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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/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/mm-arch-hooks.h> | |
26 | #include <linux/userfaultfd_k.h> | |
27 | ||
28 | #include <asm/cacheflush.h> | |
29 | #include <asm/tlbflush.h> | |
30 | ||
31 | #include "internal.h" | |
32 | ||
33 | static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr) | |
34 | { | |
35 | pgd_t *pgd; | |
36 | p4d_t *p4d; | |
37 | pud_t *pud; | |
38 | pmd_t *pmd; | |
39 | ||
40 | pgd = pgd_offset(mm, addr); | |
41 | if (pgd_none_or_clear_bad(pgd)) | |
42 | return NULL; | |
43 | ||
44 | p4d = p4d_offset(pgd, addr); | |
45 | if (p4d_none_or_clear_bad(p4d)) | |
46 | return NULL; | |
47 | ||
48 | pud = pud_offset(p4d, addr); | |
49 | if (pud_none_or_clear_bad(pud)) | |
50 | return NULL; | |
51 | ||
52 | pmd = pmd_offset(pud, addr); | |
53 | if (pmd_none(*pmd)) | |
54 | return NULL; | |
55 | ||
56 | return pmd; | |
57 | } | |
58 | ||
59 | static pmd_t *alloc_new_pmd(struct mm_struct *mm, struct vm_area_struct *vma, | |
60 | unsigned long addr) | |
61 | { | |
62 | pgd_t *pgd; | |
63 | p4d_t *p4d; | |
64 | pud_t *pud; | |
65 | pmd_t *pmd; | |
66 | ||
67 | pgd = pgd_offset(mm, addr); | |
68 | p4d = p4d_alloc(mm, pgd, addr); | |
69 | if (!p4d) | |
70 | return NULL; | |
71 | pud = pud_alloc(mm, p4d, addr); | |
72 | if (!pud) | |
73 | return NULL; | |
74 | ||
75 | pmd = pmd_alloc(mm, pud, addr); | |
76 | if (!pmd) | |
77 | return NULL; | |
78 | ||
79 | VM_BUG_ON(pmd_trans_huge(*pmd)); | |
80 | ||
81 | return pmd; | |
82 | } | |
83 | ||
84 | static void take_rmap_locks(struct vm_area_struct *vma) | |
85 | { | |
86 | if (vma->vm_file) | |
87 | i_mmap_lock_write(vma->vm_file->f_mapping); | |
88 | if (vma->anon_vma) | |
89 | anon_vma_lock_write(vma->anon_vma); | |
90 | } | |
91 | ||
92 | static void drop_rmap_locks(struct vm_area_struct *vma) | |
93 | { | |
94 | if (vma->anon_vma) | |
95 | anon_vma_unlock_write(vma->anon_vma); | |
96 | if (vma->vm_file) | |
97 | i_mmap_unlock_write(vma->vm_file->f_mapping); | |
98 | } | |
99 | ||
100 | static pte_t move_soft_dirty_pte(pte_t pte) | |
101 | { | |
102 | /* | |
103 | * Set soft dirty bit so we can notice | |
104 | * in userspace the ptes were moved. | |
105 | */ | |
106 | #ifdef CONFIG_MEM_SOFT_DIRTY | |
107 | if (pte_present(pte)) | |
108 | pte = pte_mksoft_dirty(pte); | |
109 | else if (is_swap_pte(pte)) | |
110 | pte = pte_swp_mksoft_dirty(pte); | |
111 | #endif | |
112 | return pte; | |
113 | } | |
114 | ||
115 | static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd, | |
116 | unsigned long old_addr, unsigned long old_end, | |
117 | struct vm_area_struct *new_vma, pmd_t *new_pmd, | |
118 | unsigned long new_addr, bool need_rmap_locks, bool *need_flush) | |
119 | { | |
120 | struct mm_struct *mm = vma->vm_mm; | |
121 | pte_t *old_pte, *new_pte, pte; | |
122 | spinlock_t *old_ptl, *new_ptl; | |
123 | bool force_flush = false; | |
124 | unsigned long len = old_end - old_addr; | |
125 | ||
126 | /* | |
127 | * When need_rmap_locks is true, we take the i_mmap_rwsem and anon_vma | |
128 | * locks to ensure that rmap will always observe either the old or the | |
129 | * new ptes. This is the easiest way to avoid races with | |
130 | * truncate_pagecache(), page migration, etc... | |
131 | * | |
132 | * When need_rmap_locks is false, we use other ways to avoid | |
133 | * such races: | |
134 | * | |
135 | * - During exec() shift_arg_pages(), we use a specially tagged vma | |
136 | * which rmap call sites look for using is_vma_temporary_stack(). | |
137 | * | |
138 | * - During mremap(), new_vma is often known to be placed after vma | |
139 | * in rmap traversal order. This ensures rmap will always observe | |
140 | * either the old pte, or the new pte, or both (the page table locks | |
141 | * serialize access to individual ptes, but only rmap traversal | |
142 | * order guarantees that we won't miss both the old and new ptes). | |
143 | */ | |
144 | if (need_rmap_locks) | |
145 | take_rmap_locks(vma); | |
146 | ||
147 | /* | |
148 | * We don't have to worry about the ordering of src and dst | |
149 | * pte locks because exclusive mmap_sem prevents deadlock. | |
150 | */ | |
151 | old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl); | |
152 | new_pte = pte_offset_map(new_pmd, new_addr); | |
153 | new_ptl = pte_lockptr(mm, new_pmd); | |
154 | if (new_ptl != old_ptl) | |
155 | spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); | |
156 | flush_tlb_batched_pending(vma->vm_mm); | |
157 | arch_enter_lazy_mmu_mode(); | |
158 | ||
159 | for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE, | |
160 | new_pte++, new_addr += PAGE_SIZE) { | |
161 | if (pte_none(*old_pte)) | |
162 | continue; | |
163 | ||
164 | pte = ptep_get_and_clear(mm, old_addr, old_pte); | |
165 | /* | |
166 | * If we are remapping a dirty PTE, make sure | |
167 | * to flush TLB before we drop the PTL for the | |
168 | * old PTE or we may race with page_mkclean(). | |
169 | * | |
170 | * This check has to be done after we removed the | |
171 | * old PTE from page tables or another thread may | |
172 | * dirty it after the check and before the removal. | |
173 | */ | |
174 | if (pte_present(pte) && pte_dirty(pte)) | |
175 | force_flush = true; | |
176 | pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr); | |
177 | pte = move_soft_dirty_pte(pte); | |
178 | set_pte_at(mm, new_addr, new_pte, pte); | |
179 | } | |
180 | ||
181 | arch_leave_lazy_mmu_mode(); | |
182 | if (new_ptl != old_ptl) | |
183 | spin_unlock(new_ptl); | |
184 | pte_unmap(new_pte - 1); | |
185 | if (force_flush) | |
186 | flush_tlb_range(vma, old_end - len, old_end); | |
187 | else | |
188 | *need_flush = true; | |
189 | pte_unmap_unlock(old_pte - 1, old_ptl); | |
190 | if (need_rmap_locks) | |
191 | drop_rmap_locks(vma); | |
192 | } | |
193 | ||
194 | #define LATENCY_LIMIT (64 * PAGE_SIZE) | |
195 | ||
196 | unsigned long move_page_tables(struct vm_area_struct *vma, | |
197 | unsigned long old_addr, struct vm_area_struct *new_vma, | |
198 | unsigned long new_addr, unsigned long len, | |
199 | bool need_rmap_locks) | |
200 | { | |
201 | unsigned long extent, next, old_end; | |
202 | pmd_t *old_pmd, *new_pmd; | |
203 | bool need_flush = false; | |
204 | unsigned long mmun_start; /* For mmu_notifiers */ | |
205 | unsigned long mmun_end; /* For mmu_notifiers */ | |
206 | ||
207 | old_end = old_addr + len; | |
208 | flush_cache_range(vma, old_addr, old_end); | |
209 | ||
210 | mmun_start = old_addr; | |
211 | mmun_end = old_end; | |
212 | mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end); | |
213 | ||
214 | for (; old_addr < old_end; old_addr += extent, new_addr += extent) { | |
215 | cond_resched(); | |
216 | next = (old_addr + PMD_SIZE) & PMD_MASK; | |
217 | /* even if next overflowed, extent below will be ok */ | |
218 | extent = next - old_addr; | |
219 | if (extent > old_end - old_addr) | |
220 | extent = old_end - old_addr; | |
221 | old_pmd = get_old_pmd(vma->vm_mm, old_addr); | |
222 | if (!old_pmd) | |
223 | continue; | |
224 | new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr); | |
225 | if (!new_pmd) | |
226 | break; | |
227 | if (is_swap_pmd(*old_pmd) || pmd_trans_huge(*old_pmd)) { | |
228 | if (extent == HPAGE_PMD_SIZE) { | |
229 | bool moved; | |
230 | /* See comment in move_ptes() */ | |
231 | if (need_rmap_locks) | |
232 | take_rmap_locks(vma); | |
233 | moved = move_huge_pmd(vma, old_addr, new_addr, | |
234 | old_end, old_pmd, new_pmd, | |
235 | &need_flush); | |
236 | if (need_rmap_locks) | |
237 | drop_rmap_locks(vma); | |
238 | if (moved) | |
239 | continue; | |
240 | } | |
241 | split_huge_pmd(vma, old_pmd, old_addr); | |
242 | if (pmd_trans_unstable(old_pmd)) | |
243 | continue; | |
244 | } | |
245 | if (pte_alloc(new_vma->vm_mm, new_pmd, new_addr)) | |
246 | break; | |
247 | next = (new_addr + PMD_SIZE) & PMD_MASK; | |
248 | if (extent > next - new_addr) | |
249 | extent = next - new_addr; | |
250 | if (extent > LATENCY_LIMIT) | |
251 | extent = LATENCY_LIMIT; | |
252 | move_ptes(vma, old_pmd, old_addr, old_addr + extent, new_vma, | |
253 | new_pmd, new_addr, need_rmap_locks, &need_flush); | |
254 | } | |
255 | if (need_flush) | |
256 | flush_tlb_range(vma, old_end-len, old_addr); | |
257 | ||
258 | mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end); | |
259 | ||
260 | return len + old_addr - old_end; /* how much done */ | |
261 | } | |
262 | ||
263 | static unsigned long move_vma(struct vm_area_struct *vma, | |
264 | unsigned long old_addr, unsigned long old_len, | |
265 | unsigned long new_len, unsigned long new_addr, | |
266 | bool *locked, struct vm_userfaultfd_ctx *uf, | |
267 | struct list_head *uf_unmap) | |
268 | { | |
269 | struct mm_struct *mm = vma->vm_mm; | |
270 | struct vm_area_struct *new_vma; | |
271 | unsigned long vm_flags = vma->vm_flags; | |
272 | unsigned long new_pgoff; | |
273 | unsigned long moved_len; | |
274 | unsigned long excess = 0; | |
275 | unsigned long hiwater_vm; | |
276 | int split = 0; | |
277 | int err; | |
278 | bool need_rmap_locks; | |
279 | ||
280 | /* | |
281 | * We'd prefer to avoid failure later on in do_munmap: | |
282 | * which may split one vma into three before unmapping. | |
283 | */ | |
284 | if (mm->map_count >= sysctl_max_map_count - 3) | |
285 | return -ENOMEM; | |
286 | ||
287 | /* | |
288 | * Advise KSM to break any KSM pages in the area to be moved: | |
289 | * it would be confusing if they were to turn up at the new | |
290 | * location, where they happen to coincide with different KSM | |
291 | * pages recently unmapped. But leave vma->vm_flags as it was, | |
292 | * so KSM can come around to merge on vma and new_vma afterwards. | |
293 | */ | |
294 | err = ksm_madvise(vma, old_addr, old_addr + old_len, | |
295 | MADV_UNMERGEABLE, &vm_flags); | |
296 | if (err) | |
297 | return err; | |
298 | ||
299 | new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT); | |
300 | new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff, | |
301 | &need_rmap_locks); | |
302 | if (!new_vma) | |
303 | return -ENOMEM; | |
304 | ||
305 | moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len, | |
306 | need_rmap_locks); | |
307 | if (moved_len < old_len) { | |
308 | err = -ENOMEM; | |
309 | } else if (vma->vm_ops && vma->vm_ops->mremap) { | |
310 | err = vma->vm_ops->mremap(new_vma); | |
311 | } | |
312 | ||
313 | if (unlikely(err)) { | |
314 | /* | |
315 | * On error, move entries back from new area to old, | |
316 | * which will succeed since page tables still there, | |
317 | * and then proceed to unmap new area instead of old. | |
318 | */ | |
319 | move_page_tables(new_vma, new_addr, vma, old_addr, moved_len, | |
320 | true); | |
321 | vma = new_vma; | |
322 | old_len = new_len; | |
323 | old_addr = new_addr; | |
324 | new_addr = err; | |
325 | } else { | |
326 | mremap_userfaultfd_prep(new_vma, uf); | |
327 | arch_remap(mm, old_addr, old_addr + old_len, | |
328 | new_addr, new_addr + new_len); | |
329 | } | |
330 | ||
331 | /* Conceal VM_ACCOUNT so old reservation is not undone */ | |
332 | if (vm_flags & VM_ACCOUNT) { | |
333 | vma->vm_flags &= ~VM_ACCOUNT; | |
334 | excess = vma->vm_end - vma->vm_start - old_len; | |
335 | if (old_addr > vma->vm_start && | |
336 | old_addr + old_len < vma->vm_end) | |
337 | split = 1; | |
338 | } | |
339 | ||
340 | /* | |
341 | * If we failed to move page tables we still do total_vm increment | |
342 | * since do_munmap() will decrement it by old_len == new_len. | |
343 | * | |
344 | * Since total_vm is about to be raised artificially high for a | |
345 | * moment, we need to restore high watermark afterwards: if stats | |
346 | * are taken meanwhile, total_vm and hiwater_vm appear too high. | |
347 | * If this were a serious issue, we'd add a flag to do_munmap(). | |
348 | */ | |
349 | hiwater_vm = mm->hiwater_vm; | |
350 | vm_stat_account(mm, vma->vm_flags, new_len >> PAGE_SHIFT); | |
351 | ||
352 | /* Tell pfnmap has moved from this vma */ | |
353 | if (unlikely(vma->vm_flags & VM_PFNMAP)) | |
354 | untrack_pfn_moved(vma); | |
355 | ||
356 | if (do_munmap(mm, old_addr, old_len, uf_unmap) < 0) { | |
357 | /* OOM: unable to split vma, just get accounts right */ | |
358 | vm_unacct_memory(excess >> PAGE_SHIFT); | |
359 | excess = 0; | |
360 | } | |
361 | mm->hiwater_vm = hiwater_vm; | |
362 | ||
363 | /* Restore VM_ACCOUNT if one or two pieces of vma left */ | |
364 | if (excess) { | |
365 | vma->vm_flags |= VM_ACCOUNT; | |
366 | if (split) | |
367 | vma->vm_next->vm_flags |= VM_ACCOUNT; | |
368 | } | |
369 | ||
370 | if (vm_flags & VM_LOCKED) { | |
371 | mm->locked_vm += new_len >> PAGE_SHIFT; | |
372 | *locked = true; | |
373 | } | |
374 | ||
375 | return new_addr; | |
376 | } | |
377 | ||
378 | static struct vm_area_struct *vma_to_resize(unsigned long addr, | |
379 | unsigned long old_len, unsigned long new_len, unsigned long *p) | |
380 | { | |
381 | struct mm_struct *mm = current->mm; | |
382 | struct vm_area_struct *vma = find_vma(mm, addr); | |
383 | unsigned long pgoff; | |
384 | ||
385 | if (!vma || vma->vm_start > addr) | |
386 | return ERR_PTR(-EFAULT); | |
387 | ||
388 | /* | |
389 | * !old_len is a special case where an attempt is made to 'duplicate' | |
390 | * a mapping. This makes no sense for private mappings as it will | |
391 | * instead create a fresh/new mapping unrelated to the original. This | |
392 | * is contrary to the basic idea of mremap which creates new mappings | |
393 | * based on the original. There are no known use cases for this | |
394 | * behavior. As a result, fail such attempts. | |
395 | */ | |
396 | if (!old_len && !(vma->vm_flags & (VM_SHARED | VM_MAYSHARE))) { | |
397 | pr_warn_once("%s (%d): attempted to duplicate a private mapping with mremap. This is not supported.\n", current->comm, current->pid); | |
398 | return ERR_PTR(-EINVAL); | |
399 | } | |
400 | ||
401 | if (is_vm_hugetlb_page(vma)) | |
402 | return ERR_PTR(-EINVAL); | |
403 | ||
404 | /* We can't remap across vm area boundaries */ | |
405 | if (old_len > vma->vm_end - addr) | |
406 | return ERR_PTR(-EFAULT); | |
407 | ||
408 | if (new_len == old_len) | |
409 | return vma; | |
410 | ||
411 | /* Need to be careful about a growing mapping */ | |
412 | pgoff = (addr - vma->vm_start) >> PAGE_SHIFT; | |
413 | pgoff += vma->vm_pgoff; | |
414 | if (pgoff + (new_len >> PAGE_SHIFT) < pgoff) | |
415 | return ERR_PTR(-EINVAL); | |
416 | ||
417 | if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) | |
418 | return ERR_PTR(-EFAULT); | |
419 | ||
420 | if (vma->vm_flags & VM_LOCKED) { | |
421 | unsigned long locked, lock_limit; | |
422 | locked = mm->locked_vm << PAGE_SHIFT; | |
423 | lock_limit = rlimit(RLIMIT_MEMLOCK); | |
424 | locked += new_len - old_len; | |
425 | if (locked > lock_limit && !capable(CAP_IPC_LOCK)) | |
426 | return ERR_PTR(-EAGAIN); | |
427 | } | |
428 | ||
429 | if (!may_expand_vm(mm, vma->vm_flags, | |
430 | (new_len - old_len) >> PAGE_SHIFT)) | |
431 | return ERR_PTR(-ENOMEM); | |
432 | ||
433 | if (vma->vm_flags & VM_ACCOUNT) { | |
434 | unsigned long charged = (new_len - old_len) >> PAGE_SHIFT; | |
435 | if (security_vm_enough_memory_mm(mm, charged)) | |
436 | return ERR_PTR(-ENOMEM); | |
437 | *p = charged; | |
438 | } | |
439 | ||
440 | return vma; | |
441 | } | |
442 | ||
443 | static unsigned long mremap_to(unsigned long addr, unsigned long old_len, | |
444 | unsigned long new_addr, unsigned long new_len, bool *locked, | |
445 | struct vm_userfaultfd_ctx *uf, | |
446 | struct list_head *uf_unmap_early, | |
447 | struct list_head *uf_unmap) | |
448 | { | |
449 | struct mm_struct *mm = current->mm; | |
450 | struct vm_area_struct *vma; | |
451 | unsigned long ret = -EINVAL; | |
452 | unsigned long charged = 0; | |
453 | unsigned long map_flags; | |
454 | ||
455 | if (offset_in_page(new_addr)) | |
456 | goto out; | |
457 | ||
458 | if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len) | |
459 | goto out; | |
460 | ||
461 | /* Ensure the old/new locations do not overlap */ | |
462 | if (addr + old_len > new_addr && new_addr + new_len > addr) | |
463 | goto out; | |
464 | ||
465 | ret = do_munmap(mm, new_addr, new_len, uf_unmap_early); | |
466 | if (ret) | |
467 | goto out; | |
468 | ||
469 | if (old_len >= new_len) { | |
470 | ret = do_munmap(mm, addr+new_len, old_len - new_len, uf_unmap); | |
471 | if (ret && old_len != new_len) | |
472 | goto out; | |
473 | old_len = new_len; | |
474 | } | |
475 | ||
476 | vma = vma_to_resize(addr, old_len, new_len, &charged); | |
477 | if (IS_ERR(vma)) { | |
478 | ret = PTR_ERR(vma); | |
479 | goto out; | |
480 | } | |
481 | ||
482 | map_flags = MAP_FIXED; | |
483 | if (vma->vm_flags & VM_MAYSHARE) | |
484 | map_flags |= MAP_SHARED; | |
485 | ||
486 | ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff + | |
487 | ((addr - vma->vm_start) >> PAGE_SHIFT), | |
488 | map_flags); | |
489 | if (offset_in_page(ret)) | |
490 | goto out1; | |
491 | ||
492 | ret = move_vma(vma, addr, old_len, new_len, new_addr, locked, uf, | |
493 | uf_unmap); | |
494 | if (!(offset_in_page(ret))) | |
495 | goto out; | |
496 | out1: | |
497 | vm_unacct_memory(charged); | |
498 | ||
499 | out: | |
500 | return ret; | |
501 | } | |
502 | ||
503 | static int vma_expandable(struct vm_area_struct *vma, unsigned long delta) | |
504 | { | |
505 | unsigned long end = vma->vm_end + delta; | |
506 | if (end < vma->vm_end) /* overflow */ | |
507 | return 0; | |
508 | if (vma->vm_next && vma->vm_next->vm_start < end) /* intersection */ | |
509 | return 0; | |
510 | if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start, | |
511 | 0, MAP_FIXED) & ~PAGE_MASK) | |
512 | return 0; | |
513 | return 1; | |
514 | } | |
515 | ||
516 | /* | |
517 | * Expand (or shrink) an existing mapping, potentially moving it at the | |
518 | * same time (controlled by the MREMAP_MAYMOVE flag and available VM space) | |
519 | * | |
520 | * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise | |
521 | * This option implies MREMAP_MAYMOVE. | |
522 | */ | |
523 | SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len, | |
524 | unsigned long, new_len, unsigned long, flags, | |
525 | unsigned long, new_addr) | |
526 | { | |
527 | struct mm_struct *mm = current->mm; | |
528 | struct vm_area_struct *vma; | |
529 | unsigned long ret = -EINVAL; | |
530 | unsigned long charged = 0; | |
531 | bool locked = false; | |
532 | struct vm_userfaultfd_ctx uf = NULL_VM_UFFD_CTX; | |
533 | LIST_HEAD(uf_unmap_early); | |
534 | LIST_HEAD(uf_unmap); | |
535 | ||
536 | if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE)) | |
537 | return ret; | |
538 | ||
539 | if (flags & MREMAP_FIXED && !(flags & MREMAP_MAYMOVE)) | |
540 | return ret; | |
541 | ||
542 | if (offset_in_page(addr)) | |
543 | return ret; | |
544 | ||
545 | old_len = PAGE_ALIGN(old_len); | |
546 | new_len = PAGE_ALIGN(new_len); | |
547 | ||
548 | /* | |
549 | * We allow a zero old-len as a special case | |
550 | * for DOS-emu "duplicate shm area" thing. But | |
551 | * a zero new-len is nonsensical. | |
552 | */ | |
553 | if (!new_len) | |
554 | return ret; | |
555 | ||
556 | if (down_write_killable(¤t->mm->mmap_sem)) | |
557 | return -EINTR; | |
558 | ||
559 | if (flags & MREMAP_FIXED) { | |
560 | ret = mremap_to(addr, old_len, new_addr, new_len, | |
561 | &locked, &uf, &uf_unmap_early, &uf_unmap); | |
562 | goto out; | |
563 | } | |
564 | ||
565 | /* | |
566 | * Always allow a shrinking remap: that just unmaps | |
567 | * the unnecessary pages.. | |
568 | * do_munmap does all the needed commit accounting | |
569 | */ | |
570 | if (old_len >= new_len) { | |
571 | ret = do_munmap(mm, addr+new_len, old_len - new_len, &uf_unmap); | |
572 | if (ret && old_len != new_len) | |
573 | goto out; | |
574 | ret = addr; | |
575 | goto out; | |
576 | } | |
577 | ||
578 | /* | |
579 | * Ok, we need to grow.. | |
580 | */ | |
581 | vma = vma_to_resize(addr, old_len, new_len, &charged); | |
582 | if (IS_ERR(vma)) { | |
583 | ret = PTR_ERR(vma); | |
584 | goto out; | |
585 | } | |
586 | ||
587 | /* old_len exactly to the end of the area.. | |
588 | */ | |
589 | if (old_len == vma->vm_end - addr) { | |
590 | /* can we just expand the current mapping? */ | |
591 | if (vma_expandable(vma, new_len - old_len)) { | |
592 | int pages = (new_len - old_len) >> PAGE_SHIFT; | |
593 | ||
594 | if (vma_adjust(vma, vma->vm_start, addr + new_len, | |
595 | vma->vm_pgoff, NULL)) { | |
596 | ret = -ENOMEM; | |
597 | goto out; | |
598 | } | |
599 | ||
600 | vm_stat_account(mm, vma->vm_flags, pages); | |
601 | if (vma->vm_flags & VM_LOCKED) { | |
602 | mm->locked_vm += pages; | |
603 | locked = true; | |
604 | new_addr = addr; | |
605 | } | |
606 | ret = addr; | |
607 | goto out; | |
608 | } | |
609 | } | |
610 | ||
611 | /* | |
612 | * We weren't able to just expand or shrink the area, | |
613 | * we need to create a new one and move it.. | |
614 | */ | |
615 | ret = -ENOMEM; | |
616 | if (flags & MREMAP_MAYMOVE) { | |
617 | unsigned long map_flags = 0; | |
618 | if (vma->vm_flags & VM_MAYSHARE) | |
619 | map_flags |= MAP_SHARED; | |
620 | ||
621 | new_addr = get_unmapped_area(vma->vm_file, 0, new_len, | |
622 | vma->vm_pgoff + | |
623 | ((addr - vma->vm_start) >> PAGE_SHIFT), | |
624 | map_flags); | |
625 | if (offset_in_page(new_addr)) { | |
626 | ret = new_addr; | |
627 | goto out; | |
628 | } | |
629 | ||
630 | ret = move_vma(vma, addr, old_len, new_len, new_addr, | |
631 | &locked, &uf, &uf_unmap); | |
632 | } | |
633 | out: | |
634 | if (offset_in_page(ret)) { | |
635 | vm_unacct_memory(charged); | |
636 | locked = 0; | |
637 | } | |
638 | up_write(¤t->mm->mmap_sem); | |
639 | if (locked && new_len > old_len) | |
640 | mm_populate(new_addr + old_len, new_len - old_len); | |
641 | userfaultfd_unmap_complete(mm, &uf_unmap_early); | |
642 | mremap_userfaultfd_complete(&uf, addr, new_addr, old_len); | |
643 | userfaultfd_unmap_complete(mm, &uf_unmap); | |
644 | return ret; | |
645 | } |