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1/*
2 * mm/mremap.c
3 *
4 * (C) Copyright 1996 Linus Torvalds
5 *
6 * Address space accounting code <alan@lxorguk.ukuu.org.uk>
7 * (C) Copyright 2002 Red Hat Inc, All Rights Reserved
8 */
9
10#include <linux/mm.h>
11#include <linux/hugetlb.h>
12#include <linux/shm.h>
13#include <linux/ksm.h>
14#include <linux/mman.h>
15#include <linux/swap.h>
16#include <linux/capability.h>
17#include <linux/fs.h>
18#include <linux/highmem.h>
19#include <linux/security.h>
20#include <linux/syscalls.h>
21#include <linux/mmu_notifier.h>
22
23#include <asm/uaccess.h>
24#include <asm/cacheflush.h>
25#include <asm/tlbflush.h>
26
27#include "internal.h"
28
29static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr)
30{
31 pgd_t *pgd;
32 pud_t *pud;
33 pmd_t *pmd;
34
35 pgd = pgd_offset(mm, addr);
36 if (pgd_none_or_clear_bad(pgd))
37 return NULL;
38
39 pud = pud_offset(pgd, addr);
40 if (pud_none_or_clear_bad(pud))
41 return NULL;
42
43 pmd = pmd_offset(pud, addr);
44 split_huge_page_pmd(mm, pmd);
45 if (pmd_none_or_clear_bad(pmd))
46 return NULL;
47
48 return pmd;
49}
50
51static pmd_t *alloc_new_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
52 unsigned long addr)
53{
54 pgd_t *pgd;
55 pud_t *pud;
56 pmd_t *pmd;
57
58 pgd = pgd_offset(mm, addr);
59 pud = pud_alloc(mm, pgd, addr);
60 if (!pud)
61 return NULL;
62
63 pmd = pmd_alloc(mm, pud, addr);
64 if (!pmd)
65 return NULL;
66
67 VM_BUG_ON(pmd_trans_huge(*pmd));
68 if (pmd_none(*pmd) && __pte_alloc(mm, vma, pmd, addr))
69 return NULL;
70
71 return pmd;
72}
73
74static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
75 unsigned long old_addr, unsigned long old_end,
76 struct vm_area_struct *new_vma, pmd_t *new_pmd,
77 unsigned long new_addr)
78{
79 struct address_space *mapping = NULL;
80 struct mm_struct *mm = vma->vm_mm;
81 pte_t *old_pte, *new_pte, pte;
82 spinlock_t *old_ptl, *new_ptl;
83 unsigned long old_start;
84
85 old_start = old_addr;
86 mmu_notifier_invalidate_range_start(vma->vm_mm,
87 old_start, old_end);
88 if (vma->vm_file) {
89 /*
90 * Subtle point from Rajesh Venkatasubramanian: before
91 * moving file-based ptes, we must lock truncate_pagecache
92 * out, since it might clean the dst vma before the src vma,
93 * and we propagate stale pages into the dst afterward.
94 */
95 mapping = vma->vm_file->f_mapping;
96 mutex_lock(&mapping->i_mmap_mutex);
97 }
98
99 /*
100 * We don't have to worry about the ordering of src and dst
101 * pte locks because exclusive mmap_sem prevents deadlock.
102 */
103 old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl);
104 new_pte = pte_offset_map(new_pmd, new_addr);
105 new_ptl = pte_lockptr(mm, new_pmd);
106 if (new_ptl != old_ptl)
107 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
108 arch_enter_lazy_mmu_mode();
109
110 for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE,
111 new_pte++, new_addr += PAGE_SIZE) {
112 if (pte_none(*old_pte))
113 continue;
114 pte = ptep_clear_flush(vma, old_addr, old_pte);
115 pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr);
116 set_pte_at(mm, new_addr, new_pte, pte);
117 }
118
119 arch_leave_lazy_mmu_mode();
120 if (new_ptl != old_ptl)
121 spin_unlock(new_ptl);
122 pte_unmap(new_pte - 1);
123 pte_unmap_unlock(old_pte - 1, old_ptl);
124 if (mapping)
125 mutex_unlock(&mapping->i_mmap_mutex);
126 mmu_notifier_invalidate_range_end(vma->vm_mm, old_start, old_end);
127}
128
129#define LATENCY_LIMIT (64 * PAGE_SIZE)
130
131unsigned long move_page_tables(struct vm_area_struct *vma,
132 unsigned long old_addr, struct vm_area_struct *new_vma,
133 unsigned long new_addr, unsigned long len)
134{
135 unsigned long extent, next, old_end;
136 pmd_t *old_pmd, *new_pmd;
137
138 old_end = old_addr + len;
139 flush_cache_range(vma, old_addr, old_end);
140
141 for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
142 cond_resched();
143 next = (old_addr + PMD_SIZE) & PMD_MASK;
144 if (next - 1 > old_end)
145 next = old_end;
146 extent = next - old_addr;
147 old_pmd = get_old_pmd(vma->vm_mm, old_addr);
148 if (!old_pmd)
149 continue;
150 new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr);
151 if (!new_pmd)
152 break;
153 next = (new_addr + PMD_SIZE) & PMD_MASK;
154 if (extent > next - new_addr)
155 extent = next - new_addr;
156 if (extent > LATENCY_LIMIT)
157 extent = LATENCY_LIMIT;
158 move_ptes(vma, old_pmd, old_addr, old_addr + extent,
159 new_vma, new_pmd, new_addr);
160 }
161
162 return len + old_addr - old_end; /* how much done */
163}
164
165static unsigned long move_vma(struct vm_area_struct *vma,
166 unsigned long old_addr, unsigned long old_len,
167 unsigned long new_len, unsigned long new_addr)
168{
169 struct mm_struct *mm = vma->vm_mm;
170 struct vm_area_struct *new_vma;
171 unsigned long vm_flags = vma->vm_flags;
172 unsigned long new_pgoff;
173 unsigned long moved_len;
174 unsigned long excess = 0;
175 unsigned long hiwater_vm;
176 int split = 0;
177 int err;
178
179 /*
180 * We'd prefer to avoid failure later on in do_munmap:
181 * which may split one vma into three before unmapping.
182 */
183 if (mm->map_count >= sysctl_max_map_count - 3)
184 return -ENOMEM;
185
186 /*
187 * Advise KSM to break any KSM pages in the area to be moved:
188 * it would be confusing if they were to turn up at the new
189 * location, where they happen to coincide with different KSM
190 * pages recently unmapped. But leave vma->vm_flags as it was,
191 * so KSM can come around to merge on vma and new_vma afterwards.
192 */
193 err = ksm_madvise(vma, old_addr, old_addr + old_len,
194 MADV_UNMERGEABLE, &vm_flags);
195 if (err)
196 return err;
197
198 new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
199 new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff);
200 if (!new_vma)
201 return -ENOMEM;
202
203 moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len);
204 if (moved_len < old_len) {
205 /*
206 * On error, move entries back from new area to old,
207 * which will succeed since page tables still there,
208 * and then proceed to unmap new area instead of old.
209 */
210 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len);
211 vma = new_vma;
212 old_len = new_len;
213 old_addr = new_addr;
214 new_addr = -ENOMEM;
215 }
216
217 /* Conceal VM_ACCOUNT so old reservation is not undone */
218 if (vm_flags & VM_ACCOUNT) {
219 vma->vm_flags &= ~VM_ACCOUNT;
220 excess = vma->vm_end - vma->vm_start - old_len;
221 if (old_addr > vma->vm_start &&
222 old_addr + old_len < vma->vm_end)
223 split = 1;
224 }
225
226 /*
227 * If we failed to move page tables we still do total_vm increment
228 * since do_munmap() will decrement it by old_len == new_len.
229 *
230 * Since total_vm is about to be raised artificially high for a
231 * moment, we need to restore high watermark afterwards: if stats
232 * are taken meanwhile, total_vm and hiwater_vm appear too high.
233 * If this were a serious issue, we'd add a flag to do_munmap().
234 */
235 hiwater_vm = mm->hiwater_vm;
236 mm->total_vm += new_len >> PAGE_SHIFT;
237 vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);
238
239 if (do_munmap(mm, old_addr, old_len) < 0) {
240 /* OOM: unable to split vma, just get accounts right */
241 vm_unacct_memory(excess >> PAGE_SHIFT);
242 excess = 0;
243 }
244 mm->hiwater_vm = hiwater_vm;
245
246 /* Restore VM_ACCOUNT if one or two pieces of vma left */
247 if (excess) {
248 vma->vm_flags |= VM_ACCOUNT;
249 if (split)
250 vma->vm_next->vm_flags |= VM_ACCOUNT;
251 }
252
253 if (vm_flags & VM_LOCKED) {
254 mm->locked_vm += new_len >> PAGE_SHIFT;
255 if (new_len > old_len)
256 mlock_vma_pages_range(new_vma, new_addr + old_len,
257 new_addr + new_len);
258 }
259
260 return new_addr;
261}
262
263static struct vm_area_struct *vma_to_resize(unsigned long addr,
264 unsigned long old_len, unsigned long new_len, unsigned long *p)
265{
266 struct mm_struct *mm = current->mm;
267 struct vm_area_struct *vma = find_vma(mm, addr);
268
269 if (!vma || vma->vm_start > addr)
270 goto Efault;
271
272 if (is_vm_hugetlb_page(vma))
273 goto Einval;
274
275 /* We can't remap across vm area boundaries */
276 if (old_len > vma->vm_end - addr)
277 goto Efault;
278
279 /* Need to be careful about a growing mapping */
280 if (new_len > old_len) {
281 unsigned long pgoff;
282
283 if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
284 goto Efault;
285 pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
286 pgoff += vma->vm_pgoff;
287 if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
288 goto Einval;
289 }
290
291 if (vma->vm_flags & VM_LOCKED) {
292 unsigned long locked, lock_limit;
293 locked = mm->locked_vm << PAGE_SHIFT;
294 lock_limit = rlimit(RLIMIT_MEMLOCK);
295 locked += new_len - old_len;
296 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
297 goto Eagain;
298 }
299
300 if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT))
301 goto Enomem;
302
303 if (vma->vm_flags & VM_ACCOUNT) {
304 unsigned long charged = (new_len - old_len) >> PAGE_SHIFT;
305 if (security_vm_enough_memory(charged))
306 goto Efault;
307 *p = charged;
308 }
309
310 return vma;
311
312Efault: /* very odd choice for most of the cases, but... */
313 return ERR_PTR(-EFAULT);
314Einval:
315 return ERR_PTR(-EINVAL);
316Enomem:
317 return ERR_PTR(-ENOMEM);
318Eagain:
319 return ERR_PTR(-EAGAIN);
320}
321
322static unsigned long mremap_to(unsigned long addr,
323 unsigned long old_len, unsigned long new_addr,
324 unsigned long new_len)
325{
326 struct mm_struct *mm = current->mm;
327 struct vm_area_struct *vma;
328 unsigned long ret = -EINVAL;
329 unsigned long charged = 0;
330 unsigned long map_flags;
331
332 if (new_addr & ~PAGE_MASK)
333 goto out;
334
335 if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
336 goto out;
337
338 /* Check if the location we're moving into overlaps the
339 * old location at all, and fail if it does.
340 */
341 if ((new_addr <= addr) && (new_addr+new_len) > addr)
342 goto out;
343
344 if ((addr <= new_addr) && (addr+old_len) > new_addr)
345 goto out;
346
347 ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
348 if (ret)
349 goto out;
350
351 ret = do_munmap(mm, new_addr, new_len);
352 if (ret)
353 goto out;
354
355 if (old_len >= new_len) {
356 ret = do_munmap(mm, addr+new_len, old_len - new_len);
357 if (ret && old_len != new_len)
358 goto out;
359 old_len = new_len;
360 }
361
362 vma = vma_to_resize(addr, old_len, new_len, &charged);
363 if (IS_ERR(vma)) {
364 ret = PTR_ERR(vma);
365 goto out;
366 }
367
368 map_flags = MAP_FIXED;
369 if (vma->vm_flags & VM_MAYSHARE)
370 map_flags |= MAP_SHARED;
371
372 ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff +
373 ((addr - vma->vm_start) >> PAGE_SHIFT),
374 map_flags);
375 if (ret & ~PAGE_MASK)
376 goto out1;
377
378 ret = move_vma(vma, addr, old_len, new_len, new_addr);
379 if (!(ret & ~PAGE_MASK))
380 goto out;
381out1:
382 vm_unacct_memory(charged);
383
384out:
385 return ret;
386}
387
388static int vma_expandable(struct vm_area_struct *vma, unsigned long delta)
389{
390 unsigned long end = vma->vm_end + delta;
391 if (end < vma->vm_end) /* overflow */
392 return 0;
393 if (vma->vm_next && vma->vm_next->vm_start < end) /* intersection */
394 return 0;
395 if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start,
396 0, MAP_FIXED) & ~PAGE_MASK)
397 return 0;
398 return 1;
399}
400
401/*
402 * Expand (or shrink) an existing mapping, potentially moving it at the
403 * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
404 *
405 * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
406 * This option implies MREMAP_MAYMOVE.
407 */
408unsigned long do_mremap(unsigned long addr,
409 unsigned long old_len, unsigned long new_len,
410 unsigned long flags, unsigned long new_addr)
411{
412 struct mm_struct *mm = current->mm;
413 struct vm_area_struct *vma;
414 unsigned long ret = -EINVAL;
415 unsigned long charged = 0;
416
417 if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
418 goto out;
419
420 if (addr & ~PAGE_MASK)
421 goto out;
422
423 old_len = PAGE_ALIGN(old_len);
424 new_len = PAGE_ALIGN(new_len);
425
426 /*
427 * We allow a zero old-len as a special case
428 * for DOS-emu "duplicate shm area" thing. But
429 * a zero new-len is nonsensical.
430 */
431 if (!new_len)
432 goto out;
433
434 if (flags & MREMAP_FIXED) {
435 if (flags & MREMAP_MAYMOVE)
436 ret = mremap_to(addr, old_len, new_addr, new_len);
437 goto out;
438 }
439
440 /*
441 * Always allow a shrinking remap: that just unmaps
442 * the unnecessary pages..
443 * do_munmap does all the needed commit accounting
444 */
445 if (old_len >= new_len) {
446 ret = do_munmap(mm, addr+new_len, old_len - new_len);
447 if (ret && old_len != new_len)
448 goto out;
449 ret = addr;
450 goto out;
451 }
452
453 /*
454 * Ok, we need to grow..
455 */
456 vma = vma_to_resize(addr, old_len, new_len, &charged);
457 if (IS_ERR(vma)) {
458 ret = PTR_ERR(vma);
459 goto out;
460 }
461
462 /* old_len exactly to the end of the area..
463 */
464 if (old_len == vma->vm_end - addr) {
465 /* can we just expand the current mapping? */
466 if (vma_expandable(vma, new_len - old_len)) {
467 int pages = (new_len - old_len) >> PAGE_SHIFT;
468
469 if (vma_adjust(vma, vma->vm_start, addr + new_len,
470 vma->vm_pgoff, NULL)) {
471 ret = -ENOMEM;
472 goto out;
473 }
474
475 mm->total_vm += pages;
476 vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages);
477 if (vma->vm_flags & VM_LOCKED) {
478 mm->locked_vm += pages;
479 mlock_vma_pages_range(vma, addr + old_len,
480 addr + new_len);
481 }
482 ret = addr;
483 goto out;
484 }
485 }
486
487 /*
488 * We weren't able to just expand or shrink the area,
489 * we need to create a new one and move it..
490 */
491 ret = -ENOMEM;
492 if (flags & MREMAP_MAYMOVE) {
493 unsigned long map_flags = 0;
494 if (vma->vm_flags & VM_MAYSHARE)
495 map_flags |= MAP_SHARED;
496
497 new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
498 vma->vm_pgoff +
499 ((addr - vma->vm_start) >> PAGE_SHIFT),
500 map_flags);
501 if (new_addr & ~PAGE_MASK) {
502 ret = new_addr;
503 goto out;
504 }
505
506 ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
507 if (ret)
508 goto out;
509 ret = move_vma(vma, addr, old_len, new_len, new_addr);
510 }
511out:
512 if (ret & ~PAGE_MASK)
513 vm_unacct_memory(charged);
514 return ret;
515}
516
517SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
518 unsigned long, new_len, unsigned long, flags,
519 unsigned long, new_addr)
520{
521 unsigned long ret;
522
523 down_write(¤t->mm->mmap_sem);
524 ret = do_mremap(addr, old_len, new_len, flags, new_addr);
525 up_write(¤t->mm->mmap_sem);
526 return ret;
527}
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/hugetlb.h>
13#include <linux/shm.h>
14#include <linux/ksm.h>
15#include <linux/mman.h>
16#include <linux/swap.h>
17#include <linux/capability.h>
18#include <linux/fs.h>
19#include <linux/swapops.h>
20#include <linux/highmem.h>
21#include <linux/security.h>
22#include <linux/syscalls.h>
23#include <linux/mmu_notifier.h>
24#include <linux/uaccess.h>
25#include <linux/userfaultfd_k.h>
26
27#include <asm/cacheflush.h>
28#include <asm/tlb.h>
29#include <asm/pgalloc.h>
30
31#include "internal.h"
32
33static pud_t *get_old_pud(struct mm_struct *mm, unsigned long addr)
34{
35 pgd_t *pgd;
36 p4d_t *p4d;
37 pud_t *pud;
38
39 pgd = pgd_offset(mm, addr);
40 if (pgd_none_or_clear_bad(pgd))
41 return NULL;
42
43 p4d = p4d_offset(pgd, addr);
44 if (p4d_none_or_clear_bad(p4d))
45 return NULL;
46
47 pud = pud_offset(p4d, addr);
48 if (pud_none_or_clear_bad(pud))
49 return NULL;
50
51 return pud;
52}
53
54static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr)
55{
56 pud_t *pud;
57 pmd_t *pmd;
58
59 pud = get_old_pud(mm, addr);
60 if (!pud)
61 return NULL;
62
63 pmd = pmd_offset(pud, addr);
64 if (pmd_none(*pmd))
65 return NULL;
66
67 return pmd;
68}
69
70static pud_t *alloc_new_pud(struct mm_struct *mm, struct vm_area_struct *vma,
71 unsigned long addr)
72{
73 pgd_t *pgd;
74 p4d_t *p4d;
75
76 pgd = pgd_offset(mm, addr);
77 p4d = p4d_alloc(mm, pgd, addr);
78 if (!p4d)
79 return NULL;
80
81 return pud_alloc(mm, p4d, addr);
82}
83
84static pmd_t *alloc_new_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
85 unsigned long addr)
86{
87 pud_t *pud;
88 pmd_t *pmd;
89
90 pud = alloc_new_pud(mm, vma, addr);
91 if (!pud)
92 return NULL;
93
94 pmd = pmd_alloc(mm, pud, addr);
95 if (!pmd)
96 return NULL;
97
98 VM_BUG_ON(pmd_trans_huge(*pmd));
99
100 return pmd;
101}
102
103static void take_rmap_locks(struct vm_area_struct *vma)
104{
105 if (vma->vm_file)
106 i_mmap_lock_write(vma->vm_file->f_mapping);
107 if (vma->anon_vma)
108 anon_vma_lock_write(vma->anon_vma);
109}
110
111static void drop_rmap_locks(struct vm_area_struct *vma)
112{
113 if (vma->anon_vma)
114 anon_vma_unlock_write(vma->anon_vma);
115 if (vma->vm_file)
116 i_mmap_unlock_write(vma->vm_file->f_mapping);
117}
118
119static pte_t move_soft_dirty_pte(pte_t pte)
120{
121 /*
122 * Set soft dirty bit so we can notice
123 * in userspace the ptes were moved.
124 */
125#ifdef CONFIG_MEM_SOFT_DIRTY
126 if (pte_present(pte))
127 pte = pte_mksoft_dirty(pte);
128 else if (is_swap_pte(pte))
129 pte = pte_swp_mksoft_dirty(pte);
130#endif
131 return pte;
132}
133
134static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
135 unsigned long old_addr, unsigned long old_end,
136 struct vm_area_struct *new_vma, pmd_t *new_pmd,
137 unsigned long new_addr, bool need_rmap_locks)
138{
139 struct mm_struct *mm = vma->vm_mm;
140 pte_t *old_pte, *new_pte, pte;
141 spinlock_t *old_ptl, *new_ptl;
142 bool force_flush = false;
143 unsigned long len = old_end - old_addr;
144
145 /*
146 * When need_rmap_locks is true, we take the i_mmap_rwsem and anon_vma
147 * locks to ensure that rmap will always observe either the old or the
148 * new ptes. This is the easiest way to avoid races with
149 * truncate_pagecache(), page migration, etc...
150 *
151 * When need_rmap_locks is false, we use other ways to avoid
152 * such races:
153 *
154 * - During exec() shift_arg_pages(), we use a specially tagged vma
155 * which rmap call sites look for using vma_is_temporary_stack().
156 *
157 * - During mremap(), new_vma is often known to be placed after vma
158 * in rmap traversal order. This ensures rmap will always observe
159 * either the old pte, or the new pte, or both (the page table locks
160 * serialize access to individual ptes, but only rmap traversal
161 * order guarantees that we won't miss both the old and new ptes).
162 */
163 if (need_rmap_locks)
164 take_rmap_locks(vma);
165
166 /*
167 * We don't have to worry about the ordering of src and dst
168 * pte locks because exclusive mmap_lock prevents deadlock.
169 */
170 old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl);
171 new_pte = pte_offset_map(new_pmd, new_addr);
172 new_ptl = pte_lockptr(mm, new_pmd);
173 if (new_ptl != old_ptl)
174 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
175 flush_tlb_batched_pending(vma->vm_mm);
176 arch_enter_lazy_mmu_mode();
177
178 for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE,
179 new_pte++, new_addr += PAGE_SIZE) {
180 if (pte_none(*old_pte))
181 continue;
182
183 pte = ptep_get_and_clear(mm, old_addr, old_pte);
184 /*
185 * If we are remapping a valid PTE, make sure
186 * to flush TLB before we drop the PTL for the
187 * PTE.
188 *
189 * NOTE! Both old and new PTL matter: the old one
190 * for racing with page_mkclean(), the new one to
191 * make sure the physical page stays valid until
192 * the TLB entry for the old mapping has been
193 * flushed.
194 */
195 if (pte_present(pte))
196 force_flush = true;
197 pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr);
198 pte = move_soft_dirty_pte(pte);
199 set_pte_at(mm, new_addr, new_pte, pte);
200 }
201
202 arch_leave_lazy_mmu_mode();
203 if (force_flush)
204 flush_tlb_range(vma, old_end - len, old_end);
205 if (new_ptl != old_ptl)
206 spin_unlock(new_ptl);
207 pte_unmap(new_pte - 1);
208 pte_unmap_unlock(old_pte - 1, old_ptl);
209 if (need_rmap_locks)
210 drop_rmap_locks(vma);
211}
212
213#ifndef arch_supports_page_table_move
214#define arch_supports_page_table_move arch_supports_page_table_move
215static inline bool arch_supports_page_table_move(void)
216{
217 return IS_ENABLED(CONFIG_HAVE_MOVE_PMD) ||
218 IS_ENABLED(CONFIG_HAVE_MOVE_PUD);
219}
220#endif
221
222#ifdef CONFIG_HAVE_MOVE_PMD
223static bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr,
224 unsigned long new_addr, pmd_t *old_pmd, pmd_t *new_pmd)
225{
226 spinlock_t *old_ptl, *new_ptl;
227 struct mm_struct *mm = vma->vm_mm;
228 pmd_t pmd;
229
230 if (!arch_supports_page_table_move())
231 return false;
232 /*
233 * The destination pmd shouldn't be established, free_pgtables()
234 * should have released it.
235 *
236 * However, there's a case during execve() where we use mremap
237 * to move the initial stack, and in that case the target area
238 * may overlap the source area (always moving down).
239 *
240 * If everything is PMD-aligned, that works fine, as moving
241 * each pmd down will clear the source pmd. But if we first
242 * have a few 4kB-only pages that get moved down, and then
243 * hit the "now the rest is PMD-aligned, let's do everything
244 * one pmd at a time", we will still have the old (now empty
245 * of any 4kB pages, but still there) PMD in the page table
246 * tree.
247 *
248 * Warn on it once - because we really should try to figure
249 * out how to do this better - but then say "I won't move
250 * this pmd".
251 *
252 * One alternative might be to just unmap the target pmd at
253 * this point, and verify that it really is empty. We'll see.
254 */
255 if (WARN_ON_ONCE(!pmd_none(*new_pmd)))
256 return false;
257
258 /*
259 * We don't have to worry about the ordering of src and dst
260 * ptlocks because exclusive mmap_lock prevents deadlock.
261 */
262 old_ptl = pmd_lock(vma->vm_mm, old_pmd);
263 new_ptl = pmd_lockptr(mm, new_pmd);
264 if (new_ptl != old_ptl)
265 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
266
267 /* Clear the pmd */
268 pmd = *old_pmd;
269 pmd_clear(old_pmd);
270
271 VM_BUG_ON(!pmd_none(*new_pmd));
272
273 pmd_populate(mm, new_pmd, pmd_pgtable(pmd));
274 flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
275 if (new_ptl != old_ptl)
276 spin_unlock(new_ptl);
277 spin_unlock(old_ptl);
278
279 return true;
280}
281#else
282static inline bool move_normal_pmd(struct vm_area_struct *vma,
283 unsigned long old_addr, unsigned long new_addr, pmd_t *old_pmd,
284 pmd_t *new_pmd)
285{
286 return false;
287}
288#endif
289
290#if CONFIG_PGTABLE_LEVELS > 2 && defined(CONFIG_HAVE_MOVE_PUD)
291static bool move_normal_pud(struct vm_area_struct *vma, unsigned long old_addr,
292 unsigned long new_addr, pud_t *old_pud, pud_t *new_pud)
293{
294 spinlock_t *old_ptl, *new_ptl;
295 struct mm_struct *mm = vma->vm_mm;
296 pud_t pud;
297
298 if (!arch_supports_page_table_move())
299 return false;
300 /*
301 * The destination pud shouldn't be established, free_pgtables()
302 * should have released it.
303 */
304 if (WARN_ON_ONCE(!pud_none(*new_pud)))
305 return false;
306
307 /*
308 * We don't have to worry about the ordering of src and dst
309 * ptlocks because exclusive mmap_lock prevents deadlock.
310 */
311 old_ptl = pud_lock(vma->vm_mm, old_pud);
312 new_ptl = pud_lockptr(mm, new_pud);
313 if (new_ptl != old_ptl)
314 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
315
316 /* Clear the pud */
317 pud = *old_pud;
318 pud_clear(old_pud);
319
320 VM_BUG_ON(!pud_none(*new_pud));
321
322 pud_populate(mm, new_pud, pud_pgtable(pud));
323 flush_tlb_range(vma, old_addr, old_addr + PUD_SIZE);
324 if (new_ptl != old_ptl)
325 spin_unlock(new_ptl);
326 spin_unlock(old_ptl);
327
328 return true;
329}
330#else
331static inline bool move_normal_pud(struct vm_area_struct *vma,
332 unsigned long old_addr, unsigned long new_addr, pud_t *old_pud,
333 pud_t *new_pud)
334{
335 return false;
336}
337#endif
338
339#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
340static bool move_huge_pud(struct vm_area_struct *vma, unsigned long old_addr,
341 unsigned long new_addr, pud_t *old_pud, pud_t *new_pud)
342{
343 spinlock_t *old_ptl, *new_ptl;
344 struct mm_struct *mm = vma->vm_mm;
345 pud_t pud;
346
347 /*
348 * The destination pud shouldn't be established, free_pgtables()
349 * should have released it.
350 */
351 if (WARN_ON_ONCE(!pud_none(*new_pud)))
352 return false;
353
354 /*
355 * We don't have to worry about the ordering of src and dst
356 * ptlocks because exclusive mmap_lock prevents deadlock.
357 */
358 old_ptl = pud_lock(vma->vm_mm, old_pud);
359 new_ptl = pud_lockptr(mm, new_pud);
360 if (new_ptl != old_ptl)
361 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
362
363 /* Clear the pud */
364 pud = *old_pud;
365 pud_clear(old_pud);
366
367 VM_BUG_ON(!pud_none(*new_pud));
368
369 /* Set the new pud */
370 /* mark soft_ditry when we add pud level soft dirty support */
371 set_pud_at(mm, new_addr, new_pud, pud);
372 flush_pud_tlb_range(vma, old_addr, old_addr + HPAGE_PUD_SIZE);
373 if (new_ptl != old_ptl)
374 spin_unlock(new_ptl);
375 spin_unlock(old_ptl);
376
377 return true;
378}
379#else
380static bool move_huge_pud(struct vm_area_struct *vma, unsigned long old_addr,
381 unsigned long new_addr, pud_t *old_pud, pud_t *new_pud)
382{
383 WARN_ON_ONCE(1);
384 return false;
385
386}
387#endif
388
389enum pgt_entry {
390 NORMAL_PMD,
391 HPAGE_PMD,
392 NORMAL_PUD,
393 HPAGE_PUD,
394};
395
396/*
397 * Returns an extent of the corresponding size for the pgt_entry specified if
398 * valid. Else returns a smaller extent bounded by the end of the source and
399 * destination pgt_entry.
400 */
401static __always_inline unsigned long get_extent(enum pgt_entry entry,
402 unsigned long old_addr, unsigned long old_end,
403 unsigned long new_addr)
404{
405 unsigned long next, extent, mask, size;
406
407 switch (entry) {
408 case HPAGE_PMD:
409 case NORMAL_PMD:
410 mask = PMD_MASK;
411 size = PMD_SIZE;
412 break;
413 case HPAGE_PUD:
414 case NORMAL_PUD:
415 mask = PUD_MASK;
416 size = PUD_SIZE;
417 break;
418 default:
419 BUILD_BUG();
420 break;
421 }
422
423 next = (old_addr + size) & mask;
424 /* even if next overflowed, extent below will be ok */
425 extent = next - old_addr;
426 if (extent > old_end - old_addr)
427 extent = old_end - old_addr;
428 next = (new_addr + size) & mask;
429 if (extent > next - new_addr)
430 extent = next - new_addr;
431 return extent;
432}
433
434/*
435 * Attempts to speedup the move by moving entry at the level corresponding to
436 * pgt_entry. Returns true if the move was successful, else false.
437 */
438static bool move_pgt_entry(enum pgt_entry entry, struct vm_area_struct *vma,
439 unsigned long old_addr, unsigned long new_addr,
440 void *old_entry, void *new_entry, bool need_rmap_locks)
441{
442 bool moved = false;
443
444 /* See comment in move_ptes() */
445 if (need_rmap_locks)
446 take_rmap_locks(vma);
447
448 switch (entry) {
449 case NORMAL_PMD:
450 moved = move_normal_pmd(vma, old_addr, new_addr, old_entry,
451 new_entry);
452 break;
453 case NORMAL_PUD:
454 moved = move_normal_pud(vma, old_addr, new_addr, old_entry,
455 new_entry);
456 break;
457 case HPAGE_PMD:
458 moved = IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
459 move_huge_pmd(vma, old_addr, new_addr, old_entry,
460 new_entry);
461 break;
462 case HPAGE_PUD:
463 moved = IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
464 move_huge_pud(vma, old_addr, new_addr, old_entry,
465 new_entry);
466 break;
467
468 default:
469 WARN_ON_ONCE(1);
470 break;
471 }
472
473 if (need_rmap_locks)
474 drop_rmap_locks(vma);
475
476 return moved;
477}
478
479unsigned long move_page_tables(struct vm_area_struct *vma,
480 unsigned long old_addr, struct vm_area_struct *new_vma,
481 unsigned long new_addr, unsigned long len,
482 bool need_rmap_locks)
483{
484 unsigned long extent, old_end;
485 struct mmu_notifier_range range;
486 pmd_t *old_pmd, *new_pmd;
487 pud_t *old_pud, *new_pud;
488
489 old_end = old_addr + len;
490 flush_cache_range(vma, old_addr, old_end);
491
492 mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0, vma, vma->vm_mm,
493 old_addr, old_end);
494 mmu_notifier_invalidate_range_start(&range);
495
496 for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
497 cond_resched();
498 /*
499 * If extent is PUD-sized try to speed up the move by moving at the
500 * PUD level if possible.
501 */
502 extent = get_extent(NORMAL_PUD, old_addr, old_end, new_addr);
503
504 old_pud = get_old_pud(vma->vm_mm, old_addr);
505 if (!old_pud)
506 continue;
507 new_pud = alloc_new_pud(vma->vm_mm, vma, new_addr);
508 if (!new_pud)
509 break;
510 if (pud_trans_huge(*old_pud) || pud_devmap(*old_pud)) {
511 if (extent == HPAGE_PUD_SIZE) {
512 move_pgt_entry(HPAGE_PUD, vma, old_addr, new_addr,
513 old_pud, new_pud, need_rmap_locks);
514 /* We ignore and continue on error? */
515 continue;
516 }
517 } else if (IS_ENABLED(CONFIG_HAVE_MOVE_PUD) && extent == PUD_SIZE) {
518
519 if (move_pgt_entry(NORMAL_PUD, vma, old_addr, new_addr,
520 old_pud, new_pud, true))
521 continue;
522 }
523
524 extent = get_extent(NORMAL_PMD, old_addr, old_end, new_addr);
525 old_pmd = get_old_pmd(vma->vm_mm, old_addr);
526 if (!old_pmd)
527 continue;
528 new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr);
529 if (!new_pmd)
530 break;
531 if (is_swap_pmd(*old_pmd) || pmd_trans_huge(*old_pmd) ||
532 pmd_devmap(*old_pmd)) {
533 if (extent == HPAGE_PMD_SIZE &&
534 move_pgt_entry(HPAGE_PMD, vma, old_addr, new_addr,
535 old_pmd, new_pmd, need_rmap_locks))
536 continue;
537 split_huge_pmd(vma, old_pmd, old_addr);
538 if (pmd_trans_unstable(old_pmd))
539 continue;
540 } else if (IS_ENABLED(CONFIG_HAVE_MOVE_PMD) &&
541 extent == PMD_SIZE) {
542 /*
543 * If the extent is PMD-sized, try to speed the move by
544 * moving at the PMD level if possible.
545 */
546 if (move_pgt_entry(NORMAL_PMD, vma, old_addr, new_addr,
547 old_pmd, new_pmd, true))
548 continue;
549 }
550
551 if (pte_alloc(new_vma->vm_mm, new_pmd))
552 break;
553 move_ptes(vma, old_pmd, old_addr, old_addr + extent, new_vma,
554 new_pmd, new_addr, need_rmap_locks);
555 }
556
557 mmu_notifier_invalidate_range_end(&range);
558
559 return len + old_addr - old_end; /* how much done */
560}
561
562static unsigned long move_vma(struct vm_area_struct *vma,
563 unsigned long old_addr, unsigned long old_len,
564 unsigned long new_len, unsigned long new_addr,
565 bool *locked, unsigned long flags,
566 struct vm_userfaultfd_ctx *uf, struct list_head *uf_unmap)
567{
568 struct mm_struct *mm = vma->vm_mm;
569 struct vm_area_struct *new_vma;
570 unsigned long vm_flags = vma->vm_flags;
571 unsigned long new_pgoff;
572 unsigned long moved_len;
573 unsigned long excess = 0;
574 unsigned long hiwater_vm;
575 int split = 0;
576 int err = 0;
577 bool need_rmap_locks;
578
579 /*
580 * We'd prefer to avoid failure later on in do_munmap:
581 * which may split one vma into three before unmapping.
582 */
583 if (mm->map_count >= sysctl_max_map_count - 3)
584 return -ENOMEM;
585
586 if (vma->vm_ops && vma->vm_ops->may_split) {
587 if (vma->vm_start != old_addr)
588 err = vma->vm_ops->may_split(vma, old_addr);
589 if (!err && vma->vm_end != old_addr + old_len)
590 err = vma->vm_ops->may_split(vma, old_addr + old_len);
591 if (err)
592 return err;
593 }
594
595 /*
596 * Advise KSM to break any KSM pages in the area to be moved:
597 * it would be confusing if they were to turn up at the new
598 * location, where they happen to coincide with different KSM
599 * pages recently unmapped. But leave vma->vm_flags as it was,
600 * so KSM can come around to merge on vma and new_vma afterwards.
601 */
602 err = ksm_madvise(vma, old_addr, old_addr + old_len,
603 MADV_UNMERGEABLE, &vm_flags);
604 if (err)
605 return err;
606
607 if (unlikely(flags & MREMAP_DONTUNMAP && vm_flags & VM_ACCOUNT)) {
608 if (security_vm_enough_memory_mm(mm, new_len >> PAGE_SHIFT))
609 return -ENOMEM;
610 }
611
612 new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
613 new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff,
614 &need_rmap_locks);
615 if (!new_vma) {
616 if (unlikely(flags & MREMAP_DONTUNMAP && vm_flags & VM_ACCOUNT))
617 vm_unacct_memory(new_len >> PAGE_SHIFT);
618 return -ENOMEM;
619 }
620
621 moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len,
622 need_rmap_locks);
623 if (moved_len < old_len) {
624 err = -ENOMEM;
625 } else if (vma->vm_ops && vma->vm_ops->mremap) {
626 err = vma->vm_ops->mremap(new_vma);
627 }
628
629 if (unlikely(err)) {
630 /*
631 * On error, move entries back from new area to old,
632 * which will succeed since page tables still there,
633 * and then proceed to unmap new area instead of old.
634 */
635 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len,
636 true);
637 vma = new_vma;
638 old_len = new_len;
639 old_addr = new_addr;
640 new_addr = err;
641 } else {
642 mremap_userfaultfd_prep(new_vma, uf);
643 }
644
645 /* Conceal VM_ACCOUNT so old reservation is not undone */
646 if (vm_flags & VM_ACCOUNT && !(flags & MREMAP_DONTUNMAP)) {
647 vma->vm_flags &= ~VM_ACCOUNT;
648 excess = vma->vm_end - vma->vm_start - old_len;
649 if (old_addr > vma->vm_start &&
650 old_addr + old_len < vma->vm_end)
651 split = 1;
652 }
653
654 /*
655 * If we failed to move page tables we still do total_vm increment
656 * since do_munmap() will decrement it by old_len == new_len.
657 *
658 * Since total_vm is about to be raised artificially high for a
659 * moment, we need to restore high watermark afterwards: if stats
660 * are taken meanwhile, total_vm and hiwater_vm appear too high.
661 * If this were a serious issue, we'd add a flag to do_munmap().
662 */
663 hiwater_vm = mm->hiwater_vm;
664 vm_stat_account(mm, vma->vm_flags, new_len >> PAGE_SHIFT);
665
666 /* Tell pfnmap has moved from this vma */
667 if (unlikely(vma->vm_flags & VM_PFNMAP))
668 untrack_pfn_moved(vma);
669
670 if (unlikely(!err && (flags & MREMAP_DONTUNMAP))) {
671 /* We always clear VM_LOCKED[ONFAULT] on the old vma */
672 vma->vm_flags &= VM_LOCKED_CLEAR_MASK;
673
674 /*
675 * anon_vma links of the old vma is no longer needed after its page
676 * table has been moved.
677 */
678 if (new_vma != vma && vma->vm_start == old_addr &&
679 vma->vm_end == (old_addr + old_len))
680 unlink_anon_vmas(vma);
681
682 /* Because we won't unmap we don't need to touch locked_vm */
683 return new_addr;
684 }
685
686 if (do_munmap(mm, old_addr, old_len, uf_unmap) < 0) {
687 /* OOM: unable to split vma, just get accounts right */
688 if (vm_flags & VM_ACCOUNT && !(flags & MREMAP_DONTUNMAP))
689 vm_acct_memory(new_len >> PAGE_SHIFT);
690 excess = 0;
691 }
692
693 if (vm_flags & VM_LOCKED) {
694 mm->locked_vm += new_len >> PAGE_SHIFT;
695 *locked = true;
696 }
697
698 mm->hiwater_vm = hiwater_vm;
699
700 /* Restore VM_ACCOUNT if one or two pieces of vma left */
701 if (excess) {
702 vma->vm_flags |= VM_ACCOUNT;
703 if (split)
704 vma->vm_next->vm_flags |= VM_ACCOUNT;
705 }
706
707 return new_addr;
708}
709
710static struct vm_area_struct *vma_to_resize(unsigned long addr,
711 unsigned long old_len, unsigned long new_len, unsigned long flags,
712 unsigned long *p)
713{
714 struct mm_struct *mm = current->mm;
715 struct vm_area_struct *vma;
716 unsigned long pgoff;
717
718 vma = vma_lookup(mm, addr);
719 if (!vma)
720 return ERR_PTR(-EFAULT);
721
722 /*
723 * !old_len is a special case where an attempt is made to 'duplicate'
724 * a mapping. This makes no sense for private mappings as it will
725 * instead create a fresh/new mapping unrelated to the original. This
726 * is contrary to the basic idea of mremap which creates new mappings
727 * based on the original. There are no known use cases for this
728 * behavior. As a result, fail such attempts.
729 */
730 if (!old_len && !(vma->vm_flags & (VM_SHARED | VM_MAYSHARE))) {
731 pr_warn_once("%s (%d): attempted to duplicate a private mapping with mremap. This is not supported.\n", current->comm, current->pid);
732 return ERR_PTR(-EINVAL);
733 }
734
735 if ((flags & MREMAP_DONTUNMAP) &&
736 (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)))
737 return ERR_PTR(-EINVAL);
738
739 if (is_vm_hugetlb_page(vma))
740 return ERR_PTR(-EINVAL);
741
742 /* We can't remap across vm area boundaries */
743 if (old_len > vma->vm_end - addr)
744 return ERR_PTR(-EFAULT);
745
746 if (new_len == old_len)
747 return vma;
748
749 /* Need to be careful about a growing mapping */
750 pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
751 pgoff += vma->vm_pgoff;
752 if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
753 return ERR_PTR(-EINVAL);
754
755 if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
756 return ERR_PTR(-EFAULT);
757
758 if (vma->vm_flags & VM_LOCKED) {
759 unsigned long locked, lock_limit;
760 locked = mm->locked_vm << PAGE_SHIFT;
761 lock_limit = rlimit(RLIMIT_MEMLOCK);
762 locked += new_len - old_len;
763 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
764 return ERR_PTR(-EAGAIN);
765 }
766
767 if (!may_expand_vm(mm, vma->vm_flags,
768 (new_len - old_len) >> PAGE_SHIFT))
769 return ERR_PTR(-ENOMEM);
770
771 if (vma->vm_flags & VM_ACCOUNT) {
772 unsigned long charged = (new_len - old_len) >> PAGE_SHIFT;
773 if (security_vm_enough_memory_mm(mm, charged))
774 return ERR_PTR(-ENOMEM);
775 *p = charged;
776 }
777
778 return vma;
779}
780
781static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
782 unsigned long new_addr, unsigned long new_len, bool *locked,
783 unsigned long flags, struct vm_userfaultfd_ctx *uf,
784 struct list_head *uf_unmap_early,
785 struct list_head *uf_unmap)
786{
787 struct mm_struct *mm = current->mm;
788 struct vm_area_struct *vma;
789 unsigned long ret = -EINVAL;
790 unsigned long charged = 0;
791 unsigned long map_flags = 0;
792
793 if (offset_in_page(new_addr))
794 goto out;
795
796 if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
797 goto out;
798
799 /* Ensure the old/new locations do not overlap */
800 if (addr + old_len > new_addr && new_addr + new_len > addr)
801 goto out;
802
803 /*
804 * move_vma() need us to stay 4 maps below the threshold, otherwise
805 * it will bail out at the very beginning.
806 * That is a problem if we have already unmaped the regions here
807 * (new_addr, and old_addr), because userspace will not know the
808 * state of the vma's after it gets -ENOMEM.
809 * So, to avoid such scenario we can pre-compute if the whole
810 * operation has high chances to success map-wise.
811 * Worst-scenario case is when both vma's (new_addr and old_addr) get
812 * split in 3 before unmapping it.
813 * That means 2 more maps (1 for each) to the ones we already hold.
814 * Check whether current map count plus 2 still leads us to 4 maps below
815 * the threshold, otherwise return -ENOMEM here to be more safe.
816 */
817 if ((mm->map_count + 2) >= sysctl_max_map_count - 3)
818 return -ENOMEM;
819
820 if (flags & MREMAP_FIXED) {
821 ret = do_munmap(mm, new_addr, new_len, uf_unmap_early);
822 if (ret)
823 goto out;
824 }
825
826 if (old_len >= new_len) {
827 ret = do_munmap(mm, addr+new_len, old_len - new_len, uf_unmap);
828 if (ret && old_len != new_len)
829 goto out;
830 old_len = new_len;
831 }
832
833 vma = vma_to_resize(addr, old_len, new_len, flags, &charged);
834 if (IS_ERR(vma)) {
835 ret = PTR_ERR(vma);
836 goto out;
837 }
838
839 /* MREMAP_DONTUNMAP expands by old_len since old_len == new_len */
840 if (flags & MREMAP_DONTUNMAP &&
841 !may_expand_vm(mm, vma->vm_flags, old_len >> PAGE_SHIFT)) {
842 ret = -ENOMEM;
843 goto out;
844 }
845
846 if (flags & MREMAP_FIXED)
847 map_flags |= MAP_FIXED;
848
849 if (vma->vm_flags & VM_MAYSHARE)
850 map_flags |= MAP_SHARED;
851
852 ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff +
853 ((addr - vma->vm_start) >> PAGE_SHIFT),
854 map_flags);
855 if (IS_ERR_VALUE(ret))
856 goto out1;
857
858 /* We got a new mapping */
859 if (!(flags & MREMAP_FIXED))
860 new_addr = ret;
861
862 ret = move_vma(vma, addr, old_len, new_len, new_addr, locked, flags, uf,
863 uf_unmap);
864
865 if (!(offset_in_page(ret)))
866 goto out;
867
868out1:
869 vm_unacct_memory(charged);
870
871out:
872 return ret;
873}
874
875static int vma_expandable(struct vm_area_struct *vma, unsigned long delta)
876{
877 unsigned long end = vma->vm_end + delta;
878 if (end < vma->vm_end) /* overflow */
879 return 0;
880 if (vma->vm_next && vma->vm_next->vm_start < end) /* intersection */
881 return 0;
882 if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start,
883 0, MAP_FIXED) & ~PAGE_MASK)
884 return 0;
885 return 1;
886}
887
888/*
889 * Expand (or shrink) an existing mapping, potentially moving it at the
890 * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
891 *
892 * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
893 * This option implies MREMAP_MAYMOVE.
894 */
895SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
896 unsigned long, new_len, unsigned long, flags,
897 unsigned long, new_addr)
898{
899 struct mm_struct *mm = current->mm;
900 struct vm_area_struct *vma;
901 unsigned long ret = -EINVAL;
902 unsigned long charged = 0;
903 bool locked = false;
904 bool downgraded = false;
905 struct vm_userfaultfd_ctx uf = NULL_VM_UFFD_CTX;
906 LIST_HEAD(uf_unmap_early);
907 LIST_HEAD(uf_unmap);
908
909 /*
910 * There is a deliberate asymmetry here: we strip the pointer tag
911 * from the old address but leave the new address alone. This is
912 * for consistency with mmap(), where we prevent the creation of
913 * aliasing mappings in userspace by leaving the tag bits of the
914 * mapping address intact. A non-zero tag will cause the subsequent
915 * range checks to reject the address as invalid.
916 *
917 * See Documentation/arm64/tagged-address-abi.rst for more information.
918 */
919 addr = untagged_addr(addr);
920
921 if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE | MREMAP_DONTUNMAP))
922 return ret;
923
924 if (flags & MREMAP_FIXED && !(flags & MREMAP_MAYMOVE))
925 return ret;
926
927 /*
928 * MREMAP_DONTUNMAP is always a move and it does not allow resizing
929 * in the process.
930 */
931 if (flags & MREMAP_DONTUNMAP &&
932 (!(flags & MREMAP_MAYMOVE) || old_len != new_len))
933 return ret;
934
935
936 if (offset_in_page(addr))
937 return ret;
938
939 old_len = PAGE_ALIGN(old_len);
940 new_len = PAGE_ALIGN(new_len);
941
942 /*
943 * We allow a zero old-len as a special case
944 * for DOS-emu "duplicate shm area" thing. But
945 * a zero new-len is nonsensical.
946 */
947 if (!new_len)
948 return ret;
949
950 if (mmap_write_lock_killable(current->mm))
951 return -EINTR;
952
953 if (flags & (MREMAP_FIXED | MREMAP_DONTUNMAP)) {
954 ret = mremap_to(addr, old_len, new_addr, new_len,
955 &locked, flags, &uf, &uf_unmap_early,
956 &uf_unmap);
957 goto out;
958 }
959
960 /*
961 * Always allow a shrinking remap: that just unmaps
962 * the unnecessary pages..
963 * __do_munmap does all the needed commit accounting, and
964 * downgrades mmap_lock to read if so directed.
965 */
966 if (old_len >= new_len) {
967 int retval;
968
969 retval = __do_munmap(mm, addr+new_len, old_len - new_len,
970 &uf_unmap, true);
971 if (retval < 0 && old_len != new_len) {
972 ret = retval;
973 goto out;
974 /* Returning 1 indicates mmap_lock is downgraded to read. */
975 } else if (retval == 1)
976 downgraded = true;
977 ret = addr;
978 goto out;
979 }
980
981 /*
982 * Ok, we need to grow..
983 */
984 vma = vma_to_resize(addr, old_len, new_len, flags, &charged);
985 if (IS_ERR(vma)) {
986 ret = PTR_ERR(vma);
987 goto out;
988 }
989
990 /* old_len exactly to the end of the area..
991 */
992 if (old_len == vma->vm_end - addr) {
993 /* can we just expand the current mapping? */
994 if (vma_expandable(vma, new_len - old_len)) {
995 int pages = (new_len - old_len) >> PAGE_SHIFT;
996
997 if (vma_adjust(vma, vma->vm_start, addr + new_len,
998 vma->vm_pgoff, NULL)) {
999 ret = -ENOMEM;
1000 goto out;
1001 }
1002
1003 vm_stat_account(mm, vma->vm_flags, pages);
1004 if (vma->vm_flags & VM_LOCKED) {
1005 mm->locked_vm += pages;
1006 locked = true;
1007 new_addr = addr;
1008 }
1009 ret = addr;
1010 goto out;
1011 }
1012 }
1013
1014 /*
1015 * We weren't able to just expand or shrink the area,
1016 * we need to create a new one and move it..
1017 */
1018 ret = -ENOMEM;
1019 if (flags & MREMAP_MAYMOVE) {
1020 unsigned long map_flags = 0;
1021 if (vma->vm_flags & VM_MAYSHARE)
1022 map_flags |= MAP_SHARED;
1023
1024 new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
1025 vma->vm_pgoff +
1026 ((addr - vma->vm_start) >> PAGE_SHIFT),
1027 map_flags);
1028 if (IS_ERR_VALUE(new_addr)) {
1029 ret = new_addr;
1030 goto out;
1031 }
1032
1033 ret = move_vma(vma, addr, old_len, new_len, new_addr,
1034 &locked, flags, &uf, &uf_unmap);
1035 }
1036out:
1037 if (offset_in_page(ret)) {
1038 vm_unacct_memory(charged);
1039 locked = false;
1040 }
1041 if (downgraded)
1042 mmap_read_unlock(current->mm);
1043 else
1044 mmap_write_unlock(current->mm);
1045 if (locked && new_len > old_len)
1046 mm_populate(new_addr + old_len, new_len - old_len);
1047 userfaultfd_unmap_complete(mm, &uf_unmap_early);
1048 mremap_userfaultfd_complete(&uf, addr, ret, old_len);
1049 userfaultfd_unmap_complete(mm, &uf_unmap);
1050 return ret;
1051}