mm/mprotect.c

   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@lxorguk.ukuu.org.uk>
   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/shm.h>
  14 #include <linux/mman.h>
  15 #include <linux/fs.h>
  16 #include <linux/highmem.h>
  17 #include <linux/security.h>
  18 #include <linux/mempolicy.h>
  19 #include <linux/personality.h>
  20 #include <linux/syscalls.h>
  21 #include <linux/swap.h>
  22 #include <linux/swapops.h>
  23 #include <linux/mmu_notifier.h>
  24 #include <linux/migrate.h>
  25 #include <linux/perf_event.h>
  26 #include <linux/ksm.h>
  27 #include <asm/uaccess.h>
  28 #include <asm/pgtable.h>
  29 #include <asm/cacheflush.h>
  30 #include <asm/tlbflush.h>
  31
  32 #ifndef pgprot_modify
  33 static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot)
  34 {
  35         return newprot;
  36 }
  37 #endif
  38
  39 /*
  40  * For a prot_numa update we only hold mmap_sem for read so there is a
  41  * potential race with faulting where a pmd was temporarily none. This
  42  * function checks for a transhuge pmd under the appropriate lock. It
  43  * returns a pte if it was successfully locked or NULL if it raced with
  44  * a transhuge insertion.
  45  */
  46 static pte_t *lock_pte_protection(struct vm_area_struct *vma, pmd_t *pmd,
  47                         unsigned long addr, int prot_numa, spinlock_t **ptl)
  48 {
  49         pte_t *pte;
  50         spinlock_t *pmdl;
  51
  52         /* !prot_numa is protected by mmap_sem held for write */
  53         if (!prot_numa)
  54                 return pte_offset_map_lock(vma->vm_mm, pmd, addr, ptl);
  55
  56         pmdl = pmd_lock(vma->vm_mm, pmd);
  57         if (unlikely(pmd_trans_huge(*pmd) || pmd_none(*pmd))) {
  58                 spin_unlock(pmdl);
  59                 return NULL;
  60         }
  61
  62         pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, ptl);
  63         spin_unlock(pmdl);
  64         return pte;
  65 }
  66
  67 static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
  68                 unsigned long addr, unsigned long end, pgprot_t newprot,
  69                 int dirty_accountable, int prot_numa)
  70 {
  71         struct mm_struct *mm = vma->vm_mm;
  72         pte_t *pte, oldpte;
  73         spinlock_t *ptl;
  74         unsigned long pages = 0;
  75
  76         pte = lock_pte_protection(vma, pmd, addr, prot_numa, &ptl);
  77         if (!pte)
  78                 return 0;
  79
  80         arch_enter_lazy_mmu_mode();
  81         do {
  82                 oldpte = *pte;
  83                 if (pte_present(oldpte)) {
  84                         pte_t ptent;
  85                         bool updated = false;
  86
  87                         if (!prot_numa) {
  88                                 ptent = ptep_modify_prot_start(mm, addr, pte);
  89                                 if (pte_numa(ptent))
  90                                         ptent = pte_mknonnuma(ptent);
  91                                 ptent = pte_modify(ptent, newprot);
  92                                 /*
  93                                  * Avoid taking write faults for pages we
  94                                  * know to be dirty.
  95                                  */
  96                                 if (dirty_accountable && pte_dirty(ptent))
  97                                         ptent = pte_mkwrite(ptent);
  98                                 ptep_modify_prot_commit(mm, addr, pte, ptent);
  99                                 updated = true;
 100                         } else {
 101                                 struct page *page;
 102
 103                                 page = vm_normal_page(vma, addr, oldpte);
 104                                 if (page && !PageKsm(page)) {
 105                                         if (!pte_numa(oldpte)) {
 106                                                 ptep_set_numa(mm, addr, pte);
 107                                                 updated = true;
 108                                         }
 109                                 }
 110                         }
 111                         if (updated)
 112                                 pages++;
 113                 } else if (IS_ENABLED(CONFIG_MIGRATION) && !pte_file(oldpte)) {
 114                         swp_entry_t entry = pte_to_swp_entry(oldpte);
 115
 116                         if (is_write_migration_entry(entry)) {
 117                                 pte_t newpte;
 118                                 /*
 119                                  * A protection check is difficult so
 120                                  * just be safe and disable write
 121                                  */
 122                                 make_migration_entry_read(&entry);
 123                                 newpte = swp_entry_to_pte(entry);
 124                                 if (pte_swp_soft_dirty(oldpte))
 125                                         newpte = pte_swp_mksoft_dirty(newpte);
 126                                 set_pte_at(mm, addr, pte, newpte);
 127
 128                                 pages++;
 129                         }
 130                 }
 131         } while (pte++, addr += PAGE_SIZE, addr != end);
 132         arch_leave_lazy_mmu_mode();
 133         pte_unmap_unlock(pte - 1, ptl);
 134
 135         return pages;
 136 }
 137
 138 static inline unsigned long change_pmd_range(struct vm_area_struct *vma,
 139                 pud_t *pud, unsigned long addr, unsigned long end,
 140                 pgprot_t newprot, int dirty_accountable, int prot_numa)
 141 {
 142         pmd_t *pmd;
 143         struct mm_struct *mm = vma->vm_mm;
 144         unsigned long next;
 145         unsigned long pages = 0;
 146         unsigned long nr_huge_updates = 0;
 147         unsigned long mni_start = 0;
 148
 149         pmd = pmd_offset(pud, addr);
 150         do {
 151                 unsigned long this_pages;
 152
 153                 next = pmd_addr_end(addr, end);
 154                 if (!pmd_trans_huge(*pmd) && pmd_none_or_clear_bad(pmd))
 155                         continue;
 156
 157                 /* invoke the mmu notifier if the pmd is populated */
 158                 if (!mni_start) {
 159                         mni_start = addr;
 160                         mmu_notifier_invalidate_range_start(mm, mni_start, end);
 161                 }
 162
 163                 if (pmd_trans_huge(*pmd)) {
 164                         if (next - addr != HPAGE_PMD_SIZE)
 165                                 split_huge_page_pmd(vma, addr, pmd);
 166                         else {
 167                                 int nr_ptes = change_huge_pmd(vma, pmd, addr,
 168                                                 newprot, prot_numa);
 169
 170                                 if (nr_ptes) {
 171                                         if (nr_ptes == HPAGE_PMD_NR) {
 172                                                 pages += HPAGE_PMD_NR;
 173                                                 nr_huge_updates++;
 174                                         }
 175
 176                                         /* huge pmd was handled */
 177                                         continue;
 178                                 }
 179                         }
 180                         /* fall through, the trans huge pmd just split */
 181                 }
 182                 this_pages = change_pte_range(vma, pmd, addr, next, newprot,
 183                                  dirty_accountable, prot_numa);
 184                 pages += this_pages;
 185         } while (pmd++, addr = next, addr != end);
 186
 187         if (mni_start)
 188                 mmu_notifier_invalidate_range_end(mm, mni_start, end);
 189
 190         if (nr_huge_updates)
 191                 count_vm_numa_events(NUMA_HUGE_PTE_UPDATES, nr_huge_updates);
 192         return pages;
 193 }
 194
 195 static inline unsigned long change_pud_range(struct vm_area_struct *vma,
 196                 pgd_t *pgd, unsigned long addr, unsigned long end,
 197                 pgprot_t newprot, int dirty_accountable, int prot_numa)
 198 {
 199         pud_t *pud;
 200         unsigned long next;
 201         unsigned long pages = 0;
 202
 203         pud = pud_offset(pgd, addr);
 204         do {
 205                 next = pud_addr_end(addr, end);
 206                 if (pud_none_or_clear_bad(pud))
 207                         continue;
 208                 pages += change_pmd_range(vma, pud, addr, next, newprot,
 209                                  dirty_accountable, prot_numa);
 210         } while (pud++, addr = next, addr != end);
 211
 212         return pages;
 213 }
 214
 215 static unsigned long change_protection_range(struct vm_area_struct *vma,
 216                 unsigned long addr, unsigned long end, pgprot_t newprot,
 217                 int dirty_accountable, int prot_numa)
 218 {
 219         struct mm_struct *mm = vma->vm_mm;
 220         pgd_t *pgd;
 221         unsigned long next;
 222         unsigned long start = addr;
 223         unsigned long pages = 0;
 224
 225         BUG_ON(addr >= end);
 226         pgd = pgd_offset(mm, addr);
 227         flush_cache_range(vma, addr, end);
 228         set_tlb_flush_pending(mm);
 229         do {
 230                 next = pgd_addr_end(addr, end);
 231                 if (pgd_none_or_clear_bad(pgd))
 232                         continue;
 233                 pages += change_pud_range(vma, pgd, addr, next, newprot,
 234                                  dirty_accountable, prot_numa);
 235         } while (pgd++, addr = next, addr != end);
 236
 237         /* Only flush the TLB if we actually modified any entries: */
 238         if (pages)
 239                 flush_tlb_range(vma, start, end);
 240         clear_tlb_flush_pending(mm);
 241
 242         return pages;
 243 }
 244
 245 unsigned long change_protection(struct vm_area_struct *vma, unsigned long start,
 246                        unsigned long end, pgprot_t newprot,
 247                        int dirty_accountable, int prot_numa)
 248 {
 249         unsigned long pages;
 250
 251         if (is_vm_hugetlb_page(vma))
 252                 pages = hugetlb_change_protection(vma, start, end, newprot);
 253         else
 254                 pages = change_protection_range(vma, start, end, newprot, dirty_accountable, prot_numa);
 255
 256         return pages;
 257 }
 258
 259 int
 260 mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
 261         unsigned long start, unsigned long end, unsigned long newflags)
 262 {
 263         struct mm_struct *mm = vma->vm_mm;
 264         unsigned long oldflags = vma->vm_flags;
 265         long nrpages = (end - start) >> PAGE_SHIFT;
 266         unsigned long charged = 0;
 267         pgoff_t pgoff;
 268         int error;
 269         int dirty_accountable = 0;
 270
 271         if (newflags == oldflags) {
 272                 *pprev = vma;
 273                 return 0;
 274         }
 275
 276         /*
 277          * If we make a private mapping writable we increase our commit;
 278          * but (without finer accounting) cannot reduce our commit if we
 279          * make it unwritable again. hugetlb mapping were accounted for
 280          * even if read-only so there is no need to account for them here
 281          */
 282         if (newflags & VM_WRITE) {
 283                 if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_HUGETLB|
 284                                                 VM_SHARED|VM_NORESERVE))) {
 285                         charged = nrpages;
 286                         if (security_vm_enough_memory_mm(mm, charged))
 287                                 return -ENOMEM;
 288                         newflags |= VM_ACCOUNT;
 289                 }
 290         }
 291
 292         /*
 293          * First try to merge with previous and/or next vma.
 294          */
 295         pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
 296         *pprev = vma_merge(mm, *pprev, start, end, newflags,
 297                         vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma));
 298         if (*pprev) {
 299                 vma = *pprev;
 300                 goto success;
 301         }
 302
 303         *pprev = vma;
 304
 305         if (start != vma->vm_start) {
 306                 error = split_vma(mm, vma, start, 1);
 307                 if (error)
 308                         goto fail;
 309         }
 310
 311         if (end != vma->vm_end) {
 312                 error = split_vma(mm, vma, end, 0);
 313                 if (error)
 314                         goto fail;
 315         }
 316
 317 success:
 318         /*
 319          * vm_flags and vm_page_prot are protected by the mmap_sem
 320          * held in write mode.
 321          */
 322         vma->vm_flags = newflags;
 323         vma->vm_page_prot = pgprot_modify(vma->vm_page_prot,
 324                                           vm_get_page_prot(newflags));
 325
 326         if (vma_wants_writenotify(vma)) {
 327                 vma->vm_page_prot = vm_get_page_prot(newflags & ~VM_SHARED);
 328                 dirty_accountable = 1;
 329         }
 330
 331         change_protection(vma, start, end, vma->vm_page_prot,
 332                           dirty_accountable, 0);
 333
 334         vm_stat_account(mm, oldflags, vma->vm_file, -nrpages);
 335         vm_stat_account(mm, newflags, vma->vm_file, nrpages);
 336         perf_event_mmap(vma);
 337         return 0;
 338
 339 fail:
 340         vm_unacct_memory(charged);
 341         return error;
 342 }
 343
 344 SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len,
 345                 unsigned long, prot)
 346 {
 347         unsigned long vm_flags, nstart, end, tmp, reqprot;
 348         struct vm_area_struct *vma, *prev;
 349         int error = -EINVAL;
 350         const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP);
 351         prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP);
 352         if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */
 353                 return -EINVAL;
 354
 355         if (start & ~PAGE_MASK)
 356                 return -EINVAL;
 357         if (!len)
 358                 return 0;
 359         len = PAGE_ALIGN(len);
 360         end = start + len;
 361         if (end <= start)
 362                 return -ENOMEM;
 363         if (!arch_validate_prot(prot))
 364                 return -EINVAL;
 365
 366         reqprot = prot;
 367         /*
 368          * Does the application expect PROT_READ to imply PROT_EXEC:
 369          */
 370         if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
 371                 prot |= PROT_EXEC;
 372
 373         vm_flags = calc_vm_prot_bits(prot);
 374
 375         down_write(&current->mm->mmap_sem);
 376
 377         vma = find_vma(current->mm, start);
 378         error = -ENOMEM;
 379         if (!vma)
 380                 goto out;
 381         prev = vma->vm_prev;
 382         if (unlikely(grows & PROT_GROWSDOWN)) {
 383                 if (vma->vm_start >= end)
 384                         goto out;
 385                 start = vma->vm_start;
 386                 error = -EINVAL;
 387                 if (!(vma->vm_flags & VM_GROWSDOWN))
 388                         goto out;
 389         } else {
 390                 if (vma->vm_start > start)
 391                         goto out;
 392                 if (unlikely(grows & PROT_GROWSUP)) {
 393                         end = vma->vm_end;
 394                         error = -EINVAL;
 395                         if (!(vma->vm_flags & VM_GROWSUP))
 396                                 goto out;
 397                 }
 398         }
 399         if (start > vma->vm_start)
 400                 prev = vma;
 401
 402         for (nstart = start ; ; ) {
 403                 unsigned long newflags;
 404
 405                 /* Here we know that vma->vm_start <= nstart < vma->vm_end. */
 406
 407                 newflags = vm_flags;
 408                 newflags |= (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC));
 409
 410                 /* newflags >> 4 shift VM_MAY% in place of VM_% */
 411                 if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) {
 412                         error = -EACCES;
 413                         goto out;
 414                 }
 415
 416                 error = security_file_mprotect(vma, reqprot, prot);
 417                 if (error)
 418                         goto out;
 419
 420                 tmp = vma->vm_end;
 421                 if (tmp > end)
 422                         tmp = end;
 423                 error = mprotect_fixup(vma, &prev, nstart, tmp, newflags);
 424                 if (error)
 425                         goto out;
 426                 nstart = tmp;
 427
 428                 if (nstart < prev->vm_end)
 429                         nstart = prev->vm_end;
 430                 if (nstart >= end)
 431                         goto out;
 432
 433                 vma = prev->vm_next;
 434                 if (!vma || vma->vm_start != nstart) {
 435                         error = -ENOMEM;
 436                         goto out;
 437                 }
 438         }
 439 out:
 440         up_write(&current->mm->mmap_sem);
 441         return error;
 442 }