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         if (page_in_cache && !vm_shared)
  73                 writable = false;
  74         if (writable || !page_in_cache)
  75                 _dst_pte = pte_mkdirty(_dst_pte);
  76         if (writable) {
  77                 if (wp_copy)
  78                         _dst_pte = pte_mkuffd_wp(_dst_pte);
  79                 else
  80                         _dst_pte = pte_mkwrite(_dst_pte);
  81         }
  82
  83         dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
  84
  85         if (vma_is_shmem(dst_vma)) {
  86                 /* serialize against truncate with the page table lock */
  87                 inode = dst_vma->vm_file->f_inode;
  88                 offset = linear_page_index(dst_vma, dst_addr);
  89                 max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
  90                 ret = -EFAULT;
  91                 if (unlikely(offset >= max_off))
  92                         goto out_unlock;
  93         }
  94
  95         ret = -EEXIST;
  96         if (!pte_none(*dst_pte))
  97                 goto out_unlock;
  98
  99         if (page_in_cache)
 100                 page_add_file_rmap(page, false);
 101         else
 102                 page_add_new_anon_rmap(page, dst_vma, dst_addr, false);
 103
 104         /*
 105          * Must happen after rmap, as mm_counter() checks mapping (via
 106          * PageAnon()), which is set by __page_set_anon_rmap().
 107          */
 108         inc_mm_counter(dst_mm, mm_counter(page));
 109
 110         if (newly_allocated)
 111                 lru_cache_add_inactive_or_unevictable(page, dst_vma);
 112
 113         set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
 114
 115         /* No need to invalidate - it was non-present before */
 116         update_mmu_cache(dst_vma, dst_addr, dst_pte);
 117         ret = 0;
 118 out_unlock:
 119         pte_unmap_unlock(dst_pte, ptl);
 120         return ret;
 121 }
 122
 123 static int mcopy_atomic_pte(struct mm_struct *dst_mm,
 124                             pmd_t *dst_pmd,
 125                             struct vm_area_struct *dst_vma,
 126                             unsigned long dst_addr,
 127                             unsigned long src_addr,
 128                             struct page **pagep,
 129                             bool wp_copy)
 130 {
 131         void *page_kaddr;
 132         int ret;
 133         struct page *page;
 134
 135         if (!*pagep) {
 136                 ret = -ENOMEM;
 137                 page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, dst_vma, dst_addr);
 138                 if (!page)
 139                         goto out;
 140
 141                 page_kaddr = kmap_atomic(page);
 142                 ret = copy_from_user(page_kaddr,
 143                                      (const void __user *) src_addr,
 144                                      PAGE_SIZE);
 145                 kunmap_atomic(page_kaddr);
 146
 147                 /* fallback to copy_from_user outside mmap_lock */
 148                 if (unlikely(ret)) {
 149                         ret = -ENOENT;
 150                         *pagep = page;
 151                         /* don't free the page */
 152                         goto out;
 153                 }
 154         } else {
 155                 page = *pagep;
 156                 *pagep = NULL;
 157         }
 158
 159         /*
 160          * The memory barrier inside __SetPageUptodate makes sure that
 161          * preceding stores to the page contents become visible before
 162          * the set_pte_at() write.
 163          */
 164         __SetPageUptodate(page);
 165
 166         ret = -ENOMEM;
 167         if (mem_cgroup_charge(page, dst_mm, GFP_KERNEL))
 168                 goto out_release;
 169
 170         ret = mfill_atomic_install_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
 171                                        page, true, wp_copy);
 172         if (ret)
 173                 goto out_release;
 174 out:
 175         return ret;
 176 out_release:
 177         put_page(page);
 178         goto out;
 179 }
 180
 181 static int mfill_zeropage_pte(struct mm_struct *dst_mm,
 182                               pmd_t *dst_pmd,
 183                               struct vm_area_struct *dst_vma,
 184                               unsigned long dst_addr)
 185 {
 186         pte_t _dst_pte, *dst_pte;
 187         spinlock_t *ptl;
 188         int ret;
 189         pgoff_t offset, max_off;
 190         struct inode *inode;
 191
 192         _dst_pte = pte_mkspecial(pfn_pte(my_zero_pfn(dst_addr),
 193                                          dst_vma->vm_page_prot));
 194         dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
 195         if (dst_vma->vm_file) {
 196                 /* the shmem MAP_PRIVATE case requires checking the i_size */
 197                 inode = dst_vma->vm_file->f_inode;
 198                 offset = linear_page_index(dst_vma, dst_addr);
 199                 max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
 200                 ret = -EFAULT;
 201                 if (unlikely(offset >= max_off))
 202                         goto out_unlock;
 203         }
 204         ret = -EEXIST;
 205         if (!pte_none(*dst_pte))
 206                 goto out_unlock;
 207         set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
 208         /* No need to invalidate - it was non-present before */
 209         update_mmu_cache(dst_vma, dst_addr, dst_pte);
 210         ret = 0;
 211 out_unlock:
 212         pte_unmap_unlock(dst_pte, ptl);
 213         return ret;
 214 }
 215
 216 /* Handles UFFDIO_CONTINUE for all shmem VMAs (shared or private). */
 217 static int mcontinue_atomic_pte(struct mm_struct *dst_mm,
 218                                 pmd_t *dst_pmd,
 219                                 struct vm_area_struct *dst_vma,
 220                                 unsigned long dst_addr,
 221                                 bool wp_copy)
 222 {
 223         struct inode *inode = file_inode(dst_vma->vm_file);
 224         pgoff_t pgoff = linear_page_index(dst_vma, dst_addr);
 225         struct page *page;
 226         int ret;
 227
 228         ret = shmem_getpage(inode, pgoff, &page, SGP_READ);
 229         if (ret)
 230                 goto out;
 231         if (!page) {
 232                 ret = -EFAULT;
 233                 goto out;
 234         }
 235
 236         ret = mfill_atomic_install_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
 237                                        page, false, wp_copy);
 238         if (ret)
 239                 goto out_release;
 240
 241         unlock_page(page);
 242         ret = 0;
 243 out:
 244         return ret;
 245 out_release:
 246         unlock_page(page);
 247         put_page(page);
 248         goto out;
 249 }
 250
 251 static pmd_t *mm_alloc_pmd(struct mm_struct *mm, unsigned long address)
 252 {
 253         pgd_t *pgd;
 254         p4d_t *p4d;
 255         pud_t *pud;
 256
 257         pgd = pgd_offset(mm, address);
 258         p4d = p4d_alloc(mm, pgd, address);
 259         if (!p4d)
 260                 return NULL;
 261         pud = pud_alloc(mm, p4d, address);
 262         if (!pud)
 263                 return NULL;
 264         /*
 265          * Note that we didn't run this because the pmd was
 266          * missing, the *pmd may be already established and in
 267          * turn it may also be a trans_huge_pmd.
 268          */
 269         return pmd_alloc(mm, pud, address);
 270 }
 271
 272 #ifdef CONFIG_HUGETLB_PAGE
 273 /*
 274  * __mcopy_atomic processing for HUGETLB vmas.  Note that this routine is
 275  * called with mmap_lock held, it will release mmap_lock before returning.
 276  */
 277 static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
 278                                               struct vm_area_struct *dst_vma,
 279                                               unsigned long dst_start,
 280                                               unsigned long src_start,
 281                                               unsigned long len,
 282                                               enum mcopy_atomic_mode mode)
 283 {
 284         int vm_shared = dst_vma->vm_flags & VM_SHARED;
 285         ssize_t err;
 286         pte_t *dst_pte;
 287         unsigned long src_addr, dst_addr;
 288         long copied;
 289         struct page *page;
 290         unsigned long vma_hpagesize;
 291         pgoff_t idx;
 292         u32 hash;
 293         struct address_space *mapping;
 294
 295         /*
 296          * There is no default zero huge page for all huge page sizes as
 297          * supported by hugetlb.  A PMD_SIZE huge pages may exist as used
 298          * by THP.  Since we can not reliably insert a zero page, this
 299          * feature is not supported.
 300          */
 301         if (mode == MCOPY_ATOMIC_ZEROPAGE) {
 302                 mmap_read_unlock(dst_mm);
 303                 return -EINVAL;
 304         }
 305
 306         src_addr = src_start;
 307         dst_addr = dst_start;
 308         copied = 0;
 309         page = NULL;
 310         vma_hpagesize = vma_kernel_pagesize(dst_vma);
 311
 312         /*
 313          * Validate alignment based on huge page size
 314          */
 315         err = -EINVAL;
 316         if (dst_start & (vma_hpagesize - 1) || len & (vma_hpagesize - 1))
 317                 goto out_unlock;
 318
 319 retry:
 320         /*
 321          * On routine entry dst_vma is set.  If we had to drop mmap_lock and
 322          * retry, dst_vma will be set to NULL and we must lookup again.
 323          */
 324         if (!dst_vma) {
 325                 err = -ENOENT;
 326                 dst_vma = find_dst_vma(dst_mm, dst_start, len);
 327                 if (!dst_vma || !is_vm_hugetlb_page(dst_vma))
 328                         goto out_unlock;
 329
 330                 err = -EINVAL;
 331                 if (vma_hpagesize != vma_kernel_pagesize(dst_vma))
 332                         goto out_unlock;
 333
 334                 vm_shared = dst_vma->vm_flags & VM_SHARED;
 335         }
 336
 337         /*
 338          * If not shared, ensure the dst_vma has a anon_vma.
 339          */
 340         err = -ENOMEM;
 341         if (!vm_shared) {
 342                 if (unlikely(anon_vma_prepare(dst_vma)))
 343                         goto out_unlock;
 344         }
 345
 346         while (src_addr < src_start + len) {
 347                 BUG_ON(dst_addr >= dst_start + len);
 348
 349                 /*
 350                  * Serialize via i_mmap_rwsem and hugetlb_fault_mutex.
 351                  * i_mmap_rwsem ensures the dst_pte remains valid even
 352                  * in the case of shared pmds.  fault mutex prevents
 353                  * races with other faulting threads.
 354                  */
 355                 mapping = dst_vma->vm_file->f_mapping;
 356                 i_mmap_lock_read(mapping);
 357                 idx = linear_page_index(dst_vma, dst_addr);
 358                 hash = hugetlb_fault_mutex_hash(mapping, idx);
 359                 mutex_lock(&hugetlb_fault_mutex_table[hash]);
 360
 361                 err = -ENOMEM;
 362                 dst_pte = huge_pte_alloc(dst_mm, dst_vma, dst_addr, vma_hpagesize);
 363                 if (!dst_pte) {
 364                         mutex_unlock(&hugetlb_fault_mutex_table[hash]);
 365                         i_mmap_unlock_read(mapping);
 366                         goto out_unlock;
 367                 }
 368
 369                 if (mode != MCOPY_ATOMIC_CONTINUE &&
 370                     !huge_pte_none(huge_ptep_get(dst_pte))) {
 371                         err = -EEXIST;
 372                         mutex_unlock(&hugetlb_fault_mutex_table[hash]);
 373                         i_mmap_unlock_read(mapping);
 374                         goto out_unlock;
 375                 }
 376
 377                 err = hugetlb_mcopy_atomic_pte(dst_mm, dst_pte, dst_vma,
 378                                                dst_addr, src_addr, mode, &page);
 379
 380                 mutex_unlock(&hugetlb_fault_mutex_table[hash]);
 381                 i_mmap_unlock_read(mapping);
 382
 383                 cond_resched();
 384
 385                 if (unlikely(err == -ENOENT)) {
 386                         mmap_read_unlock(dst_mm);
 387                         BUG_ON(!page);
 388
 389                         err = copy_huge_page_from_user(page,
 390                                                 (const void __user *)src_addr,
 391                                                 vma_hpagesize / PAGE_SIZE,
 392                                                 true);
 393                         if (unlikely(err)) {
 394                                 err = -EFAULT;
 395                                 goto out;
 396                         }
 397                         mmap_read_lock(dst_mm);
 398
 399                         dst_vma = NULL;
 400                         goto retry;
 401                 } else
 402                         BUG_ON(page);
 403
 404                 if (!err) {
 405                         dst_addr += vma_hpagesize;
 406                         src_addr += vma_hpagesize;
 407                         copied += vma_hpagesize;
 408
 409                         if (fatal_signal_pending(current))
 410                                 err = -EINTR;
 411                 }
 412                 if (err)
 413                         break;
 414         }
 415
 416 out_unlock:
 417         mmap_read_unlock(dst_mm);
 418 out:
 419         if (page)
 420                 put_page(page);
 421         BUG_ON(copied < 0);
 422         BUG_ON(err > 0);
 423         BUG_ON(!copied && !err);
 424         return copied ? copied : err;
 425 }
 426 #else /* !CONFIG_HUGETLB_PAGE */
 427 /* fail at build time if gcc attempts to use this */
 428 extern ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
 429                                       struct vm_area_struct *dst_vma,
 430                                       unsigned long dst_start,
 431                                       unsigned long src_start,
 432                                       unsigned long len,
 433                                       enum mcopy_atomic_mode mode);
 434 #endif /* CONFIG_HUGETLB_PAGE */
 435
 436 static __always_inline ssize_t mfill_atomic_pte(struct mm_struct *dst_mm,
 437                                                 pmd_t *dst_pmd,
 438                                                 struct vm_area_struct *dst_vma,
 439                                                 unsigned long dst_addr,
 440                                                 unsigned long src_addr,
 441                                                 struct page **page,
 442                                                 enum mcopy_atomic_mode mode,
 443                                                 bool wp_copy)
 444 {
 445         ssize_t err;
 446
 447         if (mode == MCOPY_ATOMIC_CONTINUE) {
 448                 return mcontinue_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
 449                                             wp_copy);
 450         }
 451
 452         /*
 453          * The normal page fault path for a shmem will invoke the
 454          * fault, fill the hole in the file and COW it right away. The
 455          * result generates plain anonymous memory. So when we are
 456          * asked to fill an hole in a MAP_PRIVATE shmem mapping, we'll
 457          * generate anonymous memory directly without actually filling
 458          * the hole. For the MAP_PRIVATE case the robustness check
 459          * only happens in the pagetable (to verify it's still none)
 460          * and not in the radix tree.
 461          */
 462         if (!(dst_vma->vm_flags & VM_SHARED)) {
 463                 if (mode == MCOPY_ATOMIC_NORMAL)
 464                         err = mcopy_atomic_pte(dst_mm, dst_pmd, dst_vma,
 465                                                dst_addr, src_addr, page,
 466                                                wp_copy);
 467                 else
 468                         err = mfill_zeropage_pte(dst_mm, dst_pmd,
 469                                                  dst_vma, dst_addr);
 470         } else {
 471                 VM_WARN_ON_ONCE(wp_copy);
 472                 err = shmem_mfill_atomic_pte(dst_mm, dst_pmd, dst_vma,
 473                                              dst_addr, src_addr,
 474                                              mode != MCOPY_ATOMIC_NORMAL,
 475                                              page);
 476         }
 477
 478         return err;
 479 }
 480
 481 static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm,
 482                                               unsigned long dst_start,
 483                                               unsigned long src_start,
 484                                               unsigned long len,
 485                                               enum mcopy_atomic_mode mcopy_mode,
 486                                               atomic_t *mmap_changing,
 487                                               __u64 mode)
 488 {
 489         struct vm_area_struct *dst_vma;
 490         ssize_t err;
 491         pmd_t *dst_pmd;
 492         unsigned long src_addr, dst_addr;
 493         long copied;
 494         struct page *page;
 495         bool wp_copy;
 496
 497         /*
 498          * Sanitize the command parameters:
 499          */
 500         BUG_ON(dst_start & ~PAGE_MASK);
 501         BUG_ON(len & ~PAGE_MASK);
 502
 503         /* Does the address range wrap, or is the span zero-sized? */
 504         BUG_ON(src_start + len <= src_start);
 505         BUG_ON(dst_start + len <= dst_start);
 506
 507         src_addr = src_start;
 508         dst_addr = dst_start;
 509         copied = 0;
 510         page = NULL;
 511 retry:
 512         mmap_read_lock(dst_mm);
 513
 514         /*
 515          * If memory mappings are changing because of non-cooperative
 516          * operation (e.g. mremap) running in parallel, bail out and
 517          * request the user to retry later
 518          */
 519         err = -EAGAIN;
 520         if (mmap_changing && atomic_read(mmap_changing))
 521                 goto out_unlock;
 522
 523         /*
 524          * Make sure the vma is not shared, that the dst range is
 525          * both valid and fully within a single existing vma.
 526          */
 527         err = -ENOENT;
 528         dst_vma = find_dst_vma(dst_mm, dst_start, len);
 529         if (!dst_vma)
 530                 goto out_unlock;
 531
 532         err = -EINVAL;
 533         /*
 534          * shmem_zero_setup is invoked in mmap for MAP_ANONYMOUS|MAP_SHARED but
 535          * it will overwrite vm_ops, so vma_is_anonymous must return false.
 536          */
 537         if (WARN_ON_ONCE(vma_is_anonymous(dst_vma) &&
 538             dst_vma->vm_flags & VM_SHARED))
 539                 goto out_unlock;
 540
 541         /*
 542          * validate 'mode' now that we know the dst_vma: don't allow
 543          * a wrprotect copy if the userfaultfd didn't register as WP.
 544          */
 545         wp_copy = mode & UFFDIO_COPY_MODE_WP;
 546         if (wp_copy && !(dst_vma->vm_flags & VM_UFFD_WP))
 547                 goto out_unlock;
 548
 549         /*
 550          * If this is a HUGETLB vma, pass off to appropriate routine
 551          */
 552         if (is_vm_hugetlb_page(dst_vma))
 553                 return  __mcopy_atomic_hugetlb(dst_mm, dst_vma, dst_start,
 554                                                 src_start, len, mcopy_mode);
 555
 556         if (!vma_is_anonymous(dst_vma) && !vma_is_shmem(dst_vma))
 557                 goto out_unlock;
 558         if (!vma_is_shmem(dst_vma) && mcopy_mode == MCOPY_ATOMIC_CONTINUE)
 559                 goto out_unlock;
 560
 561         /*
 562          * Ensure the dst_vma has a anon_vma or this page
 563          * would get a NULL anon_vma when moved in the
 564          * dst_vma.
 565          */
 566         err = -ENOMEM;
 567         if (!(dst_vma->vm_flags & VM_SHARED) &&
 568             unlikely(anon_vma_prepare(dst_vma)))
 569                 goto out_unlock;
 570
 571         while (src_addr < src_start + len) {
 572                 pmd_t dst_pmdval;
 573
 574                 BUG_ON(dst_addr >= dst_start + len);
 575
 576                 dst_pmd = mm_alloc_pmd(dst_mm, dst_addr);
 577                 if (unlikely(!dst_pmd)) {
 578                         err = -ENOMEM;
 579                         break;
 580                 }
 581
 582                 dst_pmdval = pmd_read_atomic(dst_pmd);
 583                 /*
 584                  * If the dst_pmd is mapped as THP don't
 585                  * override it and just be strict.
 586                  */
 587                 if (unlikely(pmd_trans_huge(dst_pmdval))) {
 588                         err = -EEXIST;
 589                         break;
 590                 }
 591                 if (unlikely(pmd_none(dst_pmdval)) &&
 592                     unlikely(__pte_alloc(dst_mm, dst_pmd))) {
 593                         err = -ENOMEM;
 594                         break;
 595                 }
 596                 /* If an huge pmd materialized from under us fail */
 597                 if (unlikely(pmd_trans_huge(*dst_pmd))) {
 598                         err = -EFAULT;
 599                         break;
 600                 }
 601
 602                 BUG_ON(pmd_none(*dst_pmd));
 603                 BUG_ON(pmd_trans_huge(*dst_pmd));
 604
 605                 err = mfill_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
 606                                        src_addr, &page, mcopy_mode, wp_copy);
 607                 cond_resched();
 608
 609                 if (unlikely(err == -ENOENT)) {
 610                         void *page_kaddr;
 611
 612                         mmap_read_unlock(dst_mm);
 613                         BUG_ON(!page);
 614
 615                         page_kaddr = kmap(page);
 616                         err = copy_from_user(page_kaddr,
 617                                              (const void __user *) src_addr,
 618                                              PAGE_SIZE);
 619                         kunmap(page);
 620                         if (unlikely(err)) {
 621                                 err = -EFAULT;
 622                                 goto out;
 623                         }
 624                         goto retry;
 625                 } else
 626                         BUG_ON(page);
 627
 628                 if (!err) {
 629                         dst_addr += PAGE_SIZE;
 630                         src_addr += PAGE_SIZE;
 631                         copied += PAGE_SIZE;
 632
 633                         if (fatal_signal_pending(current))
 634                                 err = -EINTR;
 635                 }
 636                 if (err)
 637                         break;
 638         }
 639
 640 out_unlock:
 641         mmap_read_unlock(dst_mm);
 642 out:
 643         if (page)
 644                 put_page(page);
 645         BUG_ON(copied < 0);
 646         BUG_ON(err > 0);
 647         BUG_ON(!copied && !err);
 648         return copied ? copied : err;
 649 }
 650
 651 ssize_t mcopy_atomic(struct mm_struct *dst_mm, unsigned long dst_start,
 652                      unsigned long src_start, unsigned long len,
 653                      atomic_t *mmap_changing, __u64 mode)
 654 {
 655         return __mcopy_atomic(dst_mm, dst_start, src_start, len,
 656                               MCOPY_ATOMIC_NORMAL, mmap_changing, mode);
 657 }
 658
 659 ssize_t mfill_zeropage(struct mm_struct *dst_mm, unsigned long start,
 660                        unsigned long len, atomic_t *mmap_changing)
 661 {
 662         return __mcopy_atomic(dst_mm, start, 0, len, MCOPY_ATOMIC_ZEROPAGE,
 663                               mmap_changing, 0);
 664 }
 665
 666 ssize_t mcopy_continue(struct mm_struct *dst_mm, unsigned long start,
 667                        unsigned long len, atomic_t *mmap_changing)
 668 {
 669         return __mcopy_atomic(dst_mm, start, 0, len, MCOPY_ATOMIC_CONTINUE,
 670                               mmap_changing, 0);
 671 }
 672
 673 int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start,
 674                         unsigned long len, bool enable_wp,
 675                         atomic_t *mmap_changing)
 676 {
 677         struct vm_area_struct *dst_vma;
 678         pgprot_t newprot;
 679         int err;
 680
 681         /*
 682          * Sanitize the command parameters:
 683          */
 684         BUG_ON(start & ~PAGE_MASK);
 685         BUG_ON(len & ~PAGE_MASK);
 686
 687         /* Does the address range wrap, or is the span zero-sized? */
 688         BUG_ON(start + len <= start);
 689
 690         mmap_read_lock(dst_mm);
 691
 692         /*
 693          * If memory mappings are changing because of non-cooperative
 694          * operation (e.g. mremap) running in parallel, bail out and
 695          * request the user to retry later
 696          */
 697         err = -EAGAIN;
 698         if (mmap_changing && atomic_read(mmap_changing))
 699                 goto out_unlock;
 700
 701         err = -ENOENT;
 702         dst_vma = find_dst_vma(dst_mm, start, len);
 703         /*
 704          * Make sure the vma is not shared, that the dst range is
 705          * both valid and fully within a single existing vma.
 706          */
 707         if (!dst_vma || (dst_vma->vm_flags & VM_SHARED))
 708                 goto out_unlock;
 709         if (!userfaultfd_wp(dst_vma))
 710                 goto out_unlock;
 711         if (!vma_is_anonymous(dst_vma))
 712                 goto out_unlock;
 713
 714         if (enable_wp)
 715                 newprot = vm_get_page_prot(dst_vma->vm_flags & ~(VM_WRITE));
 716         else
 717                 newprot = vm_get_page_prot(dst_vma->vm_flags);
 718
 719         change_protection(dst_vma, start, start + len, newprot,
 720                           enable_wp ? MM_CP_UFFD_WP : MM_CP_UFFD_WP_RESOLVE);
 721
 722         err = 0;
 723 out_unlock:
 724         mmap_read_unlock(dst_mm);
 725         return err;
 726 }