| 1 | /* |
| 2 | * mm/mprotect.c |
| 3 | * |
| 4 | * (C) Copyright 1994 Linus Torvalds |
| 5 | * (C) Copyright 2002 Christoph Hellwig |
| 6 | * |
| 7 | * Address space accounting code <alan@redhat.com> |
| 8 | * (C) Copyright 2002 Red Hat Inc, All Rights Reserved |
| 9 | */ |
| 10 | |
| 11 | #include <linux/mm.h> |
| 12 | #include <linux/hugetlb.h> |
| 13 | #include <linux/slab.h> |
| 14 | #include <linux/shm.h> |
| 15 | #include <linux/mman.h> |
| 16 | #include <linux/fs.h> |
| 17 | #include <linux/highmem.h> |
| 18 | #include <linux/security.h> |
| 19 | #include <linux/mempolicy.h> |
| 20 | #include <linux/personality.h> |
| 21 | #include <linux/syscalls.h> |
| 22 | #include <linux/swap.h> |
| 23 | #include <linux/swapops.h> |
| 24 | #include <linux/mmu_notifier.h> |
| 25 | #include <asm/uaccess.h> |
| 26 | #include <asm/pgtable.h> |
| 27 | #include <asm/cacheflush.h> |
| 28 | #include <asm/tlbflush.h> |
| 29 | |
| 30 | #ifndef pgprot_modify |
| 31 | static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot) |
| 32 | { |
| 33 | return newprot; |
| 34 | } |
| 35 | #endif |
| 36 | |
| 37 | static void change_pte_range(struct mm_struct *mm, pmd_t *pmd, |
| 38 | unsigned long addr, unsigned long end, pgprot_t newprot, |
| 39 | int dirty_accountable) |
| 40 | { |
| 41 | pte_t *pte, oldpte; |
| 42 | spinlock_t *ptl; |
| 43 | |
| 44 | pte = pte_offset_map_lock(mm, pmd, addr, &ptl); |
| 45 | arch_enter_lazy_mmu_mode(); |
| 46 | do { |
| 47 | oldpte = *pte; |
| 48 | if (pte_present(oldpte)) { |
| 49 | pte_t ptent; |
| 50 | |
| 51 | ptent = ptep_modify_prot_start(mm, addr, pte); |
| 52 | ptent = pte_modify(ptent, newprot); |
| 53 | |
| 54 | /* |
| 55 | * Avoid taking write faults for pages we know to be |
| 56 | * dirty. |
| 57 | */ |
| 58 | if (dirty_accountable && pte_dirty(ptent)) |
| 59 | ptent = pte_mkwrite(ptent); |
| 60 | |
| 61 | ptep_modify_prot_commit(mm, addr, pte, ptent); |
| 62 | #ifdef CONFIG_MIGRATION |
| 63 | } else if (!pte_file(oldpte)) { |
| 64 | swp_entry_t entry = pte_to_swp_entry(oldpte); |
| 65 | |
| 66 | if (is_write_migration_entry(entry)) { |
| 67 | /* |
| 68 | * A protection check is difficult so |
| 69 | * just be safe and disable write |
| 70 | */ |
| 71 | make_migration_entry_read(&entry); |
| 72 | set_pte_at(mm, addr, pte, |
| 73 | swp_entry_to_pte(entry)); |
| 74 | } |
| 75 | #endif |
| 76 | } |
| 77 | |
| 78 | } while (pte++, addr += PAGE_SIZE, addr != end); |
| 79 | arch_leave_lazy_mmu_mode(); |
| 80 | pte_unmap_unlock(pte - 1, ptl); |
| 81 | } |
| 82 | |
| 83 | static inline void change_pmd_range(struct mm_struct *mm, pud_t *pud, |
| 84 | unsigned long addr, unsigned long end, pgprot_t newprot, |
| 85 | int dirty_accountable) |
| 86 | { |
| 87 | pmd_t *pmd; |
| 88 | unsigned long next; |
| 89 | |
| 90 | pmd = pmd_offset(pud, addr); |
| 91 | do { |
| 92 | next = pmd_addr_end(addr, end); |
| 93 | if (pmd_none_or_clear_bad(pmd)) |
| 94 | continue; |
| 95 | change_pte_range(mm, pmd, addr, next, newprot, dirty_accountable); |
| 96 | } while (pmd++, addr = next, addr != end); |
| 97 | } |
| 98 | |
| 99 | static inline void change_pud_range(struct mm_struct *mm, pgd_t *pgd, |
| 100 | unsigned long addr, unsigned long end, pgprot_t newprot, |
| 101 | int dirty_accountable) |
| 102 | { |
| 103 | pud_t *pud; |
| 104 | unsigned long next; |
| 105 | |
| 106 | pud = pud_offset(pgd, addr); |
| 107 | do { |
| 108 | next = pud_addr_end(addr, end); |
| 109 | if (pud_none_or_clear_bad(pud)) |
| 110 | continue; |
| 111 | change_pmd_range(mm, pud, addr, next, newprot, dirty_accountable); |
| 112 | } while (pud++, addr = next, addr != end); |
| 113 | } |
| 114 | |
| 115 | static void change_protection(struct vm_area_struct *vma, |
| 116 | unsigned long addr, unsigned long end, pgprot_t newprot, |
| 117 | int dirty_accountable) |
| 118 | { |
| 119 | struct mm_struct *mm = vma->vm_mm; |
| 120 | pgd_t *pgd; |
| 121 | unsigned long next; |
| 122 | unsigned long start = addr; |
| 123 | |
| 124 | BUG_ON(addr >= end); |
| 125 | pgd = pgd_offset(mm, addr); |
| 126 | flush_cache_range(vma, addr, end); |
| 127 | do { |
| 128 | next = pgd_addr_end(addr, end); |
| 129 | if (pgd_none_or_clear_bad(pgd)) |
| 130 | continue; |
| 131 | change_pud_range(mm, pgd, addr, next, newprot, dirty_accountable); |
| 132 | } while (pgd++, addr = next, addr != end); |
| 133 | flush_tlb_range(vma, start, end); |
| 134 | } |
| 135 | |
| 136 | int |
| 137 | mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev, |
| 138 | unsigned long start, unsigned long end, unsigned long newflags) |
| 139 | { |
| 140 | struct mm_struct *mm = vma->vm_mm; |
| 141 | unsigned long oldflags = vma->vm_flags; |
| 142 | long nrpages = (end - start) >> PAGE_SHIFT; |
| 143 | unsigned long charged = 0; |
| 144 | pgoff_t pgoff; |
| 145 | int error; |
| 146 | int dirty_accountable = 0; |
| 147 | |
| 148 | if (newflags == oldflags) { |
| 149 | *pprev = vma; |
| 150 | return 0; |
| 151 | } |
| 152 | |
| 153 | /* |
| 154 | * If we make a private mapping writable we increase our commit; |
| 155 | * but (without finer accounting) cannot reduce our commit if we |
| 156 | * make it unwritable again. |
| 157 | */ |
| 158 | if (newflags & VM_WRITE) { |
| 159 | if (!(oldflags & (VM_ACCOUNT|VM_WRITE| |
| 160 | VM_SHARED|VM_NORESERVE))) { |
| 161 | charged = nrpages; |
| 162 | if (security_vm_enough_memory(charged)) |
| 163 | return -ENOMEM; |
| 164 | newflags |= VM_ACCOUNT; |
| 165 | } |
| 166 | } |
| 167 | |
| 168 | /* |
| 169 | * First try to merge with previous and/or next vma. |
| 170 | */ |
| 171 | pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT); |
| 172 | *pprev = vma_merge(mm, *pprev, start, end, newflags, |
| 173 | vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma)); |
| 174 | if (*pprev) { |
| 175 | vma = *pprev; |
| 176 | goto success; |
| 177 | } |
| 178 | |
| 179 | *pprev = vma; |
| 180 | |
| 181 | if (start != vma->vm_start) { |
| 182 | error = split_vma(mm, vma, start, 1); |
| 183 | if (error) |
| 184 | goto fail; |
| 185 | } |
| 186 | |
| 187 | if (end != vma->vm_end) { |
| 188 | error = split_vma(mm, vma, end, 0); |
| 189 | if (error) |
| 190 | goto fail; |
| 191 | } |
| 192 | |
| 193 | success: |
| 194 | /* |
| 195 | * vm_flags and vm_page_prot are protected by the mmap_sem |
| 196 | * held in write mode. |
| 197 | */ |
| 198 | vma->vm_flags = newflags; |
| 199 | vma->vm_page_prot = pgprot_modify(vma->vm_page_prot, |
| 200 | vm_get_page_prot(newflags)); |
| 201 | |
| 202 | if (vma_wants_writenotify(vma)) { |
| 203 | vma->vm_page_prot = vm_get_page_prot(newflags & ~VM_SHARED); |
| 204 | dirty_accountable = 1; |
| 205 | } |
| 206 | |
| 207 | mmu_notifier_invalidate_range_start(mm, start, end); |
| 208 | if (is_vm_hugetlb_page(vma)) |
| 209 | hugetlb_change_protection(vma, start, end, vma->vm_page_prot); |
| 210 | else |
| 211 | change_protection(vma, start, end, vma->vm_page_prot, dirty_accountable); |
| 212 | mmu_notifier_invalidate_range_end(mm, start, end); |
| 213 | vm_stat_account(mm, oldflags, vma->vm_file, -nrpages); |
| 214 | vm_stat_account(mm, newflags, vma->vm_file, nrpages); |
| 215 | return 0; |
| 216 | |
| 217 | fail: |
| 218 | vm_unacct_memory(charged); |
| 219 | return error; |
| 220 | } |
| 221 | |
| 222 | asmlinkage long |
| 223 | sys_mprotect(unsigned long start, size_t len, unsigned long prot) |
| 224 | { |
| 225 | unsigned long vm_flags, nstart, end, tmp, reqprot; |
| 226 | struct vm_area_struct *vma, *prev; |
| 227 | int error = -EINVAL; |
| 228 | const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP); |
| 229 | prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP); |
| 230 | if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */ |
| 231 | return -EINVAL; |
| 232 | |
| 233 | if (start & ~PAGE_MASK) |
| 234 | return -EINVAL; |
| 235 | if (!len) |
| 236 | return 0; |
| 237 | len = PAGE_ALIGN(len); |
| 238 | end = start + len; |
| 239 | if (end <= start) |
| 240 | return -ENOMEM; |
| 241 | if (!arch_validate_prot(prot)) |
| 242 | return -EINVAL; |
| 243 | |
| 244 | reqprot = prot; |
| 245 | /* |
| 246 | * Does the application expect PROT_READ to imply PROT_EXEC: |
| 247 | */ |
| 248 | if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC)) |
| 249 | prot |= PROT_EXEC; |
| 250 | |
| 251 | vm_flags = calc_vm_prot_bits(prot); |
| 252 | |
| 253 | down_write(¤t->mm->mmap_sem); |
| 254 | |
| 255 | vma = find_vma_prev(current->mm, start, &prev); |
| 256 | error = -ENOMEM; |
| 257 | if (!vma) |
| 258 | goto out; |
| 259 | if (unlikely(grows & PROT_GROWSDOWN)) { |
| 260 | if (vma->vm_start >= end) |
| 261 | goto out; |
| 262 | start = vma->vm_start; |
| 263 | error = -EINVAL; |
| 264 | if (!(vma->vm_flags & VM_GROWSDOWN)) |
| 265 | goto out; |
| 266 | } |
| 267 | else { |
| 268 | if (vma->vm_start > start) |
| 269 | goto out; |
| 270 | if (unlikely(grows & PROT_GROWSUP)) { |
| 271 | end = vma->vm_end; |
| 272 | error = -EINVAL; |
| 273 | if (!(vma->vm_flags & VM_GROWSUP)) |
| 274 | goto out; |
| 275 | } |
| 276 | } |
| 277 | if (start > vma->vm_start) |
| 278 | prev = vma; |
| 279 | |
| 280 | for (nstart = start ; ; ) { |
| 281 | unsigned long newflags; |
| 282 | |
| 283 | /* Here we know that vma->vm_start <= nstart < vma->vm_end. */ |
| 284 | |
| 285 | newflags = vm_flags | (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC)); |
| 286 | |
| 287 | /* newflags >> 4 shift VM_MAY% in place of VM_% */ |
| 288 | if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) { |
| 289 | error = -EACCES; |
| 290 | goto out; |
| 291 | } |
| 292 | |
| 293 | error = security_file_mprotect(vma, reqprot, prot); |
| 294 | if (error) |
| 295 | goto out; |
| 296 | |
| 297 | tmp = vma->vm_end; |
| 298 | if (tmp > end) |
| 299 | tmp = end; |
| 300 | error = mprotect_fixup(vma, &prev, nstart, tmp, newflags); |
| 301 | if (error) |
| 302 | goto out; |
| 303 | nstart = tmp; |
| 304 | |
| 305 | if (nstart < prev->vm_end) |
| 306 | nstart = prev->vm_end; |
| 307 | if (nstart >= end) |
| 308 | goto out; |
| 309 | |
| 310 | vma = prev->vm_next; |
| 311 | if (!vma || vma->vm_start != nstart) { |
| 312 | error = -ENOMEM; |
| 313 | goto out; |
| 314 | } |
| 315 | } |
| 316 | out: |
| 317 | up_write(¤t->mm->mmap_sem); |
| 318 | return error; |
| 319 | } |