From patchwork Wed Feb 8 11:55:46 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ard Biesheuvel X-Patchwork-Id: 9562367 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id BC4376047A for ; Wed, 8 Feb 2017 11:57:59 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id AEDDB284CD for ; Wed, 8 Feb 2017 11:57:59 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id A36B4284C9; Wed, 8 Feb 2017 11:57:59 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.1 required=2.0 tests=BAYES_00,DKIM_SIGNED, RCVD_IN_DNSWL_MED,T_DKIM_INVALID autolearn=ham version=3.3.1 Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.wl.linuxfoundation.org (Postfix) with SMTP id 66C0F284C9 for ; Wed, 8 Feb 2017 11:57:58 +0000 (UTC) Received: (qmail 13362 invoked by uid 550); 8 Feb 2017 11:56:54 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Delivered-To: mailing list kernel-hardening@lists.openwall.com Received: (qmail 11817 invoked from network); 8 Feb 2017 11:56:48 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=AmWke3QCy8R2HAHcrbeTaglGs1JjF0pp5ukWE9LJKlE=; b=j5sRaSUQzL5F/84lQWrUJ34KCBVAKNjnLR/xyfqPdCv0mXjhl5jniomsSk+7zR649Y vP0562xhcTBnsfR/IgxnmcHU5gIh1nG00hY4LogAt+k0SUo9Re6DXj2ca5xnSHD4sMWn eBWZm19/36phLAMITf09P0/TCvD3YTwpRuens= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=AmWke3QCy8R2HAHcrbeTaglGs1JjF0pp5ukWE9LJKlE=; b=oWcENRSPuxOVV1mF++Waxmzs1WjE9pIacBfxNVrFOWFUbzlysa/OFfOjy2E2GqphQ0 ZEh2+of78fW9KMmrwg0OX2PYWtn5JgY492kDnFW2epJ2EMuxk7+zXIizM+tHQJENlco/ L8Jp9A0jXoLMhyqVB3MtgyHl1+iXK/eaKO7Tl+i3DqxeJ0sPAieaean7iN5fcXhu9Y1T Ifth9kMzv3STbcN++gRBusLeRpnjhqnFmeyb9RoLYLFnwVndCUCzAxKzMYcN0xC/e5hO 7xpQIqwuEJtD+u4c99rwQDDPKWfM7R9kg6UqBbi6QPakkEL8F1nQ4OE9ds8CLLgWtHoU kQgQ== X-Gm-Message-State: AIkVDXJClgBMem0SlshhfF3a0MkTxpHuck2MocZd59w4CK/qJuPchrbTcLwKUsyJXIN2QqT6 X-Received: by 10.223.133.131 with SMTP id 3mr18744340wrt.161.1486554996812; Wed, 08 Feb 2017 03:56:36 -0800 (PST) From: Ard Biesheuvel To: linux-efi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, mark.rutland@arm.com, leif.lindholm@linaro.org Cc: catalin.marinas@arm.com, linux@armlinux.org.uk, kernel-hardening@lists.openwall.com, labbott@fedoraproject.org, Ard Biesheuvel Date: Wed, 8 Feb 2017 11:55:46 +0000 Message-Id: <1486554947-3964-14-git-send-email-ard.biesheuvel@linaro.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1486554947-3964-1-git-send-email-ard.biesheuvel@linaro.org> References: <1486554947-3964-1-git-send-email-ard.biesheuvel@linaro.org> Subject: [kernel-hardening] [PATCH v2 13/14] arm: efi: split zImage code and data into separate PE/COFF sections X-Virus-Scanned: ClamAV using ClamSMTP To prevent unintended modifications to the kernel text (malicious or otherwise) while running the EFI stub, describe the kernel image as two separate sections: a .text section with read-execute permissions, covering .text, .rodata, .piggytext and the GOT sections (which the stub does not care about anyway), and a .data section with read-write permissions, covering .data and .bss. This relies on the firmware to actually take the section permission flags into account, but this is something that is currently being implemented in EDK2, which means we will likely start seeing it in the wild between one and two years from now. Signed-off-by: Ard Biesheuvel --- arch/arm/boot/compressed/efi-header.S | 30 ++++++++++++++------ arch/arm/boot/compressed/vmlinux.lds.S | 27 +++++++++++++----- 2 files changed, 41 insertions(+), 16 deletions(-) diff --git a/arch/arm/boot/compressed/efi-header.S b/arch/arm/boot/compressed/efi-header.S index 7ff2b2f05e4c..3cf09f7efced 100644 --- a/arch/arm/boot/compressed/efi-header.S +++ b/arch/arm/boot/compressed/efi-header.S @@ -57,16 +57,16 @@ optional_header: .short PE_OPT_MAGIC_PE32 @ PE32 format .byte 0x02 @ MajorLinkerVersion .byte 0x14 @ MinorLinkerVersion - .long _end - __efi_start @ SizeOfCode - .long 0 @ SizeOfInitializedData + .long __pecoff_data_start - __efi_start @ SizeOfCode + .long __pecoff_data_size @ SizeOfInitializedData .long 0 @ SizeOfUninitializedData .long efi_stub_entry - start @ AddressOfEntryPoint .long start_offset @ BaseOfCode - .long 0 @ BaseOfData + .long __pecoff_data_start - start @ BaseOfData extra_header_fields: .long 0 @ ImageBase - .long SZ_512 @ SectionAlignment + .long SZ_4K @ SectionAlignment .long SZ_512 @ FileAlignment .short 0 @ MajorOsVersion .short 0 @ MinorOsVersion @@ -76,7 +76,7 @@ extra_header_fields: .short 0 @ MinorSubsystemVersion .long 0 @ Win32VersionValue - .long _end - start @ SizeOfImage + .long __pecoff_end - start @ SizeOfImage .long start_offset @ SizeOfHeaders .long 0 @ CheckSum .short IMAGE_SUBSYSTEM_EFI_APPLICATION @ Subsystem @@ -97,9 +97,9 @@ extra_header_fields: section_table: .ascii ".text\0\0\0" - .long _end - __efi_start @ VirtualSize + .long __pecoff_data_start - __efi_start @ VirtualSize .long __efi_start @ VirtualAddress - .long _edata - __efi_start @ SizeOfRawData + .long __pecoff_data_start - __efi_start @ SizeOfRawData .long __efi_start @ PointerToRawData .long 0 @ PointerToRelocations .long 0 @ PointerToLineNumbers @@ -107,12 +107,24 @@ section_table: .short 0 @ NumberOfLineNumbers .long IMAGE_SCN_CNT_CODE | \ IMAGE_SCN_MEM_READ | \ - IMAGE_SCN_MEM_WRITE | \ IMAGE_SCN_MEM_EXECUTE @ Characteristics + .ascii ".data\0\0\0" + .long __pecoff_data_size @ VirtualSize + .long __pecoff_data_start - start @ VirtualAddress + .long __pecoff_data_rawsize @ SizeOfRawData + .long __pecoff_data_start - start @ PointerToRawData + .long 0 @ PointerToRelocations + .long 0 @ PointerToLineNumbers + .short 0 @ NumberOfRelocations + .short 0 @ NumberOfLineNumbers + .long IMAGE_SCN_CNT_INITIALIZED_DATA | \ + IMAGE_SCN_MEM_READ | \ + IMAGE_SCN_MEM_WRITE @ Characteristics + .set section_count, (. - section_table) / 40 - .align 9 + .align 12 __efi_start: #endif .endm diff --git a/arch/arm/boot/compressed/vmlinux.lds.S b/arch/arm/boot/compressed/vmlinux.lds.S index 5d50daea466a..144e2f408292 100644 --- a/arch/arm/boot/compressed/vmlinux.lds.S +++ b/arch/arm/boot/compressed/vmlinux.lds.S @@ -51,13 +51,6 @@ SECTIONS *(.rodata) *(.rodata.*) } - .data : { - /* - * The EFI stub always executes from RAM, and runs strictly before the - * decompressor, so we can make an exception for its r/w data, and keep it - */ - *(.data.efistub) - } .piggydata : { *(.piggydata) } @@ -73,6 +66,23 @@ SECTIONS /* ensure the zImage file size is always a multiple of 64 bits */ /* (without a dummy byte, ld just ignores the empty section) */ .pad : { BYTE(0); . = ALIGN(8); } + +#ifdef CONFIG_EFI_STUB + .data : ALIGN(4096) { + __pecoff_data_start = .; + /* + * The EFI stub always executes from RAM, and runs strictly before the + * decompressor, so we can make an exception for its r/w data, and keep it + */ + *(.data.efistub) + __pecoff_data_end = .; + + . = ALIGN(512); + } + __pecoff_data_rawsize = . - ADDR(.data); + . = __pecoff_data_end; +#endif + _edata = .; _magic_sig = ZIMAGE_MAGIC(0x016f2818); @@ -87,6 +97,9 @@ SECTIONS . = ALIGN(8); /* the stack must be 64-bit aligned */ .stack : { *(.stack) } + PROVIDE(__pecoff_data_size = ALIGN(512) - ADDR(.data)); + PROVIDE(__pecoff_end = ALIGN(512)); + .stab 0 : { *(.stab) } .stabstr 0 : { *(.stabstr) } .stab.excl 0 : { *(.stab.excl) }