Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752098AbbKKB5y (ORCPT ); Tue, 10 Nov 2015 20:57:54 -0500 Received: from mx1.redhat.com ([209.132.183.28]:38830 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751912AbbKKB5r (ORCPT ); Tue, 10 Nov 2015 20:57:47 -0500 From: Laura Abbott To: Catalin Marinas , Will Deacon , Ard Biesheuvel , Zhong Jiang Cc: Laura Abbott , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Kees Cook , Xishi Qiu , Mark Rutland Subject: [PATCHv2 2/2] arm64: Allow changing of attributes outside of modules Date: Tue, 10 Nov 2015 17:57:37 -0800 Message-Id: <1447207057-11323-3-git-send-email-labbott@fedoraproject.org> In-Reply-To: <1447207057-11323-1-git-send-email-labbott@fedoraproject.org> References: <1447207057-11323-1-git-send-email-labbott@fedoraproject.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7727 Lines: 288 Currently, the set_memory_* functions that are implemented for arm64 are restricted to module addresses only. This was mostly done because arm64 maps normal zone memory with larger page sizes to improve TLB performance. This has the side effect though of making it difficult to adjust attributes at the PAGE_SIZE granularity. There are an increasing number of use cases related to security where it is necessary to change the attributes of kernel memory. Add functionality to the page attribute changing code under a Kconfig to let systems designers decide if they want to make the trade off of security for TLB pressure. Signed-off-by: Laura Abbott --- v2: Re-worked to account for the full range of addresses. Will also just update the section blocks instead of splitting if the addresses are aligned properly. --- arch/arm64/Kconfig | 12 ++++ arch/arm64/mm/mm.h | 3 + arch/arm64/mm/mmu.c | 2 +- arch/arm64/mm/pageattr.c | 174 +++++++++++++++++++++++++++++++++++++++++------ 4 files changed, 170 insertions(+), 21 deletions(-) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 851fe11..46725e8 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -521,6 +521,18 @@ config ARCH_HAS_CACHE_LINE_SIZE source "mm/Kconfig" +config DEBUG_CHANGE_PAGEATTR + bool "Allow all kernel memory to have attributes changed" + default y + help + If this option is selected, APIs that change page attributes + (RW <-> RO, X <-> NX) will be valid for all memory mapped in + the kernel space. The trade off is that there may be increased + TLB pressure from finer grained page mapping. Turn on this option + if security is more important than performance + + If in doubt, say Y + config SECCOMP bool "Enable seccomp to safely compute untrusted bytecode" ---help--- diff --git a/arch/arm64/mm/mm.h b/arch/arm64/mm/mm.h index ef47d99..7b0dcc4 100644 --- a/arch/arm64/mm/mm.h +++ b/arch/arm64/mm/mm.h @@ -1,3 +1,6 @@ extern void __init bootmem_init(void); void fixup_init(void); + +void split_pud(pud_t *old_pud, pmd_t *pmd); +void split_pmd(pmd_t *pmd, pte_t *pte); diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index 496c3fd..9353e3c 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -73,7 +73,7 @@ static void __init *early_alloc(unsigned long sz) /* * remap a PMD into pages */ -static void split_pmd(pmd_t *pmd, pte_t *pte) +void split_pmd(pmd_t *pmd, pte_t *pte) { unsigned long pfn = pmd_pfn(*pmd); unsigned long addr = pfn << PAGE_SHIFT; diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c index 3571c73..4a95fed 100644 --- a/arch/arm64/mm/pageattr.c +++ b/arch/arm64/mm/pageattr.c @@ -15,25 +15,162 @@ #include #include +#include #include #include -struct page_change_data { - pgprot_t set_mask; - pgprot_t clear_mask; -}; +#include "mm.h" -static int change_page_range(pte_t *ptep, pgtable_t token, unsigned long addr, - void *data) +static int update_pte_range(struct mm_struct *mm, pmd_t *pmd, + unsigned long addr, unsigned long end, + pgprot_t clear, pgprot_t set) { - struct page_change_data *cdata = data; - pte_t pte = *ptep; + pte_t *pte; + int err = 0; + + if (pmd_sect(*pmd)) { + if (!IS_ENABLED(CONFIG_DEBUG_CHANGE_PAGEATTR)) { + err = -EINVAL; + goto out; + } + pte = pte_alloc_one_kernel(&init_mm, addr); + if (!pte) { + err = -ENOMEM; + goto out; + } + split_pmd(pmd, pte); + __pmd_populate(pmd, __pa(pte), PMD_TYPE_TABLE); + } + + + pte = pte_offset_kernel(pmd, addr); + if (pte_none(*pte)) { + err = -EFAULT; + goto out; + } + + do { + pte_t p = *pte; + + p = clear_pte_bit(p, clear); + p = set_pte_bit(p, set); + set_pte(pte, p); + + } while (pte++, addr += PAGE_SIZE, addr != end); + +out: + return err; +} + + +static int update_pmd_range(struct mm_struct *mm, pud_t *pud, + unsigned long addr, unsigned long end, + pgprot_t clear, pgprot_t set) +{ + pmd_t *pmd; + unsigned long next; + int err = 0; + + if (pud_sect(*pud)) { + if (!IS_ENABLED(CONFIG_DEBUG_CHANGE_PAGEATTR)) { + err = -EINVAL; + goto out; + } + pmd = pmd_alloc_one(&init_mm, addr); + if (!pmd) { + err = -ENOMEM; + goto out; + } + split_pud(pud, pmd); + pud_populate(&init_mm, pud, pmd); + } + - pte = clear_pte_bit(pte, cdata->clear_mask); - pte = set_pte_bit(pte, cdata->set_mask); + pmd = pmd_offset(pud, addr); + if (pmd_none(*pmd)) { + err = -EFAULT; + goto out; + } + + do { + next = pmd_addr_end(addr, end); + if (((addr | end) & ~SECTION_MASK) == 0) { + unsigned long paddr = pmd_pfn(*pmd) << PAGE_SHIFT; + pgprot_t prot = __pgprot((pmd_val(*pmd) ^ paddr)); + + pgprot_val(prot) &= ~pgprot_val(clear); + pgprot_val(prot) |= pgprot_val(set); + set_pmd(pmd, __pmd(paddr | pgprot_val(prot))); + } else { + err = update_pte_range(mm, pmd, addr, next, clear, set); + } + if (err) + break; + } while (pmd++, addr = next, addr != end); +out: + return err; +} + + +static int update_pud_range(struct mm_struct *mm, pgd_t *pgd, + unsigned long addr, unsigned long end, + pgprot_t clear, pgprot_t set) +{ + pud_t *pud; + unsigned long next; + int err = 0; + + pud = pud_offset(pgd, addr); + if (pud_none(*pud)) { + err = -EFAULT; + goto out; + } - set_pte(ptep, pte); - return 0; + do { + next = pud_addr_end(addr, end); + if (pud_sect(*pud) && ((addr | next) & ~PUD_MASK) == 0) { + unsigned long paddr = pud_pfn(*pud) << PAGE_SHIFT; + pgprot_t prot = __pgprot(pud_val(*pud) ^ paddr); + + pgprot_val(prot) &= ~pgprot_val(clear); + pgprot_val(prot) |= pgprot_val(set); + set_pud(pud, __pud(paddr | pgprot_val(prot))); + } else { + err = update_pmd_range(mm, pud, addr, next, clear, set); + } + if (err) + break; + } while (pud++, addr = next, addr != end); + +out: + return err; +} + +static int update_page_range(unsigned long addr, + unsigned long end, pgprot_t clear, + pgprot_t set) +{ + pgd_t *pgd; + unsigned long next; + int err; + struct mm_struct *mm = &init_mm; + + BUG_ON(addr >= end); + pgd = pgd_offset(mm, addr); + if (pgd_none(*pgd)) { + err = -EFAULT; + goto out; + } + + do { + next = pgd_addr_end(addr, end); + err = update_pud_range(mm, pgd, addr, next, clear, set); + if (err) + break; + } while (pgd++, addr = next, addr != end); + +out: + return err; } static int change_memory_common(unsigned long addr, int numpages, @@ -43,7 +180,6 @@ static int change_memory_common(unsigned long addr, int numpages, unsigned long size = PAGE_SIZE*numpages; unsigned long end = start + size; int ret; - struct page_change_data data; if (!PAGE_ALIGNED(addr)) { start &= PAGE_MASK; @@ -51,17 +187,15 @@ static int change_memory_common(unsigned long addr, int numpages, WARN_ON_ONCE(1); } - if (start < MODULES_VADDR || start >= MODULES_END) + if (start < PAGE_OFFSET && !is_vmalloc_addr((void *)start) && + (start < MODULES_VADDR || start >= MODULES_END)) return -EINVAL; - if (end < MODULES_VADDR || end >= MODULES_END) + if (end < PAGE_OFFSET && !is_vmalloc_addr((void *)end) && + (end < MODULES_VADDR || end >= MODULES_END)) return -EINVAL; - data.set_mask = set_mask; - data.clear_mask = clear_mask; - - ret = apply_to_page_range(&init_mm, start, size, change_page_range, - &data); + ret = update_page_range(addr, end, clear_mask, set_mask); flush_tlb_kernel_range(start, end); return ret; -- 2.5.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/