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        pte_t *pte, oldpte;
  43        spinlock_t *ptl;
  44        unsigned long pages = 0;
  45        int target_node = NUMA_NO_NODE;
  46
  47        /*
  48         * Can be called with only the mmap_sem for reading by
  49         * prot_numa so we must check the pmd isn't constantly
  50         * changing from under us from pmd_none to pmd_trans_huge
  51         * and/or the other way around.
  52         */
  53        if (pmd_trans_unstable(pmd))
  54                return 0;
  55
  56        /*
  57         * The pmd points to a regular pte so the pmd can't change
  58         * from under us even if the mmap_sem is only hold for
  59         * reading.
  60         */
  61        pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
  62
  63        /* Get target node for single threaded private VMAs */
  64        if (prot_numa && !(vma->vm_flags & VM_SHARED) &&
  65            atomic_read(&vma->vm_mm->mm_users) == 1)
  66                target_node = numa_node_id();
  67
  68        flush_tlb_batched_pending(vma->vm_mm);
  69        arch_enter_lazy_mmu_mode();
  70        do {
  71                oldpte = *pte;
  72                if (pte_present(oldpte)) {
  73                        pte_t ptent;
  74                        bool preserve_write = prot_numa && pte_write(oldpte);
  75
  76                        /*
  77                         * Avoid trapping faults against the zero or KSM
  78                         * pages. See similar comment in change_huge_pmd.
  79                         */
  80                        if (prot_numa) {
  81                                struct page *page;
  82
  83                                page = vm_normal_page(vma, addr, oldpte);
  84                                if (!page || PageKsm(page))
  85                                        continue;
  86
  87                                /* Also skip shared copy-on-write pages */
  88                                if (is_cow_mapping(vma->vm_flags) &&
  89                                    page_mapcount(page) != 1)
  90                                        continue;
  91
  92                                /*
  93                                 * While migration can move some dirty pages,
  94                                 * it cannot move them all from MIGRATE_ASYNC
  95                                 * context.
  96                                 */
  97                                if (page_is_file_cache(page) && PageDirty(page))
  98                                        continue;
  99
 100                                /* Avoid TLB flush if possible */
 101                                if (pte_protnone(oldpte))
 102                                        continue;
 103
 104                                /*
 105                                 * Don't mess with PTEs if page is already on the node
 106                                 * a single-threaded process is running on.
 107                                 */
 108                                if (target_node == page_to_nid(page))
 109                                        continue;
 110                        }
 111
 112                        oldpte = ptep_modify_prot_start(vma, addr, pte);
 113                        ptent = pte_modify(oldpte, newprot);
 114                        if (preserve_write)
 115                                ptent = pte_mk_savedwrite(ptent);
 116
 117                        /* Avoid taking write faults for known dirty pages */
 118                        if (dirty_accountable && pte_dirty(ptent) &&
 119                                        (pte_soft_dirty(ptent) ||
 120                                         !(vma->vm_flags & VM_SOFTDIRTY))) {
 121                                ptent = pte_mkwrite(ptent);
 122                        }
 123                        ptep_modify_prot_commit(vma, addr, pte, oldpte, ptent);
 124                        pages++;
 125                } else if (IS_ENABLED(CONFIG_MIGRATION)) {
 126                        swp_entry_t entry = pte_to_swp_entry(oldpte);
 127
 128                        if (is_write_migration_entry(entry)) {
 129                                pte_t newpte;
 130                                /*
 131                                 * A protection check is difficult so
 132                                 * just be safe and disable write
 133                                 */
 134                                make_migration_entry_read(&entry);
 135                                newpte = swp_entry_to_pte(entry);
 136                                if (pte_swp_soft_dirty(oldpte))
 137                                        newpte = pte_swp_mksoft_dirty(newpte);
 138                                set_pte_at(vma->vm_mm, addr, pte, newpte);
 139
 140                                pages++;
 141                        }
 142
 143                        if (is_write_device_private_entry(entry)) {
 144                                pte_t newpte;
 145
 146                                /*
 147                                 * We do not preserve soft-dirtiness. See
 148                                 * copy_one_pte() for explanation.
 149                                 */
 150                                make_device_private_entry_read(&entry);
 151                                newpte = swp_entry_to_pte(entry);
 152                                set_pte_at(vma->vm_mm, addr, pte, newpte);
 153
 154                                pages++;
 155                        }
 156                }
 157        } while (pte++, addr += PAGE_SIZE, addr != end);
 158        arch_leave_lazy_mmu_mode();
 159        pte_unmap_unlock(pte - 1, ptl);
 160
 161        return pages;
 162}
 163
 164static inline unsigned long change_pmd_range(struct vm_area_struct *vma,
 165                pud_t *pud, unsigned long addr, unsigned long end,
 166                pgprot_t newprot, int dirty_accountable, int prot_numa)
 167{
 168        pmd_t *pmd;
 169        unsigned long next;
 170        unsigned long pages = 0;
 171        unsigned long nr_huge_updates = 0;
 172        struct mmu_notifier_range range;
 173
 174        range.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 (!range.start) {
 187                        mmu_notifier_range_init(&range,
 188                                MMU_NOTIFY_PROTECTION_VMA, 0,
 189                                vma, vma->vm_mm, addr, end);
 190                        mmu_notifier_invalidate_range_start(&range);
 191                }
 192
 193                if (is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) || pmd_devmap(*pmd)) {
 194                        if (next - addr != HPAGE_PMD_SIZE) {
 195                                __split_huge_pmd(vma, pmd, addr, false, NULL);
 196                        } else {
 197                                int nr_ptes = change_huge_pmd(vma, pmd, addr,
 198                                                newprot, prot_numa);
 199
 200                                if (nr_ptes) {
 201                                        if (nr_ptes == HPAGE_PMD_NR) {
 202                                                pages += HPAGE_PMD_NR;
 203                                                nr_huge_updates++;
 204                                        }
 205
 206                                        /* huge pmd was handled */
 207                                        goto next;
 208                                }
 209                        }
 210                        /* fall through, the trans huge pmd just split */
 211                }
 212                this_pages = change_pte_range(vma, pmd, addr, next, newprot,
 213                                 dirty_accountable, prot_numa);
 214                pages += this_pages;
 215next:
 216                cond_resched();
 217        } while (pmd++, addr = next, addr != end);
 218
 219        if (range.start)
 220                mmu_notifier_invalidate_range_end(&range);
 221
 222        if (nr_huge_updates)
 223                count_vm_numa_events(NUMA_HUGE_PTE_UPDATES, nr_huge_updates);
 224        return pages;
 225}
 226
 227static inline unsigned long change_pud_range(struct vm_area_struct *vma,
 228                p4d_t *p4d, unsigned long addr, unsigned long end,
 229                pgprot_t newprot, int dirty_accountable, int prot_numa)
 230{
 231        pud_t *pud;
 232        unsigned long next;
 233        unsigned long pages = 0;
 234
 235        pud = pud_offset(p4d, addr);
 236        do {
 237                next = pud_addr_end(addr, end);
 238                if (pud_none_or_clear_bad(pud))
 239                        continue;
 240                pages += change_pmd_range(vma, pud, addr, next, newprot,
 241                                 dirty_accountable, prot_numa);
 242        } while (pud++, addr = next, addr != end);
 243
 244        return pages;
 245}
 246
 247static inline unsigned long change_p4d_range(struct vm_area_struct *vma,
 248                pgd_t *pgd, unsigned long addr, unsigned long end,
 249                pgprot_t newprot, int dirty_accountable, int prot_numa)
 250{
 251        p4d_t *p4d;
 252        unsigned long next;
 253        unsigned long pages = 0;
 254
 255        p4d = p4d_offset(pgd, addr);
 256        do {
 257                next = p4d_addr_end(addr, end);
 258                if (p4d_none_or_clear_bad(p4d))
 259                        continue;
 260                pages += change_pud_range(vma, p4d, addr, next, newprot,
 261                                 dirty_accountable, prot_numa);
 262        } while (p4d++, addr = next, addr != end);
 263
 264        return pages;
 265}
 266
 267static unsigned long change_protection_range(struct vm_area_struct *vma,
 268                unsigned long addr, unsigned long end, pgprot_t newprot,
 269                int dirty_accountable, int prot_numa)
 270{
 271        struct mm_struct *mm = vma->vm_mm;
 272        pgd_t *pgd;
 273        unsigned long next;
 274        unsigned long start = addr;
 275        unsigned long pages = 0;
 276
 277        BUG_ON(addr >= end);
 278        pgd = pgd_offset(mm, addr);
 279        flush_cache_range(vma, addr, end);
 280        inc_tlb_flush_pending(mm);
 281        do {
 282                next = pgd_addr_end(addr, end);
 283                if (pgd_none_or_clear_bad(pgd))
 284                        continue;
 285                pages += change_p4d_range(vma, pgd, addr, next, newprot,
 286                                 dirty_accountable, prot_numa);
 287        } while (pgd++, addr = next, addr != end);
 288
 289        /* Only flush the TLB if we actually modified any entries: */
 290        if (pages)
 291                flush_tlb_range(vma, start, end);
 292        dec_tlb_flush_pending(mm);
 293
 294        return pages;
 295}
 296
 297unsigned long change_protection(struct vm_area_struct *vma, unsigned long start,
 298                       unsigned long end, pgprot_t newprot,
 299                       int dirty_accountable, int prot_numa)
 300{
 301        unsigned long pages;
 302
 303        if (is_vm_hugetlb_page(vma))
 304                pages = hugetlb_change_protection(vma, start, end, newprot);
 305        else
 306                pages = change_protection_range(vma, start, end, newprot, dirty_accountable, prot_numa);
 307
 308        return pages;
 309}
 310
 311static int prot_none_pte_entry(pte_t *pte, unsigned long addr,
 312                               unsigned long next, struct mm_walk *walk)
 313{
 314        return pfn_modify_allowed(pte_pfn(*pte), *(pgprot_t *)(walk->private)) ?
 315                0 : -EACCES;
 316}
 317
 318static int prot_none_hugetlb_entry(pte_t *pte, unsigned long hmask,
 319                                   unsigned long addr, unsigned long next,
 320                                   struct mm_walk *walk)
 321{
 322        return pfn_modify_allowed(pte_pfn(*pte), *(pgprot_t *)(walk->private)) ?
 323                0 : -EACCES;
 324}
 325
 326static int prot_none_test(unsigned long addr, unsigned long next,
 327                          struct mm_walk *walk)
 328{
 329        return 0;
 330}
 331
 332static int prot_none_walk(struct vm_area_struct *vma, unsigned long start,
 333                           unsigned long end, unsigned long newflags)
 334{
 335        pgprot_t new_pgprot = vm_get_page_prot(newflags);
 336        struct mm_walk prot_none_walk = {
 337                .pte_entry = prot_none_pte_entry,
 338                .hugetlb_entry = prot_none_hugetlb_entry,
 339                .test_walk = prot_none_test,
 340                .mm = current->mm,
 341                .private = &new_pgprot,
 342        };
 343
 344        return walk_page_range(start, end, &prot_none_walk);
 345}
 346
 347int
 348mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
 349        unsigned long start, unsigned long end, unsigned long newflags)
 350{
 351        struct mm_struct *mm = vma->vm_mm;
 352        unsigned long oldflags = vma->vm_flags;
 353        long nrpages = (end - start) >> PAGE_SHIFT;
 354        unsigned long charged = 0;
 355        pgoff_t pgoff;
 356        int error;
 357        int dirty_accountable = 0;
 358
 359        if (newflags == oldflags) {
 360                *pprev = vma;
 361                return 0;
 362        }
 363
 364        /*
 365         * Do PROT_NONE PFN permission checks here when we can still
 366         * bail out without undoing a lot of state. This is a rather
 367         * uncommon case, so doesn't need to be very optimized.
 368         */
 369        if (arch_has_pfn_modify_check() &&
 370            (vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
 371            (newflags & (VM_READ|VM_WRITE|VM_EXEC)) == 0) {
 372                error = prot_none_walk(vma, start, end, newflags);
 373                if (error)
 374                        return error;
 375        }
 376
 377        /*
 378         * If we make a private mapping writable we increase our commit;
 379         * but (without finer accounting) cannot reduce our commit if we
 380         * make it unwritable again. hugetlb mapping were accounted for
 381         * even if read-only so there is no need to account for them here
 382         */
 383        if (newflags & VM_WRITE) {
 384                /* Check space limits when area turns into data. */
 385                if (!may_expand_vm(mm, newflags, nrpages) &&
 386                                may_expand_vm(mm, oldflags, nrpages))
 387                        return -ENOMEM;
 388                if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_HUGETLB|
 389                                                VM_SHARED|VM_NORESERVE))) {
 390                        charged = nrpages;
 391                        if (security_vm_enough_memory_mm(mm, charged))
 392                                return -ENOMEM;
 393                        newflags |= VM_ACCOUNT;
 394                }
 395        }
 396
 397        /*
 398         * First try to merge with previous and/or next vma.
 399         */
 400        pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
 401        *pprev = vma_merge(mm, *pprev, start, end, newflags,
 402                           vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma),
 403                           vma->vm_userfaultfd_ctx);
 404        if (*pprev) {
 405                vma = *pprev;
 406                VM_WARN_ON((vma->vm_flags ^ newflags) & ~VM_SOFTDIRTY);
 407                goto success;
 408        }
 409
 410        *pprev = vma;
 411
 412        if (start != vma->vm_start) {
 413                error = split_vma(mm, vma, start, 1);
 414                if (error)
 415                        goto fail;
 416        }
 417
 418        if (end != vma->vm_end) {
 419                error = split_vma(mm, vma, end, 0);
 420                if (error)
 421                        goto fail;
 422        }
 423
 424success:
 425        /*
 426         * vm_flags and vm_page_prot are protected by the mmap_sem
 427         * held in write mode.
 428         */
 429        vma->vm_flags = newflags;
 430        dirty_accountable = vma_wants_writenotify(vma, vma->vm_page_prot);
 431        vma_set_page_prot(vma);
 432
 433        change_protection(vma, start, end, vma->vm_page_prot,
 434                          dirty_accountable, 0);
 435
 436        /*
 437         * Private VM_LOCKED VMA becoming writable: trigger COW to avoid major
 438         * fault on access.
 439         */
 440        if ((oldflags & (VM_WRITE | VM_SHARED | VM_LOCKED)) == VM_LOCKED &&
 441                        (newflags & VM_WRITE)) {
 442                populate_vma_page_range(vma, start, end, NULL);
 443        }
 444
 445        vm_stat_account(mm, oldflags, -nrpages);
 446        vm_stat_account(mm, newflags, nrpages);
 447        perf_event_mmap(vma);
 448        return 0;
 449
 450fail:
 451        vm_unacct_memory(charged);
 452        return error;
 453}
 454
 455/*
 456 * pkey==-1 when doing a legacy mprotect()
 457 */
 458static int do_mprotect_pkey(unsigned long start, size_t len,
 459                unsigned long prot, int pkey)
 460{
 461        unsigned long nstart, end, tmp, reqprot;
 462        struct vm_area_struct *vma, *prev;
 463        int error = -EINVAL;
 464        const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP);
 465        const bool rier = (current->personality & READ_IMPLIES_EXEC) &&
 466                                (prot & PROT_READ);
 467
 468        prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP);
 469        if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */
 470                return -EINVAL;
 471
 472        if (start & ~PAGE_MASK)
 473                return -EINVAL;
 474        if (!len)
 475                return 0;
 476        len = PAGE_ALIGN(len);
 477        end = start + len;
 478        if (end <= start)
 479                return -ENOMEM;
 480        if (!arch_validate_prot(prot, start))
 481                return -EINVAL;
 482
 483        reqprot = prot;
 484
 485        if (down_write_killable(&current->mm->mmap_sem))
 486                return -EINTR;
 487
 488        /*
 489         * If userspace did not allocate the pkey, do not let
 490         * them use it here.
 491         */
 492        error = -EINVAL;
 493        if ((pkey != -1) && !mm_pkey_is_allocated(current->mm, pkey))
 494                goto out;
 495
 496        vma = find_vma(current->mm, start);
 497        error = -ENOMEM;
 498        if (!vma)
 499                goto out;
 500        prev = vma->vm_prev;
 501        if (unlikely(grows & PROT_GROWSDOWN)) {
 502                if (vma->vm_start >= end)
 503                        goto out;
 504                start = vma->vm_start;
 505                error = -EINVAL;
 506                if (!(vma->vm_flags & VM_GROWSDOWN))
 507                        goto out;
 508        } else {
 509                if (vma->vm_start > start)
 510                        goto out;
 511                if (unlikely(grows & PROT_GROWSUP)) {
 512                        end = vma->vm_end;
 513                        error = -EINVAL;
 514                        if (!(vma->vm_flags & VM_GROWSUP))
 515                                goto out;
 516                }
 517        }
 518        if (start > vma->vm_start)
 519                prev = vma;
 520
 521        for (nstart = start ; ; ) {
 522                unsigned long mask_off_old_flags;
 523                unsigned long newflags;
 524                int new_vma_pkey;
 525
 526                /* Here we know that vma->vm_start <= nstart < vma->vm_end. */
 527
 528                /* Does the application expect PROT_READ to imply PROT_EXEC */
 529                if (rier && (vma->vm_flags & VM_MAYEXEC))
 530                        prot |= PROT_EXEC;
 531
 532                /*
 533                 * Each mprotect() call explicitly passes r/w/x permissions.
 534                 * If a permission is not passed to mprotect(), it must be
 535                 * cleared from the VMA.
 536                 */
 537                mask_off_old_flags = VM_READ | VM_WRITE | VM_EXEC |
 538                                        VM_FLAGS_CLEAR;
 539
 540                new_vma_pkey = arch_override_mprotect_pkey(vma, prot, pkey);
 541                newflags = calc_vm_prot_bits(prot, new_vma_pkey);
 542                newflags |= (vma->vm_flags & ~mask_off_old_flags);
 543
 544                /* newflags >> 4 shift VM_MAY% in place of VM_% */
 545                if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) {
 546                        error = -EACCES;
 547                        goto out;
 548                }
 549
 550                error = security_file_mprotect(vma, reqprot, prot);
 551                if (error)
 552                        goto out;
 553
 554                tmp = vma->vm_end;
 555                if (tmp > end)
 556                        tmp = end;
 557                error = mprotect_fixup(vma, &prev, nstart, tmp, newflags);
 558                if (error)
 559                        goto out;
 560                nstart = tmp;
 561
 562                if (nstart < prev->vm_end)
 563                        nstart = prev->vm_end;
 564                if (nstart >= end)
 565                        goto out;
 566
 567                vma = prev->vm_next;
 568                if (!vma || vma->vm_start != nstart) {
 569                        error = -ENOMEM;
 570                        goto out;
 571                }
 572                prot = reqprot;
 573        }
 574out:
 575        up_write(&current->mm->mmap_sem);
 576        return error;
 577}
 578
 579SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len,
 580                unsigned long, prot)
 581{
 582        return do_mprotect_pkey(start, len, prot, -1);
 583}
 584
 585#ifdef CONFIG_ARCH_HAS_PKEYS
 586
 587SYSCALL_DEFINE4(pkey_mprotect, unsigned long, start, size_t, len,
 588                unsigned long, prot, int, pkey)
 589{
 590        return do_mprotect_pkey(start, len, prot, pkey);
 591}
 592
 593SYSCALL_DEFINE2(pkey_alloc, unsigned long, flags, unsigned long, init_val)
 594{
 595        int pkey;
 596        int ret;
 597
 598        /* No flags supported yet. */
 599        if (flags)
 600                return -EINVAL;
 601        /* check for unsupported init values */
 602        if (init_val & ~PKEY_ACCESS_MASK)
 603                return -EINVAL;
 604
 605        down_write(&current->mm->mmap_sem);
 606        pkey = mm_pkey_alloc(current->mm);
 607
 608        ret = -ENOSPC;
 609        if (pkey == -1)
 610                goto out;
 611
 612        ret = arch_set_user_pkey_access(current, pkey, init_val);
 613        if (ret) {
 614                mm_pkey_free(current->mm, pkey);
 615                goto out;
 616        }
 617        ret = pkey;
 618out:
 619        up_write(&current->mm->mmap_sem);
 620        return ret;
 621}
 622
 623SYSCALL_DEFINE1(pkey_free, int, pkey)
 624{
 625        int ret;
 626
 627        down_write(&current->mm->mmap_sem);
 628        ret = mm_pkey_free(current->mm, pkey);
 629        up_write(&current->mm->mmap_sem);
 630
 631        /*
 632         * We could provie warnings or errors if any VMA still
 633         * has the pkey set here.
 634         */
 635        return ret;
 636}
 637
 638#endif /* CONFIG_ARCH_HAS_PKEYS */
 639