// SPDX-License-Identifier: GPL-2.0 /* * mm/mprotect.c * * (C) Copyright 1994 Linus Torvalds * (C) Copyright 2002 Christoph Hellwig * * Address space accounting code * (C) Copyright 2002 Red Hat Inc, All Rights Reserved */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include "internal.h" static inline bool can_change_pte_writable(struct vm_area_struct *vma, unsigned long addr, pte_t pte) { struct page *page; VM_BUG_ON(!(vma->vm_flags & VM_WRITE) || pte_write(pte)); if (pte_protnone(pte) || !pte_dirty(pte)) return false; /* Do we need write faults for softdirty tracking? */ if (vma_soft_dirty_enabled(vma) && !pte_soft_dirty(pte)) return false; /* Do we need write faults for uffd-wp tracking? */ if (userfaultfd_pte_wp(vma, pte)) return false; if (!(vma->vm_flags & VM_SHARED)) { /* * We can only special-case on exclusive anonymous pages, * because we know that our write-fault handler similarly would * map them writable without any additional checks while holding * the PT lock. */ page = vm_normal_page(vma, addr, pte); if (!page || !PageAnon(page) || !PageAnonExclusive(page)) return false; } return true; } static unsigned long change_pte_range(struct mmu_gather *tlb, struct vm_area_struct *vma, pmd_t *pmd, unsigned long addr, unsigned long end, pgprot_t newprot, unsigned long cp_flags) { pte_t *pte, oldpte; spinlock_t *ptl; unsigned long pages = 0; int target_node = NUMA_NO_NODE; bool prot_numa = cp_flags & MM_CP_PROT_NUMA; bool uffd_wp = cp_flags & MM_CP_UFFD_WP; bool uffd_wp_resolve = cp_flags & MM_CP_UFFD_WP_RESOLVE; tlb_change_page_size(tlb, PAGE_SIZE); /* * Can be called with only the mmap_lock for reading by * prot_numa so we must check the pmd isn't constantly * changing from under us from pmd_none to pmd_trans_huge * and/or the other way around. */ if (pmd_trans_unstable(pmd)) return 0; /* * The pmd points to a regular pte so the pmd can't change * from under us even if the mmap_lock is only hold for * reading. */ pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); /* Get target node for single threaded private VMAs */ if (prot_numa && !(vma->vm_flags & VM_SHARED) && atomic_read(&vma->vm_mm->mm_users) == 1) target_node = numa_node_id(); flush_tlb_batched_pending(vma->vm_mm); arch_enter_lazy_mmu_mode(); do { oldpte = *pte; if (pte_present(oldpte)) { pte_t ptent; bool preserve_write = prot_numa && pte_write(oldpte); /* * Avoid trapping faults against the zero or KSM * pages. See similar comment in change_huge_pmd. */ if (prot_numa) { struct page *page; int nid; bool toptier; /* Avoid TLB flush if possible */ if (pte_protnone(oldpte)) continue; page = vm_normal_page(vma, addr, oldpte); if (!page || is_zone_device_page(page) || PageKsm(page)) continue; /* Also skip shared copy-on-write pages */ if (is_cow_mapping(vma->vm_flags) && page_count(page) != 1) continue; /* * While migration can move some dirty pages, * it cannot move them all from MIGRATE_ASYNC * context. */ if (page_is_file_lru(page) && PageDirty(page)) continue; /* * Don't mess with PTEs if page is already on the node * a single-threaded process is running on. */ nid = page_to_nid(page); if (target_node == nid) continue; toptier = node_is_toptier(nid); /* * Skip scanning top tier node if normal numa * balancing is disabled */ if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_NORMAL) && toptier) continue; if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING && !toptier) xchg_page_access_time(page, jiffies_to_msecs(jiffies)); } oldpte = ptep_modify_prot_start(vma, addr, pte); ptent = pte_modify(oldpte, newprot); if (preserve_write) ptent = pte_mk_savedwrite(ptent); if (uffd_wp) { ptent = pte_wrprotect(ptent); ptent = pte_mkuffd_wp(ptent); } else if (uffd_wp_resolve) { ptent = pte_clear_uffd_wp(ptent); } /* * In some writable, shared mappings, we might want * to catch actual write access -- see * vma_wants_writenotify(). * * In all writable, private mappings, we have to * properly handle COW. * * In both cases, we can sometimes still change PTEs * writable and avoid the write-fault handler, for * example, if a PTE is already dirty and no other * COW or special handling is required. */ if ((cp_flags & MM_CP_TRY_CHANGE_WRITABLE) && !pte_write(ptent) && can_change_pte_writable(vma, addr, ptent)) ptent = pte_mkwrite(ptent); ptep_modify_prot_commit(vma, addr, pte, oldpte, ptent); if (pte_needs_flush(oldpte, ptent)) tlb_flush_pte_range(tlb, addr, PAGE_SIZE); pages++; } else if (is_swap_pte(oldpte)) { swp_entry_t entry = pte_to_swp_entry(oldpte); pte_t newpte; if (is_writable_migration_entry(entry)) { struct page *page = pfn_swap_entry_to_page(entry); /* * A protection check is difficult so * just be safe and disable write */ if (PageAnon(page)) entry = make_readable_exclusive_migration_entry( swp_offset(entry)); else entry = make_readable_migration_entry(swp_offset(entry)); newpte = swp_entry_to_pte(entry); if (pte_swp_soft_dirty(oldpte)) newpte = pte_swp_mksoft_dirty(newpte); if (pte_swp_uffd_wp(oldpte)) newpte = pte_swp_mkuffd_wp(newpte); } else if (is_writable_device_private_entry(entry)) { /* * We do not preserve soft-dirtiness. See * copy_one_pte() for explanation. */ entry = make_readable_device_private_entry( swp_offset(entry)); newpte = swp_entry_to_pte(entry); if (pte_swp_uffd_wp(oldpte)) newpte = pte_swp_mkuffd_wp(newpte); } else if (is_writable_device_exclusive_entry(entry)) { entry = make_readable_device_exclusive_entry( swp_offset(entry)); newpte = swp_entry_to_pte(entry); if (pte_swp_soft_dirty(oldpte)) newpte = pte_swp_mksoft_dirty(newpte); if (pte_swp_uffd_wp(oldpte)) newpte = pte_swp_mkuffd_wp(newpte); } else if (pte_marker_entry_uffd_wp(entry)) { /* * If this is uffd-wp pte marker and we'd like * to unprotect it, drop it; the next page * fault will trigger without uffd trapping. */ if (uffd_wp_resolve) { pte_clear(vma->vm_mm, addr, pte); pages++; } continue; } else { newpte = oldpte; } if (uffd_wp) newpte = pte_swp_mkuffd_wp(newpte); else if (uffd_wp_resolve) newpte = pte_swp_clear_uffd_wp(newpte); if (!pte_same(oldpte, newpte)) { set_pte_at(vma->vm_mm, addr, pte, newpte); pages++; } } else { /* It must be an none page, or what else?.. */ WARN_ON_ONCE(!pte_none(oldpte)); #ifdef CONFIG_PTE_MARKER_UFFD_WP if (unlikely(uffd_wp && !vma_is_anonymous(vma))) { /* * For file-backed mem, we need to be able to * wr-protect a none pte, because even if the * pte is none, the page/swap cache could * exist. Doing that by install a marker. */ set_pte_at(vma->vm_mm, addr, pte, make_pte_marker(PTE_MARKER_UFFD_WP)); pages++; } #endif } } while (pte++, addr += PAGE_SIZE, addr != end); arch_leave_lazy_mmu_mode(); pte_unmap_unlock(pte - 1, ptl); return pages; } /* * Used when setting automatic NUMA hinting protection where it is * critical that a numa hinting PMD is not confused with a bad PMD. */ static inline int pmd_none_or_clear_bad_unless_trans_huge(pmd_t *pmd) { pmd_t pmdval = pmd_read_atomic(pmd); /* See pmd_none_or_trans_huge_or_clear_bad for info on barrier */ #ifdef CONFIG_TRANSPARENT_HUGEPAGE barrier(); #endif if (pmd_none(pmdval)) return 1; if (pmd_trans_huge(pmdval)) return 0; if (unlikely(pmd_bad(pmdval))) { pmd_clear_bad(pmd); return 1; } return 0; } /* Return true if we're uffd wr-protecting file-backed memory, or false */ static inline bool uffd_wp_protect_file(struct vm_area_struct *vma, unsigned long cp_flags) { return (cp_flags & MM_CP_UFFD_WP) && !vma_is_anonymous(vma); } /* * If wr-protecting the range for file-backed, populate pgtable for the case * when pgtable is empty but page cache exists. When {pte|pmd|...}_alloc() * failed it means no memory, we don't have a better option but stop. */ #define change_pmd_prepare(vma, pmd, cp_flags) \ do { \ if (unlikely(uffd_wp_protect_file(vma, cp_flags))) { \ if (WARN_ON_ONCE(pte_alloc(vma->vm_mm, pmd))) \ break; \ } \ } while (0) /* * This is the general pud/p4d/pgd version of change_pmd_prepare(). We need to * have separate change_pmd_prepare() because pte_alloc() returns 0 on success, * while {pmd|pud|p4d}_alloc() returns the valid pointer on success. */ #define change_prepare(vma, high, low, addr, cp_flags) \ do { \ if (unlikely(uffd_wp_protect_file(vma, cp_flags))) { \ low##_t *p = low##_alloc(vma->vm_mm, high, addr); \ if (WARN_ON_ONCE(p == NULL)) \ break; \ } \ } while (0) static inline unsigned long change_pmd_range(struct mmu_gather *tlb, struct vm_area_struct *vma, pud_t *pud, unsigned long addr, unsigned long end, pgprot_t newprot, unsigned long cp_flags) { pmd_t *pmd; unsigned long next; unsigned long pages = 0; unsigned long nr_huge_updates = 0; struct mmu_notifier_range range; range.start = 0; pmd = pmd_offset(pud, addr); do { unsigned long this_pages; next = pmd_addr_end(addr, end); change_pmd_prepare(vma, pmd, cp_flags); /* * Automatic NUMA balancing walks the tables with mmap_lock * held for read. It's possible a parallel update to occur * between pmd_trans_huge() and a pmd_none_or_clear_bad() * check leading to a false positive and clearing. * Hence, it's necessary to atomically read the PMD value * for all the checks. */ if (!is_swap_pmd(*pmd) && !pmd_devmap(*pmd) && pmd_none_or_clear_bad_unless_trans_huge(pmd)) goto next; /* invoke the mmu notifier if the pmd is populated */ if (!range.start) { mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_VMA, 0, vma, vma->vm_mm, addr, end); mmu_notifier_invalidate_range_start(&range); } if (is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) || pmd_devmap(*pmd)) { if ((next - addr != HPAGE_PMD_SIZE) || uffd_wp_protect_file(vma, cp_flags)) { __split_huge_pmd(vma, pmd, addr, false, NULL); /* * For file-backed, the pmd could have been * cleared; make sure pmd populated if * necessary, then fall-through to pte level. */ change_pmd_prepare(vma, pmd, cp_flags); } else { /* * change_huge_pmd() does not defer TLB flushes, * so no need to propagate the tlb argument. */ int nr_ptes = change_huge_pmd(tlb, vma, pmd, addr, newprot, cp_flags); if (nr_ptes) { if (nr_ptes == HPAGE_PMD_NR) { pages += HPAGE_PMD_NR; nr_huge_updates++; } /* huge pmd was handled */ goto next; } } /* fall through, the trans huge pmd just split */ } this_pages = change_pte_range(tlb, vma, pmd, addr, next, newprot, cp_flags); pages += this_pages; next: cond_resched(); } while (pmd++, addr = next, addr != end); if (range.start) mmu_notifier_invalidate_range_end(&range); if (nr_huge_updates) count_vm_numa_events(NUMA_HUGE_PTE_UPDATES, nr_huge_updates); return pages; } static inline unsigned long change_pud_range(struct mmu_gather *tlb, struct vm_area_struct *vma, p4d_t *p4d, unsigned long addr, unsigned long end, pgprot_t newprot, unsigned long cp_flags) { pud_t *pud; unsigned long next; unsigned long pages = 0; pud = pud_offset(p4d, addr); do { next = pud_addr_end(addr, end); change_prepare(vma, pud, pmd, addr, cp_flags); if (pud_none_or_clear_bad(pud)) continue; pages += change_pmd_range(tlb, vma, pud, addr, next, newprot, cp_flags); } while (pud++, addr = next, addr != end); return pages; } static inline unsigned long change_p4d_range(struct mmu_gather *tlb, struct vm_area_struct *vma, pgd_t *pgd, unsigned long addr, unsigned long end, pgprot_t newprot, unsigned long cp_flags) { p4d_t *p4d; unsigned long next; unsigned long pages = 0; p4d = p4d_offset(pgd, addr); do { next = p4d_addr_end(addr, end); change_prepare(vma, p4d, pud, addr, cp_flags); if (p4d_none_or_clear_bad(p4d)) continue; pages += change_pud_range(tlb, vma, p4d, addr, next, newprot, cp_flags); } while (p4d++, addr = next, addr != end); return pages; } static unsigned long change_protection_range(struct mmu_gather *tlb, struct vm_area_struct *vma, unsigned long addr, unsigned long end, pgprot_t newprot, unsigned long cp_flags) { struct mm_struct *mm = vma->vm_mm; pgd_t *pgd; unsigned long next; unsigned long pages = 0; BUG_ON(addr >= end); pgd = pgd_offset(mm, addr); tlb_start_vma(tlb, vma); do { next = pgd_addr_end(addr, end); change_prepare(vma, pgd, p4d, addr, cp_flags); if (pgd_none_or_clear_bad(pgd)) continue; pages += change_p4d_range(tlb, vma, pgd, addr, next, newprot, cp_flags); } while (pgd++, addr = next, addr != end); tlb_end_vma(tlb, vma); return pages; } unsigned long change_protection(struct mmu_gather *tlb, struct vm_area_struct *vma, unsigned long start, unsigned long end, pgprot_t newprot, unsigned long cp_flags) { unsigned long pages; BUG_ON((cp_flags & MM_CP_UFFD_WP_ALL) == MM_CP_UFFD_WP_ALL); if (is_vm_hugetlb_page(vma)) pages = hugetlb_change_protection(vma, start, end, newprot, cp_flags); else pages = change_protection_range(tlb, vma, start, end, newprot, cp_flags); return pages; } static int prot_none_pte_entry(pte_t *pte, unsigned long addr, unsigned long next, struct mm_walk *walk) { return pfn_modify_allowed(pte_pfn(*pte), *(pgprot_t *)(walk->private)) ? 0 : -EACCES; } static int prot_none_hugetlb_entry(pte_t *pte, unsigned long hmask, unsigned long addr, unsigned long next, struct mm_walk *walk) { return pfn_modify_allowed(pte_pfn(*pte), *(pgprot_t *)(walk->private)) ? 0 : -EACCES; } static int prot_none_test(unsigned long addr, unsigned long next, struct mm_walk *walk) { return 0; } static const struct mm_walk_ops prot_none_walk_ops = { .pte_entry = prot_none_pte_entry, .hugetlb_entry = prot_none_hugetlb_entry, .test_walk = prot_none_test, }; int mprotect_fixup(struct mmu_gather *tlb, struct vm_area_struct *vma, struct vm_area_struct **pprev, unsigned long start, unsigned long end, unsigned long newflags) { struct mm_struct *mm = vma->vm_mm; unsigned long oldflags = vma->vm_flags; long nrpages = (end - start) >> PAGE_SHIFT; unsigned long charged = 0; bool try_change_writable; pgoff_t pgoff; int error; if (newflags == oldflags) { *pprev = vma; return 0; } /* * Do PROT_NONE PFN permission checks here when we can still * bail out without undoing a lot of state. This is a rather * uncommon case, so doesn't need to be very optimized. */ if (arch_has_pfn_modify_check() && (vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) && (newflags & VM_ACCESS_FLAGS) == 0) { pgprot_t new_pgprot = vm_get_page_prot(newflags); error = walk_page_range(current->mm, start, end, &prot_none_walk_ops, &new_pgprot); if (error) return error; } /* * If we make a private mapping writable we increase our commit; * but (without finer accounting) cannot reduce our commit if we * make it unwritable again. hugetlb mapping were accounted for * even if read-only so there is no need to account for them here */ if (newflags & VM_WRITE) { /* Check space limits when area turns into data. */ if (!may_expand_vm(mm, newflags, nrpages) && may_expand_vm(mm, oldflags, nrpages)) return -ENOMEM; if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_HUGETLB| VM_SHARED|VM_NORESERVE))) { charged = nrpages; if (security_vm_enough_memory_mm(mm, charged)) return -ENOMEM; newflags |= VM_ACCOUNT; } } /* * First try to merge with previous and/or next vma. */ pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT); *pprev = vma_merge(mm, *pprev, start, end, newflags, vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma), vma->vm_userfaultfd_ctx, anon_vma_name(vma)); if (*pprev) { vma = *pprev; VM_WARN_ON((vma->vm_flags ^ newflags) & ~VM_SOFTDIRTY); goto success; } *pprev = vma; if (start != vma->vm_start) { error = split_vma(mm, vma, start, 1); if (error) goto fail; } if (end != vma->vm_end) { error = split_vma(mm, vma, end, 0); if (error) goto fail; } success: /* * vm_flags and vm_page_prot are protected by the mmap_lock * held in write mode. */ vma->vm_flags = newflags; /* * We want to check manually if we can change individual PTEs writable * if we can't do that automatically for all PTEs in a mapping. For * private mappings, that's always the case when we have write * permissions as we properly have to handle COW. */ if (vma->vm_flags & VM_SHARED) try_change_writable = vma_wants_writenotify(vma, vma->vm_page_prot); else try_change_writable = !!(vma->vm_flags & VM_WRITE); vma_set_page_prot(vma); change_protection(tlb, vma, start, end, vma->vm_page_prot, try_change_writable ? MM_CP_TRY_CHANGE_WRITABLE : 0); /* * Private VM_LOCKED VMA becoming writable: trigger COW to avoid major * fault on access. */ if ((oldflags & (VM_WRITE | VM_SHARED | VM_LOCKED)) == VM_LOCKED && (newflags & VM_WRITE)) { populate_vma_page_range(vma, start, end, NULL); } vm_stat_account(mm, oldflags, -nrpages); vm_stat_account(mm, newflags, nrpages); perf_event_mmap(vma); return 0; fail: vm_unacct_memory(charged); return error; } /* * pkey==-1 when doing a legacy mprotect() */ static int do_mprotect_pkey(unsigned long start, size_t len, unsigned long prot, int pkey) { unsigned long nstart, end, tmp, reqprot; struct vm_area_struct *vma, *prev; int error; const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP); const bool rier = (current->personality & READ_IMPLIES_EXEC) && (prot & PROT_READ); struct mmu_gather tlb; MA_STATE(mas, ¤t->mm->mm_mt, 0, 0); start = untagged_addr(start); prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP); if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */ return -EINVAL; if (start & ~PAGE_MASK) return -EINVAL; if (!len) return 0; len = PAGE_ALIGN(len); end = start + len; if (end <= start) return -ENOMEM; if (!arch_validate_prot(prot, start)) return -EINVAL; reqprot = prot; if (mmap_write_lock_killable(current->mm)) return -EINTR; /* * If userspace did not allocate the pkey, do not let * them use it here. */ error = -EINVAL; if ((pkey != -1) && !mm_pkey_is_allocated(current->mm, pkey)) goto out; mas_set(&mas, start); vma = mas_find(&mas, ULONG_MAX); error = -ENOMEM; if (!vma) goto out; if (unlikely(grows & PROT_GROWSDOWN)) { if (vma->vm_start >= end) goto out; start = vma->vm_start; error = -EINVAL; if (!(vma->vm_flags & VM_GROWSDOWN)) goto out; } else { if (vma->vm_start > start) goto out; if (unlikely(grows & PROT_GROWSUP)) { end = vma->vm_end; error = -EINVAL; if (!(vma->vm_flags & VM_GROWSUP)) goto out; } } if (start > vma->vm_start) prev = vma; else prev = mas_prev(&mas, 0); tlb_gather_mmu(&tlb, current->mm); for (nstart = start ; ; ) { unsigned long mask_off_old_flags; unsigned long newflags; int new_vma_pkey; /* Here we know that vma->vm_start <= nstart < vma->vm_end. */ /* Does the application expect PROT_READ to imply PROT_EXEC */ if (rier && (vma->vm_flags & VM_MAYEXEC)) prot |= PROT_EXEC; /* * Each mprotect() call explicitly passes r/w/x permissions. * If a permission is not passed to mprotect(), it must be * cleared from the VMA. */ mask_off_old_flags = VM_READ | VM_WRITE | VM_EXEC | VM_FLAGS_CLEAR; new_vma_pkey = arch_override_mprotect_pkey(vma, prot, pkey); newflags = calc_vm_prot_bits(prot, new_vma_pkey); newflags |= (vma->vm_flags & ~mask_off_old_flags); /* newflags >> 4 shift VM_MAY% in place of VM_% */ if ((newflags & ~(newflags >> 4)) & VM_ACCESS_FLAGS) { error = -EACCES; break; } /* Allow architectures to sanity-check the new flags */ if (!arch_validate_flags(newflags)) { error = -EINVAL; break; } error = security_file_mprotect(vma, reqprot, prot); if (error) break; tmp = vma->vm_end; if (tmp > end) tmp = end; if (vma->vm_ops && vma->vm_ops->mprotect) { error = vma->vm_ops->mprotect(vma, nstart, tmp, newflags); if (error) break; } error = mprotect_fixup(&tlb, vma, &prev, nstart, tmp, newflags); if (error) break; nstart = tmp; if (nstart < prev->vm_end) nstart = prev->vm_end; if (nstart >= end) break; vma = find_vma(current->mm, prev->vm_end); if (!vma || vma->vm_start != nstart) { error = -ENOMEM; break; } prot = reqprot; } tlb_finish_mmu(&tlb); out: mmap_write_unlock(current->mm); return error; } SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len, unsigned long, prot) { return do_mprotect_pkey(start, len, prot, -1); } #ifdef CONFIG_ARCH_HAS_PKEYS SYSCALL_DEFINE4(pkey_mprotect, unsigned long, start, size_t, len, unsigned long, prot, int, pkey) { return do_mprotect_pkey(start, len, prot, pkey); } SYSCALL_DEFINE2(pkey_alloc, unsigned long, flags, unsigned long, init_val) { int pkey; int ret; /* No flags supported yet. */ if (flags) return -EINVAL; /* check for unsupported init values */ if (init_val & ~PKEY_ACCESS_MASK) return -EINVAL; mmap_write_lock(current->mm); pkey = mm_pkey_alloc(current->mm); ret = -ENOSPC; if (pkey == -1) goto out; ret = arch_set_user_pkey_access(current, pkey, init_val); if (ret) { mm_pkey_free(current->mm, pkey); goto out; } ret = pkey; out: mmap_write_unlock(current->mm); return ret; } SYSCALL_DEFINE1(pkey_free, int, pkey) { int ret; mmap_write_lock(current->mm); ret = mm_pkey_free(current->mm, pkey); mmap_write_unlock(current->mm); /* * We could provide warnings or errors if any VMA still * has the pkey set here. */ return ret; } #endif /* CONFIG_ARCH_HAS_PKEYS */