mm/userfaultfd.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  mm/userfaultfd.c
   4  *
   5  *  Copyright (C) 2015  Red Hat, Inc.
   6  */
   7
   8 #include <linux/mm.h>
   9 #include <linux/sched/signal.h>
  10 #include <linux/pagemap.h>
  11 #include <linux/rmap.h>
  12 #include <linux/swap.h>
  13 #include <linux/swapops.h>
  14 #include <linux/userfaultfd_k.h>
  15 #include <linux/mmu_notifier.h>
  16 #include <linux/hugetlb.h>
  17 #include <linux/shmem_fs.h>
  18 #include <asm/tlbflush.h>
  19 #include "internal.h"
  20
  21 static __always_inline
  22 struct vm_area_struct *find_dst_vma(struct mm_struct *dst_mm,
  23                                     unsigned long dst_start,
  24                                     unsigned long len)
  25 {
  26         /*
  27          * Make sure that the dst range is both valid and fully within a
  28          * single existing vma.
  29          */
  30         struct vm_area_struct *dst_vma;
  31
  32         dst_vma = find_vma(dst_mm, dst_start);
  33         if (!dst_vma)
  34                 return NULL;
  35
  36         if (dst_start < dst_vma->vm_start ||
  37             dst_start + len > dst_vma->vm_end)
  38                 return NULL;
  39
  40         /*
  41          * Check the vma is registered in uffd, this is required to
  42          * enforce the VM_MAYWRITE check done at uffd registration
  43          * time.
  44          */
  45         if (!dst_vma->vm_userfaultfd_ctx.ctx)
  46                 return NULL;
  47
  48         return dst_vma;
  49 }
  50
  51 /*
  52  * Install PTEs, to map dst_addr (within dst_vma) to page.
  53  *
  54  * This function handles both MCOPY_ATOMIC_NORMAL and _CONTINUE for both shmem
  55  * and anon, and for both shared and private VMAs.
  56  */
  57 int mfill_atomic_install_pte(struct mm_struct *dst_mm, pmd_t *dst_pmd,
  58                              struct vm_area_struct *dst_vma,
  59                              unsigned long dst_addr, struct page *page,
  60                              bool newly_allocated, bool wp_copy)
  61 {
  62         int ret;
  63         pte_t _dst_pte, *dst_pte;
  64         bool writable = dst_vma->vm_flags & VM_WRITE;
  65         bool vm_shared = dst_vma->vm_flags & VM_SHARED;
  66         bool page_in_cache = page->mapping;
  67         spinlock_t *ptl;
  68         struct inode *inode;
  69         pgoff_t offset, max_off;
  70
  71         _dst_pte = mk_pte(page, dst_vma->vm_page_prot);
  72         _dst_pte = pte_mkdirty(_dst_pte);
  73         if (page_in_cache && !vm_shared)
  74                 writable = false;
  75         if (writable) {
  76                 if (wp_copy)
  77                         _dst_pte = pte_mkuffd_wp(_dst_pte);
  78                 else
  79                         _dst_pte = pte_mkwrite(_dst_pte);
  80         }
  81
  82         dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
  83
  84         if (vma_is_shmem(dst_vma)) {
  85                 /* serialize against truncate with the page table lock */
  86                 inode = dst_vma->vm_file->f_inode;
  87                 offset = linear_page_index(dst_vma, dst_addr);
  88                 max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
  89                 ret = -EFAULT;
  90                 if (unlikely(offset >= max_off))
  91                         goto out_unlock;
  92         }
  93
  94         ret = -EEXIST;
  95         if (!pte_none(*dst_pte))
  96                 goto out_unlock;
  97
  98         if (page_in_cache)
  99                 page_add_file_rmap(page, false);
 100         else
 101                 page_add_new_anon_rmap(page, dst_vma, dst_addr, false);
 102
 103         /*
 104          * Must happen after rmap, as mm_counter() checks mapping (via
 105          * PageAnon()), which is set by __page_set_anon_rmap().
 106          */
 107         inc_mm_counter(dst_mm, mm_counter(page));
 108
 109         if (newly_allocated)
 110                 lru_cache_add_inactive_or_unevictable(page, dst_vma);
 111
 112         set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
 113
 114         /* No need to invalidate - it was non-present before */
 115         update_mmu_cache(dst_vma, dst_addr, dst_pte);
 116         ret = 0;
 117 out_unlock:
 118         pte_unmap_unlock(dst_pte, ptl);
 119         return ret;
 120 }
 121
 122 static int mcopy_atomic_pte(struct mm_struct *dst_mm,
 123                             pmd_t *dst_pmd,
 124                             struct vm_area_struct *dst_vma,
 125                             unsigned long dst_addr,
 126                             unsigned long src_addr,
 127                             struct page **pagep,
 128                             bool wp_copy)
 129 {
 130         void *page_kaddr;
 131         int ret;
 132         struct page *page;
 133
 134         if (!*pagep) {
 135                 ret = -ENOMEM;
 136                 page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, dst_vma, dst_addr);
 137                 if (!page)
 138                         goto out;
 139
 140                 page_kaddr = kmap_atomic(page);
 141                 ret = copy_from_user(page_kaddr,
 142                                      (const void __user *) src_addr,
 143                                      PAGE_SIZE);
 144                 kunmap_atomic(page_kaddr);
 145
 146                 /* fallback to copy_from_user outside mmap_lock */
 147                 if (unlikely(ret)) {
 148                         ret = -ENOENT;
 149                         *pagep = page;
 150                         /* don't free the page */
 151                         goto out;
 152                 }
 153         } else {
 154                 page = *pagep;
 155                 *pagep = NULL;
 156         }
 157
 158         /*
 159          * The memory barrier inside __SetPageUptodate makes sure that
 160          * preceding stores to the page contents become visible before
 161          * the set_pte_at() write.
 162          */
 163         __SetPageUptodate(page);
 164
 165         ret = -ENOMEM;
 166         if (mem_cgroup_charge(page_folio(page), dst_mm, GFP_KERNEL))
 167                 goto out_release;
 168
 169         ret = mfill_atomic_install_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
 170                                        page, true, wp_copy);
 171         if (ret)
 172                 goto out_release;
 173 out:
 174         return ret;
 175 out_release:
 176         put_page(page);
 177         goto out;
 178 }
 179
 180 static int mfill_zeropage_pte(struct mm_struct *dst_mm,
 181                               pmd_t *dst_pmd,
 182                               struct vm_area_struct *dst_vma,
 183                               unsigned long dst_addr)
 184 {
 185         pte_t _dst_pte, *dst_pte;
 186         spinlock_t *ptl;
 187         int ret;
 188         pgoff_t offset, max_off;
 189         struct inode *inode;
 190
 191         _dst_pte = pte_mkspecial(pfn_pte(my_zero_pfn(dst_addr),
 192                                          dst_vma->vm_page_prot));
 193         dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
 194         if (dst_vma->vm_file) {
 195                 /* the shmem MAP_PRIVATE case requires checking the i_size */
 196                 inode = dst_vma->vm_file->f_inode;
 197                 offset = linear_page_index(dst_vma, dst_addr);
 198                 max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
 199                 ret = -EFAULT;
 200                 if (unlikely(offset >= max_off))
 201                         goto out_unlock;
 202         }
 203         ret = -EEXIST;
 204         if (!pte_none(*dst_pte))
 205                 goto out_unlock;
 206         set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
 207         /* No need to invalidate - it was non-present before */
 208         update_mmu_cache(dst_vma, dst_addr, dst_pte);
 209         ret = 0;
 210 out_unlock:
 211         pte_unmap_unlock(dst_pte, ptl);
 212         return ret;
 213 }
 214
 215 /* Handles UFFDIO_CONTINUE for all shmem VMAs (shared or private). */
 216 static int mcontinue_atomic_pte(struct mm_struct *dst_mm,
 217                                 pmd_t *dst_pmd,
 218                                 struct vm_area_struct *dst_vma,
 219                                 unsigned long dst_addr,
 220                                 bool wp_copy)
 221 {
 222         struct inode *inode = file_inode(dst_vma->vm_file);
 223         pgoff_t pgoff = linear_page_index(dst_vma, dst_addr);
 224         struct page *page;
 225         int ret;
 226
 227         ret = shmem_getpage(inode, pgoff, &page, SGP_READ);
 228         if (ret)
 229                 goto out;
 230         if (!page) {
 231                 ret = -EFAULT;
 232                 goto out;
 233         }
 234
 235         ret = mfill_atomic_install_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
 236                                        page, false, wp_copy);
 237         if (ret)
 238                 goto out_release;
 239
 240         unlock_page(page);
 241         ret = 0;
 242 out:
 243         return ret;
 244 out_release:
 245         unlock_page(page);
 246         put_page(page);
 247         goto out;
 248 }
 249
 250 static pmd_t *mm_alloc_pmd(struct mm_struct *mm, unsigned long address)
 251 {
 252         pgd_t *pgd;
 253         p4d_t *p4d;
 254         pud_t *pud;
 255
 256         pgd = pgd_offset(mm, address);
 257         p4d = p4d_alloc(mm, pgd, address);
 258         if (!p4d)
 259                 return NULL;
 260         pud = pud_alloc(mm, p4d, address);
 261         if (!pud)
 262                 return NULL;
 263         /*
 264          * Note that we didn't run this because the pmd was
 265          * missing, the *pmd may be already established and in
 266          * turn it may also be a trans_huge_pmd.
 267          */
 268         return pmd_alloc(mm, pud, address);
 269 }
 270
 271 #ifdef CONFIG_HUGETLB_PAGE
 272 /*
 273  * __mcopy_atomic processing for HUGETLB vmas.  Note that this routine is
 274  * called with mmap_lock held, it will release mmap_lock before returning.
 275  */
 276 static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
 277                                               struct vm_area_struct *dst_vma,
 278                                               unsigned long dst_start,
 279                                               unsigned long src_start,
 280                                               unsigned long len,
 281                                               enum mcopy_atomic_mode mode)
 282 {
 283         int vm_shared = dst_vma->vm_flags & VM_SHARED;
 284         ssize_t err;
 285         pte_t *dst_pte;
 286         unsigned long src_addr, dst_addr;
 287         long copied;
 288         struct page *page;
 289         unsigned long vma_hpagesize;
 290         pgoff_t idx;
 291         u32 hash;
 292         struct address_space *mapping;
 293
 294         /*
 295          * There is no default zero huge page for all huge page sizes as
 296          * supported by hugetlb.  A PMD_SIZE huge pages may exist as used
 297          * by THP.  Since we can not reliably insert a zero page, this
 298          * feature is not supported.
 299          */
 300         if (mode == MCOPY_ATOMIC_ZEROPAGE) {
 301                 mmap_read_unlock(dst_mm);
 302                 return -EINVAL;
 303         }
 304
 305         src_addr = src_start;
 306         dst_addr = dst_start;
 307         copied = 0;
 308         page = NULL;
 309         vma_hpagesize = vma_kernel_pagesize(dst_vma);
 310
 311         /*
 312          * Validate alignment based on huge page size
 313          */
 314         err = -EINVAL;
 315         if (dst_start & (vma_hpagesize - 1) || len & (vma_hpagesize - 1))
 316                 goto out_unlock;
 317
 318 retry:
 319         /*
 320          * On routine entry dst_vma is set.  If we had to drop mmap_lock and
 321          * retry, dst_vma will be set to NULL and we must lookup again.
 322          */
 323         if (!dst_vma) {
 324                 err = -ENOENT;
 325                 dst_vma = find_dst_vma(dst_mm, dst_start, len);
 326                 if (!dst_vma || !is_vm_hugetlb_page(dst_vma))
 327                         goto out_unlock;
 328
 329                 err = -EINVAL;
 330                 if (vma_hpagesize != vma_kernel_pagesize(dst_vma))
 331                         goto out_unlock;
 332
 333                 vm_shared = dst_vma->vm_flags & VM_SHARED;
 334         }
 335
 336         /*
 337          * If not shared, ensure the dst_vma has a anon_vma.
 338          */
 339         err = -ENOMEM;
 340         if (!vm_shared) {
 341                 if (unlikely(anon_vma_prepare(dst_vma)))
 342                         goto out_unlock;
 343         }
 344
 345         while (src_addr < src_start + len) {
 346                 BUG_ON(dst_addr >= dst_start + len);
 347
 348                 /*
 349                  * Serialize via i_mmap_rwsem and hugetlb_fault_mutex.
 350                  * i_mmap_rwsem ensures the dst_pte remains valid even
 351                  * in the case of shared pmds.  fault mutex prevents
 352                  * races with other faulting threads.
 353                  */
 354                 mapping = dst_vma->vm_file->f_mapping;
 355                 i_mmap_lock_read(mapping);
 356                 idx = linear_page_index(dst_vma, dst_addr);
 357                 hash = hugetlb_fault_mutex_hash(mapping, idx);
 358                 mutex_lock(&hugetlb_fault_mutex_table[hash]);
 359
 360                 err = -ENOMEM;
 361                 dst_pte = huge_pte_alloc(dst_mm, dst_vma, dst_addr, vma_hpagesize);
 362                 if (!dst_pte) {
 363                         mutex_unlock(&hugetlb_fault_mutex_table[hash]);
 364                         i_mmap_unlock_read(mapping);
 365                         goto out_unlock;
 366                 }
 367
 368                 if (mode != MCOPY_ATOMIC_CONTINUE &&
 369                     !huge_pte_none(huge_ptep_get(dst_pte))) {
 370                         err = -EEXIST;
 371                         mutex_unlock(&hugetlb_fault_mutex_table[hash]);
 372                         i_mmap_unlock_read(mapping);
 373                         goto out_unlock;
 374                 }
 375
 376                 err = hugetlb_mcopy_atomic_pte(dst_mm, dst_pte, dst_vma,
 377                                                dst_addr, src_addr, mode, &page);
 378
 379                 mutex_unlock(&hugetlb_fault_mutex_table[hash]);
 380                 i_mmap_unlock_read(mapping);
 381
 382                 cond_resched();
 383
 384                 if (unlikely(err == -ENOENT)) {
 385                         mmap_read_unlock(dst_mm);
 386                         BUG_ON(!page);
 387
 388                         err = copy_huge_page_from_user(page,
 389                                                 (const void __user *)src_addr,
 390                                                 vma_hpagesize / PAGE_SIZE,
 391                                                 true);
 392                         if (unlikely(err)) {
 393                                 err = -EFAULT;
 394                                 goto out;
 395                         }
 396                         mmap_read_lock(dst_mm);
 397
 398                         dst_vma = NULL;
 399                         goto retry;
 400                 } else
 401                         BUG_ON(page);
 402
 403                 if (!err) {
 404                         dst_addr += vma_hpagesize;
 405                         src_addr += vma_hpagesize;
 406                         copied += vma_hpagesize;
 407
 408                         if (fatal_signal_pending(current))
 409                                 err = -EINTR;
 410                 }
 411                 if (err)
 412                         break;
 413         }
 414
 415 out_unlock:
 416         mmap_read_unlock(dst_mm);
 417 out:
 418         if (page)
 419                 put_page(page);
 420         BUG_ON(copied < 0);
 421         BUG_ON(err > 0);
 422         BUG_ON(!copied && !err);
 423         return copied ? copied : err;
 424 }
 425 #else /* !CONFIG_HUGETLB_PAGE */
 426 /* fail at build time if gcc attempts to use this */
 427 extern ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
 428                                       struct vm_area_struct *dst_vma,
 429                                       unsigned long dst_start,
 430                                       unsigned long src_start,
 431                                       unsigned long len,
 432                                       enum mcopy_atomic_mode mode);
 433 #endif /* CONFIG_HUGETLB_PAGE */
 434
 435 static __always_inline ssize_t mfill_atomic_pte(struct mm_struct *dst_mm,
 436                                                 pmd_t *dst_pmd,
 437                                                 struct vm_area_struct *dst_vma,
 438                                                 unsigned long dst_addr,
 439                                                 unsigned long src_addr,
 440                                                 struct page **page,
 441                                                 enum mcopy_atomic_mode mode,
 442                                                 bool wp_copy)
 443 {
 444         ssize_t err;
 445
 446         if (mode == MCOPY_ATOMIC_CONTINUE) {
 447                 return mcontinue_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
 448                                             wp_copy);
 449         }
 450
 451         /*
 452          * The normal page fault path for a shmem will invoke the
 453          * fault, fill the hole in the file and COW it right away. The
 454          * result generates plain anonymous memory. So when we are
 455          * asked to fill an hole in a MAP_PRIVATE shmem mapping, we'll
 456          * generate anonymous memory directly without actually filling
 457          * the hole. For the MAP_PRIVATE case the robustness check
 458          * only happens in the pagetable (to verify it's still none)
 459          * and not in the radix tree.
 460          */
 461         if (!(dst_vma->vm_flags & VM_SHARED)) {
 462                 if (mode == MCOPY_ATOMIC_NORMAL)
 463                         err = mcopy_atomic_pte(dst_mm, dst_pmd, dst_vma,
 464                                                dst_addr, src_addr, page,
 465                                                wp_copy);
 466                 else
 467                         err = mfill_zeropage_pte(dst_mm, dst_pmd,
 468                                                  dst_vma, dst_addr);
 469         } else {
 470                 VM_WARN_ON_ONCE(wp_copy);
 471                 err = shmem_mfill_atomic_pte(dst_mm, dst_pmd, dst_vma,
 472                                              dst_addr, src_addr,
 473                                              mode != MCOPY_ATOMIC_NORMAL,
 474                                              page);
 475         }
 476
 477         return err;
 478 }
 479
 480 static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm,
 481                                               unsigned long dst_start,
 482                                               unsigned long src_start,
 483                                               unsigned long len,
 484                                               enum mcopy_atomic_mode mcopy_mode,
 485                                               atomic_t *mmap_changing,
 486                                               __u64 mode)
 487 {
 488         struct vm_area_struct *dst_vma;
 489         ssize_t err;
 490         pmd_t *dst_pmd;
 491         unsigned long src_addr, dst_addr;
 492         long copied;
 493         struct page *page;
 494         bool wp_copy;
 495
 496         /*
 497          * Sanitize the command parameters:
 498          */
 499         BUG_ON(dst_start & ~PAGE_MASK);
 500         BUG_ON(len & ~PAGE_MASK);
 501
 502         /* Does the address range wrap, or is the span zero-sized? */
 503         BUG_ON(src_start + len <= src_start);
 504         BUG_ON(dst_start + len <= dst_start);
 505
 506         src_addr = src_start;
 507         dst_addr = dst_start;
 508         copied = 0;
 509         page = NULL;
 510 retry:
 511         mmap_read_lock(dst_mm);
 512
 513         /*
 514          * If memory mappings are changing because of non-cooperative
 515          * operation (e.g. mremap) running in parallel, bail out and
 516          * request the user to retry later
 517          */
 518         err = -EAGAIN;
 519         if (mmap_changing && atomic_read(mmap_changing))
 520                 goto out_unlock;
 521
 522         /*
 523          * Make sure the vma is not shared, that the dst range is
 524          * both valid and fully within a single existing vma.
 525          */
 526         err = -ENOENT;
 527         dst_vma = find_dst_vma(dst_mm, dst_start, len);
 528         if (!dst_vma)
 529                 goto out_unlock;
 530
 531         err = -EINVAL;
 532         /*
 533          * shmem_zero_setup is invoked in mmap for MAP_ANONYMOUS|MAP_SHARED but
 534          * it will overwrite vm_ops, so vma_is_anonymous must return false.
 535          */
 536         if (WARN_ON_ONCE(vma_is_anonymous(dst_vma) &&
 537             dst_vma->vm_flags & VM_SHARED))
 538                 goto out_unlock;
 539
 540         /*
 541          * validate 'mode' now that we know the dst_vma: don't allow
 542          * a wrprotect copy if the userfaultfd didn't register as WP.
 543          */
 544         wp_copy = mode & UFFDIO_COPY_MODE_WP;
 545         if (wp_copy && !(dst_vma->vm_flags & VM_UFFD_WP))
 546                 goto out_unlock;
 547
 548         /*
 549          * If this is a HUGETLB vma, pass off to appropriate routine
 550          */
 551         if (is_vm_hugetlb_page(dst_vma))
 552                 return  __mcopy_atomic_hugetlb(dst_mm, dst_vma, dst_start,
 553                                                 src_start, len, mcopy_mode);
 554
 555         if (!vma_is_anonymous(dst_vma) && !vma_is_shmem(dst_vma))
 556                 goto out_unlock;
 557         if (!vma_is_shmem(dst_vma) && mcopy_mode == MCOPY_ATOMIC_CONTINUE)
 558                 goto out_unlock;
 559
 560         /*
 561          * Ensure the dst_vma has a anon_vma or this page
 562          * would get a NULL anon_vma when moved in the
 563          * dst_vma.
 564          */
 565         err = -ENOMEM;
 566         if (!(dst_vma->vm_flags & VM_SHARED) &&
 567             unlikely(anon_vma_prepare(dst_vma)))
 568                 goto out_unlock;
 569
 570         while (src_addr < src_start + len) {
 571                 pmd_t dst_pmdval;
 572
 573                 BUG_ON(dst_addr >= dst_start + len);
 574
 575                 dst_pmd = mm_alloc_pmd(dst_mm, dst_addr);
 576                 if (unlikely(!dst_pmd)) {
 577                         err = -ENOMEM;
 578                         break;
 579                 }
 580
 581                 dst_pmdval = pmd_read_atomic(dst_pmd);
 582                 /*
 583                  * If the dst_pmd is mapped as THP don't
 584                  * override it and just be strict.
 585                  */
 586                 if (unlikely(pmd_trans_huge(dst_pmdval))) {
 587                         err = -EEXIST;
 588                         break;
 589                 }
 590                 if (unlikely(pmd_none(dst_pmdval)) &&
 591                     unlikely(__pte_alloc(dst_mm, dst_pmd))) {
 592                         err = -ENOMEM;
 593                         break;
 594                 }
 595                 /* If an huge pmd materialized from under us fail */
 596                 if (unlikely(pmd_trans_huge(*dst_pmd))) {
 597                         err = -EFAULT;
 598                         break;
 599                 }
 600
 601                 BUG_ON(pmd_none(*dst_pmd));
 602                 BUG_ON(pmd_trans_huge(*dst_pmd));
 603
 604                 err = mfill_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
 605                                        src_addr, &page, mcopy_mode, wp_copy);
 606                 cond_resched();
 607
 608                 if (unlikely(err == -ENOENT)) {
 609                         void *page_kaddr;
 610
 611                         mmap_read_unlock(dst_mm);
 612                         BUG_ON(!page);
 613
 614                         page_kaddr = kmap(page);
 615                         err = copy_from_user(page_kaddr,
 616                                              (const void __user *) src_addr,
 617                                              PAGE_SIZE);
 618                         kunmap(page);
 619                         if (unlikely(err)) {
 620                                 err = -EFAULT;
 621                                 goto out;
 622                         }
 623                         goto retry;
 624                 } else
 625                         BUG_ON(page);
 626
 627                 if (!err) {
 628                         dst_addr += PAGE_SIZE;
 629                         src_addr += PAGE_SIZE;
 630                         copied += PAGE_SIZE;
 631
 632                         if (fatal_signal_pending(current))
 633                                 err = -EINTR;
 634                 }
 635                 if (err)
 636                         break;
 637         }
 638
 639 out_unlock:
 640         mmap_read_unlock(dst_mm);
 641 out:
 642         if (page)
 643                 put_page(page);
 644         BUG_ON(copied < 0);
 645         BUG_ON(err > 0);
 646         BUG_ON(!copied && !err);
 647         return copied ? copied : err;
 648 }
 649
 650 ssize_t mcopy_atomic(struct mm_struct *dst_mm, unsigned long dst_start,
 651                      unsigned long src_start, unsigned long len,
 652                      atomic_t *mmap_changing, __u64 mode)
 653 {
 654         return __mcopy_atomic(dst_mm, dst_start, src_start, len,
 655                               MCOPY_ATOMIC_NORMAL, mmap_changing, mode);
 656 }
 657
 658 ssize_t mfill_zeropage(struct mm_struct *dst_mm, unsigned long start,
 659                        unsigned long len, atomic_t *mmap_changing)
 660 {
 661         return __mcopy_atomic(dst_mm, start, 0, len, MCOPY_ATOMIC_ZEROPAGE,
 662                               mmap_changing, 0);
 663 }
 664
 665 ssize_t mcopy_continue(struct mm_struct *dst_mm, unsigned long start,
 666                        unsigned long len, atomic_t *mmap_changing)
 667 {
 668         return __mcopy_atomic(dst_mm, start, 0, len, MCOPY_ATOMIC_CONTINUE,
 669                               mmap_changing, 0);
 670 }
 671
 672 int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start,
 673                         unsigned long len, bool enable_wp,
 674                         atomic_t *mmap_changing)
 675 {
 676         struct vm_area_struct *dst_vma;
 677         pgprot_t newprot;
 678         int err;
 679
 680         /*
 681          * Sanitize the command parameters:
 682          */
 683         BUG_ON(start & ~PAGE_MASK);
 684         BUG_ON(len & ~PAGE_MASK);
 685
 686         /* Does the address range wrap, or is the span zero-sized? */
 687         BUG_ON(start + len <= start);
 688
 689         mmap_read_lock(dst_mm);
 690
 691         /*
 692          * If memory mappings are changing because of non-cooperative
 693          * operation (e.g. mremap) running in parallel, bail out and
 694          * request the user to retry later
 695          */
 696         err = -EAGAIN;
 697         if (mmap_changing && atomic_read(mmap_changing))
 698                 goto out_unlock;
 699
 700         err = -ENOENT;
 701         dst_vma = find_dst_vma(dst_mm, start, len);
 702         /*
 703          * Make sure the vma is not shared, that the dst range is
 704          * both valid and fully within a single existing vma.
 705          */
 706         if (!dst_vma || (dst_vma->vm_flags & VM_SHARED))
 707                 goto out_unlock;
 708         if (!userfaultfd_wp(dst_vma))
 709                 goto out_unlock;
 710         if (!vma_is_anonymous(dst_vma))
 711                 goto out_unlock;
 712
 713         if (enable_wp)
 714                 newprot = vm_get_page_prot(dst_vma->vm_flags & ~(VM_WRITE));
 715         else
 716                 newprot = vm_get_page_prot(dst_vma->vm_flags);
 717
 718         change_protection(dst_vma, start, start + len, newprot,
 719                           enable_wp ? MM_CP_UFFD_WP : MM_CP_UFFD_WP_RESOLVE);
 720
 721         err = 0;
 722 out_unlock:
 723         mmap_read_unlock(dst_mm);
 724         return err;
 725 }