From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750918AbdGZEAc (ORCPT ); Wed, 26 Jul 2017 00:00:32 -0400 Received: from mx1.redhat.com ([209.132.183.28]:43604 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750710AbdGZEAb (ORCPT ); Wed, 26 Jul 2017 00:00:31 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com EA12E7F3F8 Authentication-Results: ext-mx01.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx01.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=bhe@redhat.com From: Baoquan He To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, keescook@chromium.org, matt@codeblueprint.co.uk, tglx@linutronix.de, hpa@zytor.com, izumi.taku@jp.fujitsu.com, fanc.fnst@cn.fujitsu.com, thgarnie@google.com, n-horiguchi@ah.jp.nec.com, dyoung@redhat.com, Baoquan He Subject: [PATCH v7] x86/boot/KASLR: Restrict kernel to be randomized in mirror regions Date: Wed, 26 Jul 2017 12:00:20 +0800 Message-Id: <1501041620-4965-1-git-send-email-bhe@redhat.com> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.25]); Wed, 26 Jul 2017 04:00:31 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Currently KASLR will parse all e820 entries of RAM type and add all candidate position into slots array. Then we will choose one slot randomly as the new position which kernel will be decompressed into and run at. On system with EFI enabled, e820 memory regions are coming from EFI memory regions by combining adjacent regions. While these EFI memory regions have more attributes to mark their different use. Mirror attribute is such kind. The physical memory region whose descriptors in EFI memory map has EFI_MEMORY_MORE_RELIABLE attribute (bit: 16) are mirrored. The address range mirroring feature of kernel arranges such mirror region into normal zone and other region into movable zone. And with mirroring feature enabled, the code and date of kernel can only be located in more reliable mirror region. However, the current KASLR code doesn't check EFI memory entries, and could choose new position in non-mirrored region. This will break the functionality of the address range mirroring feature. So if EFI is detected, iterate EFI memory map and pick the mirror region to process for adding candidate of randomization slot. If EFI is disabled or no mirror region found, still process e820 memory map. Signed-off-by: Baoquan He --- v6->v7: Ingo pointed out several incorrect line break issues and unclear description of patch log. Correct them and rewrite patch log. And also rewrite the EFI warning message that if EFI memmap is above 4G in 32bit system since 32bit system can not handle data above 4G at kernel decompression stage. This is suggested by Ingo too. v5->v6: Code style issue fix according to Kees's comment. This is based on tip/x86/boot, patch 1,2,3/4 in v5 post has been put into tip/x86/boot now. arch/x86/boot/compressed/kaslr.c | 68 ++++++++++++++++++++++++++++++++++++++-- 1 file changed, 66 insertions(+), 2 deletions(-) diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c index 99c7194f7ea6..e1dd59ea8a8f 100644 --- a/arch/x86/boot/compressed/kaslr.c +++ b/arch/x86/boot/compressed/kaslr.c @@ -37,7 +37,9 @@ #include #include #include +#include #include +#include /* Macros used by the included decompressor code below. */ #define STATIC @@ -558,6 +560,65 @@ static void process_mem_region(struct mem_vector *entry, } } +#ifdef CONFIG_EFI +/* + * Returns true if mirror region found (and must have been processed + * for slots adding) + */ +static bool +process_efi_entries(unsigned long minimum, unsigned long image_size) +{ + struct efi_info *e = &boot_params->efi_info; + bool efi_mirror_found = false; + struct mem_vector region; + efi_memory_desc_t *md; + unsigned long pmap; + char *signature; + u32 nr_desc; + int i; + + signature = (char *)&e->efi_loader_signature; + if (strncmp(signature, EFI32_LOADER_SIGNATURE, 4) && + strncmp(signature, EFI64_LOADER_SIGNATURE, 4)) + return false; + +#ifdef CONFIG_X86_32 + /* Can't handle data above 4GB at this time */ + if (e->efi_memmap_hi) { + warn("EFI memmap is above 4GB, can't be handled now on x86_32. EFI should be disabled.\n"); + return false; + } + pmap = e->efi_memmap; +#else + pmap = (e->efi_memmap | ((__u64)e->efi_memmap_hi << 32)); +#endif + + nr_desc = e->efi_memmap_size / e->efi_memdesc_size; + for (i = 0; i < nr_desc; i++) { + md = (efi_memory_desc_t *)(pmap + (i * e->efi_memdesc_size)); + if (md->attribute & EFI_MEMORY_MORE_RELIABLE) { + region.start = md->phys_addr; + region.size = md->num_pages << EFI_PAGE_SHIFT; + process_mem_region(®ion, minimum, image_size); + efi_mirror_found = true; + + if (slot_area_index == MAX_SLOT_AREA) { + debug_putstr("Aborted EFI scan (slot_areas full)!\n"); + break; + } + } + } + + return efi_mirror_found; +} +#else +static inline bool +process_efi_entries(unsigned long minimum, unsigned long image_size) +{ + return false; +} +#endif + static void process_e820_entries(unsigned long minimum, unsigned long image_size) { @@ -586,13 +647,16 @@ static unsigned long find_random_phys_addr(unsigned long minimum, { /* Check if we had too many memmaps. */ if (memmap_too_large) { - debug_putstr("Aborted e820 scan (more than 4 memmap= args)!\n"); + debug_putstr("Aborted memory entries scan (more than 4 memmap= args)!\n"); return 0; } /* Make sure minimum is aligned. */ minimum = ALIGN(minimum, CONFIG_PHYSICAL_ALIGN); + if (process_efi_entries(minimum, image_size)) + return slots_fetch_random(); + process_e820_entries(minimum, image_size); return slots_fetch_random(); } @@ -652,7 +716,7 @@ void choose_random_location(unsigned long input, */ min_addr = min(*output, 512UL << 20); - /* Walk e820 and find a random address. */ + /* Walk available memory entries to find a random address. */ random_addr = find_random_phys_addr(min_addr, output_size); if (!random_addr) { warn("Physical KASLR disabled: no suitable memory region!"); -- 2.5.5