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