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