dvo=; 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=t6aFGp4wngLVlSj3vwD0rZiYJeY/Jd4m8kSqZyT1/lDyJa0ZUv7fBgj7HxOjUYTrj v61em7sNHccpyMHSKygSWY3+TirpNOPLiEBGWv51LIUHHC3Y2m2aUx++TB+GsOii2c GOmkXq3gP7NSt2ZY2PxUlpI3Pxgt6WXfYsFMZmIg= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by sourceware.org (Postfix) with ESMTPS id C60C9388881B for ; Mon, 12 Jul 2021 11:57:01 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org C60C9388881B Received: by mail.kernel.org (Postfix) with ESMTPSA id 43353610E6; Mon, 12 Jul 2021 11:57:00 +0000 (UTC) To: Catalin Marinas , Will Deacon Subject: [PATCH v4 2/4] arm64: Enable BTI for main executable as well as the interpreter Date: Mon, 12 Jul 2021 12:52:57 +0100 Message-Id: <20210712115259.29547-3-broonie@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20210712115259.29547-1-broonie@kernel.org> References: <20210712115259.29547-1-broonie@kernel.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3439; h=from:subject; bh=ljZ0Ar2vQIoqNXA7Uu8g3LQE3bTDHREWhpRUBkTTMGg=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBg7C0YxbctBBxOVXO1gju9IJD3nnsiskpsDgry/8qL T29c1jyJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCYOwtGAAKCRAk1otyXVSH0NIkB/ 9n5vaAL44C15qVYFgOjjvf719q5n45OMOlh1nk74wIXKSibe+6LIW1wFhO6YzeREAflnsZuSk1JlEC iWSFi9qYRPtVWZgiGeAYkHoDZb+3TNOqNXn41CqOJhRJQkOrymep3MluBuP4vZxT2m0MERBAIgeSOP j7La7EJrzm/7HI54AAHz0nOMaPxhU7yCRZJ3jYFGXgLih+w/4c8FmAt23IJhiFDmwqtA404f78GqZz RhqRo5haCq4sOqzhlMkIGQXvjzJT6wiXE7hYi9Tcv9P5JWsnUOU+ugJ6Zh8lPQiaok7jwwWTQvoFm/ +eceAnAajaB+Wi1TDE2CzobBQj05zO X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB X-Spam-Status: No, score=-11.2 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: Dave Martin --- 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; + } + } } 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))) prot |= PROT_BTI; return prot;