From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kees Cook Subject: [PATCH v5 29/36] x86/build: Enforce an empty .got.plt section Date: Fri, 31 Jul 2020 16:08:13 -0700 Message-ID: <20200731230820.1742553-30-keescook@chromium.org> References: <20200731230820.1742553-1-keescook@chromium.org> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47298 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727790AbgGaXSN (ORCPT ); Fri, 31 Jul 2020 19:18:13 -0400 Received: from mail-pj1-x1041.google.com (mail-pj1-x1041.google.com [IPv6:2607:f8b0:4864:20::1041]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C2662C06174A for ; Fri, 31 Jul 2020 16:18:13 -0700 (PDT) Received: by mail-pj1-x1041.google.com with SMTP id lx9so8528829pjb.2 for ; Fri, 31 Jul 2020 16:18:13 -0700 (PDT) In-Reply-To: <20200731230820.1742553-1-keescook@chromium.org> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Thomas Gleixner , Will Deacon Cc: Kees Cook , Catalin Marinas , Mark Rutland , Ard Biesheuvel , Peter Collingbourne , James Morse , Borislav Petkov , Ingo Molnar , Russell King , Masahiro Yamada , Arvind Sankar , Nick Desaulniers , Nathan Chancellor , Arnd Bergmann , x86@kernel.org, clang-built-linux@googlegroups.com, linux-arch@vger.kernel.org, linux-efi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org The .got.plt section should always be zero (or filled only with the linker-generated lazy dispatch entry). Enforce this with an assert and mark the section as NOLOAD. This is more sensitive than just blindly discarding the section. Signed-off-by: Kees Cook --- arch/x86/kernel/vmlinux.lds.S | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S index 0cc035cb15f1..7faffe7414d6 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -414,8 +414,20 @@ SECTIONS ELF_DETAILS DISCARDS -} + /* + * Make sure that the .got.plt is either completely empty or it + * contains only the lazy dispatch entries. + */ + .got.plt (NOLOAD) : { *(.got.plt) } + ASSERT(SIZEOF(.got.plt) == 0 || +#ifdef CONFIG_X86_64 + SIZEOF(.got.plt) == 0x18, +#else + SIZEOF(.got.plt) == 0xc, +#endif + "Unexpected GOT/PLT entries detected!") +} #ifdef CONFIG_X86_32 /* -- 2.25.1