LXR linux/mm/mprotect.c

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 *  mm/mprotect.c
   4 *
   5 *  (C) Copyright 1994 Linus Torvalds
   6 *  (C) Copyright 2002 Christoph Hellwig
   7 *
   8 *  Address space accounting code       <alan@lxorguk.ukuu.org.uk>
   9 *  (C) Copyright 2002 Red Hat Inc, All Rights Reserved
  10 */
  11
  12#include <linux/mm.h>
  13#include <linux/hugetlb.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 <linux/migrate.h>
  26#include <linux/perf_event.h>
  27#include <linux/pkeys.h>
  28#include <linux/ksm.h>
  29#include <linux/uaccess.h>
  30#include <linux/mm_inline.h>
  31#include <asm/pgtable.h>
  32#include <asm/cacheflush.h>
  33#include <asm/mmu_context.h>
  34#include <asm/tlbflush.h>
  35
  36#include "internal.h"
  37
  38static 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)
  41{
  42        struct mm_struct *mm = vma->vm_mm;
  43        pte_t *pte, oldpte;
  44        spinlock_t *ptl;
  45        unsigned long pages = 0;
  46        int target_node = NUMA_NO_NODE;
  47
  48        /*
  49         * Can be called with only the mmap_sem for reading by
  50         * prot_numa so we must check the pmd isn't constantly
  51         * changing from under us from pmd_none to pmd_trans_huge
  52         * and/or the other way around.
  53         */
  54        if (pmd_trans_unstable(pmd))
  55                return 0;
  56
  57        /*
  58         * The pmd points to a regular pte so the pmd can't change
  59         * from under us even if the mmap_sem is only hold for
  60         * reading.
  61         */
  62        pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
  63
  64        /* Get target node for single threaded private VMAs */
  65        if (prot_numa && !(vma->vm_flags & VM_SHARED) &&
  66            atomic_read(&vma->vm_mm->mm_users) == 1)
  67                target_node = numa_node_id();
  68
  69        flush_tlb_batched_pending(vma->vm_mm);
  70        arch_enter_lazy_mmu_mode();
  71        do {
  72                oldpte = *pte;
  73                if (pte_present(oldpte)) {
  74                        pte_t ptent;
  75                        bool preserve_write = prot_numa && pte_write(oldpte);
  76
  77                        /*
  78                         * Avoid trapping faults against the zero or KSM
  79                         * pages. See similar comment in change_huge_pmd.
  80                         */
  81                        if (prot_numa) {
  82                                struct page *page;
  83
  84                                page = vm_normal_page(vma, addr, oldpte);
  85                                if (!page || PageKsm(page))
  86                                        continue;
  87
  88                                /* Also skip shared copy-on-write pages */
  89                                if (is_cow_mapping(vma->vm_flags) &&
  90                                    page_mapcount(page) != 1)
  91                                        continue;
  92
  93                                /*
  94                                 * While migration can move some dirty pages,
  95                                 * it cannot move them all from MIGRATE_ASYNC
  96                                 * context.
  97                                 */
  98                                if (page_is_file_cache(page) && PageDirty(page))
  99                                        continue;
 100
 101                                /* Avoid TLB flush if possible */
 102                                if (pte_protnone(oldpte))
 103                                        continue;
 104
 105                                /*
 106                                 * Don't mess with PTEs if page is already on the node
 107                                 * a single-threaded process is running on.
 108                                 */
 109                                if (target_node == page_to_nid(page))
 110                                        continue;
 111                        }
 112
 113                        ptent = ptep_modify_prot_start(mm, addr, pte);
 114                        ptent = pte_modify(ptent, newprot);
 115                        if (preserve_write)
 116                                ptent = pte_mk_savedwrite(ptent);
 117
 118                        /* Avoid taking write faults for known dirty pages */
 119                        if (dirty_accountable && pte_dirty(ptent) &&
 120                                        (pte_soft_dirty(ptent) ||
 121                                         !(vma->vm_flags & VM_SOFTDIRTY))) {
 122                                ptent = pte_mkwrite(ptent);
 123                        }
 124                        ptep_modify_prot_commit(mm, addr, pte, ptent);
 125                        pages++;
 126                } else if (IS_ENABLED(CONFIG_MIGRATION)) {
 127                        swp_entry_t entry = pte_to_swp_entry(oldpte);
 128
 129                        if (is_write_migration_entry(entry)) {
 130                                pte_t newpte;
 131                                /*
 132                                 * A protection check is difficult so
 133                                 * just be safe and disable write
 134                                 */
 135                                make_migration_entry_read(&entry);
 136                                newpte = swp_entry_to_pte(entry);
 137                                if (pte_swp_soft_dirty(oldpte))
 138                                        newpte = pte_swp_mksoft_dirty(newpte);
 139                                set_pte_at(mm, addr, pte, newpte);
 140
 141                                pages++;
 142                        }
 143
 144                        if (is_write_device_private_entry(entry)) {
 145                                pte_t newpte;
 146
 147                                /*
 148                                 * We do not preserve soft-dirtiness. See
 149                                 * copy_one_pte() for explanation.
 150                                 */
 151                                make_device_private_entry_read(&entry);
 152                                newpte = swp_entry_to_pte(entry);
 153                                set_pte_at(mm, addr, pte, newpte);
 154
 155                                pages++;
 156                        }
 157                }
 158        } while (pte++, addr += PAGE_SIZE, addr != end);
 159        arch_leave_lazy_mmu_mode();
 160        pte_unmap_unlock(pte - 1, ptl);
 161
 162        return pages;
 163}
 164
 165static inline unsigned long change_pmd_range(struct vm_area_struct *vma,
 166                pud_t *pud, unsigned long addr, unsigned long end,
 167                pgprot_t newprot, int dirty_accountable, int prot_numa)
 168{
 169        pmd_t *pmd;
 170        struct mm_struct *mm = vma->vm_mm;
 171        unsigned long next;
 172        unsigned long pages = 0;
 173        unsigned long nr_huge_updates = 0;
 174        unsigned long mni_start = 0;
 175
 176        pmd = pmd_offset(pud, addr);
 177        do {
 178                unsigned long this_pages;
 179
 180                next = pmd_addr_end(addr, end);
 181                if (!is_swap_pmd(*pmd) && !pmd_trans_huge(*pmd) && !pmd_devmap(*pmd)
 182                                && pmd_none_or_clear_bad(pmd))
 183                        goto next;
 184
 185                /* invoke the mmu notifier if the pmd is populated */
 186                if (!mni_start) {
 187                        mni_start = addr;
 188                        mmu_notifier_invalidate_range_start(mm, mni_start, end);
 189                }
 190
 191                if (is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) || pmd_devmap(*pmd)) {
 192                        if (next - addr != HPAGE_PMD_SIZE) {
 193                                __split_huge_pmd(vma, pmd, addr, false, NULL);
 194                        } else {
 195                                int nr_ptes = change_huge_pmd(vma, pmd, addr,
 196                                                newprot, prot_numa);
 197
 198                                if (nr_ptes) {
 199                                        if (nr_ptes == HPAGE_PMD_NR) {
 200                                                pages += HPAGE_PMD_NR;
 201                                                nr_huge_updates++;
 202                                        }
 203
 204                                        /* huge pmd was handled */
 205                                        goto next;
 206                                }
 207                        }
 208                        /* fall through, the trans huge pmd just split */
 209                }
 210                this_pages = change_pte_range(vma, pmd, addr, next, newprot,
 211                                 dirty_accountable, prot_numa);
 212                pages += this_pages;
 213next:
 214                cond_resched();
 215        } while (pmd++, addr = next, addr != end);
 216
 217        if (mni_start)
 218                mmu_notifier_invalidate_range_end(mm, mni_start, end);
 219
 220        if (nr_huge_updates)
 221                count_vm_numa_events(NUMA_HUGE_PTE_UPDATES, nr_huge_updates);
 222        return pages;
 223}
 224
 225static inline unsigned long change_pud_range(struct vm_area_struct *vma,
 226                p4d_t *p4d, unsigned long addr, unsigned long end,
 227                pgprot_t newprot, int dirty_accountable, int prot_numa)
 228{
 229        pud_t *pud;
 230        unsigned long next;
 231        unsigned long pages = 0;
 232
 233        pud = pud_offset(p4d, addr);
 234        do {
 235                next = pud_addr_end(addr, end);
 236                if (pud_none_or_clear_bad(pud))
 237                        continue;
 238                pages += change_pmd_range(vma, pud, addr, next, newprot,
 239                                 dirty_accountable, prot_numa);
 240        } while (pud++, addr = next, addr != end);
 241
 242        return pages;
 243}
 244
 245static inline unsigned long change_p4d_range(struct vm_area_struct *vma,
 246                pgd_t *pgd, unsigned long addr, unsigned long end,
 247                pgprot_t newprot, int dirty_accountable, int prot_numa)
 248{
 249        p4d_t *p4d;
 250        unsigned long next;
 251        unsigned long pages = 0;
 252
 253        p4d = p4d_offset(pgd, addr);
 254        do {
 255                next = p4d_addr_end(addr, end);
 256                if (p4d_none_or_clear_bad(p4d))
 257                        continue;
 258                pages += change_pud_range(vma, p4d, addr, next, newprot,
 259                                 dirty_accountable, prot_numa);
 260        } while (p4d++, addr = next, addr != end);
 261
 262        return pages;
 263}
 264
 265static unsigned long change_protection_range(struct vm_area_struct *vma,
 266                unsigned long addr, unsigned long end, pgprot_t newprot,
 267                int dirty_accountable, int prot_numa)
 268{
 269        struct mm_struct *mm = vma->vm_mm;
 270        pgd_t *pgd;
 271        unsigned long next;
 272        unsigned long start = addr;
 273        unsigned long pages = 0;
 274
 275        BUG_ON(addr >= end);
 276        pgd = pgd_offset(mm, addr);
 277        flush_cache_range(vma, addr, end);
 278        inc_tlb_flush_pending(mm);
 279        do {
 280                next = pgd_addr_end(addr, end);
 281                if (pgd_none_or_clear_bad(pgd))
 282                        continue;
 283                pages += change_p4d_range(vma, pgd, addr, next, newprot,
 284                                 dirty_accountable, prot_numa);
 285        } while (pgd++, addr = next, addr != end);
 286
 287        /* Only flush the TLB if we actually modified any entries: */
 288        if (pages)
 289                flush_tlb_range(vma, start, end);
 290        dec_tlb_flush_pending(mm);
 291
 292        return pages;
 293}
 294
 295unsigned long change_protection(struct vm_area_struct *vma, unsigned long start,
 296                       unsigned long end, pgprot_t newprot,
 297                       int dirty_accountable, int prot_numa)
 298{
 299        unsigned long pages;
 300
 301        if (is_vm_hugetlb_page(vma))
 302                pages = hugetlb_change_protection(vma, start, end, newprot);
 303        else
 304                pages = change_protection_range(vma, start, end, newprot, dirty_accountable, prot_numa);
 305
 306        return pages;
 307}
 308
 309static int prot_none_pte_entry(pte_t *pte, unsigned long addr,
 310                               unsigned long next, struct mm_walk *walk)
 311{
 312        return pfn_modify_allowed(pte_pfn(*pte), *(pgprot_t *)(walk->private)) ?
 313                0 : -EACCES;
 314}
 315
 316static int prot_none_hugetlb_entry(pte_t *pte, unsigned long hmask,
 317                                   unsigned long addr, unsigned long next,
 318                                   struct mm_walk *walk)
 319{
 320        return pfn_modify_allowed(pte_pfn(*pte), *(pgprot_t *)(walk->private)) ?
 321                0 : -EACCES;
 322}
 323
 324static int prot_none_test(unsigned long addr, unsigned long next,
 325                          struct mm_walk *walk)
 326{
 327        return 0;
 328}
 329
 330static int prot_none_walk(struct vm_area_struct *vma, unsigned long start,
 331                           unsigned long end, unsigned long newflags)
 332{
 333        pgprot_t new_pgprot = vm_get_page_prot(newflags);
 334        struct mm_walk prot_none_walk = {
 335                .pte_entry = prot_none_pte_entry,
 336                .hugetlb_entry = prot_none_hugetlb_entry,
 337                .test_walk = prot_none_test,
 338                .mm = current->mm,
 339                .private = &new_pgprot,
 340        };
 341
 342        return walk_page_range(start, end, &prot_none_walk);
 343}
 344
 345int
 346mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
 347        unsigned long start, unsigned long end, unsigned long newflags)
 348{
 349        struct mm_struct *mm = vma->vm_mm;
 350        unsigned long oldflags = vma->vm_flags;
 351        long nrpages = (end - start) >> PAGE_SHIFT;
 352        unsigned long charged = 0;
 353        pgoff_t pgoff;
 354        int error;
 355        int dirty_accountable = 0;
 356
 357        if (newflags == oldflags) {
 358                *pprev = vma;
 359                return 0;
 360        }
 361
 362        /*
 363         * Do PROT_NONE PFN permission checks here when we can still
 364         * bail out without undoing a lot of state. This is a rather
 365         * uncommon case, so doesn't need to be very optimized.
 366         */
 367        if (arch_has_pfn_modify_check() &&
 368            (vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
 369            (newflags & (VM_READ|VM_WRITE|VM_EXEC)) == 0) {
 370                error = prot_none_walk(vma, start, end, newflags);
 371                if (error)
 372                        return error;
 373        }
 374
 375        /*
 376         * If we make a private mapping writable we increase our commit;
 377         * but (without finer accounting) cannot reduce our commit if we
 378         * make it unwritable again. hugetlb mapping were accounted for
 379         * even if read-only so there is no need to account for them here
 380         */
 381        if (newflags & VM_WRITE) {
 382                /* Check space limits when area turns into data. */
 383                if (!may_expand_vm(mm, newflags, nrpages) &&
 384                                may_expand_vm(mm, oldflags, nrpages))
 385                        return -ENOMEM;
 386                if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_HUGETLB|
 387                                                VM_SHARED|VM_NORESERVE))) {
 388                        charged = nrpages;
 389                        if (security_vm_enough_memory_mm(mm, charged))
 390                                return -ENOMEM;
 391                        newflags |= VM_ACCOUNT;
 392                }
 393        }
 394
 395        /*
 396         * First try to merge with previous and/or next vma.
 397         */
 398        pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
 399        *pprev = vma_merge(mm, *pprev, start, end, newflags,
 400                           vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma),
 401                           vma->vm_userfaultfd_ctx);
 402        if (*pprev) {
 403                vma = *pprev;
 404                VM_WARN_ON((vma->vm_flags ^ newflags) & ~VM_SOFTDIRTY);
 405                goto success;
 406        }
 407
 408        *pprev = vma;
 409
 410        if (start != vma->vm_start) {
 411                error = split_vma(mm, vma, start, 1);
 412                if (error)
 413                        goto fail;
 414        }
 415
 416        if (end != vma->vm_end) {
 417                error = split_vma(mm, vma, end, 0);
 418                if (error)
 419                        goto fail;
 420        }
 421
 422success:
 423        /*
 424         * vm_flags and vm_page_prot are protected by the mmap_sem
 425         * held in write mode.
 426         */
 427        vma->vm_flags = newflags;
 428        dirty_accountable = vma_wants_writenotify(vma, vma->vm_page_prot);
 429        vma_set_page_prot(vma);
 430
 431        change_protection(vma, start, end, vma->vm_page_prot,
 432                          dirty_accountable, 0);
 433
 434        /*
 435         * Private VM_LOCKED VMA becoming writable: trigger COW to avoid major
 436         * fault on access.
 437         */
 438        if ((oldflags & (VM_WRITE | VM_SHARED | VM_LOCKED)) == VM_LOCKED &&
 439                        (newflags & VM_WRITE)) {
 440                populate_vma_page_range(vma, start, end, NULL);
 441        }
 442
 443        vm_stat_account(mm, oldflags, -nrpages);
 444        vm_stat_account(mm, newflags, nrpages);
 445        perf_event_mmap(vma);
 446        return 0;
 447
 448fail:
 449        vm_unacct_memory(charged);
 450        return error;
 451}
 452
 453/*
 454 * pkey==-1 when doing a legacy mprotect()
 455 */
 456static int do_mprotect_pkey(unsigned long start, size_t len,
 457                unsigned long prot, int pkey)
 458{
 459        unsigned long nstart, end, tmp, reqprot;
 460        struct vm_area_struct *vma, *prev;
 461        int error = -EINVAL;
 462        const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP);
 463        const bool rier = (current->personality & READ_IMPLIES_EXEC) &&
 464                                (prot & PROT_READ);
 465
 466        prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP);
 467        if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */
 468                return -EINVAL;
 469
 470        if (start & ~PAGE_MASK)
 471                return -EINVAL;
 472        if (!len)
 473                return 0;
 474        len = PAGE_ALIGN(len);
 475        end = start + len;
 476        if (end <= start)
 477                return -ENOMEM;
 478        if (!arch_validate_prot(prot, start))
 479                return -EINVAL;
 480
 481        reqprot = prot;
 482
 483        if (down_write_killable(&current->mm->mmap_sem))
 484                return -EINTR;
 485
 486        /*
 487         * If userspace did not allocate the pkey, do not let
 488         * them use it here.
 489         */
 490        error = -EINVAL;
 491        if ((pkey != -1) && !mm_pkey_is_allocated(current->mm, pkey))
 492                goto out;
 493
 494        vma = find_vma(current->mm, start);
 495        error = -ENOMEM;
 496        if (!vma)
 497                goto out;
 498        prev = vma->vm_prev;
 499        if (unlikely(grows & PROT_GROWSDOWN)) {
 500                if (vma->vm_start >= end)
 501                        goto out;
 502                start = vma->vm_start;
 503                error = -EINVAL;
 504                if (!(vma->vm_flags & VM_GROWSDOWN))
 505                        goto out;
 506        } else {
 507                if (vma->vm_start > start)
 508                        goto out;
 509                if (unlikely(grows & PROT_GROWSUP)) {
 510                        end = vma->vm_end;
 511                        error = -EINVAL;
 512                        if (!(vma->vm_flags & VM_GROWSUP))
 513                                goto out;
 514                }
 515        }
 516        if (start > vma->vm_start)
 517                prev = vma;
 518
 519        for (nstart = start ; ; ) {
 520                unsigned long mask_off_old_flags;
 521                unsigned long newflags;
 522                int new_vma_pkey;
 523
 524                /* Here we know that vma->vm_start <= nstart < vma->vm_end. */
 525
 526                /* Does the application expect PROT_READ to imply PROT_EXEC */
 527                if (rier && (vma->vm_flags & VM_MAYEXEC))
 528                        prot |= PROT_EXEC;
 529
 530                /*
 531                 * Each mprotect() call explicitly passes r/w/x permissions.
 532                 * If a permission is not passed to mprotect(), it must be
 533                 * cleared from the VMA.
 534                 */
 535                mask_off_old_flags = VM_READ | VM_WRITE | VM_EXEC |
 536                                        VM_FLAGS_CLEAR;
 537
 538                new_vma_pkey = arch_override_mprotect_pkey(vma, prot, pkey);
 539                newflags = calc_vm_prot_bits(prot, new_vma_pkey);
 540                newflags |= (vma->vm_flags & ~mask_off_old_flags);
 541
 542                /* newflags >> 4 shift VM_MAY% in place of VM_% */
 543                if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) {
 544                        error = -EACCES;
 545                        goto out;
 546                }
 547
 548                error = security_file_mprotect(vma, reqprot, prot);
 549                if (error)
 550                        goto out;
 551
 552                tmp = vma->vm_end;
 553                if (tmp > end)
 554                        tmp = end;
 555                error = mprotect_fixup(vma, &prev, nstart, tmp, newflags);
 556                if (error)
 557                        goto out;
 558                nstart = tmp;
 559
 560                if (nstart < prev->vm_end)
 561                        nstart = prev->vm_end;
 562                if (nstart >= end)
 563                        goto out;
 564
 565                vma = prev->vm_next;
 566                if (!vma || vma->vm_start != nstart) {
 567                        error = -ENOMEM;
 568                        goto out;
 569                }
 570                prot = reqprot;
 571        }
 572out:
 573        up_write(&current->mm->mmap_sem);
 574        return error;
 575}
 576
 577SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len,
 578                unsigned long, prot)
 579{
 580        return do_mprotect_pkey(start, len, prot, -1);
 581}
 582
 583#ifdef CONFIG_ARCH_HAS_PKEYS
 584
 585SYSCALL_DEFINE4(pkey_mprotect, unsigned long, start, size_t, len,
 586                unsigned long, prot, int, pkey)
 587{
 588        return do_mprotect_pkey(start, len, prot, pkey);
 589}
 590
 591SYSCALL_DEFINE2(pkey_alloc, unsigned long, flags, unsigned long, init_val)
 592{
 593        int pkey;
 594        int ret;
 595
 596        /* No flags supported yet. */
 597        if (flags)
 598                return -EINVAL;
 599        /* check for unsupported init values */
 600        if (init_val & ~PKEY_ACCESS_MASK)
 601                return -EINVAL;
 602
 603        down_write(&current->mm->mmap_sem);
 604        pkey = mm_pkey_alloc(current->mm);
 605
 606        ret = -ENOSPC;
 607        if (pkey == -1)
 608                goto out;
 609
 610        ret = arch_set_user_pkey_access(current, pkey, init_val);
 611        if (ret) {
 612                mm_pkey_free(current->mm, pkey);
 613                goto out;
 614        }
 615        ret = pkey;
 616out:
 617        up_write(&current->mm->mmap_sem);
 618        return ret;
 619}
 620
 621SYSCALL_DEFINE1(pkey_free, int, pkey)
 622{
 623        int ret;
 624
 625        down_write(&current->mm->mmap_sem);
 626        ret = mm_pkey_free(current->mm, pkey);
 627        up_write(&current->mm->mmap_sem);
 628
 629        /*
 630         * We could provie warnings or errors if any VMA still
 631         * has the pkey set here.
 632         */
 633        return ret;
 634}
 635
 636#endif /* CONFIG_ARCH_HAS_PKEYS */
 637