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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 | // SPDX-License-Identifier: GPL-2.0+ /* * flexible mmap layout support * * Copyright 2003-2004 Red Hat Inc., Durham, North Carolina. * All Rights Reserved. * * Started by Ingo Molnar <mingo@elte.hu> */ #include <linux/elf-randomize.h> #include <linux/personality.h> #include <linux/mm.h> #include <linux/mman.h> #include <linux/sched/signal.h> #include <linux/sched/mm.h> #include <linux/random.h> #include <linux/compat.h> #include <linux/security.h> #include <asm/elf.h> static unsigned long stack_maxrandom_size(void) { if (!(current->flags & PF_RANDOMIZE)) return 0; return STACK_RND_MASK << PAGE_SHIFT; } static inline int mmap_is_legacy(struct rlimit *rlim_stack) { if (current->personality & ADDR_COMPAT_LAYOUT) return 1; if (rlim_stack->rlim_cur == RLIM_INFINITY) return 1; return sysctl_legacy_va_layout; } unsigned long arch_mmap_rnd(void) { return (get_random_u32() & MMAP_RND_MASK) << PAGE_SHIFT; } static unsigned long mmap_base_legacy(unsigned long rnd) { return TASK_UNMAPPED_BASE + rnd; } static inline unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stack) { unsigned long gap = rlim_stack->rlim_cur; unsigned long pad = stack_maxrandom_size() + stack_guard_gap; unsigned long gap_min, gap_max; /* Values close to RLIM_INFINITY can overflow. */ if (gap + pad > gap) gap += pad; /* * Top of mmap area (just below the process stack). * Leave at least a ~128 MB hole. */ gap_min = SZ_128M; gap_max = (STACK_TOP / 6) * 5; if (gap < gap_min) gap = gap_min; else if (gap > gap_max) gap = gap_max; return PAGE_ALIGN(STACK_TOP - gap - rnd); } static int get_align_mask(struct file *filp, unsigned long flags) { if (!(current->flags & PF_RANDOMIZE)) return 0; if (filp || (flags & MAP_SHARED)) return MMAP_ALIGN_MASK << PAGE_SHIFT; return 0; } unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr, unsigned long len, unsigned long pgoff, unsigned long flags) { struct mm_struct *mm = current->mm; struct vm_area_struct *vma; struct vm_unmapped_area_info info = {}; if (len > TASK_SIZE - mmap_min_addr) return -ENOMEM; if (flags & MAP_FIXED) goto check_asce_limit; if (addr) { addr = PAGE_ALIGN(addr); vma = find_vma(mm, addr); if (TASK_SIZE - len >= addr && addr >= mmap_min_addr && (!vma || addr + len <= vm_start_gap(vma))) goto check_asce_limit; } info.length = len; info.low_limit = mm->mmap_base; info.high_limit = TASK_SIZE; info.align_mask = get_align_mask(filp, flags); info.align_offset = pgoff << PAGE_SHIFT; addr = vm_unmapped_area(&info); if (offset_in_page(addr)) return addr; check_asce_limit: return check_asce_limit(mm, addr, len); } unsigned long arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr, unsigned long len, unsigned long pgoff, unsigned long flags) { struct vm_area_struct *vma; struct mm_struct *mm = current->mm; struct vm_unmapped_area_info info = {}; /* requested length too big for entire address space */ if (len > TASK_SIZE - mmap_min_addr) return -ENOMEM; if (flags & MAP_FIXED) goto check_asce_limit; /* requesting a specific address */ if (addr) { addr = PAGE_ALIGN(addr); vma = find_vma(mm, addr); if (TASK_SIZE - len >= addr && addr >= mmap_min_addr && (!vma || addr + len <= vm_start_gap(vma))) goto check_asce_limit; } info.flags = VM_UNMAPPED_AREA_TOPDOWN; info.length = len; info.low_limit = PAGE_SIZE; info.high_limit = mm->mmap_base; info.align_mask = get_align_mask(filp, flags); info.align_offset = pgoff << PAGE_SHIFT; addr = vm_unmapped_area(&info); /* * A failed mmap() very likely causes application failure, * so fall back to the bottom-up function here. This scenario * can happen with large stack limits and large mmap() * allocations. */ if (offset_in_page(addr)) { VM_BUG_ON(addr != -ENOMEM); info.flags = 0; info.low_limit = TASK_UNMAPPED_BASE; info.high_limit = TASK_SIZE; addr = vm_unmapped_area(&info); if (offset_in_page(addr)) return addr; } check_asce_limit: return check_asce_limit(mm, addr, len); } /* * This function, called very early during the creation of a new * process VM image, sets up which VM layout function to use: */ void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack) { unsigned long random_factor = 0UL; if (current->flags & PF_RANDOMIZE) random_factor = arch_mmap_rnd(); /* * Fall back to the standard layout if the personality * bit is set, or if the expected stack growth is unlimited: */ if (mmap_is_legacy(rlim_stack)) { mm->mmap_base = mmap_base_legacy(random_factor); clear_bit(MMF_TOPDOWN, &mm->flags); } else { mm->mmap_base = mmap_base(random_factor, rlim_stack); set_bit(MMF_TOPDOWN, &mm->flags); } } static const pgprot_t protection_map[16] = { [VM_NONE] = PAGE_NONE, [VM_READ] = PAGE_RO, [VM_WRITE] = PAGE_RO, [VM_WRITE | VM_READ] = PAGE_RO, [VM_EXEC] = PAGE_RX, [VM_EXEC | VM_READ] = PAGE_RX, [VM_EXEC | VM_WRITE] = PAGE_RX, [VM_EXEC | VM_WRITE | VM_READ] = PAGE_RX, [VM_SHARED] = PAGE_NONE, [VM_SHARED | VM_READ] = PAGE_RO, [VM_SHARED | VM_WRITE] = PAGE_RW, [VM_SHARED | VM_WRITE | VM_READ] = PAGE_RW, [VM_SHARED | VM_EXEC] = PAGE_RX, [VM_SHARED | VM_EXEC | VM_READ] = PAGE_RX, [VM_SHARED | VM_EXEC | VM_WRITE] = PAGE_RWX, [VM_SHARED | VM_EXEC | VM_WRITE | VM_READ] = PAGE_RWX }; DECLARE_VM_GET_PAGE_PROT |