| /* |
| * mm/userfaultfd.c |
| * |
| * Copyright (C) 2015 Red Hat, Inc. |
| * |
| * This work is licensed under the terms of the GNU GPL, version 2. See |
| * the COPYING file in the top-level directory. |
| */ |
| |
| #include <linux/mm.h> |
| #include <linux/sched/signal.h> |
| #include <linux/pagemap.h> |
| #include <linux/rmap.h> |
| #include <linux/swap.h> |
| #include <linux/swapops.h> |
| #include <linux/userfaultfd_k.h> |
| #include <linux/mmu_notifier.h> |
| #include <linux/hugetlb.h> |
| #include <linux/pagemap.h> |
| #include <linux/shmem_fs.h> |
| #include <asm/tlbflush.h> |
| #include "internal.h" |
| |
| static int mcopy_atomic_pte(struct mm_struct *dst_mm, |
| pmd_t *dst_pmd, |
| struct vm_area_struct *dst_vma, |
| unsigned long dst_addr, |
| unsigned long src_addr, |
| struct page **pagep) |
| { |
| struct mem_cgroup *memcg; |
| pte_t _dst_pte, *dst_pte; |
| spinlock_t *ptl; |
| void *page_kaddr; |
| int ret; |
| struct page *page; |
| pgoff_t offset, max_off; |
| struct inode *inode; |
| |
| if (!*pagep) { |
| ret = -ENOMEM; |
| page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, dst_vma, dst_addr); |
| if (!page) |
| goto out; |
| |
| page_kaddr = kmap_atomic(page); |
| ret = copy_from_user(page_kaddr, |
| (const void __user *) src_addr, |
| PAGE_SIZE); |
| kunmap_atomic(page_kaddr); |
| |
| /* fallback to copy_from_user outside mmap_sem */ |
| if (unlikely(ret)) { |
| ret = -ENOENT; |
| *pagep = page; |
| /* don't free the page */ |
| goto out; |
| } |
| |
| flush_dcache_page(page); |
| } else { |
| page = *pagep; |
| *pagep = NULL; |
| } |
| |
| /* |
| * The memory barrier inside __SetPageUptodate makes sure that |
| * preceeding stores to the page contents become visible before |
| * the set_pte_at() write. |
| */ |
| __SetPageUptodate(page); |
| |
| ret = -ENOMEM; |
| if (mem_cgroup_try_charge(page, dst_mm, GFP_KERNEL, &memcg, false)) |
| goto out_release; |
| |
| _dst_pte = mk_pte(page, dst_vma->vm_page_prot); |
| if (dst_vma->vm_flags & VM_WRITE) |
| _dst_pte = pte_mkwrite(pte_mkdirty(_dst_pte)); |
| |
| dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl); |
| if (dst_vma->vm_file) { |
| /* the shmem MAP_PRIVATE case requires checking the i_size */ |
| inode = dst_vma->vm_file->f_inode; |
| offset = linear_page_index(dst_vma, dst_addr); |
| max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); |
| ret = -EFAULT; |
| if (unlikely(offset >= max_off)) |
| goto out_release_uncharge_unlock; |
| } |
| ret = -EEXIST; |
| if (!pte_none(*dst_pte)) |
| goto out_release_uncharge_unlock; |
| |
| inc_mm_counter(dst_mm, MM_ANONPAGES); |
| page_add_new_anon_rmap(page, dst_vma, dst_addr, false); |
| mem_cgroup_commit_charge(page, memcg, false, false); |
| lru_cache_add_active_or_unevictable(page, dst_vma); |
| |
| set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte); |
| |
| /* No need to invalidate - it was non-present before */ |
| update_mmu_cache(dst_vma, dst_addr, dst_pte); |
| |
| pte_unmap_unlock(dst_pte, ptl); |
| ret = 0; |
| out: |
| return ret; |
| out_release_uncharge_unlock: |
| pte_unmap_unlock(dst_pte, ptl); |
| mem_cgroup_cancel_charge(page, memcg, false); |
| out_release: |
| put_page(page); |
| goto out; |
| } |
| |
| static int mfill_zeropage_pte(struct mm_struct *dst_mm, |
| pmd_t *dst_pmd, |
| struct vm_area_struct *dst_vma, |
| unsigned long dst_addr) |
| { |
| pte_t _dst_pte, *dst_pte; |
| spinlock_t *ptl; |
| int ret; |
| pgoff_t offset, max_off; |
| struct inode *inode; |
| |
| _dst_pte = pte_mkspecial(pfn_pte(my_zero_pfn(dst_addr), |
| dst_vma->vm_page_prot)); |
| dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl); |
| if (dst_vma->vm_file) { |
| /* the shmem MAP_PRIVATE case requires checking the i_size */ |
| inode = dst_vma->vm_file->f_inode; |
| offset = linear_page_index(dst_vma, dst_addr); |
| max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); |
| ret = -EFAULT; |
| if (unlikely(offset >= max_off)) |
| goto out_unlock; |
| } |
| ret = -EEXIST; |
| if (!pte_none(*dst_pte)) |
| goto out_unlock; |
| set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte); |
| /* No need to invalidate - it was non-present before */ |
| update_mmu_cache(dst_vma, dst_addr, dst_pte); |
| ret = 0; |
| out_unlock: |
| pte_unmap_unlock(dst_pte, ptl); |
| return ret; |
| } |
| |
| static pmd_t *mm_alloc_pmd(struct mm_struct *mm, unsigned long address) |
| { |
| pgd_t *pgd; |
| p4d_t *p4d; |
| pud_t *pud; |
| |
| pgd = pgd_offset(mm, address); |
| p4d = p4d_alloc(mm, pgd, address); |
| if (!p4d) |
| return NULL; |
| pud = pud_alloc(mm, p4d, address); |
| if (!pud) |
| return NULL; |
| /* |
| * Note that we didn't run this because the pmd was |
| * missing, the *pmd may be already established and in |
| * turn it may also be a trans_huge_pmd. |
| */ |
| return pmd_alloc(mm, pud, address); |
| } |
| |
| #ifdef CONFIG_HUGETLB_PAGE |
| /* |
| * __mcopy_atomic processing for HUGETLB vmas. Note that this routine is |
| * called with mmap_sem held, it will release mmap_sem before returning. |
| */ |
| static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm, |
| struct vm_area_struct *dst_vma, |
| unsigned long dst_start, |
| unsigned long src_start, |
| unsigned long len, |
| bool zeropage) |
| { |
| int vm_alloc_shared = dst_vma->vm_flags & VM_SHARED; |
| int vm_shared = dst_vma->vm_flags & VM_SHARED; |
| ssize_t err; |
| pte_t *dst_pte; |
| unsigned long src_addr, dst_addr; |
| long copied; |
| struct page *page; |
| struct hstate *h; |
| unsigned long vma_hpagesize; |
| pgoff_t idx; |
| u32 hash; |
| struct address_space *mapping; |
| |
| /* |
| * There is no default zero huge page for all huge page sizes as |
| * supported by hugetlb. A PMD_SIZE huge pages may exist as used |
| * by THP. Since we can not reliably insert a zero page, this |
| * feature is not supported. |
| */ |
| if (zeropage) { |
| up_read(&dst_mm->mmap_sem); |
| return -EINVAL; |
| } |
| |
| src_addr = src_start; |
| dst_addr = dst_start; |
| copied = 0; |
| page = NULL; |
| vma_hpagesize = vma_kernel_pagesize(dst_vma); |
| |
| /* |
| * Validate alignment based on huge page size |
| */ |
| err = -EINVAL; |
| if (dst_start & (vma_hpagesize - 1) || len & (vma_hpagesize - 1)) |
| goto out_unlock; |
| |
| retry: |
| /* |
| * On routine entry dst_vma is set. If we had to drop mmap_sem and |
| * retry, dst_vma will be set to NULL and we must lookup again. |
| */ |
| if (!dst_vma) { |
| err = -ENOENT; |
| dst_vma = find_vma(dst_mm, dst_start); |
| if (!dst_vma || !is_vm_hugetlb_page(dst_vma)) |
| goto out_unlock; |
| /* |
| * Check the vma is registered in uffd, this is |
| * required to enforce the VM_MAYWRITE check done at |
| * uffd registration time. |
| */ |
| if (!dst_vma->vm_userfaultfd_ctx.ctx) |
| goto out_unlock; |
| |
| if (dst_start < dst_vma->vm_start || |
| dst_start + len > dst_vma->vm_end) |
| goto out_unlock; |
| |
| err = -EINVAL; |
| if (vma_hpagesize != vma_kernel_pagesize(dst_vma)) |
| goto out_unlock; |
| |
| vm_shared = dst_vma->vm_flags & VM_SHARED; |
| } |
| |
| if (WARN_ON(dst_addr & (vma_hpagesize - 1) || |
| (len - copied) & (vma_hpagesize - 1))) |
| goto out_unlock; |
| |
| /* |
| * If not shared, ensure the dst_vma has a anon_vma. |
| */ |
| err = -ENOMEM; |
| if (!vm_shared) { |
| if (unlikely(anon_vma_prepare(dst_vma))) |
| goto out_unlock; |
| } |
| |
| h = hstate_vma(dst_vma); |
| |
| while (src_addr < src_start + len) { |
| pte_t dst_pteval; |
| |
| BUG_ON(dst_addr >= dst_start + len); |
| VM_BUG_ON(dst_addr & ~huge_page_mask(h)); |
| |
| /* |
| * Serialize via hugetlb_fault_mutex |
| */ |
| idx = linear_page_index(dst_vma, dst_addr); |
| mapping = dst_vma->vm_file->f_mapping; |
| hash = hugetlb_fault_mutex_hash(h, mapping, idx); |
| mutex_lock(&hugetlb_fault_mutex_table[hash]); |
| |
| err = -ENOMEM; |
| dst_pte = huge_pte_alloc(dst_mm, dst_vma, dst_addr, huge_page_size(h)); |
| if (!dst_pte) { |
| mutex_unlock(&hugetlb_fault_mutex_table[hash]); |
| goto out_unlock; |
| } |
| |
| err = -EEXIST; |
| dst_pteval = huge_ptep_get(dst_pte); |
| if (!huge_pte_none(dst_pteval)) { |
| mutex_unlock(&hugetlb_fault_mutex_table[hash]); |
| goto out_unlock; |
| } |
| |
| err = hugetlb_mcopy_atomic_pte(dst_mm, dst_pte, dst_vma, |
| dst_addr, src_addr, &page); |
| |
| mutex_unlock(&hugetlb_fault_mutex_table[hash]); |
| vm_alloc_shared = vm_shared; |
| |
| cond_resched(); |
| |
| if (unlikely(err == -ENOENT)) { |
| up_read(&dst_mm->mmap_sem); |
| BUG_ON(!page); |
| |
| err = copy_huge_page_from_user(page, |
| (const void __user *)src_addr, |
| pages_per_huge_page(h), true); |
| if (unlikely(err)) { |
| err = -EFAULT; |
| goto out; |
| } |
| down_read(&dst_mm->mmap_sem); |
| |
| dst_vma = NULL; |
| goto retry; |
| } else |
| BUG_ON(page); |
| |
| if (!err) { |
| dst_addr += vma_hpagesize; |
| src_addr += vma_hpagesize; |
| copied += vma_hpagesize; |
| |
| if (fatal_signal_pending(current)) |
| err = -EINTR; |
| } |
| if (err) |
| break; |
| } |
| |
| out_unlock: |
| up_read(&dst_mm->mmap_sem); |
| out: |
| if (page) { |
| /* |
| * We encountered an error and are about to free a newly |
| * allocated huge page. |
| * |
| * Reservation handling is very subtle, and is different for |
| * private and shared mappings. See the routine |
| * restore_reserve_on_error for details. Unfortunately, we |
| * can not call restore_reserve_on_error now as it would |
| * require holding mmap_sem. |
| * |
| * If a reservation for the page existed in the reservation |
| * map of a private mapping, the map was modified to indicate |
| * the reservation was consumed when the page was allocated. |
| * We clear the PagePrivate flag now so that the global |
| * reserve count will not be incremented in free_huge_page. |
| * The reservation map will still indicate the reservation |
| * was consumed and possibly prevent later page allocation. |
| * This is better than leaking a global reservation. If no |
| * reservation existed, it is still safe to clear PagePrivate |
| * as no adjustments to reservation counts were made during |
| * allocation. |
| * |
| * The reservation map for shared mappings indicates which |
| * pages have reservations. When a huge page is allocated |
| * for an address with a reservation, no change is made to |
| * the reserve map. In this case PagePrivate will be set |
| * to indicate that the global reservation count should be |
| * incremented when the page is freed. This is the desired |
| * behavior. However, when a huge page is allocated for an |
| * address without a reservation a reservation entry is added |
| * to the reservation map, and PagePrivate will not be set. |
| * When the page is freed, the global reserve count will NOT |
| * be incremented and it will appear as though we have leaked |
| * reserved page. In this case, set PagePrivate so that the |
| * global reserve count will be incremented to match the |
| * reservation map entry which was created. |
| * |
| * Note that vm_alloc_shared is based on the flags of the vma |
| * for which the page was originally allocated. dst_vma could |
| * be different or NULL on error. |
| */ |
| if (vm_alloc_shared) |
| SetPagePrivate(page); |
| else |
| ClearPagePrivate(page); |
| put_page(page); |
| } |
| BUG_ON(copied < 0); |
| BUG_ON(err > 0); |
| BUG_ON(!copied && !err); |
| return copied ? copied : err; |
| } |
| #else /* !CONFIG_HUGETLB_PAGE */ |
| /* fail at build time if gcc attempts to use this */ |
| extern ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm, |
| struct vm_area_struct *dst_vma, |
| unsigned long dst_start, |
| unsigned long src_start, |
| unsigned long len, |
| bool zeropage); |
| #endif /* CONFIG_HUGETLB_PAGE */ |
| |
| static __always_inline ssize_t mfill_atomic_pte(struct mm_struct *dst_mm, |
| pmd_t *dst_pmd, |
| struct vm_area_struct *dst_vma, |
| unsigned long dst_addr, |
| unsigned long src_addr, |
| struct page **page, |
| bool zeropage) |
| { |
| ssize_t err; |
| |
| /* |
| * The normal page fault path for a shmem will invoke the |
| * fault, fill the hole in the file and COW it right away. The |
| * result generates plain anonymous memory. So when we are |
| * asked to fill an hole in a MAP_PRIVATE shmem mapping, we'll |
| * generate anonymous memory directly without actually filling |
| * the hole. For the MAP_PRIVATE case the robustness check |
| * only happens in the pagetable (to verify it's still none) |
| * and not in the radix tree. |
| */ |
| if (!(dst_vma->vm_flags & VM_SHARED)) { |
| if (!zeropage) |
| err = mcopy_atomic_pte(dst_mm, dst_pmd, dst_vma, |
| dst_addr, src_addr, page); |
| else |
| err = mfill_zeropage_pte(dst_mm, dst_pmd, |
| dst_vma, dst_addr); |
| } else { |
| if (!zeropage) |
| err = shmem_mcopy_atomic_pte(dst_mm, dst_pmd, |
| dst_vma, dst_addr, |
| src_addr, page); |
| else |
| err = shmem_mfill_zeropage_pte(dst_mm, dst_pmd, |
| dst_vma, dst_addr); |
| } |
| |
| return err; |
| } |
| |
| static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm, |
| unsigned long dst_start, |
| unsigned long src_start, |
| unsigned long len, |
| bool zeropage, |
| bool *mmap_changing) |
| { |
| struct vm_area_struct *dst_vma; |
| ssize_t err; |
| pmd_t *dst_pmd; |
| unsigned long src_addr, dst_addr; |
| long copied; |
| struct page *page; |
| |
| /* |
| * Sanitize the command parameters: |
| */ |
| BUG_ON(dst_start & ~PAGE_MASK); |
| BUG_ON(len & ~PAGE_MASK); |
| |
| /* Does the address range wrap, or is the span zero-sized? */ |
| BUG_ON(src_start + len <= src_start); |
| BUG_ON(dst_start + len <= dst_start); |
| |
| src_addr = src_start; |
| dst_addr = dst_start; |
| copied = 0; |
| page = NULL; |
| retry: |
| down_read(&dst_mm->mmap_sem); |
| |
| /* |
| * If memory mappings are changing because of non-cooperative |
| * operation (e.g. mremap) running in parallel, bail out and |
| * request the user to retry later |
| */ |
| err = -EAGAIN; |
| if (mmap_changing && READ_ONCE(*mmap_changing)) |
| goto out_unlock; |
| |
| /* |
| * Make sure the vma is not shared, that the dst range is |
| * both valid and fully within a single existing vma. |
| */ |
| err = -ENOENT; |
| dst_vma = find_vma(dst_mm, dst_start); |
| if (!dst_vma) |
| goto out_unlock; |
| /* |
| * Check the vma is registered in uffd, this is required to |
| * enforce the VM_MAYWRITE check done at uffd registration |
| * time. |
| */ |
| if (!dst_vma->vm_userfaultfd_ctx.ctx) |
| goto out_unlock; |
| |
| if (dst_start < dst_vma->vm_start || |
| dst_start + len > dst_vma->vm_end) |
| goto out_unlock; |
| |
| err = -EINVAL; |
| /* |
| * shmem_zero_setup is invoked in mmap for MAP_ANONYMOUS|MAP_SHARED but |
| * it will overwrite vm_ops, so vma_is_anonymous must return false. |
| */ |
| if (WARN_ON_ONCE(vma_is_anonymous(dst_vma) && |
| dst_vma->vm_flags & VM_SHARED)) |
| goto out_unlock; |
| |
| /* |
| * If this is a HUGETLB vma, pass off to appropriate routine |
| */ |
| if (is_vm_hugetlb_page(dst_vma)) |
| return __mcopy_atomic_hugetlb(dst_mm, dst_vma, dst_start, |
| src_start, len, zeropage); |
| |
| if (!vma_is_anonymous(dst_vma) && !vma_is_shmem(dst_vma)) |
| goto out_unlock; |
| |
| /* |
| * Ensure the dst_vma has a anon_vma or this page |
| * would get a NULL anon_vma when moved in the |
| * dst_vma. |
| */ |
| err = -ENOMEM; |
| if (!(dst_vma->vm_flags & VM_SHARED) && |
| unlikely(anon_vma_prepare(dst_vma))) |
| goto out_unlock; |
| |
| while (src_addr < src_start + len) { |
| pmd_t dst_pmdval; |
| |
| BUG_ON(dst_addr >= dst_start + len); |
| |
| dst_pmd = mm_alloc_pmd(dst_mm, dst_addr); |
| if (unlikely(!dst_pmd)) { |
| err = -ENOMEM; |
| break; |
| } |
| |
| dst_pmdval = pmd_read_atomic(dst_pmd); |
| /* |
| * If the dst_pmd is mapped as THP don't |
| * override it and just be strict. |
| */ |
| if (unlikely(pmd_trans_huge(dst_pmdval))) { |
| err = -EEXIST; |
| break; |
| } |
| if (unlikely(pmd_none(dst_pmdval)) && |
| unlikely(__pte_alloc(dst_mm, dst_pmd, dst_addr))) { |
| err = -ENOMEM; |
| break; |
| } |
| /* If an huge pmd materialized from under us fail */ |
| if (unlikely(pmd_trans_huge(*dst_pmd))) { |
| err = -EFAULT; |
| break; |
| } |
| |
| BUG_ON(pmd_none(*dst_pmd)); |
| BUG_ON(pmd_trans_huge(*dst_pmd)); |
| |
| err = mfill_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr, |
| src_addr, &page, zeropage); |
| cond_resched(); |
| |
| if (unlikely(err == -ENOENT)) { |
| void *page_kaddr; |
| |
| up_read(&dst_mm->mmap_sem); |
| BUG_ON(!page); |
| |
| page_kaddr = kmap(page); |
| err = copy_from_user(page_kaddr, |
| (const void __user *) src_addr, |
| PAGE_SIZE); |
| kunmap(page); |
| if (unlikely(err)) { |
| err = -EFAULT; |
| goto out; |
| } |
| flush_dcache_page(page); |
| goto retry; |
| } else |
| BUG_ON(page); |
| |
| if (!err) { |
| dst_addr += PAGE_SIZE; |
| src_addr += PAGE_SIZE; |
| copied += PAGE_SIZE; |
| |
| if (fatal_signal_pending(current)) |
| err = -EINTR; |
| } |
| if (err) |
| break; |
| } |
| |
| out_unlock: |
| up_read(&dst_mm->mmap_sem); |
| out: |
| if (page) |
| put_page(page); |
| BUG_ON(copied < 0); |
| BUG_ON(err > 0); |
| BUG_ON(!copied && !err); |
| return copied ? copied : err; |
| } |
| |
| ssize_t mcopy_atomic(struct mm_struct *dst_mm, unsigned long dst_start, |
| unsigned long src_start, unsigned long len, |
| bool *mmap_changing) |
| { |
| return __mcopy_atomic(dst_mm, dst_start, src_start, len, false, |
| mmap_changing); |
| } |
| |
| ssize_t mfill_zeropage(struct mm_struct *dst_mm, unsigned long start, |
| unsigned long len, bool *mmap_changing) |
| { |
| return __mcopy_atomic(dst_mm, start, 0, len, true, mmap_changing); |
| } |