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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * mm/mremap.c
4 *
5 * (C) Copyright 1996 Linus Torvalds
6 *
7 * Address space accounting code <alan@lxorguk.ukuu.org.uk>
8 * (C) Copyright 2002 Red Hat Inc, All Rights Reserved
9 */
10
11#include <linux/mm.h>
12#include <linux/mm_inline.h>
13#include <linux/hugetlb.h>
14#include <linux/shm.h>
15#include <linux/ksm.h>
16#include <linux/mman.h>
17#include <linux/swap.h>
18#include <linux/capability.h>
19#include <linux/fs.h>
20#include <linux/swapops.h>
21#include <linux/highmem.h>
22#include <linux/security.h>
23#include <linux/syscalls.h>
24#include <linux/mmu_notifier.h>
25#include <linux/uaccess.h>
26#include <linux/userfaultfd_k.h>
27#include <linux/mempolicy.h>
28
29#include <asm/cacheflush.h>
30#include <asm/tlb.h>
31#include <asm/pgalloc.h>
32
33#include "internal.h"
34
35static pud_t *get_old_pud(struct mm_struct *mm, unsigned long addr)
36{
37 pgd_t *pgd;
38 p4d_t *p4d;
39 pud_t *pud;
40
41 pgd = pgd_offset(mm, addr);
42 if (pgd_none_or_clear_bad(pgd))
43 return NULL;
44
45 p4d = p4d_offset(pgd, addr);
46 if (p4d_none_or_clear_bad(p4d))
47 return NULL;
48
49 pud = pud_offset(p4d, addr);
50 if (pud_none_or_clear_bad(pud))
51 return NULL;
52
53 return pud;
54}
55
56static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr)
57{
58 pud_t *pud;
59 pmd_t *pmd;
60
61 pud = get_old_pud(mm, addr);
62 if (!pud)
63 return NULL;
64
65 pmd = pmd_offset(pud, addr);
66 if (pmd_none(*pmd))
67 return NULL;
68
69 return pmd;
70}
71
72static pud_t *alloc_new_pud(struct mm_struct *mm, struct vm_area_struct *vma,
73 unsigned long addr)
74{
75 pgd_t *pgd;
76 p4d_t *p4d;
77
78 pgd = pgd_offset(mm, addr);
79 p4d = p4d_alloc(mm, pgd, addr);
80 if (!p4d)
81 return NULL;
82
83 return pud_alloc(mm, p4d, addr);
84}
85
86static pmd_t *alloc_new_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
87 unsigned long addr)
88{
89 pud_t *pud;
90 pmd_t *pmd;
91
92 pud = alloc_new_pud(mm, vma, addr);
93 if (!pud)
94 return NULL;
95
96 pmd = pmd_alloc(mm, pud, addr);
97 if (!pmd)
98 return NULL;
99
100 VM_BUG_ON(pmd_trans_huge(*pmd));
101
102 return pmd;
103}
104
105static void take_rmap_locks(struct vm_area_struct *vma)
106{
107 if (vma->vm_file)
108 i_mmap_lock_write(vma->vm_file->f_mapping);
109 if (vma->anon_vma)
110 anon_vma_lock_write(vma->anon_vma);
111}
112
113static void drop_rmap_locks(struct vm_area_struct *vma)
114{
115 if (vma->anon_vma)
116 anon_vma_unlock_write(vma->anon_vma);
117 if (vma->vm_file)
118 i_mmap_unlock_write(vma->vm_file->f_mapping);
119}
120
121static pte_t move_soft_dirty_pte(pte_t pte)
122{
123 /*
124 * Set soft dirty bit so we can notice
125 * in userspace the ptes were moved.
126 */
127#ifdef CONFIG_MEM_SOFT_DIRTY
128 if (pte_present(pte))
129 pte = pte_mksoft_dirty(pte);
130 else if (is_swap_pte(pte))
131 pte = pte_swp_mksoft_dirty(pte);
132#endif
133 return pte;
134}
135
136static int move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
137 unsigned long old_addr, unsigned long old_end,
138 struct vm_area_struct *new_vma, pmd_t *new_pmd,
139 unsigned long new_addr, bool need_rmap_locks)
140{
141 struct mm_struct *mm = vma->vm_mm;
142 pte_t *old_pte, *new_pte, pte;
143 spinlock_t *old_ptl, *new_ptl;
144 bool force_flush = false;
145 unsigned long len = old_end - old_addr;
146 int err = 0;
147
148 /*
149 * When need_rmap_locks is true, we take the i_mmap_rwsem and anon_vma
150 * locks to ensure that rmap will always observe either the old or the
151 * new ptes. This is the easiest way to avoid races with
152 * truncate_pagecache(), page migration, etc...
153 *
154 * When need_rmap_locks is false, we use other ways to avoid
155 * such races:
156 *
157 * - During exec() shift_arg_pages(), we use a specially tagged vma
158 * which rmap call sites look for using vma_is_temporary_stack().
159 *
160 * - During mremap(), new_vma is often known to be placed after vma
161 * in rmap traversal order. This ensures rmap will always observe
162 * either the old pte, or the new pte, or both (the page table locks
163 * serialize access to individual ptes, but only rmap traversal
164 * order guarantees that we won't miss both the old and new ptes).
165 */
166 if (need_rmap_locks)
167 take_rmap_locks(vma);
168
169 /*
170 * We don't have to worry about the ordering of src and dst
171 * pte locks because exclusive mmap_lock prevents deadlock.
172 */
173 old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl);
174 if (!old_pte) {
175 err = -EAGAIN;
176 goto out;
177 }
178 new_pte = pte_offset_map_nolock(mm, new_pmd, new_addr, &new_ptl);
179 if (!new_pte) {
180 pte_unmap_unlock(old_pte, old_ptl);
181 err = -EAGAIN;
182 goto out;
183 }
184 if (new_ptl != old_ptl)
185 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
186 flush_tlb_batched_pending(vma->vm_mm);
187 arch_enter_lazy_mmu_mode();
188
189 for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE,
190 new_pte++, new_addr += PAGE_SIZE) {
191 if (pte_none(ptep_get(old_pte)))
192 continue;
193
194 pte = ptep_get_and_clear(mm, old_addr, old_pte);
195 /*
196 * If we are remapping a valid PTE, make sure
197 * to flush TLB before we drop the PTL for the
198 * PTE.
199 *
200 * NOTE! Both old and new PTL matter: the old one
201 * for racing with page_mkclean(), the new one to
202 * make sure the physical page stays valid until
203 * the TLB entry for the old mapping has been
204 * flushed.
205 */
206 if (pte_present(pte))
207 force_flush = true;
208 pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr);
209 pte = move_soft_dirty_pte(pte);
210 set_pte_at(mm, new_addr, new_pte, pte);
211 }
212
213 arch_leave_lazy_mmu_mode();
214 if (force_flush)
215 flush_tlb_range(vma, old_end - len, old_end);
216 if (new_ptl != old_ptl)
217 spin_unlock(new_ptl);
218 pte_unmap(new_pte - 1);
219 pte_unmap_unlock(old_pte - 1, old_ptl);
220out:
221 if (need_rmap_locks)
222 drop_rmap_locks(vma);
223 return err;
224}
225
226#ifndef arch_supports_page_table_move
227#define arch_supports_page_table_move arch_supports_page_table_move
228static inline bool arch_supports_page_table_move(void)
229{
230 return IS_ENABLED(CONFIG_HAVE_MOVE_PMD) ||
231 IS_ENABLED(CONFIG_HAVE_MOVE_PUD);
232}
233#endif
234
235#ifdef CONFIG_HAVE_MOVE_PMD
236static bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr,
237 unsigned long new_addr, pmd_t *old_pmd, pmd_t *new_pmd)
238{
239 spinlock_t *old_ptl, *new_ptl;
240 struct mm_struct *mm = vma->vm_mm;
241 pmd_t pmd;
242
243 if (!arch_supports_page_table_move())
244 return false;
245 /*
246 * The destination pmd shouldn't be established, free_pgtables()
247 * should have released it.
248 *
249 * However, there's a case during execve() where we use mremap
250 * to move the initial stack, and in that case the target area
251 * may overlap the source area (always moving down).
252 *
253 * If everything is PMD-aligned, that works fine, as moving
254 * each pmd down will clear the source pmd. But if we first
255 * have a few 4kB-only pages that get moved down, and then
256 * hit the "now the rest is PMD-aligned, let's do everything
257 * one pmd at a time", we will still have the old (now empty
258 * of any 4kB pages, but still there) PMD in the page table
259 * tree.
260 *
261 * Warn on it once - because we really should try to figure
262 * out how to do this better - but then say "I won't move
263 * this pmd".
264 *
265 * One alternative might be to just unmap the target pmd at
266 * this point, and verify that it really is empty. We'll see.
267 */
268 if (WARN_ON_ONCE(!pmd_none(*new_pmd)))
269 return false;
270
271 /*
272 * We don't have to worry about the ordering of src and dst
273 * ptlocks because exclusive mmap_lock prevents deadlock.
274 */
275 old_ptl = pmd_lock(vma->vm_mm, old_pmd);
276 new_ptl = pmd_lockptr(mm, new_pmd);
277 if (new_ptl != old_ptl)
278 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
279
280 /* Clear the pmd */
281 pmd = *old_pmd;
282 pmd_clear(old_pmd);
283
284 VM_BUG_ON(!pmd_none(*new_pmd));
285
286 pmd_populate(mm, new_pmd, pmd_pgtable(pmd));
287 flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
288 if (new_ptl != old_ptl)
289 spin_unlock(new_ptl);
290 spin_unlock(old_ptl);
291
292 return true;
293}
294#else
295static inline bool move_normal_pmd(struct vm_area_struct *vma,
296 unsigned long old_addr, unsigned long new_addr, pmd_t *old_pmd,
297 pmd_t *new_pmd)
298{
299 return false;
300}
301#endif
302
303#if CONFIG_PGTABLE_LEVELS > 2 && defined(CONFIG_HAVE_MOVE_PUD)
304static bool move_normal_pud(struct vm_area_struct *vma, unsigned long old_addr,
305 unsigned long new_addr, pud_t *old_pud, pud_t *new_pud)
306{
307 spinlock_t *old_ptl, *new_ptl;
308 struct mm_struct *mm = vma->vm_mm;
309 pud_t pud;
310
311 if (!arch_supports_page_table_move())
312 return false;
313 /*
314 * The destination pud shouldn't be established, free_pgtables()
315 * should have released it.
316 */
317 if (WARN_ON_ONCE(!pud_none(*new_pud)))
318 return false;
319
320 /*
321 * We don't have to worry about the ordering of src and dst
322 * ptlocks because exclusive mmap_lock prevents deadlock.
323 */
324 old_ptl = pud_lock(vma->vm_mm, old_pud);
325 new_ptl = pud_lockptr(mm, new_pud);
326 if (new_ptl != old_ptl)
327 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
328
329 /* Clear the pud */
330 pud = *old_pud;
331 pud_clear(old_pud);
332
333 VM_BUG_ON(!pud_none(*new_pud));
334
335 pud_populate(mm, new_pud, pud_pgtable(pud));
336 flush_tlb_range(vma, old_addr, old_addr + PUD_SIZE);
337 if (new_ptl != old_ptl)
338 spin_unlock(new_ptl);
339 spin_unlock(old_ptl);
340
341 return true;
342}
343#else
344static inline bool move_normal_pud(struct vm_area_struct *vma,
345 unsigned long old_addr, unsigned long new_addr, pud_t *old_pud,
346 pud_t *new_pud)
347{
348 return false;
349}
350#endif
351
352#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && defined(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD)
353static bool move_huge_pud(struct vm_area_struct *vma, unsigned long old_addr,
354 unsigned long new_addr, pud_t *old_pud, pud_t *new_pud)
355{
356 spinlock_t *old_ptl, *new_ptl;
357 struct mm_struct *mm = vma->vm_mm;
358 pud_t pud;
359
360 /*
361 * The destination pud shouldn't be established, free_pgtables()
362 * should have released it.
363 */
364 if (WARN_ON_ONCE(!pud_none(*new_pud)))
365 return false;
366
367 /*
368 * We don't have to worry about the ordering of src and dst
369 * ptlocks because exclusive mmap_lock prevents deadlock.
370 */
371 old_ptl = pud_lock(vma->vm_mm, old_pud);
372 new_ptl = pud_lockptr(mm, new_pud);
373 if (new_ptl != old_ptl)
374 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
375
376 /* Clear the pud */
377 pud = *old_pud;
378 pud_clear(old_pud);
379
380 VM_BUG_ON(!pud_none(*new_pud));
381
382 /* Set the new pud */
383 /* mark soft_ditry when we add pud level soft dirty support */
384 set_pud_at(mm, new_addr, new_pud, pud);
385 flush_pud_tlb_range(vma, old_addr, old_addr + HPAGE_PUD_SIZE);
386 if (new_ptl != old_ptl)
387 spin_unlock(new_ptl);
388 spin_unlock(old_ptl);
389
390 return true;
391}
392#else
393static bool move_huge_pud(struct vm_area_struct *vma, unsigned long old_addr,
394 unsigned long new_addr, pud_t *old_pud, pud_t *new_pud)
395{
396 WARN_ON_ONCE(1);
397 return false;
398
399}
400#endif
401
402enum pgt_entry {
403 NORMAL_PMD,
404 HPAGE_PMD,
405 NORMAL_PUD,
406 HPAGE_PUD,
407};
408
409/*
410 * Returns an extent of the corresponding size for the pgt_entry specified if
411 * valid. Else returns a smaller extent bounded by the end of the source and
412 * destination pgt_entry.
413 */
414static __always_inline unsigned long get_extent(enum pgt_entry entry,
415 unsigned long old_addr, unsigned long old_end,
416 unsigned long new_addr)
417{
418 unsigned long next, extent, mask, size;
419
420 switch (entry) {
421 case HPAGE_PMD:
422 case NORMAL_PMD:
423 mask = PMD_MASK;
424 size = PMD_SIZE;
425 break;
426 case HPAGE_PUD:
427 case NORMAL_PUD:
428 mask = PUD_MASK;
429 size = PUD_SIZE;
430 break;
431 default:
432 BUILD_BUG();
433 break;
434 }
435
436 next = (old_addr + size) & mask;
437 /* even if next overflowed, extent below will be ok */
438 extent = next - old_addr;
439 if (extent > old_end - old_addr)
440 extent = old_end - old_addr;
441 next = (new_addr + size) & mask;
442 if (extent > next - new_addr)
443 extent = next - new_addr;
444 return extent;
445}
446
447/*
448 * Attempts to speedup the move by moving entry at the level corresponding to
449 * pgt_entry. Returns true if the move was successful, else false.
450 */
451static bool move_pgt_entry(enum pgt_entry entry, struct vm_area_struct *vma,
452 unsigned long old_addr, unsigned long new_addr,
453 void *old_entry, void *new_entry, bool need_rmap_locks)
454{
455 bool moved = false;
456
457 /* See comment in move_ptes() */
458 if (need_rmap_locks)
459 take_rmap_locks(vma);
460
461 switch (entry) {
462 case NORMAL_PMD:
463 moved = move_normal_pmd(vma, old_addr, new_addr, old_entry,
464 new_entry);
465 break;
466 case NORMAL_PUD:
467 moved = move_normal_pud(vma, old_addr, new_addr, old_entry,
468 new_entry);
469 break;
470 case HPAGE_PMD:
471 moved = IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
472 move_huge_pmd(vma, old_addr, new_addr, old_entry,
473 new_entry);
474 break;
475 case HPAGE_PUD:
476 moved = IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
477 move_huge_pud(vma, old_addr, new_addr, old_entry,
478 new_entry);
479 break;
480
481 default:
482 WARN_ON_ONCE(1);
483 break;
484 }
485
486 if (need_rmap_locks)
487 drop_rmap_locks(vma);
488
489 return moved;
490}
491
492/*
493 * A helper to check if aligning down is OK. The aligned address should fall
494 * on *no mapping*. For the stack moving down, that's a special move within
495 * the VMA that is created to span the source and destination of the move,
496 * so we make an exception for it.
497 */
498static bool can_align_down(struct vm_area_struct *vma, unsigned long addr_to_align,
499 unsigned long mask, bool for_stack)
500{
501 unsigned long addr_masked = addr_to_align & mask;
502
503 /*
504 * If @addr_to_align of either source or destination is not the beginning
505 * of the corresponding VMA, we can't align down or we will destroy part
506 * of the current mapping.
507 */
508 if (!for_stack && vma->vm_start != addr_to_align)
509 return false;
510
511 /* In the stack case we explicitly permit in-VMA alignment. */
512 if (for_stack && addr_masked >= vma->vm_start)
513 return true;
514
515 /*
516 * Make sure the realignment doesn't cause the address to fall on an
517 * existing mapping.
518 */
519 return find_vma_intersection(vma->vm_mm, addr_masked, vma->vm_start) == NULL;
520}
521
522/* Opportunistically realign to specified boundary for faster copy. */
523static void try_realign_addr(unsigned long *old_addr, struct vm_area_struct *old_vma,
524 unsigned long *new_addr, struct vm_area_struct *new_vma,
525 unsigned long mask, bool for_stack)
526{
527 /* Skip if the addresses are already aligned. */
528 if ((*old_addr & ~mask) == 0)
529 return;
530
531 /* Only realign if the new and old addresses are mutually aligned. */
532 if ((*old_addr & ~mask) != (*new_addr & ~mask))
533 return;
534
535 /* Ensure realignment doesn't cause overlap with existing mappings. */
536 if (!can_align_down(old_vma, *old_addr, mask, for_stack) ||
537 !can_align_down(new_vma, *new_addr, mask, for_stack))
538 return;
539
540 *old_addr = *old_addr & mask;
541 *new_addr = *new_addr & mask;
542}
543
544unsigned long move_page_tables(struct vm_area_struct *vma,
545 unsigned long old_addr, struct vm_area_struct *new_vma,
546 unsigned long new_addr, unsigned long len,
547 bool need_rmap_locks, bool for_stack)
548{
549 unsigned long extent, old_end;
550 struct mmu_notifier_range range;
551 pmd_t *old_pmd, *new_pmd;
552 pud_t *old_pud, *new_pud;
553
554 if (!len)
555 return 0;
556
557 old_end = old_addr + len;
558
559 if (is_vm_hugetlb_page(vma))
560 return move_hugetlb_page_tables(vma, new_vma, old_addr,
561 new_addr, len);
562
563 /*
564 * If possible, realign addresses to PMD boundary for faster copy.
565 * Only realign if the mremap copying hits a PMD boundary.
566 */
567 if (len >= PMD_SIZE - (old_addr & ~PMD_MASK))
568 try_realign_addr(&old_addr, vma, &new_addr, new_vma, PMD_MASK,
569 for_stack);
570
571 flush_cache_range(vma, old_addr, old_end);
572 mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0, vma->vm_mm,
573 old_addr, old_end);
574 mmu_notifier_invalidate_range_start(&range);
575
576 for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
577 cond_resched();
578 /*
579 * If extent is PUD-sized try to speed up the move by moving at the
580 * PUD level if possible.
581 */
582 extent = get_extent(NORMAL_PUD, old_addr, old_end, new_addr);
583
584 old_pud = get_old_pud(vma->vm_mm, old_addr);
585 if (!old_pud)
586 continue;
587 new_pud = alloc_new_pud(vma->vm_mm, vma, new_addr);
588 if (!new_pud)
589 break;
590 if (pud_trans_huge(*old_pud) || pud_devmap(*old_pud)) {
591 if (extent == HPAGE_PUD_SIZE) {
592 move_pgt_entry(HPAGE_PUD, vma, old_addr, new_addr,
593 old_pud, new_pud, need_rmap_locks);
594 /* We ignore and continue on error? */
595 continue;
596 }
597 } else if (IS_ENABLED(CONFIG_HAVE_MOVE_PUD) && extent == PUD_SIZE) {
598
599 if (move_pgt_entry(NORMAL_PUD, vma, old_addr, new_addr,
600 old_pud, new_pud, true))
601 continue;
602 }
603
604 extent = get_extent(NORMAL_PMD, old_addr, old_end, new_addr);
605 old_pmd = get_old_pmd(vma->vm_mm, old_addr);
606 if (!old_pmd)
607 continue;
608 new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr);
609 if (!new_pmd)
610 break;
611again:
612 if (is_swap_pmd(*old_pmd) || pmd_trans_huge(*old_pmd) ||
613 pmd_devmap(*old_pmd)) {
614 if (extent == HPAGE_PMD_SIZE &&
615 move_pgt_entry(HPAGE_PMD, vma, old_addr, new_addr,
616 old_pmd, new_pmd, need_rmap_locks))
617 continue;
618 split_huge_pmd(vma, old_pmd, old_addr);
619 } else if (IS_ENABLED(CONFIG_HAVE_MOVE_PMD) &&
620 extent == PMD_SIZE) {
621 /*
622 * If the extent is PMD-sized, try to speed the move by
623 * moving at the PMD level if possible.
624 */
625 if (move_pgt_entry(NORMAL_PMD, vma, old_addr, new_addr,
626 old_pmd, new_pmd, true))
627 continue;
628 }
629 if (pmd_none(*old_pmd))
630 continue;
631 if (pte_alloc(new_vma->vm_mm, new_pmd))
632 break;
633 if (move_ptes(vma, old_pmd, old_addr, old_addr + extent,
634 new_vma, new_pmd, new_addr, need_rmap_locks) < 0)
635 goto again;
636 }
637
638 mmu_notifier_invalidate_range_end(&range);
639
640 /*
641 * Prevent negative return values when {old,new}_addr was realigned
642 * but we broke out of the above loop for the first PMD itself.
643 */
644 if (len + old_addr < old_end)
645 return 0;
646
647 return len + old_addr - old_end; /* how much done */
648}
649
650static unsigned long move_vma(struct vm_area_struct *vma,
651 unsigned long old_addr, unsigned long old_len,
652 unsigned long new_len, unsigned long new_addr,
653 bool *locked, unsigned long flags,
654 struct vm_userfaultfd_ctx *uf, struct list_head *uf_unmap)
655{
656 long to_account = new_len - old_len;
657 struct mm_struct *mm = vma->vm_mm;
658 struct vm_area_struct *new_vma;
659 unsigned long vm_flags = vma->vm_flags;
660 unsigned long new_pgoff;
661 unsigned long moved_len;
662 unsigned long account_start = 0;
663 unsigned long account_end = 0;
664 unsigned long hiwater_vm;
665 int err = 0;
666 bool need_rmap_locks;
667 struct vma_iterator vmi;
668
669 /*
670 * We'd prefer to avoid failure later on in do_munmap:
671 * which may split one vma into three before unmapping.
672 */
673 if (mm->map_count >= sysctl_max_map_count - 3)
674 return -ENOMEM;
675
676 if (unlikely(flags & MREMAP_DONTUNMAP))
677 to_account = new_len;
678
679 if (vma->vm_ops && vma->vm_ops->may_split) {
680 if (vma->vm_start != old_addr)
681 err = vma->vm_ops->may_split(vma, old_addr);
682 if (!err && vma->vm_end != old_addr + old_len)
683 err = vma->vm_ops->may_split(vma, old_addr + old_len);
684 if (err)
685 return err;
686 }
687
688 /*
689 * Advise KSM to break any KSM pages in the area to be moved:
690 * it would be confusing if they were to turn up at the new
691 * location, where they happen to coincide with different KSM
692 * pages recently unmapped. But leave vma->vm_flags as it was,
693 * so KSM can come around to merge on vma and new_vma afterwards.
694 */
695 err = ksm_madvise(vma, old_addr, old_addr + old_len,
696 MADV_UNMERGEABLE, &vm_flags);
697 if (err)
698 return err;
699
700 if (vm_flags & VM_ACCOUNT) {
701 if (security_vm_enough_memory_mm(mm, to_account >> PAGE_SHIFT))
702 return -ENOMEM;
703 }
704
705 vma_start_write(vma);
706 new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
707 new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff,
708 &need_rmap_locks);
709 if (!new_vma) {
710 if (vm_flags & VM_ACCOUNT)
711 vm_unacct_memory(to_account >> PAGE_SHIFT);
712 return -ENOMEM;
713 }
714
715 moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len,
716 need_rmap_locks, false);
717 if (moved_len < old_len) {
718 err = -ENOMEM;
719 } else if (vma->vm_ops && vma->vm_ops->mremap) {
720 err = vma->vm_ops->mremap(new_vma);
721 }
722
723 if (unlikely(err)) {
724 /*
725 * On error, move entries back from new area to old,
726 * which will succeed since page tables still there,
727 * and then proceed to unmap new area instead of old.
728 */
729 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len,
730 true, false);
731 vma = new_vma;
732 old_len = new_len;
733 old_addr = new_addr;
734 new_addr = err;
735 } else {
736 mremap_userfaultfd_prep(new_vma, uf);
737 }
738
739 if (is_vm_hugetlb_page(vma)) {
740 clear_vma_resv_huge_pages(vma);
741 }
742
743 /* Conceal VM_ACCOUNT so old reservation is not undone */
744 if (vm_flags & VM_ACCOUNT && !(flags & MREMAP_DONTUNMAP)) {
745 vm_flags_clear(vma, VM_ACCOUNT);
746 if (vma->vm_start < old_addr)
747 account_start = vma->vm_start;
748 if (vma->vm_end > old_addr + old_len)
749 account_end = vma->vm_end;
750 }
751
752 /*
753 * If we failed to move page tables we still do total_vm increment
754 * since do_munmap() will decrement it by old_len == new_len.
755 *
756 * Since total_vm is about to be raised artificially high for a
757 * moment, we need to restore high watermark afterwards: if stats
758 * are taken meanwhile, total_vm and hiwater_vm appear too high.
759 * If this were a serious issue, we'd add a flag to do_munmap().
760 */
761 hiwater_vm = mm->hiwater_vm;
762 vm_stat_account(mm, vma->vm_flags, new_len >> PAGE_SHIFT);
763
764 /* Tell pfnmap has moved from this vma */
765 if (unlikely(vma->vm_flags & VM_PFNMAP))
766 untrack_pfn_clear(vma);
767
768 if (unlikely(!err && (flags & MREMAP_DONTUNMAP))) {
769 /* We always clear VM_LOCKED[ONFAULT] on the old vma */
770 vm_flags_clear(vma, VM_LOCKED_MASK);
771
772 /*
773 * anon_vma links of the old vma is no longer needed after its page
774 * table has been moved.
775 */
776 if (new_vma != vma && vma->vm_start == old_addr &&
777 vma->vm_end == (old_addr + old_len))
778 unlink_anon_vmas(vma);
779
780 /* Because we won't unmap we don't need to touch locked_vm */
781 return new_addr;
782 }
783
784 vma_iter_init(&vmi, mm, old_addr);
785 if (do_vmi_munmap(&vmi, mm, old_addr, old_len, uf_unmap, false) < 0) {
786 /* OOM: unable to split vma, just get accounts right */
787 if (vm_flags & VM_ACCOUNT && !(flags & MREMAP_DONTUNMAP))
788 vm_acct_memory(old_len >> PAGE_SHIFT);
789 account_start = account_end = 0;
790 }
791
792 if (vm_flags & VM_LOCKED) {
793 mm->locked_vm += new_len >> PAGE_SHIFT;
794 *locked = true;
795 }
796
797 mm->hiwater_vm = hiwater_vm;
798
799 /* Restore VM_ACCOUNT if one or two pieces of vma left */
800 if (account_start) {
801 vma = vma_prev(&vmi);
802 vm_flags_set(vma, VM_ACCOUNT);
803 }
804
805 if (account_end) {
806 vma = vma_next(&vmi);
807 vm_flags_set(vma, VM_ACCOUNT);
808 }
809
810 return new_addr;
811}
812
813static struct vm_area_struct *vma_to_resize(unsigned long addr,
814 unsigned long old_len, unsigned long new_len, unsigned long flags)
815{
816 struct mm_struct *mm = current->mm;
817 struct vm_area_struct *vma;
818 unsigned long pgoff;
819
820 vma = vma_lookup(mm, addr);
821 if (!vma)
822 return ERR_PTR(-EFAULT);
823
824 /*
825 * !old_len is a special case where an attempt is made to 'duplicate'
826 * a mapping. This makes no sense for private mappings as it will
827 * instead create a fresh/new mapping unrelated to the original. This
828 * is contrary to the basic idea of mremap which creates new mappings
829 * based on the original. There are no known use cases for this
830 * behavior. As a result, fail such attempts.
831 */
832 if (!old_len && !(vma->vm_flags & (VM_SHARED | VM_MAYSHARE))) {
833 pr_warn_once("%s (%d): attempted to duplicate a private mapping with mremap. This is not supported.\n", current->comm, current->pid);
834 return ERR_PTR(-EINVAL);
835 }
836
837 if ((flags & MREMAP_DONTUNMAP) &&
838 (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)))
839 return ERR_PTR(-EINVAL);
840
841 /* We can't remap across vm area boundaries */
842 if (old_len > vma->vm_end - addr)
843 return ERR_PTR(-EFAULT);
844
845 if (new_len == old_len)
846 return vma;
847
848 /* Need to be careful about a growing mapping */
849 pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
850 pgoff += vma->vm_pgoff;
851 if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
852 return ERR_PTR(-EINVAL);
853
854 if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
855 return ERR_PTR(-EFAULT);
856
857 if (!mlock_future_ok(mm, vma->vm_flags, new_len - old_len))
858 return ERR_PTR(-EAGAIN);
859
860 if (!may_expand_vm(mm, vma->vm_flags,
861 (new_len - old_len) >> PAGE_SHIFT))
862 return ERR_PTR(-ENOMEM);
863
864 return vma;
865}
866
867static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
868 unsigned long new_addr, unsigned long new_len, bool *locked,
869 unsigned long flags, struct vm_userfaultfd_ctx *uf,
870 struct list_head *uf_unmap_early,
871 struct list_head *uf_unmap)
872{
873 struct mm_struct *mm = current->mm;
874 struct vm_area_struct *vma;
875 unsigned long ret = -EINVAL;
876 unsigned long map_flags = 0;
877
878 if (offset_in_page(new_addr))
879 goto out;
880
881 if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
882 goto out;
883
884 /* Ensure the old/new locations do not overlap */
885 if (addr + old_len > new_addr && new_addr + new_len > addr)
886 goto out;
887
888 /*
889 * move_vma() need us to stay 4 maps below the threshold, otherwise
890 * it will bail out at the very beginning.
891 * That is a problem if we have already unmaped the regions here
892 * (new_addr, and old_addr), because userspace will not know the
893 * state of the vma's after it gets -ENOMEM.
894 * So, to avoid such scenario we can pre-compute if the whole
895 * operation has high chances to success map-wise.
896 * Worst-scenario case is when both vma's (new_addr and old_addr) get
897 * split in 3 before unmapping it.
898 * That means 2 more maps (1 for each) to the ones we already hold.
899 * Check whether current map count plus 2 still leads us to 4 maps below
900 * the threshold, otherwise return -ENOMEM here to be more safe.
901 */
902 if ((mm->map_count + 2) >= sysctl_max_map_count - 3)
903 return -ENOMEM;
904
905 if (flags & MREMAP_FIXED) {
906 ret = do_munmap(mm, new_addr, new_len, uf_unmap_early);
907 if (ret)
908 goto out;
909 }
910
911 if (old_len > new_len) {
912 ret = do_munmap(mm, addr+new_len, old_len - new_len, uf_unmap);
913 if (ret)
914 goto out;
915 old_len = new_len;
916 }
917
918 vma = vma_to_resize(addr, old_len, new_len, flags);
919 if (IS_ERR(vma)) {
920 ret = PTR_ERR(vma);
921 goto out;
922 }
923
924 /* MREMAP_DONTUNMAP expands by old_len since old_len == new_len */
925 if (flags & MREMAP_DONTUNMAP &&
926 !may_expand_vm(mm, vma->vm_flags, old_len >> PAGE_SHIFT)) {
927 ret = -ENOMEM;
928 goto out;
929 }
930
931 if (flags & MREMAP_FIXED)
932 map_flags |= MAP_FIXED;
933
934 if (vma->vm_flags & VM_MAYSHARE)
935 map_flags |= MAP_SHARED;
936
937 ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff +
938 ((addr - vma->vm_start) >> PAGE_SHIFT),
939 map_flags);
940 if (IS_ERR_VALUE(ret))
941 goto out;
942
943 /* We got a new mapping */
944 if (!(flags & MREMAP_FIXED))
945 new_addr = ret;
946
947 ret = move_vma(vma, addr, old_len, new_len, new_addr, locked, flags, uf,
948 uf_unmap);
949
950out:
951 return ret;
952}
953
954static int vma_expandable(struct vm_area_struct *vma, unsigned long delta)
955{
956 unsigned long end = vma->vm_end + delta;
957
958 if (end < vma->vm_end) /* overflow */
959 return 0;
960 if (find_vma_intersection(vma->vm_mm, vma->vm_end, end))
961 return 0;
962 if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start,
963 0, MAP_FIXED) & ~PAGE_MASK)
964 return 0;
965 return 1;
966}
967
968/*
969 * Expand (or shrink) an existing mapping, potentially moving it at the
970 * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
971 *
972 * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
973 * This option implies MREMAP_MAYMOVE.
974 */
975SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
976 unsigned long, new_len, unsigned long, flags,
977 unsigned long, new_addr)
978{
979 struct mm_struct *mm = current->mm;
980 struct vm_area_struct *vma;
981 unsigned long ret = -EINVAL;
982 bool locked = false;
983 struct vm_userfaultfd_ctx uf = NULL_VM_UFFD_CTX;
984 LIST_HEAD(uf_unmap_early);
985 LIST_HEAD(uf_unmap);
986
987 /*
988 * There is a deliberate asymmetry here: we strip the pointer tag
989 * from the old address but leave the new address alone. This is
990 * for consistency with mmap(), where we prevent the creation of
991 * aliasing mappings in userspace by leaving the tag bits of the
992 * mapping address intact. A non-zero tag will cause the subsequent
993 * range checks to reject the address as invalid.
994 *
995 * See Documentation/arch/arm64/tagged-address-abi.rst for more
996 * information.
997 */
998 addr = untagged_addr(addr);
999
1000 if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE | MREMAP_DONTUNMAP))
1001 return ret;
1002
1003 if (flags & MREMAP_FIXED && !(flags & MREMAP_MAYMOVE))
1004 return ret;
1005
1006 /*
1007 * MREMAP_DONTUNMAP is always a move and it does not allow resizing
1008 * in the process.
1009 */
1010 if (flags & MREMAP_DONTUNMAP &&
1011 (!(flags & MREMAP_MAYMOVE) || old_len != new_len))
1012 return ret;
1013
1014
1015 if (offset_in_page(addr))
1016 return ret;
1017
1018 old_len = PAGE_ALIGN(old_len);
1019 new_len = PAGE_ALIGN(new_len);
1020
1021 /*
1022 * We allow a zero old-len as a special case
1023 * for DOS-emu "duplicate shm area" thing. But
1024 * a zero new-len is nonsensical.
1025 */
1026 if (!new_len)
1027 return ret;
1028
1029 if (mmap_write_lock_killable(current->mm))
1030 return -EINTR;
1031 vma = vma_lookup(mm, addr);
1032 if (!vma) {
1033 ret = -EFAULT;
1034 goto out;
1035 }
1036
1037 if (is_vm_hugetlb_page(vma)) {
1038 struct hstate *h __maybe_unused = hstate_vma(vma);
1039
1040 old_len = ALIGN(old_len, huge_page_size(h));
1041 new_len = ALIGN(new_len, huge_page_size(h));
1042
1043 /* addrs must be huge page aligned */
1044 if (addr & ~huge_page_mask(h))
1045 goto out;
1046 if (new_addr & ~huge_page_mask(h))
1047 goto out;
1048
1049 /*
1050 * Don't allow remap expansion, because the underlying hugetlb
1051 * reservation is not yet capable to handle split reservation.
1052 */
1053 if (new_len > old_len)
1054 goto out;
1055 }
1056
1057 if (flags & (MREMAP_FIXED | MREMAP_DONTUNMAP)) {
1058 ret = mremap_to(addr, old_len, new_addr, new_len,
1059 &locked, flags, &uf, &uf_unmap_early,
1060 &uf_unmap);
1061 goto out;
1062 }
1063
1064 /*
1065 * Always allow a shrinking remap: that just unmaps
1066 * the unnecessary pages..
1067 * do_vmi_munmap does all the needed commit accounting, and
1068 * unlocks the mmap_lock if so directed.
1069 */
1070 if (old_len >= new_len) {
1071 VMA_ITERATOR(vmi, mm, addr + new_len);
1072
1073 if (old_len == new_len) {
1074 ret = addr;
1075 goto out;
1076 }
1077
1078 ret = do_vmi_munmap(&vmi, mm, addr + new_len, old_len - new_len,
1079 &uf_unmap, true);
1080 if (ret)
1081 goto out;
1082
1083 ret = addr;
1084 goto out_unlocked;
1085 }
1086
1087 /*
1088 * Ok, we need to grow..
1089 */
1090 vma = vma_to_resize(addr, old_len, new_len, flags);
1091 if (IS_ERR(vma)) {
1092 ret = PTR_ERR(vma);
1093 goto out;
1094 }
1095
1096 /* old_len exactly to the end of the area..
1097 */
1098 if (old_len == vma->vm_end - addr) {
1099 unsigned long delta = new_len - old_len;
1100
1101 /* can we just expand the current mapping? */
1102 if (vma_expandable(vma, delta)) {
1103 long pages = delta >> PAGE_SHIFT;
1104 VMA_ITERATOR(vmi, mm, vma->vm_end);
1105 long charged = 0;
1106
1107 if (vma->vm_flags & VM_ACCOUNT) {
1108 if (security_vm_enough_memory_mm(mm, pages)) {
1109 ret = -ENOMEM;
1110 goto out;
1111 }
1112 charged = pages;
1113 }
1114
1115 /*
1116 * Function vma_merge_extend() is called on the
1117 * extension we are adding to the already existing vma,
1118 * vma_merge_extend() will merge this extension with the
1119 * already existing vma (expand operation itself) and
1120 * possibly also with the next vma if it becomes
1121 * adjacent to the expanded vma and otherwise
1122 * compatible.
1123 */
1124 vma = vma_merge_extend(&vmi, vma, delta);
1125 if (!vma) {
1126 vm_unacct_memory(charged);
1127 ret = -ENOMEM;
1128 goto out;
1129 }
1130
1131 vm_stat_account(mm, vma->vm_flags, pages);
1132 if (vma->vm_flags & VM_LOCKED) {
1133 mm->locked_vm += pages;
1134 locked = true;
1135 new_addr = addr;
1136 }
1137 ret = addr;
1138 goto out;
1139 }
1140 }
1141
1142 /*
1143 * We weren't able to just expand or shrink the area,
1144 * we need to create a new one and move it..
1145 */
1146 ret = -ENOMEM;
1147 if (flags & MREMAP_MAYMOVE) {
1148 unsigned long map_flags = 0;
1149 if (vma->vm_flags & VM_MAYSHARE)
1150 map_flags |= MAP_SHARED;
1151
1152 new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
1153 vma->vm_pgoff +
1154 ((addr - vma->vm_start) >> PAGE_SHIFT),
1155 map_flags);
1156 if (IS_ERR_VALUE(new_addr)) {
1157 ret = new_addr;
1158 goto out;
1159 }
1160
1161 ret = move_vma(vma, addr, old_len, new_len, new_addr,
1162 &locked, flags, &uf, &uf_unmap);
1163 }
1164out:
1165 if (offset_in_page(ret))
1166 locked = false;
1167 mmap_write_unlock(current->mm);
1168 if (locked && new_len > old_len)
1169 mm_populate(new_addr + old_len, new_len - old_len);
1170out_unlocked:
1171 userfaultfd_unmap_complete(mm, &uf_unmap_early);
1172 mremap_userfaultfd_complete(&uf, addr, ret, old_len);
1173 userfaultfd_unmap_complete(mm, &uf_unmap);
1174 return ret;
1175}
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * mm/mremap.c
4 *
5 * (C) Copyright 1996 Linus Torvalds
6 *
7 * Address space accounting code <alan@lxorguk.ukuu.org.uk>
8 * (C) Copyright 2002 Red Hat Inc, All Rights Reserved
9 */
10
11#include <linux/mm.h>
12#include <linux/mm_inline.h>
13#include <linux/hugetlb.h>
14#include <linux/shm.h>
15#include <linux/ksm.h>
16#include <linux/mman.h>
17#include <linux/swap.h>
18#include <linux/capability.h>
19#include <linux/fs.h>
20#include <linux/swapops.h>
21#include <linux/highmem.h>
22#include <linux/security.h>
23#include <linux/syscalls.h>
24#include <linux/mmu_notifier.h>
25#include <linux/uaccess.h>
26#include <linux/userfaultfd_k.h>
27#include <linux/mempolicy.h>
28
29#include <asm/cacheflush.h>
30#include <asm/tlb.h>
31#include <asm/pgalloc.h>
32
33#include "internal.h"
34
35static pud_t *get_old_pud(struct mm_struct *mm, unsigned long addr)
36{
37 pgd_t *pgd;
38 p4d_t *p4d;
39 pud_t *pud;
40
41 pgd = pgd_offset(mm, addr);
42 if (pgd_none_or_clear_bad(pgd))
43 return NULL;
44
45 p4d = p4d_offset(pgd, addr);
46 if (p4d_none_or_clear_bad(p4d))
47 return NULL;
48
49 pud = pud_offset(p4d, addr);
50 if (pud_none_or_clear_bad(pud))
51 return NULL;
52
53 return pud;
54}
55
56static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr)
57{
58 pud_t *pud;
59 pmd_t *pmd;
60
61 pud = get_old_pud(mm, addr);
62 if (!pud)
63 return NULL;
64
65 pmd = pmd_offset(pud, addr);
66 if (pmd_none(*pmd))
67 return NULL;
68
69 return pmd;
70}
71
72static pud_t *alloc_new_pud(struct mm_struct *mm, struct vm_area_struct *vma,
73 unsigned long addr)
74{
75 pgd_t *pgd;
76 p4d_t *p4d;
77
78 pgd = pgd_offset(mm, addr);
79 p4d = p4d_alloc(mm, pgd, addr);
80 if (!p4d)
81 return NULL;
82
83 return pud_alloc(mm, p4d, addr);
84}
85
86static pmd_t *alloc_new_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
87 unsigned long addr)
88{
89 pud_t *pud;
90 pmd_t *pmd;
91
92 pud = alloc_new_pud(mm, vma, addr);
93 if (!pud)
94 return NULL;
95
96 pmd = pmd_alloc(mm, pud, addr);
97 if (!pmd)
98 return NULL;
99
100 VM_BUG_ON(pmd_trans_huge(*pmd));
101
102 return pmd;
103}
104
105static void take_rmap_locks(struct vm_area_struct *vma)
106{
107 if (vma->vm_file)
108 i_mmap_lock_write(vma->vm_file->f_mapping);
109 if (vma->anon_vma)
110 anon_vma_lock_write(vma->anon_vma);
111}
112
113static void drop_rmap_locks(struct vm_area_struct *vma)
114{
115 if (vma->anon_vma)
116 anon_vma_unlock_write(vma->anon_vma);
117 if (vma->vm_file)
118 i_mmap_unlock_write(vma->vm_file->f_mapping);
119}
120
121static pte_t move_soft_dirty_pte(pte_t pte)
122{
123 /*
124 * Set soft dirty bit so we can notice
125 * in userspace the ptes were moved.
126 */
127#ifdef CONFIG_MEM_SOFT_DIRTY
128 if (pte_present(pte))
129 pte = pte_mksoft_dirty(pte);
130 else if (is_swap_pte(pte))
131 pte = pte_swp_mksoft_dirty(pte);
132#endif
133 return pte;
134}
135
136static int move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
137 unsigned long old_addr, unsigned long old_end,
138 struct vm_area_struct *new_vma, pmd_t *new_pmd,
139 unsigned long new_addr, bool need_rmap_locks)
140{
141 bool need_clear_uffd_wp = vma_has_uffd_without_event_remap(vma);
142 struct mm_struct *mm = vma->vm_mm;
143 pte_t *old_pte, *new_pte, pte;
144 pmd_t dummy_pmdval;
145 spinlock_t *old_ptl, *new_ptl;
146 bool force_flush = false;
147 unsigned long len = old_end - old_addr;
148 int err = 0;
149
150 /*
151 * When need_rmap_locks is true, we take the i_mmap_rwsem and anon_vma
152 * locks to ensure that rmap will always observe either the old or the
153 * new ptes. This is the easiest way to avoid races with
154 * truncate_pagecache(), page migration, etc...
155 *
156 * When need_rmap_locks is false, we use other ways to avoid
157 * such races:
158 *
159 * - During exec() shift_arg_pages(), we use a specially tagged vma
160 * which rmap call sites look for using vma_is_temporary_stack().
161 *
162 * - During mremap(), new_vma is often known to be placed after vma
163 * in rmap traversal order. This ensures rmap will always observe
164 * either the old pte, or the new pte, or both (the page table locks
165 * serialize access to individual ptes, but only rmap traversal
166 * order guarantees that we won't miss both the old and new ptes).
167 */
168 if (need_rmap_locks)
169 take_rmap_locks(vma);
170
171 /*
172 * We don't have to worry about the ordering of src and dst
173 * pte locks because exclusive mmap_lock prevents deadlock.
174 */
175 old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl);
176 if (!old_pte) {
177 err = -EAGAIN;
178 goto out;
179 }
180 /*
181 * Now new_pte is none, so hpage_collapse_scan_file() path can not find
182 * this by traversing file->f_mapping, so there is no concurrency with
183 * retract_page_tables(). In addition, we already hold the exclusive
184 * mmap_lock, so this new_pte page is stable, so there is no need to get
185 * pmdval and do pmd_same() check.
186 */
187 new_pte = pte_offset_map_rw_nolock(mm, new_pmd, new_addr, &dummy_pmdval,
188 &new_ptl);
189 if (!new_pte) {
190 pte_unmap_unlock(old_pte, old_ptl);
191 err = -EAGAIN;
192 goto out;
193 }
194 if (new_ptl != old_ptl)
195 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
196 flush_tlb_batched_pending(vma->vm_mm);
197 arch_enter_lazy_mmu_mode();
198
199 for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE,
200 new_pte++, new_addr += PAGE_SIZE) {
201 if (pte_none(ptep_get(old_pte)))
202 continue;
203
204 pte = ptep_get_and_clear(mm, old_addr, old_pte);
205 /*
206 * If we are remapping a valid PTE, make sure
207 * to flush TLB before we drop the PTL for the
208 * PTE.
209 *
210 * NOTE! Both old and new PTL matter: the old one
211 * for racing with folio_mkclean(), the new one to
212 * make sure the physical page stays valid until
213 * the TLB entry for the old mapping has been
214 * flushed.
215 */
216 if (pte_present(pte))
217 force_flush = true;
218 pte = move_pte(pte, old_addr, new_addr);
219 pte = move_soft_dirty_pte(pte);
220
221 if (need_clear_uffd_wp && pte_marker_uffd_wp(pte))
222 pte_clear(mm, new_addr, new_pte);
223 else {
224 if (need_clear_uffd_wp) {
225 if (pte_present(pte))
226 pte = pte_clear_uffd_wp(pte);
227 else if (is_swap_pte(pte))
228 pte = pte_swp_clear_uffd_wp(pte);
229 }
230 set_pte_at(mm, new_addr, new_pte, pte);
231 }
232 }
233
234 arch_leave_lazy_mmu_mode();
235 if (force_flush)
236 flush_tlb_range(vma, old_end - len, old_end);
237 if (new_ptl != old_ptl)
238 spin_unlock(new_ptl);
239 pte_unmap(new_pte - 1);
240 pte_unmap_unlock(old_pte - 1, old_ptl);
241out:
242 if (need_rmap_locks)
243 drop_rmap_locks(vma);
244 return err;
245}
246
247#ifndef arch_supports_page_table_move
248#define arch_supports_page_table_move arch_supports_page_table_move
249static inline bool arch_supports_page_table_move(void)
250{
251 return IS_ENABLED(CONFIG_HAVE_MOVE_PMD) ||
252 IS_ENABLED(CONFIG_HAVE_MOVE_PUD);
253}
254#endif
255
256#ifdef CONFIG_HAVE_MOVE_PMD
257static bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr,
258 unsigned long new_addr, pmd_t *old_pmd, pmd_t *new_pmd)
259{
260 spinlock_t *old_ptl, *new_ptl;
261 struct mm_struct *mm = vma->vm_mm;
262 bool res = false;
263 pmd_t pmd;
264
265 if (!arch_supports_page_table_move())
266 return false;
267 /*
268 * The destination pmd shouldn't be established, free_pgtables()
269 * should have released it.
270 *
271 * However, there's a case during execve() where we use mremap
272 * to move the initial stack, and in that case the target area
273 * may overlap the source area (always moving down).
274 *
275 * If everything is PMD-aligned, that works fine, as moving
276 * each pmd down will clear the source pmd. But if we first
277 * have a few 4kB-only pages that get moved down, and then
278 * hit the "now the rest is PMD-aligned, let's do everything
279 * one pmd at a time", we will still have the old (now empty
280 * of any 4kB pages, but still there) PMD in the page table
281 * tree.
282 *
283 * Warn on it once - because we really should try to figure
284 * out how to do this better - but then say "I won't move
285 * this pmd".
286 *
287 * One alternative might be to just unmap the target pmd at
288 * this point, and verify that it really is empty. We'll see.
289 */
290 if (WARN_ON_ONCE(!pmd_none(*new_pmd)))
291 return false;
292
293 /* If this pmd belongs to a uffd vma with remap events disabled, we need
294 * to ensure that the uffd-wp state is cleared from all pgtables. This
295 * means recursing into lower page tables in move_page_tables(), and we
296 * can reuse the existing code if we simply treat the entry as "not
297 * moved".
298 */
299 if (vma_has_uffd_without_event_remap(vma))
300 return false;
301
302 /*
303 * We don't have to worry about the ordering of src and dst
304 * ptlocks because exclusive mmap_lock prevents deadlock.
305 */
306 old_ptl = pmd_lock(vma->vm_mm, old_pmd);
307 new_ptl = pmd_lockptr(mm, new_pmd);
308 if (new_ptl != old_ptl)
309 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
310
311 pmd = *old_pmd;
312
313 /* Racing with collapse? */
314 if (unlikely(!pmd_present(pmd) || pmd_leaf(pmd)))
315 goto out_unlock;
316 /* Clear the pmd */
317 pmd_clear(old_pmd);
318 res = true;
319
320 VM_BUG_ON(!pmd_none(*new_pmd));
321
322 pmd_populate(mm, new_pmd, pmd_pgtable(pmd));
323 flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
324out_unlock:
325 if (new_ptl != old_ptl)
326 spin_unlock(new_ptl);
327 spin_unlock(old_ptl);
328
329 return res;
330}
331#else
332static inline bool move_normal_pmd(struct vm_area_struct *vma,
333 unsigned long old_addr, unsigned long new_addr, pmd_t *old_pmd,
334 pmd_t *new_pmd)
335{
336 return false;
337}
338#endif
339
340#if CONFIG_PGTABLE_LEVELS > 2 && defined(CONFIG_HAVE_MOVE_PUD)
341static bool move_normal_pud(struct vm_area_struct *vma, unsigned long old_addr,
342 unsigned long new_addr, pud_t *old_pud, pud_t *new_pud)
343{
344 spinlock_t *old_ptl, *new_ptl;
345 struct mm_struct *mm = vma->vm_mm;
346 pud_t pud;
347
348 if (!arch_supports_page_table_move())
349 return false;
350 /*
351 * The destination pud shouldn't be established, free_pgtables()
352 * should have released it.
353 */
354 if (WARN_ON_ONCE(!pud_none(*new_pud)))
355 return false;
356
357 /* If this pud belongs to a uffd vma with remap events disabled, we need
358 * to ensure that the uffd-wp state is cleared from all pgtables. This
359 * means recursing into lower page tables in move_page_tables(), and we
360 * can reuse the existing code if we simply treat the entry as "not
361 * moved".
362 */
363 if (vma_has_uffd_without_event_remap(vma))
364 return false;
365
366 /*
367 * We don't have to worry about the ordering of src and dst
368 * ptlocks because exclusive mmap_lock prevents deadlock.
369 */
370 old_ptl = pud_lock(vma->vm_mm, old_pud);
371 new_ptl = pud_lockptr(mm, new_pud);
372 if (new_ptl != old_ptl)
373 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
374
375 /* Clear the pud */
376 pud = *old_pud;
377 pud_clear(old_pud);
378
379 VM_BUG_ON(!pud_none(*new_pud));
380
381 pud_populate(mm, new_pud, pud_pgtable(pud));
382 flush_tlb_range(vma, old_addr, old_addr + PUD_SIZE);
383 if (new_ptl != old_ptl)
384 spin_unlock(new_ptl);
385 spin_unlock(old_ptl);
386
387 return true;
388}
389#else
390static inline bool move_normal_pud(struct vm_area_struct *vma,
391 unsigned long old_addr, unsigned long new_addr, pud_t *old_pud,
392 pud_t *new_pud)
393{
394 return false;
395}
396#endif
397
398#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && defined(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD)
399static bool move_huge_pud(struct vm_area_struct *vma, unsigned long old_addr,
400 unsigned long new_addr, pud_t *old_pud, pud_t *new_pud)
401{
402 spinlock_t *old_ptl, *new_ptl;
403 struct mm_struct *mm = vma->vm_mm;
404 pud_t pud;
405
406 /*
407 * The destination pud shouldn't be established, free_pgtables()
408 * should have released it.
409 */
410 if (WARN_ON_ONCE(!pud_none(*new_pud)))
411 return false;
412
413 /*
414 * We don't have to worry about the ordering of src and dst
415 * ptlocks because exclusive mmap_lock prevents deadlock.
416 */
417 old_ptl = pud_lock(vma->vm_mm, old_pud);
418 new_ptl = pud_lockptr(mm, new_pud);
419 if (new_ptl != old_ptl)
420 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
421
422 /* Clear the pud */
423 pud = *old_pud;
424 pud_clear(old_pud);
425
426 VM_BUG_ON(!pud_none(*new_pud));
427
428 /* Set the new pud */
429 /* mark soft_ditry when we add pud level soft dirty support */
430 set_pud_at(mm, new_addr, new_pud, pud);
431 flush_pud_tlb_range(vma, old_addr, old_addr + HPAGE_PUD_SIZE);
432 if (new_ptl != old_ptl)
433 spin_unlock(new_ptl);
434 spin_unlock(old_ptl);
435
436 return true;
437}
438#else
439static bool move_huge_pud(struct vm_area_struct *vma, unsigned long old_addr,
440 unsigned long new_addr, pud_t *old_pud, pud_t *new_pud)
441{
442 WARN_ON_ONCE(1);
443 return false;
444
445}
446#endif
447
448enum pgt_entry {
449 NORMAL_PMD,
450 HPAGE_PMD,
451 NORMAL_PUD,
452 HPAGE_PUD,
453};
454
455/*
456 * Returns an extent of the corresponding size for the pgt_entry specified if
457 * valid. Else returns a smaller extent bounded by the end of the source and
458 * destination pgt_entry.
459 */
460static __always_inline unsigned long get_extent(enum pgt_entry entry,
461 unsigned long old_addr, unsigned long old_end,
462 unsigned long new_addr)
463{
464 unsigned long next, extent, mask, size;
465
466 switch (entry) {
467 case HPAGE_PMD:
468 case NORMAL_PMD:
469 mask = PMD_MASK;
470 size = PMD_SIZE;
471 break;
472 case HPAGE_PUD:
473 case NORMAL_PUD:
474 mask = PUD_MASK;
475 size = PUD_SIZE;
476 break;
477 default:
478 BUILD_BUG();
479 break;
480 }
481
482 next = (old_addr + size) & mask;
483 /* even if next overflowed, extent below will be ok */
484 extent = next - old_addr;
485 if (extent > old_end - old_addr)
486 extent = old_end - old_addr;
487 next = (new_addr + size) & mask;
488 if (extent > next - new_addr)
489 extent = next - new_addr;
490 return extent;
491}
492
493/*
494 * Attempts to speedup the move by moving entry at the level corresponding to
495 * pgt_entry. Returns true if the move was successful, else false.
496 */
497static bool move_pgt_entry(enum pgt_entry entry, struct vm_area_struct *vma,
498 unsigned long old_addr, unsigned long new_addr,
499 void *old_entry, void *new_entry, bool need_rmap_locks)
500{
501 bool moved = false;
502
503 /* See comment in move_ptes() */
504 if (need_rmap_locks)
505 take_rmap_locks(vma);
506
507 switch (entry) {
508 case NORMAL_PMD:
509 moved = move_normal_pmd(vma, old_addr, new_addr, old_entry,
510 new_entry);
511 break;
512 case NORMAL_PUD:
513 moved = move_normal_pud(vma, old_addr, new_addr, old_entry,
514 new_entry);
515 break;
516 case HPAGE_PMD:
517 moved = IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
518 move_huge_pmd(vma, old_addr, new_addr, old_entry,
519 new_entry);
520 break;
521 case HPAGE_PUD:
522 moved = IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
523 move_huge_pud(vma, old_addr, new_addr, old_entry,
524 new_entry);
525 break;
526
527 default:
528 WARN_ON_ONCE(1);
529 break;
530 }
531
532 if (need_rmap_locks)
533 drop_rmap_locks(vma);
534
535 return moved;
536}
537
538/*
539 * A helper to check if aligning down is OK. The aligned address should fall
540 * on *no mapping*. For the stack moving down, that's a special move within
541 * the VMA that is created to span the source and destination of the move,
542 * so we make an exception for it.
543 */
544static bool can_align_down(struct vm_area_struct *vma, unsigned long addr_to_align,
545 unsigned long mask, bool for_stack)
546{
547 unsigned long addr_masked = addr_to_align & mask;
548
549 /*
550 * If @addr_to_align of either source or destination is not the beginning
551 * of the corresponding VMA, we can't align down or we will destroy part
552 * of the current mapping.
553 */
554 if (!for_stack && vma->vm_start != addr_to_align)
555 return false;
556
557 /* In the stack case we explicitly permit in-VMA alignment. */
558 if (for_stack && addr_masked >= vma->vm_start)
559 return true;
560
561 /*
562 * Make sure the realignment doesn't cause the address to fall on an
563 * existing mapping.
564 */
565 return find_vma_intersection(vma->vm_mm, addr_masked, vma->vm_start) == NULL;
566}
567
568/* Opportunistically realign to specified boundary for faster copy. */
569static void try_realign_addr(unsigned long *old_addr, struct vm_area_struct *old_vma,
570 unsigned long *new_addr, struct vm_area_struct *new_vma,
571 unsigned long mask, bool for_stack)
572{
573 /* Skip if the addresses are already aligned. */
574 if ((*old_addr & ~mask) == 0)
575 return;
576
577 /* Only realign if the new and old addresses are mutually aligned. */
578 if ((*old_addr & ~mask) != (*new_addr & ~mask))
579 return;
580
581 /* Ensure realignment doesn't cause overlap with existing mappings. */
582 if (!can_align_down(old_vma, *old_addr, mask, for_stack) ||
583 !can_align_down(new_vma, *new_addr, mask, for_stack))
584 return;
585
586 *old_addr = *old_addr & mask;
587 *new_addr = *new_addr & mask;
588}
589
590unsigned long move_page_tables(struct vm_area_struct *vma,
591 unsigned long old_addr, struct vm_area_struct *new_vma,
592 unsigned long new_addr, unsigned long len,
593 bool need_rmap_locks, bool for_stack)
594{
595 unsigned long extent, old_end;
596 struct mmu_notifier_range range;
597 pmd_t *old_pmd, *new_pmd;
598 pud_t *old_pud, *new_pud;
599
600 if (!len)
601 return 0;
602
603 old_end = old_addr + len;
604
605 if (is_vm_hugetlb_page(vma))
606 return move_hugetlb_page_tables(vma, new_vma, old_addr,
607 new_addr, len);
608
609 /*
610 * If possible, realign addresses to PMD boundary for faster copy.
611 * Only realign if the mremap copying hits a PMD boundary.
612 */
613 if (len >= PMD_SIZE - (old_addr & ~PMD_MASK))
614 try_realign_addr(&old_addr, vma, &new_addr, new_vma, PMD_MASK,
615 for_stack);
616
617 flush_cache_range(vma, old_addr, old_end);
618 mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0, vma->vm_mm,
619 old_addr, old_end);
620 mmu_notifier_invalidate_range_start(&range);
621
622 for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
623 cond_resched();
624 /*
625 * If extent is PUD-sized try to speed up the move by moving at the
626 * PUD level if possible.
627 */
628 extent = get_extent(NORMAL_PUD, old_addr, old_end, new_addr);
629
630 old_pud = get_old_pud(vma->vm_mm, old_addr);
631 if (!old_pud)
632 continue;
633 new_pud = alloc_new_pud(vma->vm_mm, vma, new_addr);
634 if (!new_pud)
635 break;
636 if (pud_trans_huge(*old_pud) || pud_devmap(*old_pud)) {
637 if (extent == HPAGE_PUD_SIZE) {
638 move_pgt_entry(HPAGE_PUD, vma, old_addr, new_addr,
639 old_pud, new_pud, need_rmap_locks);
640 /* We ignore and continue on error? */
641 continue;
642 }
643 } else if (IS_ENABLED(CONFIG_HAVE_MOVE_PUD) && extent == PUD_SIZE) {
644
645 if (move_pgt_entry(NORMAL_PUD, vma, old_addr, new_addr,
646 old_pud, new_pud, true))
647 continue;
648 }
649
650 extent = get_extent(NORMAL_PMD, old_addr, old_end, new_addr);
651 old_pmd = get_old_pmd(vma->vm_mm, old_addr);
652 if (!old_pmd)
653 continue;
654 new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr);
655 if (!new_pmd)
656 break;
657again:
658 if (is_swap_pmd(*old_pmd) || pmd_trans_huge(*old_pmd) ||
659 pmd_devmap(*old_pmd)) {
660 if (extent == HPAGE_PMD_SIZE &&
661 move_pgt_entry(HPAGE_PMD, vma, old_addr, new_addr,
662 old_pmd, new_pmd, need_rmap_locks))
663 continue;
664 split_huge_pmd(vma, old_pmd, old_addr);
665 } else if (IS_ENABLED(CONFIG_HAVE_MOVE_PMD) &&
666 extent == PMD_SIZE) {
667 /*
668 * If the extent is PMD-sized, try to speed the move by
669 * moving at the PMD level if possible.
670 */
671 if (move_pgt_entry(NORMAL_PMD, vma, old_addr, new_addr,
672 old_pmd, new_pmd, true))
673 continue;
674 }
675 if (pmd_none(*old_pmd))
676 continue;
677 if (pte_alloc(new_vma->vm_mm, new_pmd))
678 break;
679 if (move_ptes(vma, old_pmd, old_addr, old_addr + extent,
680 new_vma, new_pmd, new_addr, need_rmap_locks) < 0)
681 goto again;
682 }
683
684 mmu_notifier_invalidate_range_end(&range);
685
686 /*
687 * Prevent negative return values when {old,new}_addr was realigned
688 * but we broke out of the above loop for the first PMD itself.
689 */
690 if (old_addr < old_end - len)
691 return 0;
692
693 return len + old_addr - old_end; /* how much done */
694}
695
696static unsigned long move_vma(struct vm_area_struct *vma,
697 unsigned long old_addr, unsigned long old_len,
698 unsigned long new_len, unsigned long new_addr,
699 bool *locked, unsigned long flags,
700 struct vm_userfaultfd_ctx *uf, struct list_head *uf_unmap)
701{
702 long to_account = new_len - old_len;
703 struct mm_struct *mm = vma->vm_mm;
704 struct vm_area_struct *new_vma;
705 unsigned long vm_flags = vma->vm_flags;
706 unsigned long new_pgoff;
707 unsigned long moved_len;
708 unsigned long account_start = 0;
709 unsigned long account_end = 0;
710 unsigned long hiwater_vm;
711 int err = 0;
712 bool need_rmap_locks;
713 struct vma_iterator vmi;
714
715 /*
716 * We'd prefer to avoid failure later on in do_munmap:
717 * which may split one vma into three before unmapping.
718 */
719 if (mm->map_count >= sysctl_max_map_count - 3)
720 return -ENOMEM;
721
722 if (unlikely(flags & MREMAP_DONTUNMAP))
723 to_account = new_len;
724
725 if (vma->vm_ops && vma->vm_ops->may_split) {
726 if (vma->vm_start != old_addr)
727 err = vma->vm_ops->may_split(vma, old_addr);
728 if (!err && vma->vm_end != old_addr + old_len)
729 err = vma->vm_ops->may_split(vma, old_addr + old_len);
730 if (err)
731 return err;
732 }
733
734 /*
735 * Advise KSM to break any KSM pages in the area to be moved:
736 * it would be confusing if they were to turn up at the new
737 * location, where they happen to coincide with different KSM
738 * pages recently unmapped. But leave vma->vm_flags as it was,
739 * so KSM can come around to merge on vma and new_vma afterwards.
740 */
741 err = ksm_madvise(vma, old_addr, old_addr + old_len,
742 MADV_UNMERGEABLE, &vm_flags);
743 if (err)
744 return err;
745
746 if (vm_flags & VM_ACCOUNT) {
747 if (security_vm_enough_memory_mm(mm, to_account >> PAGE_SHIFT))
748 return -ENOMEM;
749 }
750
751 vma_start_write(vma);
752 new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
753 new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff,
754 &need_rmap_locks);
755 if (!new_vma) {
756 if (vm_flags & VM_ACCOUNT)
757 vm_unacct_memory(to_account >> PAGE_SHIFT);
758 return -ENOMEM;
759 }
760
761 moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len,
762 need_rmap_locks, false);
763 if (moved_len < old_len) {
764 err = -ENOMEM;
765 } else if (vma->vm_ops && vma->vm_ops->mremap) {
766 err = vma->vm_ops->mremap(new_vma);
767 }
768
769 if (unlikely(err)) {
770 /*
771 * On error, move entries back from new area to old,
772 * which will succeed since page tables still there,
773 * and then proceed to unmap new area instead of old.
774 */
775 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len,
776 true, false);
777 vma = new_vma;
778 old_len = new_len;
779 old_addr = new_addr;
780 new_addr = err;
781 } else {
782 mremap_userfaultfd_prep(new_vma, uf);
783 }
784
785 if (is_vm_hugetlb_page(vma)) {
786 clear_vma_resv_huge_pages(vma);
787 }
788
789 /* Conceal VM_ACCOUNT so old reservation is not undone */
790 if (vm_flags & VM_ACCOUNT && !(flags & MREMAP_DONTUNMAP)) {
791 vm_flags_clear(vma, VM_ACCOUNT);
792 if (vma->vm_start < old_addr)
793 account_start = vma->vm_start;
794 if (vma->vm_end > old_addr + old_len)
795 account_end = vma->vm_end;
796 }
797
798 /*
799 * If we failed to move page tables we still do total_vm increment
800 * since do_munmap() will decrement it by old_len == new_len.
801 *
802 * Since total_vm is about to be raised artificially high for a
803 * moment, we need to restore high watermark afterwards: if stats
804 * are taken meanwhile, total_vm and hiwater_vm appear too high.
805 * If this were a serious issue, we'd add a flag to do_munmap().
806 */
807 hiwater_vm = mm->hiwater_vm;
808 vm_stat_account(mm, vma->vm_flags, new_len >> PAGE_SHIFT);
809
810 /* Tell pfnmap has moved from this vma */
811 if (unlikely(vma->vm_flags & VM_PFNMAP))
812 untrack_pfn_clear(vma);
813
814 if (unlikely(!err && (flags & MREMAP_DONTUNMAP))) {
815 /* We always clear VM_LOCKED[ONFAULT] on the old vma */
816 vm_flags_clear(vma, VM_LOCKED_MASK);
817
818 /*
819 * anon_vma links of the old vma is no longer needed after its page
820 * table has been moved.
821 */
822 if (new_vma != vma && vma->vm_start == old_addr &&
823 vma->vm_end == (old_addr + old_len))
824 unlink_anon_vmas(vma);
825
826 /* Because we won't unmap we don't need to touch locked_vm */
827 return new_addr;
828 }
829
830 vma_iter_init(&vmi, mm, old_addr);
831 if (do_vmi_munmap(&vmi, mm, old_addr, old_len, uf_unmap, false) < 0) {
832 /* OOM: unable to split vma, just get accounts right */
833 if (vm_flags & VM_ACCOUNT && !(flags & MREMAP_DONTUNMAP))
834 vm_acct_memory(old_len >> PAGE_SHIFT);
835 account_start = account_end = 0;
836 }
837
838 if (vm_flags & VM_LOCKED) {
839 mm->locked_vm += new_len >> PAGE_SHIFT;
840 *locked = true;
841 }
842
843 mm->hiwater_vm = hiwater_vm;
844
845 /* Restore VM_ACCOUNT if one or two pieces of vma left */
846 if (account_start) {
847 vma = vma_prev(&vmi);
848 vm_flags_set(vma, VM_ACCOUNT);
849 }
850
851 if (account_end) {
852 vma = vma_next(&vmi);
853 vm_flags_set(vma, VM_ACCOUNT);
854 }
855
856 return new_addr;
857}
858
859/*
860 * resize_is_valid() - Ensure the vma can be resized to the new length at the give
861 * address.
862 *
863 * @vma: The vma to resize
864 * @addr: The old address
865 * @old_len: The current size
866 * @new_len: The desired size
867 * @flags: The vma flags
868 *
869 * Return 0 on success, error otherwise.
870 */
871static int resize_is_valid(struct vm_area_struct *vma, unsigned long addr,
872 unsigned long old_len, unsigned long new_len, unsigned long flags)
873{
874 struct mm_struct *mm = current->mm;
875 unsigned long pgoff;
876
877 /*
878 * !old_len is a special case where an attempt is made to 'duplicate'
879 * a mapping. This makes no sense for private mappings as it will
880 * instead create a fresh/new mapping unrelated to the original. This
881 * is contrary to the basic idea of mremap which creates new mappings
882 * based on the original. There are no known use cases for this
883 * behavior. As a result, fail such attempts.
884 */
885 if (!old_len && !(vma->vm_flags & (VM_SHARED | VM_MAYSHARE))) {
886 pr_warn_once("%s (%d): attempted to duplicate a private mapping with mremap. This is not supported.\n", current->comm, current->pid);
887 return -EINVAL;
888 }
889
890 if ((flags & MREMAP_DONTUNMAP) &&
891 (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)))
892 return -EINVAL;
893
894 /* We can't remap across vm area boundaries */
895 if (old_len > vma->vm_end - addr)
896 return -EFAULT;
897
898 if (new_len == old_len)
899 return 0;
900
901 /* Need to be careful about a growing mapping */
902 pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
903 pgoff += vma->vm_pgoff;
904 if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
905 return -EINVAL;
906
907 if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
908 return -EFAULT;
909
910 if (!mlock_future_ok(mm, vma->vm_flags, new_len - old_len))
911 return -EAGAIN;
912
913 if (!may_expand_vm(mm, vma->vm_flags,
914 (new_len - old_len) >> PAGE_SHIFT))
915 return -ENOMEM;
916
917 return 0;
918}
919
920/*
921 * mremap_to() - remap a vma to a new location
922 * @addr: The old address
923 * @old_len: The old size
924 * @new_addr: The target address
925 * @new_len: The new size
926 * @locked: If the returned vma is locked (VM_LOCKED)
927 * @flags: the mremap flags
928 * @uf: The mremap userfaultfd context
929 * @uf_unmap_early: The userfaultfd unmap early context
930 * @uf_unmap: The userfaultfd unmap context
931 *
932 * Returns: The new address of the vma or an error.
933 */
934static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
935 unsigned long new_addr, unsigned long new_len, bool *locked,
936 unsigned long flags, struct vm_userfaultfd_ctx *uf,
937 struct list_head *uf_unmap_early,
938 struct list_head *uf_unmap)
939{
940 struct mm_struct *mm = current->mm;
941 struct vm_area_struct *vma;
942 unsigned long ret;
943 unsigned long map_flags = 0;
944
945 if (offset_in_page(new_addr))
946 return -EINVAL;
947
948 if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
949 return -EINVAL;
950
951 /* Ensure the old/new locations do not overlap */
952 if (addr + old_len > new_addr && new_addr + new_len > addr)
953 return -EINVAL;
954
955 /*
956 * move_vma() need us to stay 4 maps below the threshold, otherwise
957 * it will bail out at the very beginning.
958 * That is a problem if we have already unmaped the regions here
959 * (new_addr, and old_addr), because userspace will not know the
960 * state of the vma's after it gets -ENOMEM.
961 * So, to avoid such scenario we can pre-compute if the whole
962 * operation has high chances to success map-wise.
963 * Worst-scenario case is when both vma's (new_addr and old_addr) get
964 * split in 3 before unmapping it.
965 * That means 2 more maps (1 for each) to the ones we already hold.
966 * Check whether current map count plus 2 still leads us to 4 maps below
967 * the threshold, otherwise return -ENOMEM here to be more safe.
968 */
969 if ((mm->map_count + 2) >= sysctl_max_map_count - 3)
970 return -ENOMEM;
971
972 if (flags & MREMAP_FIXED) {
973 /*
974 * In mremap_to().
975 * VMA is moved to dst address, and munmap dst first.
976 * do_munmap will check if dst is sealed.
977 */
978 ret = do_munmap(mm, new_addr, new_len, uf_unmap_early);
979 if (ret)
980 return ret;
981 }
982
983 if (old_len > new_len) {
984 ret = do_munmap(mm, addr+new_len, old_len - new_len, uf_unmap);
985 if (ret)
986 return ret;
987 old_len = new_len;
988 }
989
990 vma = vma_lookup(mm, addr);
991 if (!vma)
992 return -EFAULT;
993
994 ret = resize_is_valid(vma, addr, old_len, new_len, flags);
995 if (ret)
996 return ret;
997
998 /* MREMAP_DONTUNMAP expands by old_len since old_len == new_len */
999 if (flags & MREMAP_DONTUNMAP &&
1000 !may_expand_vm(mm, vma->vm_flags, old_len >> PAGE_SHIFT)) {
1001 return -ENOMEM;
1002 }
1003
1004 if (flags & MREMAP_FIXED)
1005 map_flags |= MAP_FIXED;
1006
1007 if (vma->vm_flags & VM_MAYSHARE)
1008 map_flags |= MAP_SHARED;
1009
1010 ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff +
1011 ((addr - vma->vm_start) >> PAGE_SHIFT),
1012 map_flags);
1013 if (IS_ERR_VALUE(ret))
1014 return ret;
1015
1016 /* We got a new mapping */
1017 if (!(flags & MREMAP_FIXED))
1018 new_addr = ret;
1019
1020 return move_vma(vma, addr, old_len, new_len, new_addr, locked, flags,
1021 uf, uf_unmap);
1022}
1023
1024static int vma_expandable(struct vm_area_struct *vma, unsigned long delta)
1025{
1026 unsigned long end = vma->vm_end + delta;
1027
1028 if (end < vma->vm_end) /* overflow */
1029 return 0;
1030 if (find_vma_intersection(vma->vm_mm, vma->vm_end, end))
1031 return 0;
1032 if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start,
1033 0, MAP_FIXED) & ~PAGE_MASK)
1034 return 0;
1035 return 1;
1036}
1037
1038/*
1039 * Expand (or shrink) an existing mapping, potentially moving it at the
1040 * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
1041 *
1042 * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
1043 * This option implies MREMAP_MAYMOVE.
1044 */
1045SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
1046 unsigned long, new_len, unsigned long, flags,
1047 unsigned long, new_addr)
1048{
1049 struct mm_struct *mm = current->mm;
1050 struct vm_area_struct *vma;
1051 unsigned long ret = -EINVAL;
1052 bool locked = false;
1053 struct vm_userfaultfd_ctx uf = NULL_VM_UFFD_CTX;
1054 LIST_HEAD(uf_unmap_early);
1055 LIST_HEAD(uf_unmap);
1056
1057 /*
1058 * There is a deliberate asymmetry here: we strip the pointer tag
1059 * from the old address but leave the new address alone. This is
1060 * for consistency with mmap(), where we prevent the creation of
1061 * aliasing mappings in userspace by leaving the tag bits of the
1062 * mapping address intact. A non-zero tag will cause the subsequent
1063 * range checks to reject the address as invalid.
1064 *
1065 * See Documentation/arch/arm64/tagged-address-abi.rst for more
1066 * information.
1067 */
1068 addr = untagged_addr(addr);
1069
1070 if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE | MREMAP_DONTUNMAP))
1071 return ret;
1072
1073 if (flags & MREMAP_FIXED && !(flags & MREMAP_MAYMOVE))
1074 return ret;
1075
1076 /*
1077 * MREMAP_DONTUNMAP is always a move and it does not allow resizing
1078 * in the process.
1079 */
1080 if (flags & MREMAP_DONTUNMAP &&
1081 (!(flags & MREMAP_MAYMOVE) || old_len != new_len))
1082 return ret;
1083
1084
1085 if (offset_in_page(addr))
1086 return ret;
1087
1088 old_len = PAGE_ALIGN(old_len);
1089 new_len = PAGE_ALIGN(new_len);
1090
1091 /*
1092 * We allow a zero old-len as a special case
1093 * for DOS-emu "duplicate shm area" thing. But
1094 * a zero new-len is nonsensical.
1095 */
1096 if (!new_len)
1097 return ret;
1098
1099 if (mmap_write_lock_killable(current->mm))
1100 return -EINTR;
1101 vma = vma_lookup(mm, addr);
1102 if (!vma) {
1103 ret = -EFAULT;
1104 goto out;
1105 }
1106
1107 /* Don't allow remapping vmas when they have already been sealed */
1108 if (!can_modify_vma(vma)) {
1109 ret = -EPERM;
1110 goto out;
1111 }
1112
1113 if (is_vm_hugetlb_page(vma)) {
1114 struct hstate *h __maybe_unused = hstate_vma(vma);
1115
1116 old_len = ALIGN(old_len, huge_page_size(h));
1117 new_len = ALIGN(new_len, huge_page_size(h));
1118
1119 /* addrs must be huge page aligned */
1120 if (addr & ~huge_page_mask(h))
1121 goto out;
1122 if (new_addr & ~huge_page_mask(h))
1123 goto out;
1124
1125 /*
1126 * Don't allow remap expansion, because the underlying hugetlb
1127 * reservation is not yet capable to handle split reservation.
1128 */
1129 if (new_len > old_len)
1130 goto out;
1131 }
1132
1133 if (flags & (MREMAP_FIXED | MREMAP_DONTUNMAP)) {
1134 ret = mremap_to(addr, old_len, new_addr, new_len,
1135 &locked, flags, &uf, &uf_unmap_early,
1136 &uf_unmap);
1137 goto out;
1138 }
1139
1140 /*
1141 * Always allow a shrinking remap: that just unmaps
1142 * the unnecessary pages..
1143 * do_vmi_munmap does all the needed commit accounting, and
1144 * unlocks the mmap_lock if so directed.
1145 */
1146 if (old_len >= new_len) {
1147 VMA_ITERATOR(vmi, mm, addr + new_len);
1148
1149 if (old_len == new_len) {
1150 ret = addr;
1151 goto out;
1152 }
1153
1154 ret = do_vmi_munmap(&vmi, mm, addr + new_len, old_len - new_len,
1155 &uf_unmap, true);
1156 if (ret)
1157 goto out;
1158
1159 ret = addr;
1160 goto out_unlocked;
1161 }
1162
1163 /*
1164 * Ok, we need to grow..
1165 */
1166 ret = resize_is_valid(vma, addr, old_len, new_len, flags);
1167 if (ret)
1168 goto out;
1169
1170 /* old_len exactly to the end of the area..
1171 */
1172 if (old_len == vma->vm_end - addr) {
1173 unsigned long delta = new_len - old_len;
1174
1175 /* can we just expand the current mapping? */
1176 if (vma_expandable(vma, delta)) {
1177 long pages = delta >> PAGE_SHIFT;
1178 VMA_ITERATOR(vmi, mm, vma->vm_end);
1179 long charged = 0;
1180
1181 if (vma->vm_flags & VM_ACCOUNT) {
1182 if (security_vm_enough_memory_mm(mm, pages)) {
1183 ret = -ENOMEM;
1184 goto out;
1185 }
1186 charged = pages;
1187 }
1188
1189 /*
1190 * Function vma_merge_extend() is called on the
1191 * extension we are adding to the already existing vma,
1192 * vma_merge_extend() will merge this extension with the
1193 * already existing vma (expand operation itself) and
1194 * possibly also with the next vma if it becomes
1195 * adjacent to the expanded vma and otherwise
1196 * compatible.
1197 */
1198 vma = vma_merge_extend(&vmi, vma, delta);
1199 if (!vma) {
1200 vm_unacct_memory(charged);
1201 ret = -ENOMEM;
1202 goto out;
1203 }
1204
1205 vm_stat_account(mm, vma->vm_flags, pages);
1206 if (vma->vm_flags & VM_LOCKED) {
1207 mm->locked_vm += pages;
1208 locked = true;
1209 new_addr = addr;
1210 }
1211 ret = addr;
1212 goto out;
1213 }
1214 }
1215
1216 /*
1217 * We weren't able to just expand or shrink the area,
1218 * we need to create a new one and move it..
1219 */
1220 ret = -ENOMEM;
1221 if (flags & MREMAP_MAYMOVE) {
1222 unsigned long map_flags = 0;
1223 if (vma->vm_flags & VM_MAYSHARE)
1224 map_flags |= MAP_SHARED;
1225
1226 new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
1227 vma->vm_pgoff +
1228 ((addr - vma->vm_start) >> PAGE_SHIFT),
1229 map_flags);
1230 if (IS_ERR_VALUE(new_addr)) {
1231 ret = new_addr;
1232 goto out;
1233 }
1234
1235 ret = move_vma(vma, addr, old_len, new_len, new_addr,
1236 &locked, flags, &uf, &uf_unmap);
1237 }
1238out:
1239 if (offset_in_page(ret))
1240 locked = false;
1241 mmap_write_unlock(current->mm);
1242 if (locked && new_len > old_len)
1243 mm_populate(new_addr + old_len, new_len - old_len);
1244out_unlocked:
1245 userfaultfd_unmap_complete(mm, &uf_unmap_early);
1246 mremap_userfaultfd_complete(&uf, addr, ret, old_len);
1247 userfaultfd_unmap_complete(mm, &uf_unmap);
1248 return ret;
1249}