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 <asm/tlb.h>
  20 #include "internal.h"
  21
  22 static __always_inline
  23 struct vm_area_struct *find_dst_vma(struct mm_struct *dst_mm,
  24                                     unsigned long dst_start,
  25                                     unsigned long len)
  26 {
  27         /*
  28          * Make sure that the dst range is both valid and fully within a
  29          * single existing vma.
  30          */
  31         struct vm_area_struct *dst_vma;
  32
  33         dst_vma = find_vma(dst_mm, dst_start);
  34         if (!dst_vma)
  35                 return NULL;
  36
  37         if (dst_start < dst_vma->vm_start ||
  38             dst_start + len > dst_vma->vm_end)
  39                 return NULL;
  40
  41         /*
  42          * Check the vma is registered in uffd, this is required to
  43          * enforce the VM_MAYWRITE check done at uffd registration
  44          * time.
  45          */
  46         if (!dst_vma->vm_userfaultfd_ctx.ctx)
  47                 return NULL;
  48
  49         return dst_vma;
  50 }
  51
  52 /*
  53  * Install PTEs, to map dst_addr (within dst_vma) to page.
  54  *
  55  * This function handles both MCOPY_ATOMIC_NORMAL and _CONTINUE for both shmem
  56  * and anon, and for both shared and private VMAs.
  57  */
  58 int mfill_atomic_install_pte(struct mm_struct *dst_mm, pmd_t *dst_pmd,
  59                              struct vm_area_struct *dst_vma,
  60                              unsigned long dst_addr, struct page *page,
  61                              bool newly_allocated, bool wp_copy)
  62 {
  63         int ret;
  64         pte_t _dst_pte, *dst_pte;
  65         bool writable = dst_vma->vm_flags & VM_WRITE;
  66         bool vm_shared = dst_vma->vm_flags & VM_SHARED;
  67         bool page_in_cache = page->mapping;
  68         spinlock_t *ptl;
  69         struct inode *inode;
  70         pgoff_t offset, max_off;
  71
  72         _dst_pte = mk_pte(page, dst_vma->vm_page_prot);
  73         _dst_pte = pte_mkdirty(_dst_pte);
  74         if (page_in_cache && !vm_shared)
  75                 writable = false;
  76
  77         /*
  78          * Always mark a PTE as write-protected when needed, regardless of
  79          * VM_WRITE, which the user might change.
  80          */
  81         if (wp_copy) {
  82                 _dst_pte = pte_mkuffd_wp(_dst_pte);
  83                 writable = false;
  84         }
  85
  86         if (writable)
  87                 _dst_pte = pte_mkwrite(_dst_pte);
  88         else
  89                 /*
  90                  * We need this to make sure write bit removed; as mk_pte()
  91                  * could return a pte with write bit set.
  92                  */
  93                 _dst_pte = pte_wrprotect(_dst_pte);
  94
  95         dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
  96
  97         if (vma_is_shmem(dst_vma)) {
  98                 /* serialize against truncate with the page table lock */
  99                 inode = dst_vma->vm_file->f_inode;
 100                 offset = linear_page_index(dst_vma, dst_addr);
 101                 max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
 102                 ret = -EFAULT;
 103                 if (unlikely(offset >= max_off))
 104                         goto out_unlock;
 105         }
 106
 107         ret = -EEXIST;
 108         /*
 109          * We allow to overwrite a pte marker: consider when both MISSING|WP
 110          * registered, we firstly wr-protect a none pte which has no page cache
 111          * page backing it, then access the page.
 112          */
 113         if (!pte_none_mostly(*dst_pte))
 114                 goto out_unlock;
 115
 116         if (page_in_cache) {
 117                 /* Usually, cache pages are already added to LRU */
 118                 if (newly_allocated)
 119                         lru_cache_add(page);
 120                 page_add_file_rmap(page, dst_vma, false);
 121         } else {
 122                 page_add_new_anon_rmap(page, dst_vma, dst_addr);
 123                 lru_cache_add_inactive_or_unevictable(page, dst_vma);
 124         }
 125
 126         /*
 127          * Must happen after rmap, as mm_counter() checks mapping (via
 128          * PageAnon()), which is set by __page_set_anon_rmap().
 129          */
 130         inc_mm_counter(dst_mm, mm_counter(page));
 131
 132         set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
 133
 134         /* No need to invalidate - it was non-present before */
 135         update_mmu_cache(dst_vma, dst_addr, dst_pte);
 136         ret = 0;
 137 out_unlock:
 138         pte_unmap_unlock(dst_pte, ptl);
 139         return ret;
 140 }
 141
 142 static int mcopy_atomic_pte(struct mm_struct *dst_mm,
 143                             pmd_t *dst_pmd,
 144                             struct vm_area_struct *dst_vma,
 145                             unsigned long dst_addr,
 146                             unsigned long src_addr,
 147                             struct page **pagep,
 148                             bool wp_copy)
 149 {
 150         void *page_kaddr;
 151         int ret;
 152         struct page *page;
 153
 154         if (!*pagep) {
 155                 ret = -ENOMEM;
 156                 page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, dst_vma, dst_addr);
 157                 if (!page)
 158                         goto out;
 159
 160                 page_kaddr = kmap_atomic(page);
 161                 ret = copy_from_user(page_kaddr,
 162                                      (const void __user *) src_addr,
 163                                      PAGE_SIZE);
 164                 kunmap_atomic(page_kaddr);
 165
 166                 /* fallback to copy_from_user outside mmap_lock */
 167                 if (unlikely(ret)) {
 168                         ret = -ENOENT;
 169                         *pagep = page;
 170                         /* don't free the page */
 171                         goto out;
 172                 }
 173
 174                 flush_dcache_page(page);
 175         } else {
 176                 page = *pagep;
 177                 *pagep = NULL;
 178         }
 179
 180         /*
 181          * The memory barrier inside __SetPageUptodate makes sure that
 182          * preceding stores to the page contents become visible before
 183          * the set_pte_at() write.
 184          */
 185         __SetPageUptodate(page);
 186
 187         ret = -ENOMEM;
 188         if (mem_cgroup_charge(page_folio(page), dst_mm, GFP_KERNEL))
 189                 goto out_release;
 190
 191         ret = mfill_atomic_install_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
 192                                        page, true, wp_copy);
 193         if (ret)
 194                 goto out_release;
 195 out:
 196         return ret;
 197 out_release:
 198         put_page(page);
 199         goto out;
 200 }
 201
 202 static int mfill_zeropage_pte(struct mm_struct *dst_mm,
 203                               pmd_t *dst_pmd,
 204                               struct vm_area_struct *dst_vma,
 205                               unsigned long dst_addr)
 206 {
 207         pte_t _dst_pte, *dst_pte;
 208         spinlock_t *ptl;
 209         int ret;
 210         pgoff_t offset, max_off;
 211         struct inode *inode;
 212
 213         _dst_pte = pte_mkspecial(pfn_pte(my_zero_pfn(dst_addr),
 214                                          dst_vma->vm_page_prot));
 215         dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
 216         if (dst_vma->vm_file) {
 217                 /* the shmem MAP_PRIVATE case requires checking the i_size */
 218                 inode = dst_vma->vm_file->f_inode;
 219                 offset = linear_page_index(dst_vma, dst_addr);
 220                 max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
 221                 ret = -EFAULT;
 222                 if (unlikely(offset >= max_off))
 223                         goto out_unlock;
 224         }
 225         ret = -EEXIST;
 226         if (!pte_none(*dst_pte))
 227                 goto out_unlock;
 228         set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
 229         /* No need to invalidate - it was non-present before */
 230         update_mmu_cache(dst_vma, dst_addr, dst_pte);
 231         ret = 0;
 232 out_unlock:
 233         pte_unmap_unlock(dst_pte, ptl);
 234         return ret;
 235 }
 236
 237 /* Handles UFFDIO_CONTINUE for all shmem VMAs (shared or private). */
 238 static int mcontinue_atomic_pte(struct mm_struct *dst_mm,
 239                                 pmd_t *dst_pmd,
 240                                 struct vm_area_struct *dst_vma,
 241                                 unsigned long dst_addr,
 242                                 bool wp_copy)
 243 {
 244         struct inode *inode = file_inode(dst_vma->vm_file);
 245         pgoff_t pgoff = linear_page_index(dst_vma, dst_addr);
 246         struct page *page;
 247         int ret;
 248
 249         ret = shmem_getpage(inode, pgoff, &page, SGP_NOALLOC);
 250         /* Our caller expects us to return -EFAULT if we failed to find page. */
 251         if (ret == -ENOENT)
 252                 ret = -EFAULT;
 253         if (ret)
 254                 goto out;
 255         if (!page) {
 256                 ret = -EFAULT;
 257                 goto out;
 258         }
 259
 260         if (PageHWPoison(page)) {
 261                 ret = -EIO;
 262                 goto out_release;
 263         }
 264
 265         ret = mfill_atomic_install_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
 266                                        page, false, wp_copy);
 267         if (ret)
 268                 goto out_release;
 269
 270         unlock_page(page);
 271         ret = 0;
 272 out:
 273         return ret;
 274 out_release:
 275         unlock_page(page);
 276         put_page(page);
 277         goto out;
 278 }
 279
 280 static pmd_t *mm_alloc_pmd(struct mm_struct *mm, unsigned long address)
 281 {
 282         pgd_t *pgd;
 283         p4d_t *p4d;
 284         pud_t *pud;
 285
 286         pgd = pgd_offset(mm, address);
 287         p4d = p4d_alloc(mm, pgd, address);
 288         if (!p4d)
 289                 return NULL;
 290         pud = pud_alloc(mm, p4d, address);
 291         if (!pud)
 292                 return NULL;
 293         /*
 294          * Note that we didn't run this because the pmd was
 295          * missing, the *pmd may be already established and in
 296          * turn it may also be a trans_huge_pmd.
 297          */
 298         return pmd_alloc(mm, pud, address);
 299 }
 300
 301 #ifdef CONFIG_HUGETLB_PAGE
 302 /*
 303  * __mcopy_atomic processing for HUGETLB vmas.  Note that this routine is
 304  * called with mmap_lock held, it will release mmap_lock before returning.
 305  */
 306 static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
 307                                               struct vm_area_struct *dst_vma,
 308                                               unsigned long dst_start,
 309                                               unsigned long src_start,
 310                                               unsigned long len,
 311                                               enum mcopy_atomic_mode mode,
 312                                               bool wp_copy)
 313 {
 314         int vm_shared = dst_vma->vm_flags & VM_SHARED;
 315         ssize_t err;
 316         pte_t *dst_pte;
 317         unsigned long src_addr, dst_addr;
 318         long copied;
 319         struct page *page;
 320         unsigned long vma_hpagesize;
 321         pgoff_t idx;
 322         u32 hash;
 323         struct address_space *mapping;
 324
 325         /*
 326          * There is no default zero huge page for all huge page sizes as
 327          * supported by hugetlb.  A PMD_SIZE huge pages may exist as used
 328          * by THP.  Since we can not reliably insert a zero page, this
 329          * feature is not supported.
 330          */
 331         if (mode == MCOPY_ATOMIC_ZEROPAGE) {
 332                 mmap_read_unlock(dst_mm);
 333                 return -EINVAL;
 334         }
 335
 336         src_addr = src_start;
 337         dst_addr = dst_start;
 338         copied = 0;
 339         page = NULL;
 340         vma_hpagesize = vma_kernel_pagesize(dst_vma);
 341
 342         /*
 343          * Validate alignment based on huge page size
 344          */
 345         err = -EINVAL;
 346         if (dst_start & (vma_hpagesize - 1) || len & (vma_hpagesize - 1))
 347                 goto out_unlock;
 348
 349 retry:
 350         /*
 351          * On routine entry dst_vma is set.  If we had to drop mmap_lock and
 352          * retry, dst_vma will be set to NULL and we must lookup again.
 353          */
 354         if (!dst_vma) {
 355                 err = -ENOENT;
 356                 dst_vma = find_dst_vma(dst_mm, dst_start, len);
 357                 if (!dst_vma || !is_vm_hugetlb_page(dst_vma))
 358                         goto out_unlock;
 359
 360                 err = -EINVAL;
 361                 if (vma_hpagesize != vma_kernel_pagesize(dst_vma))
 362                         goto out_unlock;
 363
 364                 vm_shared = dst_vma->vm_flags & VM_SHARED;
 365         }
 366
 367         /*
 368          * If not shared, ensure the dst_vma has a anon_vma.
 369          */
 370         err = -ENOMEM;
 371         if (!vm_shared) {
 372                 if (unlikely(anon_vma_prepare(dst_vma)))
 373                         goto out_unlock;
 374         }
 375
 376         while (src_addr < src_start + len) {
 377                 BUG_ON(dst_addr >= dst_start + len);
 378
 379                 /*
 380                  * Serialize via i_mmap_rwsem and hugetlb_fault_mutex.
 381                  * i_mmap_rwsem ensures the dst_pte remains valid even
 382                  * in the case of shared pmds.  fault mutex prevents
 383                  * races with other faulting threads.
 384                  */
 385                 mapping = dst_vma->vm_file->f_mapping;
 386                 i_mmap_lock_read(mapping);
 387                 idx = linear_page_index(dst_vma, dst_addr);
 388                 hash = hugetlb_fault_mutex_hash(mapping, idx);
 389                 mutex_lock(&hugetlb_fault_mutex_table[hash]);
 390
 391                 err = -ENOMEM;
 392                 dst_pte = huge_pte_alloc(dst_mm, dst_vma, dst_addr, vma_hpagesize);
 393                 if (!dst_pte) {
 394                         mutex_unlock(&hugetlb_fault_mutex_table[hash]);
 395                         i_mmap_unlock_read(mapping);
 396                         goto out_unlock;
 397                 }
 398
 399                 if (mode != MCOPY_ATOMIC_CONTINUE &&
 400                     !huge_pte_none_mostly(huge_ptep_get(dst_pte))) {
 401                         err = -EEXIST;
 402                         mutex_unlock(&hugetlb_fault_mutex_table[hash]);
 403                         i_mmap_unlock_read(mapping);
 404                         goto out_unlock;
 405                 }
 406
 407                 err = hugetlb_mcopy_atomic_pte(dst_mm, dst_pte, dst_vma,
 408                                                dst_addr, src_addr, mode, &page,
 409                                                wp_copy);
 410
 411                 mutex_unlock(&hugetlb_fault_mutex_table[hash]);
 412                 i_mmap_unlock_read(mapping);
 413
 414                 cond_resched();
 415
 416                 if (unlikely(err == -ENOENT)) {
 417                         mmap_read_unlock(dst_mm);
 418                         BUG_ON(!page);
 419
 420                         err = copy_huge_page_from_user(page,
 421                                                 (const void __user *)src_addr,
 422                                                 vma_hpagesize / PAGE_SIZE,
 423                                                 true);
 424                         if (unlikely(err)) {
 425                                 err = -EFAULT;
 426                                 goto out;
 427                         }
 428                         mmap_read_lock(dst_mm);
 429
 430                         dst_vma = NULL;
 431                         goto retry;
 432                 } else
 433                         BUG_ON(page);
 434
 435                 if (!err) {
 436                         dst_addr += vma_hpagesize;
 437                         src_addr += vma_hpagesize;
 438                         copied += vma_hpagesize;
 439
 440                         if (fatal_signal_pending(current))
 441                                 err = -EINTR;
 442                 }
 443                 if (err)
 444                         break;
 445         }
 446
 447 out_unlock:
 448         mmap_read_unlock(dst_mm);
 449 out:
 450         if (page)
 451                 put_page(page);
 452         BUG_ON(copied < 0);
 453         BUG_ON(err > 0);
 454         BUG_ON(!copied && !err);
 455         return copied ? copied : err;
 456 }
 457 #else /* !CONFIG_HUGETLB_PAGE */
 458 /* fail at build time if gcc attempts to use this */
 459 extern ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
 460                                       struct vm_area_struct *dst_vma,
 461                                       unsigned long dst_start,
 462                                       unsigned long src_start,
 463                                       unsigned long len,
 464                                       enum mcopy_atomic_mode mode,
 465                                       bool wp_copy);
 466 #endif /* CONFIG_HUGETLB_PAGE */
 467
 468 static __always_inline ssize_t mfill_atomic_pte(struct mm_struct *dst_mm,
 469                                                 pmd_t *dst_pmd,
 470                                                 struct vm_area_struct *dst_vma,
 471                                                 unsigned long dst_addr,
 472                                                 unsigned long src_addr,
 473                                                 struct page **page,
 474                                                 enum mcopy_atomic_mode mode,
 475                                                 bool wp_copy)
 476 {
 477         ssize_t err;
 478
 479         if (mode == MCOPY_ATOMIC_CONTINUE) {
 480                 return mcontinue_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
 481                                             wp_copy);
 482         }
 483
 484         /*
 485          * The normal page fault path for a shmem will invoke the
 486          * fault, fill the hole in the file and COW it right away. The
 487          * result generates plain anonymous memory. So when we are
 488          * asked to fill an hole in a MAP_PRIVATE shmem mapping, we'll
 489          * generate anonymous memory directly without actually filling
 490          * the hole. For the MAP_PRIVATE case the robustness check
 491          * only happens in the pagetable (to verify it's still none)
 492          * and not in the radix tree.
 493          */
 494         if (!(dst_vma->vm_flags & VM_SHARED)) {
 495                 if (mode == MCOPY_ATOMIC_NORMAL)
 496                         err = mcopy_atomic_pte(dst_mm, dst_pmd, dst_vma,
 497                                                dst_addr, src_addr, page,
 498                                                wp_copy);
 499                 else
 500                         err = mfill_zeropage_pte(dst_mm, dst_pmd,
 501                                                  dst_vma, dst_addr);
 502         } else {
 503                 err = shmem_mfill_atomic_pte(dst_mm, dst_pmd, dst_vma,
 504                                              dst_addr, src_addr,
 505                                              mode != MCOPY_ATOMIC_NORMAL,
 506                                              wp_copy, page);
 507         }
 508
 509         return err;
 510 }
 511
 512 static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm,
 513                                               unsigned long dst_start,
 514                                               unsigned long src_start,
 515                                               unsigned long len,
 516                                               enum mcopy_atomic_mode mcopy_mode,
 517                                               atomic_t *mmap_changing,
 518                                               __u64 mode)
 519 {
 520         struct vm_area_struct *dst_vma;
 521         ssize_t err;
 522         pmd_t *dst_pmd;
 523         unsigned long src_addr, dst_addr;
 524         long copied;
 525         struct page *page;
 526         bool wp_copy;
 527
 528         /*
 529          * Sanitize the command parameters:
 530          */
 531         BUG_ON(dst_start & ~PAGE_MASK);
 532         BUG_ON(len & ~PAGE_MASK);
 533
 534         /* Does the address range wrap, or is the span zero-sized? */
 535         BUG_ON(src_start + len <= src_start);
 536         BUG_ON(dst_start + len <= dst_start);
 537
 538         src_addr = src_start;
 539         dst_addr = dst_start;
 540         copied = 0;
 541         page = NULL;
 542 retry:
 543         mmap_read_lock(dst_mm);
 544
 545         /*
 546          * If memory mappings are changing because of non-cooperative
 547          * operation (e.g. mremap) running in parallel, bail out and
 548          * request the user to retry later
 549          */
 550         err = -EAGAIN;
 551         if (mmap_changing && atomic_read(mmap_changing))
 552                 goto out_unlock;
 553
 554         /*
 555          * Make sure the vma is not shared, that the dst range is
 556          * both valid and fully within a single existing vma.
 557          */
 558         err = -ENOENT;
 559         dst_vma = find_dst_vma(dst_mm, dst_start, len);
 560         if (!dst_vma)
 561                 goto out_unlock;
 562
 563         err = -EINVAL;
 564         /*
 565          * shmem_zero_setup is invoked in mmap for MAP_ANONYMOUS|MAP_SHARED but
 566          * it will overwrite vm_ops, so vma_is_anonymous must return false.
 567          */
 568         if (WARN_ON_ONCE(vma_is_anonymous(dst_vma) &&
 569             dst_vma->vm_flags & VM_SHARED))
 570                 goto out_unlock;
 571
 572         /*
 573          * validate 'mode' now that we know the dst_vma: don't allow
 574          * a wrprotect copy if the userfaultfd didn't register as WP.
 575          */
 576         wp_copy = mode & UFFDIO_COPY_MODE_WP;
 577         if (wp_copy && !(dst_vma->vm_flags & VM_UFFD_WP))
 578                 goto out_unlock;
 579
 580         /*
 581          * If this is a HUGETLB vma, pass off to appropriate routine
 582          */
 583         if (is_vm_hugetlb_page(dst_vma))
 584                 return  __mcopy_atomic_hugetlb(dst_mm, dst_vma, dst_start,
 585                                                src_start, len, mcopy_mode,
 586                                                wp_copy);
 587
 588         if (!vma_is_anonymous(dst_vma) && !vma_is_shmem(dst_vma))
 589                 goto out_unlock;
 590         if (!vma_is_shmem(dst_vma) && mcopy_mode == MCOPY_ATOMIC_CONTINUE)
 591                 goto out_unlock;
 592
 593         /*
 594          * Ensure the dst_vma has a anon_vma or this page
 595          * would get a NULL anon_vma when moved in the
 596          * dst_vma.
 597          */
 598         err = -ENOMEM;
 599         if (!(dst_vma->vm_flags & VM_SHARED) &&
 600             unlikely(anon_vma_prepare(dst_vma)))
 601                 goto out_unlock;
 602
 603         while (src_addr < src_start + len) {
 604                 pmd_t dst_pmdval;
 605
 606                 BUG_ON(dst_addr >= dst_start + len);
 607
 608                 dst_pmd = mm_alloc_pmd(dst_mm, dst_addr);
 609                 if (unlikely(!dst_pmd)) {
 610                         err = -ENOMEM;
 611                         break;
 612                 }
 613
 614                 dst_pmdval = pmd_read_atomic(dst_pmd);
 615                 /*
 616                  * If the dst_pmd is mapped as THP don't
 617                  * override it and just be strict.
 618                  */
 619                 if (unlikely(pmd_trans_huge(dst_pmdval))) {
 620                         err = -EEXIST;
 621                         break;
 622                 }
 623                 if (unlikely(pmd_none(dst_pmdval)) &&
 624                     unlikely(__pte_alloc(dst_mm, dst_pmd))) {
 625                         err = -ENOMEM;
 626                         break;
 627                 }
 628                 /* If an huge pmd materialized from under us fail */
 629                 if (unlikely(pmd_trans_huge(*dst_pmd))) {
 630                         err = -EFAULT;
 631                         break;
 632                 }
 633
 634                 BUG_ON(pmd_none(*dst_pmd));
 635                 BUG_ON(pmd_trans_huge(*dst_pmd));
 636
 637                 err = mfill_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
 638                                        src_addr, &page, mcopy_mode, wp_copy);
 639                 cond_resched();
 640
 641                 if (unlikely(err == -ENOENT)) {
 642                         void *page_kaddr;
 643
 644                         mmap_read_unlock(dst_mm);
 645                         BUG_ON(!page);
 646
 647                         page_kaddr = kmap(page);
 648                         err = copy_from_user(page_kaddr,
 649                                              (const void __user *) src_addr,
 650                                              PAGE_SIZE);
 651                         kunmap(page);
 652                         if (unlikely(err)) {
 653                                 err = -EFAULT;
 654                                 goto out;
 655                         }
 656                         flush_dcache_page(page);
 657                         goto retry;
 658                 } else
 659                         BUG_ON(page);
 660
 661                 if (!err) {
 662                         dst_addr += PAGE_SIZE;
 663                         src_addr += PAGE_SIZE;
 664                         copied += PAGE_SIZE;
 665
 666                         if (fatal_signal_pending(current))
 667                                 err = -EINTR;
 668                 }
 669                 if (err)
 670                         break;
 671         }
 672
 673 out_unlock:
 674         mmap_read_unlock(dst_mm);
 675 out:
 676         if (page)
 677                 put_page(page);
 678         BUG_ON(copied < 0);
 679         BUG_ON(err > 0);
 680         BUG_ON(!copied && !err);
 681         return copied ? copied : err;
 682 }
 683
 684 ssize_t mcopy_atomic(struct mm_struct *dst_mm, unsigned long dst_start,
 685                      unsigned long src_start, unsigned long len,
 686                      atomic_t *mmap_changing, __u64 mode)
 687 {
 688         return __mcopy_atomic(dst_mm, dst_start, src_start, len,
 689                               MCOPY_ATOMIC_NORMAL, mmap_changing, mode);
 690 }
 691
 692 ssize_t mfill_zeropage(struct mm_struct *dst_mm, unsigned long start,
 693                        unsigned long len, atomic_t *mmap_changing)
 694 {
 695         return __mcopy_atomic(dst_mm, start, 0, len, MCOPY_ATOMIC_ZEROPAGE,
 696                               mmap_changing, 0);
 697 }
 698
 699 ssize_t mcopy_continue(struct mm_struct *dst_mm, unsigned long start,
 700                        unsigned long len, atomic_t *mmap_changing)
 701 {
 702         return __mcopy_atomic(dst_mm, start, 0, len, MCOPY_ATOMIC_CONTINUE,
 703                               mmap_changing, 0);
 704 }
 705
 706 int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start,
 707                         unsigned long len, bool enable_wp,
 708                         atomic_t *mmap_changing)
 709 {
 710         struct vm_area_struct *dst_vma;
 711         unsigned long page_mask;
 712         struct mmu_gather tlb;
 713         pgprot_t newprot;
 714         int err;
 715
 716         /*
 717          * Sanitize the command parameters:
 718          */
 719         BUG_ON(start & ~PAGE_MASK);
 720         BUG_ON(len & ~PAGE_MASK);
 721
 722         /* Does the address range wrap, or is the span zero-sized? */
 723         BUG_ON(start + len <= start);
 724
 725         mmap_read_lock(dst_mm);
 726
 727         /*
 728          * If memory mappings are changing because of non-cooperative
 729          * operation (e.g. mremap) running in parallel, bail out and
 730          * request the user to retry later
 731          */
 732         err = -EAGAIN;
 733         if (mmap_changing && atomic_read(mmap_changing))
 734                 goto out_unlock;
 735
 736         err = -ENOENT;
 737         dst_vma = find_dst_vma(dst_mm, start, len);
 738
 739         if (!dst_vma)
 740                 goto out_unlock;
 741         if (!userfaultfd_wp(dst_vma))
 742                 goto out_unlock;
 743         if (!vma_can_userfault(dst_vma, dst_vma->vm_flags))
 744                 goto out_unlock;
 745
 746         if (is_vm_hugetlb_page(dst_vma)) {
 747                 err = -EINVAL;
 748                 page_mask = vma_kernel_pagesize(dst_vma) - 1;
 749                 if ((start & page_mask) || (len & page_mask))
 750                         goto out_unlock;
 751         }
 752
 753         if (enable_wp)
 754                 newprot = vm_get_page_prot(dst_vma->vm_flags & ~(VM_WRITE));
 755         else
 756                 newprot = vm_get_page_prot(dst_vma->vm_flags);
 757
 758         tlb_gather_mmu(&tlb, dst_mm);
 759         change_protection(&tlb, dst_vma, start, start + len, newprot,
 760                           enable_wp ? MM_CP_UFFD_WP : MM_CP_UFFD_WP_RESOLVE);
 761         tlb_finish_mmu(&tlb);
 762
 763         err = 0;
 764 out_unlock:
 765         mmap_read_unlock(dst_mm);
 766         return err;
 767 }