| // SPDX-License-Identifier: GPL-2.0 |
| /* |
| * mm/mremap.c |
| * |
| * (C) Copyright 1996 Linus Torvalds |
| * |
| * Address space accounting code <alan@lxorguk.ukuu.org.uk> |
| * (C) Copyright 2002 Red Hat Inc, All Rights Reserved |
| */ |
| |
| #include <linux/mm.h> |
| #include <linux/hugetlb.h> |
| #include <linux/shm.h> |
| #include <linux/ksm.h> |
| #include <linux/mman.h> |
| #include <linux/swap.h> |
| #include <linux/capability.h> |
| #include <linux/fs.h> |
| #include <linux/swapops.h> |
| #include <linux/highmem.h> |
| #include <linux/security.h> |
| #include <linux/syscalls.h> |
| #include <linux/mmu_notifier.h> |
| #include <linux/uaccess.h> |
| #include <linux/userfaultfd_k.h> |
| |
| #include <asm/cacheflush.h> |
| #include <asm/tlb.h> |
| #include <asm/pgalloc.h> |
| |
| #include "internal.h" |
| |
| static pud_t *get_old_pud(struct mm_struct *mm, unsigned long addr) |
| { |
| pgd_t *pgd; |
| p4d_t *p4d; |
| pud_t *pud; |
| |
| pgd = pgd_offset(mm, addr); |
| if (pgd_none_or_clear_bad(pgd)) |
| return NULL; |
| |
| p4d = p4d_offset(pgd, addr); |
| if (p4d_none_or_clear_bad(p4d)) |
| return NULL; |
| |
| pud = pud_offset(p4d, addr); |
| if (pud_none_or_clear_bad(pud)) |
| return NULL; |
| |
| return pud; |
| } |
| |
| static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr) |
| { |
| pud_t *pud; |
| pmd_t *pmd; |
| |
| pud = get_old_pud(mm, addr); |
| if (!pud) |
| return NULL; |
| |
| pmd = pmd_offset(pud, addr); |
| if (pmd_none(*pmd)) |
| return NULL; |
| |
| return pmd; |
| } |
| |
| static pud_t *alloc_new_pud(struct mm_struct *mm, struct vm_area_struct *vma, |
| unsigned long addr) |
| { |
| pgd_t *pgd; |
| p4d_t *p4d; |
| |
| pgd = pgd_offset(mm, addr); |
| p4d = p4d_alloc(mm, pgd, addr); |
| if (!p4d) |
| return NULL; |
| |
| return pud_alloc(mm, p4d, addr); |
| } |
| |
| static pmd_t *alloc_new_pmd(struct mm_struct *mm, struct vm_area_struct *vma, |
| unsigned long addr) |
| { |
| pud_t *pud; |
| pmd_t *pmd; |
| |
| pud = alloc_new_pud(mm, vma, addr); |
| if (!pud) |
| return NULL; |
| |
| pmd = pmd_alloc(mm, pud, addr); |
| if (!pmd) |
| return NULL; |
| |
| VM_BUG_ON(pmd_trans_huge(*pmd)); |
| |
| return pmd; |
| } |
| |
| static void take_rmap_locks(struct vm_area_struct *vma) |
| { |
| if (vma->vm_file) |
| i_mmap_lock_write(vma->vm_file->f_mapping); |
| if (vma->anon_vma) |
| anon_vma_lock_write(vma->anon_vma); |
| } |
| |
| static void drop_rmap_locks(struct vm_area_struct *vma) |
| { |
| if (vma->anon_vma) |
| anon_vma_unlock_write(vma->anon_vma); |
| if (vma->vm_file) |
| i_mmap_unlock_write(vma->vm_file->f_mapping); |
| } |
| |
| static pte_t move_soft_dirty_pte(pte_t pte) |
| { |
| /* |
| * Set soft dirty bit so we can notice |
| * in userspace the ptes were moved. |
| */ |
| #ifdef CONFIG_MEM_SOFT_DIRTY |
| if (pte_present(pte)) |
| pte = pte_mksoft_dirty(pte); |
| else if (is_swap_pte(pte)) |
| pte = pte_swp_mksoft_dirty(pte); |
| #endif |
| return pte; |
| } |
| |
| static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd, |
| unsigned long old_addr, unsigned long old_end, |
| struct vm_area_struct *new_vma, pmd_t *new_pmd, |
| unsigned long new_addr, bool need_rmap_locks) |
| { |
| struct mm_struct *mm = vma->vm_mm; |
| pte_t *old_pte, *new_pte, pte; |
| spinlock_t *old_ptl, *new_ptl; |
| bool force_flush = false; |
| unsigned long len = old_end - old_addr; |
| |
| /* |
| * When need_rmap_locks is true, we take the i_mmap_rwsem and anon_vma |
| * locks to ensure that rmap will always observe either the old or the |
| * new ptes. This is the easiest way to avoid races with |
| * truncate_pagecache(), page migration, etc... |
| * |
| * When need_rmap_locks is false, we use other ways to avoid |
| * such races: |
| * |
| * - During exec() shift_arg_pages(), we use a specially tagged vma |
| * which rmap call sites look for using vma_is_temporary_stack(). |
| * |
| * - During mremap(), new_vma is often known to be placed after vma |
| * in rmap traversal order. This ensures rmap will always observe |
| * either the old pte, or the new pte, or both (the page table locks |
| * serialize access to individual ptes, but only rmap traversal |
| * order guarantees that we won't miss both the old and new ptes). |
| */ |
| if (need_rmap_locks) |
| take_rmap_locks(vma); |
| |
| /* |
| * We don't have to worry about the ordering of src and dst |
| * pte locks because exclusive mmap_lock prevents deadlock. |
| */ |
| old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl); |
| new_pte = pte_offset_map(new_pmd, new_addr); |
| new_ptl = pte_lockptr(mm, new_pmd); |
| if (new_ptl != old_ptl) |
| spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); |
| flush_tlb_batched_pending(vma->vm_mm); |
| arch_enter_lazy_mmu_mode(); |
| |
| for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE, |
| new_pte++, new_addr += PAGE_SIZE) { |
| if (pte_none(*old_pte)) |
| continue; |
| |
| pte = ptep_get_and_clear(mm, old_addr, old_pte); |
| /* |
| * If we are remapping a valid PTE, make sure |
| * to flush TLB before we drop the PTL for the |
| * PTE. |
| * |
| * NOTE! Both old and new PTL matter: the old one |
| * for racing with page_mkclean(), the new one to |
| * make sure the physical page stays valid until |
| * the TLB entry for the old mapping has been |
| * flushed. |
| */ |
| if (pte_present(pte)) |
| force_flush = true; |
| pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr); |
| pte = move_soft_dirty_pte(pte); |
| set_pte_at(mm, new_addr, new_pte, pte); |
| } |
| |
| arch_leave_lazy_mmu_mode(); |
| if (force_flush) |
| flush_tlb_range(vma, old_end - len, old_end); |
| if (new_ptl != old_ptl) |
| spin_unlock(new_ptl); |
| pte_unmap(new_pte - 1); |
| pte_unmap_unlock(old_pte - 1, old_ptl); |
| if (need_rmap_locks) |
| drop_rmap_locks(vma); |
| } |
| |
| #ifndef arch_supports_page_table_move |
| #define arch_supports_page_table_move arch_supports_page_table_move |
| static inline bool arch_supports_page_table_move(void) |
| { |
| return IS_ENABLED(CONFIG_HAVE_MOVE_PMD) || |
| IS_ENABLED(CONFIG_HAVE_MOVE_PUD); |
| } |
| #endif |
| |
| #ifdef CONFIG_HAVE_MOVE_PMD |
| static bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr, |
| unsigned long new_addr, pmd_t *old_pmd, pmd_t *new_pmd) |
| { |
| spinlock_t *old_ptl, *new_ptl; |
| struct mm_struct *mm = vma->vm_mm; |
| pmd_t pmd; |
| |
| if (!arch_supports_page_table_move()) |
| return false; |
| /* |
| * The destination pmd shouldn't be established, free_pgtables() |
| * should have released it. |
| * |
| * However, there's a case during execve() where we use mremap |
| * to move the initial stack, and in that case the target area |
| * may overlap the source area (always moving down). |
| * |
| * If everything is PMD-aligned, that works fine, as moving |
| * each pmd down will clear the source pmd. But if we first |
| * have a few 4kB-only pages that get moved down, and then |
| * hit the "now the rest is PMD-aligned, let's do everything |
| * one pmd at a time", we will still have the old (now empty |
| * of any 4kB pages, but still there) PMD in the page table |
| * tree. |
| * |
| * Warn on it once - because we really should try to figure |
| * out how to do this better - but then say "I won't move |
| * this pmd". |
| * |
| * One alternative might be to just unmap the target pmd at |
| * this point, and verify that it really is empty. We'll see. |
| */ |
| if (WARN_ON_ONCE(!pmd_none(*new_pmd))) |
| return false; |
| |
| /* |
| * We don't have to worry about the ordering of src and dst |
| * ptlocks because exclusive mmap_lock prevents deadlock. |
| */ |
| old_ptl = pmd_lock(vma->vm_mm, old_pmd); |
| new_ptl = pmd_lockptr(mm, new_pmd); |
| if (new_ptl != old_ptl) |
| spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); |
| |
| /* Clear the pmd */ |
| pmd = *old_pmd; |
| pmd_clear(old_pmd); |
| |
| VM_BUG_ON(!pmd_none(*new_pmd)); |
| |
| pmd_populate(mm, new_pmd, pmd_pgtable(pmd)); |
| flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE); |
| if (new_ptl != old_ptl) |
| spin_unlock(new_ptl); |
| spin_unlock(old_ptl); |
| |
| return true; |
| } |
| #else |
| static inline bool move_normal_pmd(struct vm_area_struct *vma, |
| unsigned long old_addr, unsigned long new_addr, pmd_t *old_pmd, |
| pmd_t *new_pmd) |
| { |
| return false; |
| } |
| #endif |
| |
| #if CONFIG_PGTABLE_LEVELS > 2 && defined(CONFIG_HAVE_MOVE_PUD) |
| static bool move_normal_pud(struct vm_area_struct *vma, unsigned long old_addr, |
| unsigned long new_addr, pud_t *old_pud, pud_t *new_pud) |
| { |
| spinlock_t *old_ptl, *new_ptl; |
| struct mm_struct *mm = vma->vm_mm; |
| pud_t pud; |
| |
| if (!arch_supports_page_table_move()) |
| return false; |
| /* |
| * The destination pud shouldn't be established, free_pgtables() |
| * should have released it. |
| */ |
| if (WARN_ON_ONCE(!pud_none(*new_pud))) |
| return false; |
| |
| /* |
| * We don't have to worry about the ordering of src and dst |
| * ptlocks because exclusive mmap_lock prevents deadlock. |
| */ |
| old_ptl = pud_lock(vma->vm_mm, old_pud); |
| new_ptl = pud_lockptr(mm, new_pud); |
| if (new_ptl != old_ptl) |
| spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); |
| |
| /* Clear the pud */ |
| pud = *old_pud; |
| pud_clear(old_pud); |
| |
| VM_BUG_ON(!pud_none(*new_pud)); |
| |
| pud_populate(mm, new_pud, pud_pgtable(pud)); |
| flush_tlb_range(vma, old_addr, old_addr + PUD_SIZE); |
| if (new_ptl != old_ptl) |
| spin_unlock(new_ptl); |
| spin_unlock(old_ptl); |
| |
| return true; |
| } |
| #else |
| static inline bool move_normal_pud(struct vm_area_struct *vma, |
| unsigned long old_addr, unsigned long new_addr, pud_t *old_pud, |
| pud_t *new_pud) |
| { |
| return false; |
| } |
| #endif |
| |
| #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD |
| static bool move_huge_pud(struct vm_area_struct *vma, unsigned long old_addr, |
| unsigned long new_addr, pud_t *old_pud, pud_t *new_pud) |
| { |
| spinlock_t *old_ptl, *new_ptl; |
| struct mm_struct *mm = vma->vm_mm; |
| pud_t pud; |
| |
| /* |
| * The destination pud shouldn't be established, free_pgtables() |
| * should have released it. |
| */ |
| if (WARN_ON_ONCE(!pud_none(*new_pud))) |
| return false; |
| |
| /* |
| * We don't have to worry about the ordering of src and dst |
| * ptlocks because exclusive mmap_lock prevents deadlock. |
| */ |
| old_ptl = pud_lock(vma->vm_mm, old_pud); |
| new_ptl = pud_lockptr(mm, new_pud); |
| if (new_ptl != old_ptl) |
| spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); |
| |
| /* Clear the pud */ |
| pud = *old_pud; |
| pud_clear(old_pud); |
| |
| VM_BUG_ON(!pud_none(*new_pud)); |
| |
| /* Set the new pud */ |
| /* mark soft_ditry when we add pud level soft dirty support */ |
| set_pud_at(mm, new_addr, new_pud, pud); |
| flush_pud_tlb_range(vma, old_addr, old_addr + HPAGE_PUD_SIZE); |
| if (new_ptl != old_ptl) |
| spin_unlock(new_ptl); |
| spin_unlock(old_ptl); |
| |
| return true; |
| } |
| #else |
| static bool move_huge_pud(struct vm_area_struct *vma, unsigned long old_addr, |
| unsigned long new_addr, pud_t *old_pud, pud_t *new_pud) |
| { |
| WARN_ON_ONCE(1); |
| return false; |
| |
| } |
| #endif |
| |
| enum pgt_entry { |
| NORMAL_PMD, |
| HPAGE_PMD, |
| NORMAL_PUD, |
| HPAGE_PUD, |
| }; |
| |
| /* |
| * Returns an extent of the corresponding size for the pgt_entry specified if |
| * valid. Else returns a smaller extent bounded by the end of the source and |
| * destination pgt_entry. |
| */ |
| static __always_inline unsigned long get_extent(enum pgt_entry entry, |
| unsigned long old_addr, unsigned long old_end, |
| unsigned long new_addr) |
| { |
| unsigned long next, extent, mask, size; |
| |
| switch (entry) { |
| case HPAGE_PMD: |
| case NORMAL_PMD: |
| mask = PMD_MASK; |
| size = PMD_SIZE; |
| break; |
| case HPAGE_PUD: |
| case NORMAL_PUD: |
| mask = PUD_MASK; |
| size = PUD_SIZE; |
| break; |
| default: |
| BUILD_BUG(); |
| break; |
| } |
| |
| next = (old_addr + size) & mask; |
| /* even if next overflowed, extent below will be ok */ |
| extent = next - old_addr; |
| if (extent > old_end - old_addr) |
| extent = old_end - old_addr; |
| next = (new_addr + size) & mask; |
| if (extent > next - new_addr) |
| extent = next - new_addr; |
| return extent; |
| } |
| |
| /* |
| * Attempts to speedup the move by moving entry at the level corresponding to |
| * pgt_entry. Returns true if the move was successful, else false. |
| */ |
| static bool move_pgt_entry(enum pgt_entry entry, struct vm_area_struct *vma, |
| unsigned long old_addr, unsigned long new_addr, |
| void *old_entry, void *new_entry, bool need_rmap_locks) |
| { |
| bool moved = false; |
| |
| /* See comment in move_ptes() */ |
| if (need_rmap_locks) |
| take_rmap_locks(vma); |
| |
| switch (entry) { |
| case NORMAL_PMD: |
| moved = move_normal_pmd(vma, old_addr, new_addr, old_entry, |
| new_entry); |
| break; |
| case NORMAL_PUD: |
| moved = move_normal_pud(vma, old_addr, new_addr, old_entry, |
| new_entry); |
| break; |
| case HPAGE_PMD: |
| moved = IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && |
| move_huge_pmd(vma, old_addr, new_addr, old_entry, |
| new_entry); |
| break; |
| case HPAGE_PUD: |
| moved = IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && |
| move_huge_pud(vma, old_addr, new_addr, old_entry, |
| new_entry); |
| break; |
| |
| default: |
| WARN_ON_ONCE(1); |
| break; |
| } |
| |
| if (need_rmap_locks) |
| drop_rmap_locks(vma); |
| |
| return moved; |
| } |
| |
| unsigned long move_page_tables(struct vm_area_struct *vma, |
| unsigned long old_addr, struct vm_area_struct *new_vma, |
| unsigned long new_addr, unsigned long len, |
| bool need_rmap_locks) |
| { |
| unsigned long extent, old_end; |
| struct mmu_notifier_range range; |
| pmd_t *old_pmd, *new_pmd; |
| pud_t *old_pud, *new_pud; |
| |
| if (!len) |
| return 0; |
| |
| old_end = old_addr + len; |
| flush_cache_range(vma, old_addr, old_end); |
| |
| mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0, vma, vma->vm_mm, |
| old_addr, old_end); |
| mmu_notifier_invalidate_range_start(&range); |
| |
| for (; old_addr < old_end; old_addr += extent, new_addr += extent) { |
| cond_resched(); |
| /* |
| * If extent is PUD-sized try to speed up the move by moving at the |
| * PUD level if possible. |
| */ |
| extent = get_extent(NORMAL_PUD, old_addr, old_end, new_addr); |
| |
| old_pud = get_old_pud(vma->vm_mm, old_addr); |
| if (!old_pud) |
| continue; |
| new_pud = alloc_new_pud(vma->vm_mm, vma, new_addr); |
| if (!new_pud) |
| break; |
| if (pud_trans_huge(*old_pud) || pud_devmap(*old_pud)) { |
| if (extent == HPAGE_PUD_SIZE) { |
| move_pgt_entry(HPAGE_PUD, vma, old_addr, new_addr, |
| old_pud, new_pud, need_rmap_locks); |
| /* We ignore and continue on error? */ |
| continue; |
| } |
| } else if (IS_ENABLED(CONFIG_HAVE_MOVE_PUD) && extent == PUD_SIZE) { |
| |
| if (move_pgt_entry(NORMAL_PUD, vma, old_addr, new_addr, |
| old_pud, new_pud, true)) |
| continue; |
| } |
| |
| extent = get_extent(NORMAL_PMD, old_addr, old_end, new_addr); |
| old_pmd = get_old_pmd(vma->vm_mm, old_addr); |
| if (!old_pmd) |
| continue; |
| new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr); |
| if (!new_pmd) |
| break; |
| if (is_swap_pmd(*old_pmd) || pmd_trans_huge(*old_pmd) || |
| pmd_devmap(*old_pmd)) { |
| if (extent == HPAGE_PMD_SIZE && |
| move_pgt_entry(HPAGE_PMD, vma, old_addr, new_addr, |
| old_pmd, new_pmd, need_rmap_locks)) |
| continue; |
| split_huge_pmd(vma, old_pmd, old_addr); |
| if (pmd_trans_unstable(old_pmd)) |
| continue; |
| } else if (IS_ENABLED(CONFIG_HAVE_MOVE_PMD) && |
| extent == PMD_SIZE) { |
| /* |
| * If the extent is PMD-sized, try to speed the move by |
| * moving at the PMD level if possible. |
| */ |
| if (move_pgt_entry(NORMAL_PMD, vma, old_addr, new_addr, |
| old_pmd, new_pmd, true)) |
| continue; |
| } |
| |
| if (pte_alloc(new_vma->vm_mm, new_pmd)) |
| break; |
| move_ptes(vma, old_pmd, old_addr, old_addr + extent, new_vma, |
| new_pmd, new_addr, need_rmap_locks); |
| } |
| |
| mmu_notifier_invalidate_range_end(&range); |
| |
| return len + old_addr - old_end; /* how much done */ |
| } |
| |
| static unsigned long move_vma(struct vm_area_struct *vma, |
| unsigned long old_addr, unsigned long old_len, |
| unsigned long new_len, unsigned long new_addr, |
| bool *locked, unsigned long flags, |
| struct vm_userfaultfd_ctx *uf, struct list_head *uf_unmap) |
| { |
| struct mm_struct *mm = vma->vm_mm; |
| struct vm_area_struct *new_vma; |
| unsigned long vm_flags = vma->vm_flags; |
| unsigned long new_pgoff; |
| unsigned long moved_len; |
| unsigned long excess = 0; |
| unsigned long hiwater_vm; |
| int split = 0; |
| int err = 0; |
| bool need_rmap_locks; |
| |
| /* |
| * We'd prefer to avoid failure later on in do_munmap: |
| * which may split one vma into three before unmapping. |
| */ |
| if (mm->map_count >= sysctl_max_map_count - 3) |
| return -ENOMEM; |
| |
| if (vma->vm_ops && vma->vm_ops->may_split) { |
| if (vma->vm_start != old_addr) |
| err = vma->vm_ops->may_split(vma, old_addr); |
| if (!err && vma->vm_end != old_addr + old_len) |
| err = vma->vm_ops->may_split(vma, old_addr + old_len); |
| if (err) |
| return err; |
| } |
| |
| /* |
| * Advise KSM to break any KSM pages in the area to be moved: |
| * it would be confusing if they were to turn up at the new |
| * location, where they happen to coincide with different KSM |
| * pages recently unmapped. But leave vma->vm_flags as it was, |
| * so KSM can come around to merge on vma and new_vma afterwards. |
| */ |
| err = ksm_madvise(vma, old_addr, old_addr + old_len, |
| MADV_UNMERGEABLE, &vm_flags); |
| if (err) |
| return err; |
| |
| if (unlikely(flags & MREMAP_DONTUNMAP && vm_flags & VM_ACCOUNT)) { |
| if (security_vm_enough_memory_mm(mm, new_len >> PAGE_SHIFT)) |
| return -ENOMEM; |
| } |
| |
| new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT); |
| new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff, |
| &need_rmap_locks); |
| if (!new_vma) { |
| if (unlikely(flags & MREMAP_DONTUNMAP && vm_flags & VM_ACCOUNT)) |
| vm_unacct_memory(new_len >> PAGE_SHIFT); |
| return -ENOMEM; |
| } |
| |
| moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len, |
| need_rmap_locks); |
| if (moved_len < old_len) { |
| err = -ENOMEM; |
| } else if (vma->vm_ops && vma->vm_ops->mremap) { |
| err = vma->vm_ops->mremap(new_vma); |
| } |
| |
| if (unlikely(err)) { |
| /* |
| * On error, move entries back from new area to old, |
| * which will succeed since page tables still there, |
| * and then proceed to unmap new area instead of old. |
| */ |
| move_page_tables(new_vma, new_addr, vma, old_addr, moved_len, |
| true); |
| vma = new_vma; |
| old_len = new_len; |
| old_addr = new_addr; |
| new_addr = err; |
| } else { |
| mremap_userfaultfd_prep(new_vma, uf); |
| } |
| |
| /* Conceal VM_ACCOUNT so old reservation is not undone */ |
| if (vm_flags & VM_ACCOUNT && !(flags & MREMAP_DONTUNMAP)) { |
| vma->vm_flags &= ~VM_ACCOUNT; |
| excess = vma->vm_end - vma->vm_start - old_len; |
| if (old_addr > vma->vm_start && |
| old_addr + old_len < vma->vm_end) |
| split = 1; |
| } |
| |
| /* |
| * If we failed to move page tables we still do total_vm increment |
| * since do_munmap() will decrement it by old_len == new_len. |
| * |
| * Since total_vm is about to be raised artificially high for a |
| * moment, we need to restore high watermark afterwards: if stats |
| * are taken meanwhile, total_vm and hiwater_vm appear too high. |
| * If this were a serious issue, we'd add a flag to do_munmap(). |
| */ |
| hiwater_vm = mm->hiwater_vm; |
| vm_stat_account(mm, vma->vm_flags, new_len >> PAGE_SHIFT); |
| |
| /* Tell pfnmap has moved from this vma */ |
| if (unlikely(vma->vm_flags & VM_PFNMAP)) |
| untrack_pfn_moved(vma); |
| |
| if (unlikely(!err && (flags & MREMAP_DONTUNMAP))) { |
| /* We always clear VM_LOCKED[ONFAULT] on the old vma */ |
| vma->vm_flags &= VM_LOCKED_CLEAR_MASK; |
| |
| /* |
| * anon_vma links of the old vma is no longer needed after its page |
| * table has been moved. |
| */ |
| if (new_vma != vma && vma->vm_start == old_addr && |
| vma->vm_end == (old_addr + old_len)) |
| unlink_anon_vmas(vma); |
| |
| /* Because we won't unmap we don't need to touch locked_vm */ |
| return new_addr; |
| } |
| |
| if (do_munmap(mm, old_addr, old_len, uf_unmap) < 0) { |
| /* OOM: unable to split vma, just get accounts right */ |
| if (vm_flags & VM_ACCOUNT && !(flags & MREMAP_DONTUNMAP)) |
| vm_acct_memory(old_len >> PAGE_SHIFT); |
| excess = 0; |
| } |
| |
| if (vm_flags & VM_LOCKED) { |
| mm->locked_vm += new_len >> PAGE_SHIFT; |
| *locked = true; |
| } |
| |
| mm->hiwater_vm = hiwater_vm; |
| |
| /* Restore VM_ACCOUNT if one or two pieces of vma left */ |
| if (excess) { |
| vma->vm_flags |= VM_ACCOUNT; |
| if (split) |
| vma->vm_next->vm_flags |= VM_ACCOUNT; |
| } |
| |
| return new_addr; |
| } |
| |
| static struct vm_area_struct *vma_to_resize(unsigned long addr, |
| unsigned long old_len, unsigned long new_len, unsigned long flags, |
| unsigned long *p) |
| { |
| struct mm_struct *mm = current->mm; |
| struct vm_area_struct *vma; |
| unsigned long pgoff; |
| |
| vma = vma_lookup(mm, addr); |
| if (!vma) |
| return ERR_PTR(-EFAULT); |
| |
| /* |
| * !old_len is a special case where an attempt is made to 'duplicate' |
| * a mapping. This makes no sense for private mappings as it will |
| * instead create a fresh/new mapping unrelated to the original. This |
| * is contrary to the basic idea of mremap which creates new mappings |
| * based on the original. There are no known use cases for this |
| * behavior. As a result, fail such attempts. |
| */ |
| if (!old_len && !(vma->vm_flags & (VM_SHARED | VM_MAYSHARE))) { |
| pr_warn_once("%s (%d): attempted to duplicate a private mapping with mremap. This is not supported.\n", current->comm, current->pid); |
| return ERR_PTR(-EINVAL); |
| } |
| |
| if ((flags & MREMAP_DONTUNMAP) && |
| (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))) |
| return ERR_PTR(-EINVAL); |
| |
| if (is_vm_hugetlb_page(vma)) |
| return ERR_PTR(-EINVAL); |
| |
| /* We can't remap across vm area boundaries */ |
| if (old_len > vma->vm_end - addr) |
| return ERR_PTR(-EFAULT); |
| |
| if (new_len == old_len) |
| return vma; |
| |
| /* Need to be careful about a growing mapping */ |
| pgoff = (addr - vma->vm_start) >> PAGE_SHIFT; |
| pgoff += vma->vm_pgoff; |
| if (pgoff + (new_len >> PAGE_SHIFT) < pgoff) |
| return ERR_PTR(-EINVAL); |
| |
| if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) |
| return ERR_PTR(-EFAULT); |
| |
| if (vma->vm_flags & VM_LOCKED) { |
| unsigned long locked, lock_limit; |
| locked = mm->locked_vm << PAGE_SHIFT; |
| lock_limit = rlimit(RLIMIT_MEMLOCK); |
| locked += new_len - old_len; |
| if (locked > lock_limit && !capable(CAP_IPC_LOCK)) |
| return ERR_PTR(-EAGAIN); |
| } |
| |
| if (!may_expand_vm(mm, vma->vm_flags, |
| (new_len - old_len) >> PAGE_SHIFT)) |
| return ERR_PTR(-ENOMEM); |
| |
| if (vma->vm_flags & VM_ACCOUNT) { |
| unsigned long charged = (new_len - old_len) >> PAGE_SHIFT; |
| if (security_vm_enough_memory_mm(mm, charged)) |
| return ERR_PTR(-ENOMEM); |
| *p = charged; |
| } |
| |
| return vma; |
| } |
| |
| static unsigned long mremap_to(unsigned long addr, unsigned long old_len, |
| unsigned long new_addr, unsigned long new_len, bool *locked, |
| unsigned long flags, struct vm_userfaultfd_ctx *uf, |
| struct list_head *uf_unmap_early, |
| struct list_head *uf_unmap) |
| { |
| struct mm_struct *mm = current->mm; |
| struct vm_area_struct *vma; |
| unsigned long ret = -EINVAL; |
| unsigned long charged = 0; |
| unsigned long map_flags = 0; |
| |
| if (offset_in_page(new_addr)) |
| goto out; |
| |
| if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len) |
| goto out; |
| |
| /* Ensure the old/new locations do not overlap */ |
| if (addr + old_len > new_addr && new_addr + new_len > addr) |
| goto out; |
| |
| /* |
| * move_vma() need us to stay 4 maps below the threshold, otherwise |
| * it will bail out at the very beginning. |
| * That is a problem if we have already unmaped the regions here |
| * (new_addr, and old_addr), because userspace will not know the |
| * state of the vma's after it gets -ENOMEM. |
| * So, to avoid such scenario we can pre-compute if the whole |
| * operation has high chances to success map-wise. |
| * Worst-scenario case is when both vma's (new_addr and old_addr) get |
| * split in 3 before unmapping it. |
| * That means 2 more maps (1 for each) to the ones we already hold. |
| * Check whether current map count plus 2 still leads us to 4 maps below |
| * the threshold, otherwise return -ENOMEM here to be more safe. |
| */ |
| if ((mm->map_count + 2) >= sysctl_max_map_count - 3) |
| return -ENOMEM; |
| |
| if (flags & MREMAP_FIXED) { |
| ret = do_munmap(mm, new_addr, new_len, uf_unmap_early); |
| if (ret) |
| goto out; |
| } |
| |
| if (old_len >= new_len) { |
| ret = do_munmap(mm, addr+new_len, old_len - new_len, uf_unmap); |
| if (ret && old_len != new_len) |
| goto out; |
| old_len = new_len; |
| } |
| |
| vma = vma_to_resize(addr, old_len, new_len, flags, &charged); |
| if (IS_ERR(vma)) { |
| ret = PTR_ERR(vma); |
| goto out; |
| } |
| |
| /* MREMAP_DONTUNMAP expands by old_len since old_len == new_len */ |
| if (flags & MREMAP_DONTUNMAP && |
| !may_expand_vm(mm, vma->vm_flags, old_len >> PAGE_SHIFT)) { |
| ret = -ENOMEM; |
| goto out; |
| } |
| |
| if (flags & MREMAP_FIXED) |
| map_flags |= MAP_FIXED; |
| |
| if (vma->vm_flags & VM_MAYSHARE) |
| map_flags |= MAP_SHARED; |
| |
| ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff + |
| ((addr - vma->vm_start) >> PAGE_SHIFT), |
| map_flags); |
| if (IS_ERR_VALUE(ret)) |
| goto out1; |
| |
| /* We got a new mapping */ |
| if (!(flags & MREMAP_FIXED)) |
| new_addr = ret; |
| |
| ret = move_vma(vma, addr, old_len, new_len, new_addr, locked, flags, uf, |
| uf_unmap); |
| |
| if (!(offset_in_page(ret))) |
| goto out; |
| |
| out1: |
| vm_unacct_memory(charged); |
| |
| out: |
| return ret; |
| } |
| |
| static int vma_expandable(struct vm_area_struct *vma, unsigned long delta) |
| { |
| unsigned long end = vma->vm_end + delta; |
| if (end < vma->vm_end) /* overflow */ |
| return 0; |
| if (vma->vm_next && vma->vm_next->vm_start < end) /* intersection */ |
| return 0; |
| if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start, |
| 0, MAP_FIXED) & ~PAGE_MASK) |
| return 0; |
| return 1; |
| } |
| |
| /* |
| * Expand (or shrink) an existing mapping, potentially moving it at the |
| * same time (controlled by the MREMAP_MAYMOVE flag and available VM space) |
| * |
| * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise |
| * This option implies MREMAP_MAYMOVE. |
| */ |
| SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len, |
| unsigned long, new_len, unsigned long, flags, |
| unsigned long, new_addr) |
| { |
| struct mm_struct *mm = current->mm; |
| struct vm_area_struct *vma; |
| unsigned long ret = -EINVAL; |
| unsigned long charged = 0; |
| bool locked = false; |
| bool downgraded = false; |
| struct vm_userfaultfd_ctx uf = NULL_VM_UFFD_CTX; |
| LIST_HEAD(uf_unmap_early); |
| LIST_HEAD(uf_unmap); |
| |
| /* |
| * There is a deliberate asymmetry here: we strip the pointer tag |
| * from the old address but leave the new address alone. This is |
| * for consistency with mmap(), where we prevent the creation of |
| * aliasing mappings in userspace by leaving the tag bits of the |
| * mapping address intact. A non-zero tag will cause the subsequent |
| * range checks to reject the address as invalid. |
| * |
| * See Documentation/arm64/tagged-address-abi.rst for more information. |
| */ |
| addr = untagged_addr(addr); |
| |
| if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE | MREMAP_DONTUNMAP)) |
| return ret; |
| |
| if (flags & MREMAP_FIXED && !(flags & MREMAP_MAYMOVE)) |
| return ret; |
| |
| /* |
| * MREMAP_DONTUNMAP is always a move and it does not allow resizing |
| * in the process. |
| */ |
| if (flags & MREMAP_DONTUNMAP && |
| (!(flags & MREMAP_MAYMOVE) || old_len != new_len)) |
| return ret; |
| |
| |
| if (offset_in_page(addr)) |
| return ret; |
| |
| old_len = PAGE_ALIGN(old_len); |
| new_len = PAGE_ALIGN(new_len); |
| |
| /* |
| * We allow a zero old-len as a special case |
| * for DOS-emu "duplicate shm area" thing. But |
| * a zero new-len is nonsensical. |
| */ |
| if (!new_len) |
| return ret; |
| |
| if (mmap_write_lock_killable(current->mm)) |
| return -EINTR; |
| |
| if (flags & (MREMAP_FIXED | MREMAP_DONTUNMAP)) { |
| ret = mremap_to(addr, old_len, new_addr, new_len, |
| &locked, flags, &uf, &uf_unmap_early, |
| &uf_unmap); |
| goto out; |
| } |
| |
| /* |
| * Always allow a shrinking remap: that just unmaps |
| * the unnecessary pages.. |
| * __do_munmap does all the needed commit accounting, and |
| * downgrades mmap_lock to read if so directed. |
| */ |
| if (old_len >= new_len) { |
| int retval; |
| |
| retval = __do_munmap(mm, addr+new_len, old_len - new_len, |
| &uf_unmap, true); |
| if (retval < 0 && old_len != new_len) { |
| ret = retval; |
| goto out; |
| /* Returning 1 indicates mmap_lock is downgraded to read. */ |
| } else if (retval == 1) |
| downgraded = true; |
| ret = addr; |
| goto out; |
| } |
| |
| /* |
| * Ok, we need to grow.. |
| */ |
| vma = vma_to_resize(addr, old_len, new_len, flags, &charged); |
| if (IS_ERR(vma)) { |
| ret = PTR_ERR(vma); |
| goto out; |
| } |
| |
| /* old_len exactly to the end of the area.. |
| */ |
| if (old_len == vma->vm_end - addr) { |
| /* can we just expand the current mapping? */ |
| if (vma_expandable(vma, new_len - old_len)) { |
| int pages = (new_len - old_len) >> PAGE_SHIFT; |
| |
| if (vma_adjust(vma, vma->vm_start, addr + new_len, |
| vma->vm_pgoff, NULL)) { |
| ret = -ENOMEM; |
| goto out; |
| } |
| |
| vm_stat_account(mm, vma->vm_flags, pages); |
| if (vma->vm_flags & VM_LOCKED) { |
| mm->locked_vm += pages; |
| locked = true; |
| new_addr = addr; |
| } |
| ret = addr; |
| goto out; |
| } |
| } |
| |
| /* |
| * We weren't able to just expand or shrink the area, |
| * we need to create a new one and move it.. |
| */ |
| ret = -ENOMEM; |
| if (flags & MREMAP_MAYMOVE) { |
| unsigned long map_flags = 0; |
| if (vma->vm_flags & VM_MAYSHARE) |
| map_flags |= MAP_SHARED; |
| |
| new_addr = get_unmapped_area(vma->vm_file, 0, new_len, |
| vma->vm_pgoff + |
| ((addr - vma->vm_start) >> PAGE_SHIFT), |
| map_flags); |
| if (IS_ERR_VALUE(new_addr)) { |
| ret = new_addr; |
| goto out; |
| } |
| |
| ret = move_vma(vma, addr, old_len, new_len, new_addr, |
| &locked, flags, &uf, &uf_unmap); |
| } |
| out: |
| if (offset_in_page(ret)) { |
| vm_unacct_memory(charged); |
| locked = false; |
| } |
| if (downgraded) |
| mmap_read_unlock(current->mm); |
| else |
| mmap_write_unlock(current->mm); |
| if (locked && new_len > old_len) |
| mm_populate(new_addr + old_len, new_len - old_len); |
| userfaultfd_unmap_complete(mm, &uf_unmap_early); |
| mremap_userfaultfd_complete(&uf, addr, ret, old_len); |
| userfaultfd_unmap_complete(mm, &uf_unmap); |
| return ret; |
| } |