Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756196AbaDHDSG (ORCPT ); Mon, 7 Apr 2014 23:18:06 -0400 Received: from smtp.outflux.net ([198.145.64.163]:50387 "EHLO smtp.outflux.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756000AbaDHDSE (ORCPT ); Mon, 7 Apr 2014 23:18:04 -0400 From: Kees Cook To: linux-arm-kernel@lists.infradead.org Cc: Rabin Vincent , Laura Abbott , Alexander Holler , Catalin Marinas , Will Deacon , Russell King , linux-kernel@vger.kernel.org, Kees Cook Subject: [PATCH v2 1/2] ARM: mm: allow non-text sections to be non-executable Date: Mon, 7 Apr 2014 20:15:09 -0700 Message-Id: <1396926910-11227-2-git-send-email-keescook@chromium.org> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1396926910-11227-1-git-send-email-keescook@chromium.org> References: <1396926910-11227-1-git-send-email-keescook@chromium.org> X-HELO: www.outflux.net Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Adds CONFIG_ARM_KERNMEM_PERMS to separate the kernel memory regions into section-sized areas that can have different permisions. Performs the NX permission changes during free_initmem, so that init memory can be reclaimed. This uses section size instead of PMD size to reduce memory lost to padding on non-LPAE systems. Based on work by Brad Spengler, Larry Bassel, and Laura Abbott. Signed-off-by: Kees Cook --- arch/arm/kernel/vmlinux.lds.S | 17 +++++++ arch/arm/mm/Kconfig | 9 ++++ arch/arm/mm/init.c | 106 +++++++++++++++++++++++++++++++++++++++++ arch/arm/mm/mmu.c | 13 ++++- 4 files changed, 144 insertions(+), 1 deletion(-) diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S index 7bcee5c9b604..08fa667ef2f1 100644 --- a/arch/arm/kernel/vmlinux.lds.S +++ b/arch/arm/kernel/vmlinux.lds.S @@ -8,6 +8,9 @@ #include #include #include +#ifdef CONFIG_ARM_KERNMEM_PERMS +#include +#endif #define PROC_INFO \ . = ALIGN(4); \ @@ -90,6 +93,11 @@ SECTIONS _text = .; HEAD_TEXT } + +#ifdef CONFIG_ARM_KERNMEM_PERMS + . = ALIGN(1< #include +#ifdef CONFIG_ARM_KERNMEM_PERMS +#include +#include +#endif + #include #include @@ -623,11 +628,112 @@ void __init mem_init(void) } } +#ifdef CONFIG_ARM_KERNMEM_PERMS +struct section_perm { + unsigned long start; + unsigned long end; + pmdval_t mask; + pmdval_t prot; +}; + +struct section_perm nx_perms[] = { + /* Make pages tables, etc before _stext RW (set NX). */ + { + .start = PAGE_OFFSET, + .end = (unsigned long)_stext, + .mask = ~PMD_SECT_XN, + .prot = PMD_SECT_XN, + }, + /* Make init RW (set NX). */ + { + .start = (unsigned long)__init_begin, + .end = (unsigned long)_sdata, + .mask = ~PMD_SECT_XN, + .prot = PMD_SECT_XN, + }, +}; + +/* + * Updates section permissions only for the current mm (sections are + * copied into each mm). During startup, this is the init_mm. + */ +static inline void section_update(unsigned long addr, pmdval_t mask, + pmdval_t prot) +{ + struct mm_struct *mm; + pmd_t *pmd; + + mm = current->active_mm; + pmd = pmd_offset(pud_offset(pgd_offset(mm, addr), addr), addr); + +#ifdef CONFIG_ARM_LPAE + pmd[0] = __pmd((pmd_val(pmd[0]) & mask) | prot); +#else + if (addr & SECTION_SIZE) + pmd[1] = __pmd((pmd_val(pmd[1]) & mask) | prot); + else + pmd[0] = __pmd((pmd_val(pmd[0]) & mask) | prot); +#endif + flush_pmd_entry(pmd); + local_flush_tlb_kernel_range(addr, addr + SECTION_SIZE); +} + +/* Make sure extended page tables are in use. */ +static inline bool arch_has_strict_perms(void) +{ + unsigned int cr; + + if (cpu_architecture() < CPU_ARCH_ARMv6) + return false; + + cr = get_cr(); + if (!(cr & CR_XP)) + return false; + + return true; +} + +#define set_section_perms(perms, field) { \ + size_t i; \ + unsigned long addr; \ + \ + if (!arch_has_strict_perms()) \ + return; \ + \ + for (i = 0; i < ARRAY_SIZE(perms); i++) { \ + if (!IS_ALIGNED(perms[i].start, SECTION_SIZE) || \ + !IS_ALIGNED(perms[i].end, SECTION_SIZE)) { \ + pr_err("BUG: section %lx-%lx not aligned to %lx\n", \ + perms[i].start, perms[i].end, \ + SECTION_SIZE); \ + continue; \ + } \ + \ + for (addr = perms[i].start; \ + addr < perms[i].end; \ + addr += SECTION_SIZE) \ + section_update(addr, perms[i].mask, \ + perms[i].field); \ + } \ +} + +static inline void fix_kernmem_perms(void) +{ + set_section_perms(nx_perms, prot); +} +#else +static inline void fix_kernmem_perms(void) { } +#endif /* CONFIG_ARM_KERNMEM_PERMS */ + void free_initmem(void) { #ifdef CONFIG_HAVE_TCM extern char __tcm_start, __tcm_end; +#endif + + fix_kernmem_perms(); +#ifdef CONFIG_HAVE_TCM poison_init_mem(&__tcm_start, &__tcm_end - &__tcm_start); free_reserved_area(&__tcm_start, &__tcm_end, -1, "TCM link"); #endif diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c index b68c6b22e1c8..3e163071bdcb 100644 --- a/arch/arm/mm/mmu.c +++ b/arch/arm/mm/mmu.c @@ -1379,13 +1379,24 @@ static void __init map_lowmem(void) if (start >= end) break; - if (end < kernel_x_start || start >= kernel_x_end) { + if (end < kernel_x_start) { map.pfn = __phys_to_pfn(start); map.virtual = __phys_to_virt(start); map.length = end - start; map.type = MT_MEMORY_RWX; create_mapping(&map); + } else if (start >= kernel_x_end) { + map.pfn = __phys_to_pfn(start); + map.virtual = __phys_to_virt(start); + map.length = end - start; +#ifdef CONFIG_ARM_KERNMEM_PERMS + map.type = MT_MEMORY_RW; +#else + map.type = MT_MEMORY_RWX; +#endif + + create_mapping(&map); } else { /* This better cover the entire kernel */ if (start < kernel_x_start) { -- 1.7.9.5 -- 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/