Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net
[sfrench/cifs-2.6.git] / mm / mremap.c
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(&current->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(&current->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 }