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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) | |
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 valid PTE, make sure | |
167 | * to flush TLB before we drop the PTL for the | |
168 | * PTE. | |
169 | * | |
170 | * NOTE! Both old and new PTL matter: the old one | |
171 | * for racing with page_mkclean(), the new one to | |
172 | * make sure the physical page stays valid until | |
173 | * the TLB entry for the old mapping has been | |
174 | * flushed. | |
175 | */ | |
176 | if (pte_present(pte)) | |
177 | force_flush = true; | |
178 | pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr); | |
179 | pte = move_soft_dirty_pte(pte); | |
180 | set_pte_at(mm, new_addr, new_pte, pte); | |
181 | } | |
182 | ||
183 | arch_leave_lazy_mmu_mode(); | |
184 | if (force_flush) | |
185 | flush_tlb_range(vma, old_end - len, old_end); | |
186 | if (new_ptl != old_ptl) | |
187 | spin_unlock(new_ptl); | |
188 | pte_unmap(new_pte - 1); | |
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 | unsigned long mmun_start; /* For mmu_notifiers */ | |
204 | unsigned long mmun_end; /* For mmu_notifiers */ | |
205 | ||
206 | old_end = old_addr + len; | |
207 | flush_cache_range(vma, old_addr, old_end); | |
208 | ||
209 | mmun_start = old_addr; | |
210 | mmun_end = old_end; | |
211 | mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end); | |
212 | ||
213 | for (; old_addr < old_end; old_addr += extent, new_addr += extent) { | |
214 | cond_resched(); | |
215 | next = (old_addr + PMD_SIZE) & PMD_MASK; | |
216 | /* even if next overflowed, extent below will be ok */ | |
217 | extent = next - old_addr; | |
218 | if (extent > old_end - old_addr) | |
219 | extent = old_end - old_addr; | |
220 | old_pmd = get_old_pmd(vma->vm_mm, old_addr); | |
221 | if (!old_pmd) | |
222 | continue; | |
223 | new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr); | |
224 | if (!new_pmd) | |
225 | break; | |
226 | if (is_swap_pmd(*old_pmd) || pmd_trans_huge(*old_pmd)) { | |
227 | if (extent == HPAGE_PMD_SIZE) { | |
228 | bool moved; | |
229 | /* See comment in move_ptes() */ | |
230 | if (need_rmap_locks) | |
231 | take_rmap_locks(vma); | |
232 | moved = move_huge_pmd(vma, old_addr, new_addr, | |
233 | old_end, old_pmd, new_pmd); | |
234 | if (need_rmap_locks) | |
235 | drop_rmap_locks(vma); | |
236 | if (moved) | |
237 | continue; | |
238 | } | |
239 | split_huge_pmd(vma, old_pmd, old_addr); | |
240 | if (pmd_trans_unstable(old_pmd)) | |
241 | continue; | |
242 | } | |
243 | if (pte_alloc(new_vma->vm_mm, new_pmd, new_addr)) | |
244 | break; | |
245 | next = (new_addr + PMD_SIZE) & PMD_MASK; | |
246 | if (extent > next - new_addr) | |
247 | extent = next - new_addr; | |
248 | if (extent > LATENCY_LIMIT) | |
249 | extent = LATENCY_LIMIT; | |
250 | move_ptes(vma, old_pmd, old_addr, old_addr + extent, new_vma, | |
251 | new_pmd, new_addr, need_rmap_locks); | |
252 | } | |
253 | ||
254 | mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end); | |
255 | ||
256 | return len + old_addr - old_end; /* how much done */ | |
257 | } | |
258 | ||
259 | static unsigned long move_vma(struct vm_area_struct *vma, | |
260 | unsigned long old_addr, unsigned long old_len, | |
261 | unsigned long new_len, unsigned long new_addr, | |
262 | bool *locked, struct vm_userfaultfd_ctx *uf, | |
263 | struct list_head *uf_unmap) | |
264 | { | |
265 | struct mm_struct *mm = vma->vm_mm; | |
266 | struct vm_area_struct *new_vma; | |
267 | unsigned long vm_flags = vma->vm_flags; | |
268 | unsigned long new_pgoff; | |
269 | unsigned long moved_len; | |
270 | unsigned long excess = 0; | |
271 | unsigned long hiwater_vm; | |
272 | int split = 0; | |
273 | int err; | |
274 | bool need_rmap_locks; | |
275 | ||
276 | /* | |
277 | * We'd prefer to avoid failure later on in do_munmap: | |
278 | * which may split one vma into three before unmapping. | |
279 | */ | |
280 | if (mm->map_count >= sysctl_max_map_count - 3) | |
281 | return -ENOMEM; | |
282 | ||
283 | /* | |
284 | * Advise KSM to break any KSM pages in the area to be moved: | |
285 | * it would be confusing if they were to turn up at the new | |
286 | * location, where they happen to coincide with different KSM | |
287 | * pages recently unmapped. But leave vma->vm_flags as it was, | |
288 | * so KSM can come around to merge on vma and new_vma afterwards. | |
289 | */ | |
290 | err = ksm_madvise(vma, old_addr, old_addr + old_len, | |
291 | MADV_UNMERGEABLE, &vm_flags); | |
292 | if (err) | |
293 | return err; | |
294 | ||
295 | new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT); | |
296 | new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff, | |
297 | &need_rmap_locks); | |
298 | if (!new_vma) | |
299 | return -ENOMEM; | |
300 | ||
301 | moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len, | |
302 | need_rmap_locks); | |
303 | if (moved_len < old_len) { | |
304 | err = -ENOMEM; | |
305 | } else if (vma->vm_ops && vma->vm_ops->mremap) { | |
306 | err = vma->vm_ops->mremap(new_vma); | |
307 | } | |
308 | ||
309 | if (unlikely(err)) { | |
310 | /* | |
311 | * On error, move entries back from new area to old, | |
312 | * which will succeed since page tables still there, | |
313 | * and then proceed to unmap new area instead of old. | |
314 | */ | |
315 | move_page_tables(new_vma, new_addr, vma, old_addr, moved_len, | |
316 | true); | |
317 | vma = new_vma; | |
318 | old_len = new_len; | |
319 | old_addr = new_addr; | |
320 | new_addr = err; | |
321 | } else { | |
322 | mremap_userfaultfd_prep(new_vma, uf); | |
323 | arch_remap(mm, old_addr, old_addr + old_len, | |
324 | new_addr, new_addr + new_len); | |
325 | } | |
326 | ||
327 | /* Conceal VM_ACCOUNT so old reservation is not undone */ | |
328 | if (vm_flags & VM_ACCOUNT) { | |
329 | vma->vm_flags &= ~VM_ACCOUNT; | |
330 | excess = vma->vm_end - vma->vm_start - old_len; | |
331 | if (old_addr > vma->vm_start && | |
332 | old_addr + old_len < vma->vm_end) | |
333 | split = 1; | |
334 | } | |
335 | ||
336 | /* | |
337 | * If we failed to move page tables we still do total_vm increment | |
338 | * since do_munmap() will decrement it by old_len == new_len. | |
339 | * | |
340 | * Since total_vm is about to be raised artificially high for a | |
341 | * moment, we need to restore high watermark afterwards: if stats | |
342 | * are taken meanwhile, total_vm and hiwater_vm appear too high. | |
343 | * If this were a serious issue, we'd add a flag to do_munmap(). | |
344 | */ | |
345 | hiwater_vm = mm->hiwater_vm; | |
346 | vm_stat_account(mm, vma->vm_flags, new_len >> PAGE_SHIFT); | |
347 | ||
348 | /* Tell pfnmap has moved from this vma */ | |
349 | if (unlikely(vma->vm_flags & VM_PFNMAP)) | |
350 | untrack_pfn_moved(vma); | |
351 | ||
352 | if (do_munmap(mm, old_addr, old_len, uf_unmap) < 0) { | |
353 | /* OOM: unable to split vma, just get accounts right */ | |
354 | vm_unacct_memory(excess >> PAGE_SHIFT); | |
355 | excess = 0; | |
356 | } | |
357 | mm->hiwater_vm = hiwater_vm; | |
358 | ||
359 | /* Restore VM_ACCOUNT if one or two pieces of vma left */ | |
360 | if (excess) { | |
361 | vma->vm_flags |= VM_ACCOUNT; | |
362 | if (split) | |
363 | vma->vm_next->vm_flags |= VM_ACCOUNT; | |
364 | } | |
365 | ||
366 | if (vm_flags & VM_LOCKED) { | |
367 | mm->locked_vm += new_len >> PAGE_SHIFT; | |
368 | *locked = true; | |
369 | } | |
370 | ||
371 | return new_addr; | |
372 | } | |
373 | ||
374 | static struct vm_area_struct *vma_to_resize(unsigned long addr, | |
375 | unsigned long old_len, unsigned long new_len, unsigned long *p) | |
376 | { | |
377 | struct mm_struct *mm = current->mm; | |
378 | struct vm_area_struct *vma = find_vma(mm, addr); | |
379 | unsigned long pgoff; | |
380 | ||
381 | if (!vma || vma->vm_start > addr) | |
382 | return ERR_PTR(-EFAULT); | |
383 | ||
384 | /* | |
385 | * !old_len is a special case where an attempt is made to 'duplicate' | |
386 | * a mapping. This makes no sense for private mappings as it will | |
387 | * instead create a fresh/new mapping unrelated to the original. This | |
388 | * is contrary to the basic idea of mremap which creates new mappings | |
389 | * based on the original. There are no known use cases for this | |
390 | * behavior. As a result, fail such attempts. | |
391 | */ | |
392 | if (!old_len && !(vma->vm_flags & (VM_SHARED | VM_MAYSHARE))) { | |
393 | pr_warn_once("%s (%d): attempted to duplicate a private mapping with mremap. This is not supported.\n", current->comm, current->pid); | |
394 | return ERR_PTR(-EINVAL); | |
395 | } | |
396 | ||
397 | if (is_vm_hugetlb_page(vma)) | |
398 | return ERR_PTR(-EINVAL); | |
399 | ||
400 | /* We can't remap across vm area boundaries */ | |
401 | if (old_len > vma->vm_end - addr) | |
402 | return ERR_PTR(-EFAULT); | |
403 | ||
404 | if (new_len == old_len) | |
405 | return vma; | |
406 | ||
407 | /* Need to be careful about a growing mapping */ | |
408 | pgoff = (addr - vma->vm_start) >> PAGE_SHIFT; | |
409 | pgoff += vma->vm_pgoff; | |
410 | if (pgoff + (new_len >> PAGE_SHIFT) < pgoff) | |
411 | return ERR_PTR(-EINVAL); | |
412 | ||
413 | if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) | |
414 | return ERR_PTR(-EFAULT); | |
415 | ||
416 | if (vma->vm_flags & VM_LOCKED) { | |
417 | unsigned long locked, lock_limit; | |
418 | locked = mm->locked_vm << PAGE_SHIFT; | |
419 | lock_limit = rlimit(RLIMIT_MEMLOCK); | |
420 | locked += new_len - old_len; | |
421 | if (locked > lock_limit && !capable(CAP_IPC_LOCK)) | |
422 | return ERR_PTR(-EAGAIN); | |
423 | } | |
424 | ||
425 | if (!may_expand_vm(mm, vma->vm_flags, | |
426 | (new_len - old_len) >> PAGE_SHIFT)) | |
427 | return ERR_PTR(-ENOMEM); | |
428 | ||
429 | if (vma->vm_flags & VM_ACCOUNT) { | |
430 | unsigned long charged = (new_len - old_len) >> PAGE_SHIFT; | |
431 | if (security_vm_enough_memory_mm(mm, charged)) | |
432 | return ERR_PTR(-ENOMEM); | |
433 | *p = charged; | |
434 | } | |
435 | ||
436 | return vma; | |
437 | } | |
438 | ||
439 | static unsigned long mremap_to(unsigned long addr, unsigned long old_len, | |
440 | unsigned long new_addr, unsigned long new_len, bool *locked, | |
441 | struct vm_userfaultfd_ctx *uf, | |
442 | struct list_head *uf_unmap_early, | |
443 | struct list_head *uf_unmap) | |
444 | { | |
445 | struct mm_struct *mm = current->mm; | |
446 | struct vm_area_struct *vma; | |
447 | unsigned long ret = -EINVAL; | |
448 | unsigned long charged = 0; | |
449 | unsigned long map_flags; | |
450 | ||
451 | if (offset_in_page(new_addr)) | |
452 | goto out; | |
453 | ||
454 | if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len) | |
455 | goto out; | |
456 | ||
457 | /* Ensure the old/new locations do not overlap */ | |
458 | if (addr + old_len > new_addr && new_addr + new_len > addr) | |
459 | goto out; | |
460 | ||
461 | ret = do_munmap(mm, new_addr, new_len, uf_unmap_early); | |
462 | if (ret) | |
463 | goto out; | |
464 | ||
465 | if (old_len >= new_len) { | |
466 | ret = do_munmap(mm, addr+new_len, old_len - new_len, uf_unmap); | |
467 | if (ret && old_len != new_len) | |
468 | goto out; | |
469 | old_len = new_len; | |
470 | } | |
471 | ||
472 | vma = vma_to_resize(addr, old_len, new_len, &charged); | |
473 | if (IS_ERR(vma)) { | |
474 | ret = PTR_ERR(vma); | |
475 | goto out; | |
476 | } | |
477 | ||
478 | map_flags = MAP_FIXED; | |
479 | if (vma->vm_flags & VM_MAYSHARE) | |
480 | map_flags |= MAP_SHARED; | |
481 | ||
482 | ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff + | |
483 | ((addr - vma->vm_start) >> PAGE_SHIFT), | |
484 | map_flags); | |
485 | if (offset_in_page(ret)) | |
486 | goto out1; | |
487 | ||
488 | ret = move_vma(vma, addr, old_len, new_len, new_addr, locked, uf, | |
489 | uf_unmap); | |
490 | if (!(offset_in_page(ret))) | |
491 | goto out; | |
492 | out1: | |
493 | vm_unacct_memory(charged); | |
494 | ||
495 | out: | |
496 | return ret; | |
497 | } | |
498 | ||
499 | static int vma_expandable(struct vm_area_struct *vma, unsigned long delta) | |
500 | { | |
501 | unsigned long end = vma->vm_end + delta; | |
502 | if (end < vma->vm_end) /* overflow */ | |
503 | return 0; | |
504 | if (vma->vm_next && vma->vm_next->vm_start < end) /* intersection */ | |
505 | return 0; | |
506 | if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start, | |
507 | 0, MAP_FIXED) & ~PAGE_MASK) | |
508 | return 0; | |
509 | return 1; | |
510 | } | |
511 | ||
512 | /* | |
513 | * Expand (or shrink) an existing mapping, potentially moving it at the | |
514 | * same time (controlled by the MREMAP_MAYMOVE flag and available VM space) | |
515 | * | |
516 | * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise | |
517 | * This option implies MREMAP_MAYMOVE. | |
518 | */ | |
519 | SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len, | |
520 | unsigned long, new_len, unsigned long, flags, | |
521 | unsigned long, new_addr) | |
522 | { | |
523 | struct mm_struct *mm = current->mm; | |
524 | struct vm_area_struct *vma; | |
525 | unsigned long ret = -EINVAL; | |
526 | unsigned long charged = 0; | |
527 | bool locked = false; | |
528 | struct vm_userfaultfd_ctx uf = NULL_VM_UFFD_CTX; | |
529 | LIST_HEAD(uf_unmap_early); | |
530 | LIST_HEAD(uf_unmap); | |
531 | ||
532 | if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE)) | |
533 | return ret; | |
534 | ||
535 | if (flags & MREMAP_FIXED && !(flags & MREMAP_MAYMOVE)) | |
536 | return ret; | |
537 | ||
538 | if (offset_in_page(addr)) | |
539 | return ret; | |
540 | ||
541 | old_len = PAGE_ALIGN(old_len); | |
542 | new_len = PAGE_ALIGN(new_len); | |
543 | ||
544 | /* | |
545 | * We allow a zero old-len as a special case | |
546 | * for DOS-emu "duplicate shm area" thing. But | |
547 | * a zero new-len is nonsensical. | |
548 | */ | |
549 | if (!new_len) | |
550 | return ret; | |
551 | ||
552 | if (down_write_killable(¤t->mm->mmap_sem)) | |
553 | return -EINTR; | |
554 | ||
555 | if (flags & MREMAP_FIXED) { | |
556 | ret = mremap_to(addr, old_len, new_addr, new_len, | |
557 | &locked, &uf, &uf_unmap_early, &uf_unmap); | |
558 | goto out; | |
559 | } | |
560 | ||
561 | /* | |
562 | * Always allow a shrinking remap: that just unmaps | |
563 | * the unnecessary pages.. | |
564 | * do_munmap does all the needed commit accounting | |
565 | */ | |
566 | if (old_len >= new_len) { | |
567 | ret = do_munmap(mm, addr+new_len, old_len - new_len, &uf_unmap); | |
568 | if (ret && old_len != new_len) | |
569 | goto out; | |
570 | ret = addr; | |
571 | goto out; | |
572 | } | |
573 | ||
574 | /* | |
575 | * Ok, we need to grow.. | |
576 | */ | |
577 | vma = vma_to_resize(addr, old_len, new_len, &charged); | |
578 | if (IS_ERR(vma)) { | |
579 | ret = PTR_ERR(vma); | |
580 | goto out; | |
581 | } | |
582 | ||
583 | /* old_len exactly to the end of the area.. | |
584 | */ | |
585 | if (old_len == vma->vm_end - addr) { | |
586 | /* can we just expand the current mapping? */ | |
587 | if (vma_expandable(vma, new_len - old_len)) { | |
588 | int pages = (new_len - old_len) >> PAGE_SHIFT; | |
589 | ||
590 | if (vma_adjust(vma, vma->vm_start, addr + new_len, | |
591 | vma->vm_pgoff, NULL)) { | |
592 | ret = -ENOMEM; | |
593 | goto out; | |
594 | } | |
595 | ||
596 | vm_stat_account(mm, vma->vm_flags, pages); | |
597 | if (vma->vm_flags & VM_LOCKED) { | |
598 | mm->locked_vm += pages; | |
599 | locked = true; | |
600 | new_addr = addr; | |
601 | } | |
602 | ret = addr; | |
603 | goto out; | |
604 | } | |
605 | } | |
606 | ||
607 | /* | |
608 | * We weren't able to just expand or shrink the area, | |
609 | * we need to create a new one and move it.. | |
610 | */ | |
611 | ret = -ENOMEM; | |
612 | if (flags & MREMAP_MAYMOVE) { | |
613 | unsigned long map_flags = 0; | |
614 | if (vma->vm_flags & VM_MAYSHARE) | |
615 | map_flags |= MAP_SHARED; | |
616 | ||
617 | new_addr = get_unmapped_area(vma->vm_file, 0, new_len, | |
618 | vma->vm_pgoff + | |
619 | ((addr - vma->vm_start) >> PAGE_SHIFT), | |
620 | map_flags); | |
621 | if (offset_in_page(new_addr)) { | |
622 | ret = new_addr; | |
623 | goto out; | |
624 | } | |
625 | ||
626 | ret = move_vma(vma, addr, old_len, new_len, new_addr, | |
627 | &locked, &uf, &uf_unmap); | |
628 | } | |
629 | out: | |
630 | if (offset_in_page(ret)) { | |
631 | vm_unacct_memory(charged); | |
632 | locked = 0; | |
633 | } | |
634 | up_write(¤t->mm->mmap_sem); | |
635 | if (locked && new_len > old_len) | |
636 | mm_populate(new_addr + old_len, new_len - old_len); | |
637 | userfaultfd_unmap_complete(mm, &uf_unmap_early); | |
638 | mremap_userfaultfd_complete(&uf, addr, new_addr, old_len); | |
639 | userfaultfd_unmap_complete(mm, &uf_unmap); | |
640 | return ret; | |
641 | } |