diff options
Diffstat (limited to 'mm/mprotect.c')
| -rw-r--r-- | mm/mprotect.c | 463 |
1 files changed, 287 insertions, 176 deletions
diff --git a/mm/mprotect.c b/mm/mprotect.c index 130db91d3a8c..283889e4f1ce 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -29,9 +29,8 @@ #include <linux/uaccess.h> #include <linux/mm_inline.h> #include <linux/pgtable.h> -#include <linux/sched/sysctl.h> #include <linux/userfaultfd_k.h> -#include <linux/memory-tiers.h> +#include <uapi/linux/mman.h> #include <asm/cacheflush.h> #include <asm/mmu_context.h> #include <asm/tlbflush.h> @@ -39,11 +38,8 @@ #include "internal.h" -bool can_change_pte_writable(struct vm_area_struct *vma, unsigned long addr, - pte_t pte) +static bool maybe_change_pte_writable(struct vm_area_struct *vma, pte_t pte) { - struct page *page; - if (WARN_ON_ONCE(!(vma->vm_flags & VM_WRITE))) return false; @@ -52,23 +48,41 @@ bool can_change_pte_writable(struct vm_area_struct *vma, unsigned long addr, return false; /* Do we need write faults for softdirty tracking? */ - if (vma_soft_dirty_enabled(vma) && !pte_soft_dirty(pte)) + if (pte_needs_soft_dirty_wp(vma, 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)) { - /* - * Writable MAP_PRIVATE mapping: 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); - return page && PageAnon(page) && PageAnonExclusive(page); - } + return true; +} + +static bool can_change_private_pte_writable(struct vm_area_struct *vma, + unsigned long addr, pte_t pte) +{ + struct page *page; + + if (!maybe_change_pte_writable(vma, pte)) + return false; + + /* + * Writable MAP_PRIVATE mapping: 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); + return page && PageAnon(page) && PageAnonExclusive(page); +} + +static bool can_change_shared_pte_writable(struct vm_area_struct *vma, + pte_t pte) +{ + if (!maybe_change_pte_writable(vma, pte)) + return false; + + VM_WARN_ON_ONCE(is_zero_pfn(pte_pfn(pte)) && pte_dirty(pte)); /* * Writable MAP_SHARED mapping: "clean" might indicate that the FS still @@ -80,6 +94,123 @@ bool can_change_pte_writable(struct vm_area_struct *vma, unsigned long addr, return pte_dirty(pte); } +bool can_change_pte_writable(struct vm_area_struct *vma, unsigned long addr, + pte_t pte) +{ + if (!(vma->vm_flags & VM_SHARED)) + return can_change_private_pte_writable(vma, addr, pte); + + return can_change_shared_pte_writable(vma, pte); +} + +static int mprotect_folio_pte_batch(struct folio *folio, pte_t *ptep, + pte_t pte, int max_nr_ptes, fpb_t flags) +{ + /* No underlying folio, so cannot batch */ + if (!folio) + return 1; + + if (!folio_test_large(folio)) + return 1; + + return folio_pte_batch_flags(folio, NULL, ptep, &pte, max_nr_ptes, flags); +} + +/* Set nr_ptes number of ptes, starting from idx */ +static void prot_commit_flush_ptes(struct vm_area_struct *vma, unsigned long addr, + pte_t *ptep, pte_t oldpte, pte_t ptent, int nr_ptes, + int idx, bool set_write, struct mmu_gather *tlb) +{ + /* + * Advance the position in the batch by idx; note that if idx > 0, + * then the nr_ptes passed here is <= batch size - idx. + */ + addr += idx * PAGE_SIZE; + ptep += idx; + oldpte = pte_advance_pfn(oldpte, idx); + ptent = pte_advance_pfn(ptent, idx); + + if (set_write) + ptent = pte_mkwrite(ptent, vma); + + modify_prot_commit_ptes(vma, addr, ptep, oldpte, ptent, nr_ptes); + if (pte_needs_flush(oldpte, ptent)) + tlb_flush_pte_range(tlb, addr, nr_ptes * PAGE_SIZE); +} + +/* + * Get max length of consecutive ptes pointing to PageAnonExclusive() pages or + * !PageAnonExclusive() pages, starting from start_idx. Caller must enforce + * that the ptes point to consecutive pages of the same anon large folio. + */ +static int page_anon_exclusive_sub_batch(int start_idx, int max_len, + struct page *first_page, bool expected_anon_exclusive) +{ + int idx; + + for (idx = start_idx + 1; idx < start_idx + max_len; ++idx) { + if (expected_anon_exclusive != PageAnonExclusive(first_page + idx)) + break; + } + return idx - start_idx; +} + +/* + * This function is a result of trying our very best to retain the + * "avoid the write-fault handler" optimization. In can_change_pte_writable(), + * if the vma is a private vma, and we cannot determine whether to change + * the pte to writable just from the vma and the pte, we then need to look + * at the actual page pointed to by the pte. Unfortunately, if we have a + * batch of ptes pointing to consecutive pages of the same anon large folio, + * the anon-exclusivity (or the negation) of the first page does not guarantee + * the anon-exclusivity (or the negation) of the other pages corresponding to + * the pte batch; hence in this case it is incorrect to decide to change or + * not change the ptes to writable just by using information from the first + * pte of the batch. Therefore, we must individually check all pages and + * retrieve sub-batches. + */ +static void commit_anon_folio_batch(struct vm_area_struct *vma, + struct folio *folio, struct page *first_page, unsigned long addr, pte_t *ptep, + pte_t oldpte, pte_t ptent, int nr_ptes, struct mmu_gather *tlb) +{ + bool expected_anon_exclusive; + int sub_batch_idx = 0; + int len; + + while (nr_ptes) { + expected_anon_exclusive = PageAnonExclusive(first_page + sub_batch_idx); + len = page_anon_exclusive_sub_batch(sub_batch_idx, nr_ptes, + first_page, expected_anon_exclusive); + prot_commit_flush_ptes(vma, addr, ptep, oldpte, ptent, len, + sub_batch_idx, expected_anon_exclusive, tlb); + sub_batch_idx += len; + nr_ptes -= len; + } +} + +static void set_write_prot_commit_flush_ptes(struct vm_area_struct *vma, + struct folio *folio, struct page *page, unsigned long addr, pte_t *ptep, + pte_t oldpte, pte_t ptent, int nr_ptes, struct mmu_gather *tlb) +{ + bool set_write; + + if (vma->vm_flags & VM_SHARED) { + set_write = can_change_shared_pte_writable(vma, ptent); + prot_commit_flush_ptes(vma, addr, ptep, oldpte, ptent, nr_ptes, + /* idx = */ 0, set_write, tlb); + return; + } + + set_write = maybe_change_pte_writable(vma, ptent) && + (folio && folio_test_anon(folio)); + if (!set_write) { + prot_commit_flush_ptes(vma, addr, ptep, oldpte, ptent, nr_ptes, + /* idx = */ 0, set_write, tlb); + return; + } + commit_anon_folio_batch(vma, folio, page, addr, ptep, oldpte, ptent, nr_ptes, tlb); +} + static 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) @@ -87,81 +218,57 @@ static long change_pte_range(struct mmu_gather *tlb, pte_t *pte, oldpte; spinlock_t *ptl; long pages = 0; - int target_node = NUMA_NO_NODE; + bool is_private_single_threaded; 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; + int nr_ptes; tlb_change_page_size(tlb, PAGE_SIZE); pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); if (!pte) return -EAGAIN; - /* 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(); + if (prot_numa) + is_private_single_threaded = vma_is_single_threaded_private(vma); flush_tlb_batched_pending(vma->vm_mm); arch_enter_lazy_mmu_mode(); do { + nr_ptes = 1; oldpte = ptep_get(pte); if (pte_present(oldpte)) { + const fpb_t flags = FPB_RESPECT_SOFT_DIRTY | FPB_RESPECT_WRITE; + int max_nr_ptes = (end - addr) >> PAGE_SHIFT; + struct folio *folio = NULL; + struct page *page; pte_t ptent; + /* Already in the desired state. */ + if (prot_numa && pte_protnone(oldpte)) + continue; + + page = vm_normal_page(vma, addr, oldpte); + if (page) + folio = page_folio(page); + /* * 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; + if (prot_numa && + !folio_can_map_prot_numa(folio, vma, + is_private_single_threaded)) { - 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)); + /* determine batch to skip */ + nr_ptes = mprotect_folio_pte_batch(folio, + pte, oldpte, max_nr_ptes, /* flags = */ 0); + continue; } - oldpte = ptep_modify_prot_start(vma, addr, pte); + nr_ptes = mprotect_folio_pte_batch(folio, pte, oldpte, max_nr_ptes, flags); + + oldpte = modify_prot_start_ptes(vma, addr, pte, nr_ptes); ptent = pte_modify(oldpte, newprot); if (uffd_wp) @@ -183,26 +290,44 @@ static long change_pte_range(struct mmu_gather *tlb, * 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_write(ptent)) + set_write_prot_commit_flush_ptes(vma, folio, page, + addr, pte, oldpte, ptent, nr_ptes, tlb); + else + prot_commit_flush_ptes(vma, addr, pte, oldpte, ptent, + nr_ptes, /* idx = */ 0, /* set_write = */ false, tlb); + pages += nr_ptes; + } else if (pte_none(oldpte)) { + /* + * Nobody plays with any none ptes besides + * userfaultfd when applying the protections. + */ + if (likely(!uffd_wp)) + continue; + + if (userfaultfd_wp_use_markers(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++; + } + } else { + softleaf_t entry = softleaf_from_pte(oldpte); pte_t newpte; - if (is_writable_migration_entry(entry)) { - struct page *page = pfn_swap_entry_to_page(entry); + if (softleaf_is_migration_write(entry)) { + const struct folio *folio = softleaf_to_folio(entry); /* * A protection check is difficult so * just be safe and disable write */ - if (PageAnon(page)) + if (folio_test_anon(folio)) entry = make_readable_exclusive_migration_entry( swp_offset(entry)); else @@ -210,7 +335,7 @@ static long change_pte_range(struct mmu_gather *tlb, newpte = swp_entry_to_pte(entry); if (pte_swp_soft_dirty(oldpte)) newpte = pte_swp_mksoft_dirty(newpte); - } else if (is_writable_device_private_entry(entry)) { + } else if (softleaf_is_device_private_write(entry)) { /* * We do not preserve soft-dirtiness. See * copy_nonpresent_pte() for explanation. @@ -220,20 +345,14 @@ static long change_pte_range(struct mmu_gather *tlb, 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 (is_pte_marker_entry(entry)) { + } else if (softleaf_is_marker(entry)) { /* * Ignore error swap entries unconditionally, - * because any access should sigbus anyway. + * because any access should sigbus/sigsegv + * anyway. */ - if (is_poisoned_swp_entry(entry)) + if (softleaf_is_poison_marker(entry) || + softleaf_is_guard_marker(entry)) continue; /* * If this is uffd-wp pte marker and we'd like @@ -258,30 +377,8 @@ static long change_pte_range(struct mmu_gather *tlb, 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)); - - /* - * Nobody plays with any none ptes besides - * userfaultfd when applying the protections. - */ - if (likely(!uffd_wp)) - continue; - - if (userfaultfd_wp_use_markers(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++; - } } - } while (pte++, addr += PAGE_SIZE, addr != end); + } while (pte += nr_ptes, addr += nr_ptes * PAGE_SIZE, addr != end); arch_leave_lazy_mmu_mode(); pte_unmap_unlock(pte - 1, ptl); @@ -297,8 +394,9 @@ pgtable_split_needed(struct vm_area_struct *vma, unsigned long cp_flags) { /* * pte markers only resides in pte level, if we need pte markers, - * we need to split. We cannot wr-protect shmem thp because file - * thp is handled differently when split by erasing the pmd so far. + * we need to split. For example, we cannot wr-protect a file thp + * (e.g. 2M shmem) because file thp is handled differently when + * split by erasing the pmd so far. */ return (cp_flags & MM_CP_UFFD_WP) && !vma_is_anonymous(vma); } @@ -358,9 +456,6 @@ static inline long change_pmd_range(struct mmu_gather *tlb, unsigned long next; long pages = 0; unsigned long nr_huge_updates = 0; - struct mmu_notifier_range range; - - range.start = 0; pmd = pmd_offset(pud, addr); do { @@ -378,19 +473,11 @@ again: if (pmd_none(*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->vm_mm, addr, end); - mmu_notifier_invalidate_range_start(&range); - } - _pmd = pmdp_get_lockless(pmd); - if (is_swap_pmd(_pmd) || pmd_trans_huge(_pmd) || pmd_devmap(_pmd)) { + if (pmd_is_huge(_pmd)) { if ((next - addr != HPAGE_PMD_SIZE) || pgtable_split_needed(vma, cp_flags)) { - __split_huge_pmd(vma, pmd, addr, false, NULL); + __split_huge_pmd(vma, pmd, addr, false); /* * For file-backed, the pmd could have been * cleared; make sure pmd populated if @@ -426,9 +513,6 @@ 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; @@ -438,21 +522,57 @@ static inline 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; + struct mmu_notifier_range range; + pud_t *pudp, pud; unsigned long next; long pages = 0, ret; - pud = pud_offset(p4d, addr); + range.start = 0; + + pudp = pud_offset(p4d, addr); do { +again: next = pud_addr_end(addr, end); - ret = change_prepare(vma, pud, pmd, addr, cp_flags); - if (ret) - return ret; - if (pud_none_or_clear_bad(pud)) + ret = change_prepare(vma, pudp, pmd, addr, cp_flags); + if (ret) { + pages = ret; + break; + } + + pud = pudp_get(pudp); + if (pud_none(pud)) continue; - pages += change_pmd_range(tlb, vma, pud, addr, next, newprot, + + if (!range.start) { + mmu_notifier_range_init(&range, + MMU_NOTIFY_PROTECTION_VMA, 0, + vma->vm_mm, addr, end); + mmu_notifier_invalidate_range_start(&range); + } + + if (pud_leaf(pud)) { + if ((next - addr != PUD_SIZE) || + pgtable_split_needed(vma, cp_flags)) { + __split_huge_pud(vma, pudp, addr); + goto again; + } else { + ret = change_huge_pud(tlb, vma, pudp, + addr, newprot, cp_flags); + if (ret == 0) + goto again; + /* huge pud was handled */ + if (ret == HPAGE_PUD_NR) + pages += HPAGE_PUD_NR; + continue; + } + } + + pages += change_pmd_range(tlb, vma, pudp, addr, next, newprot, cp_flags); - } while (pud++, addr = next, addr != end); + } while (pudp++, addr = next, addr != end); + + if (range.start) + mmu_notifier_invalidate_range_end(&range); return pages; } @@ -574,16 +694,18 @@ static const struct mm_walk_ops prot_none_walk_ops = { int mprotect_fixup(struct vma_iterator *vmi, struct mmu_gather *tlb, struct vm_area_struct *vma, struct vm_area_struct **pprev, - unsigned long start, unsigned long end, unsigned long newflags) + unsigned long start, unsigned long end, vm_flags_t newflags) { struct mm_struct *mm = vma->vm_mm; - unsigned long oldflags = vma->vm_flags; + vm_flags_t oldflags = READ_ONCE(vma->vm_flags); long nrpages = (end - start) >> PAGE_SHIFT; unsigned int mm_cp_flags = 0; unsigned long charged = 0; - pgoff_t pgoff; int error; + if (vma_is_sealed(vma)) + return -EPERM; + if (newflags == oldflags) { *pprev = vma; return 0; @@ -595,7 +717,7 @@ mprotect_fixup(struct vma_iterator *vmi, struct mmu_gather *tlb, * uncommon case, so doesn't need to be very optimized. */ if (arch_has_pfn_modify_check() && - (vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) && + (oldflags & (VM_PFNMAP|VM_MIXEDMAP)) && (newflags & VM_ACCESS_FLAGS) == 0) { pgprot_t new_pgprot = vm_get_page_prot(newflags); @@ -608,8 +730,11 @@ mprotect_fixup(struct vma_iterator *vmi, struct mmu_gather *tlb, /* * 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 + * make it unwritable again except in the anonymous case where no + * anon_vma has yet to be assigned. + * + * 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. */ @@ -623,48 +748,34 @@ mprotect_fixup(struct vma_iterator *vmi, struct mmu_gather *tlb, return -ENOMEM; newflags |= VM_ACCOUNT; } + } else if ((oldflags & VM_ACCOUNT) && vma_is_anonymous(vma) && + !vma->anon_vma) { + 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(vmi, 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; + vma = vma_modify_flags(vmi, *pprev, vma, start, end, &newflags); + if (IS_ERR(vma)) { + error = PTR_ERR(vma); + goto fail; } *pprev = vma; - if (start != vma->vm_start) { - error = split_vma(vmi, vma, start, 1); - if (error) - goto fail; - } - - if (end != vma->vm_end) { - error = split_vma(vmi, 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_start_write(vma); - vm_flags_reset(vma, newflags); + vm_flags_reset_once(vma, newflags); if (vma_wants_manual_pte_write_upgrade(vma)) mm_cp_flags |= MM_CP_TRY_CHANGE_WRITABLE; vma_set_page_prot(vma); change_protection(tlb, vma, start, end, mm_cp_flags); + if ((oldflags & VM_ACCOUNT) && !(newflags & VM_ACCOUNT)) + vm_unacct_memory(nrpages); + /* * Private VM_LOCKED VMA becoming writable: trigger COW to avoid major * fault on access. @@ -761,8 +872,8 @@ static int do_mprotect_pkey(unsigned long start, size_t len, nstart = start; tmp = vma->vm_start; for_each_vma_range(vmi, vma, end) { - unsigned long mask_off_old_flags; - unsigned long newflags; + vm_flags_t mask_off_old_flags; + vm_flags_t newflags; int new_vma_pkey; if (vma->vm_start != tmp) { @@ -791,7 +902,7 @@ static int do_mprotect_pkey(unsigned long start, size_t len, break; } - if (map_deny_write_exec(vma, newflags)) { + if (map_deny_write_exec(vma->vm_flags, newflags)) { error = -EACCES; break; } |