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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * linux/mm/mlock.c
4 *
5 * (C) Copyright 1995 Linus Torvalds
6 * (C) Copyright 2002 Christoph Hellwig
7 */
8
9#include <linux/capability.h>
10#include <linux/mman.h>
11#include <linux/mm.h>
12#include <linux/sched/user.h>
13#include <linux/swap.h>
14#include <linux/swapops.h>
15#include <linux/pagemap.h>
16#include <linux/pagevec.h>
17#include <linux/mempolicy.h>
18#include <linux/syscalls.h>
19#include <linux/sched.h>
20#include <linux/export.h>
21#include <linux/rmap.h>
22#include <linux/mmzone.h>
23#include <linux/hugetlb.h>
24#include <linux/memcontrol.h>
25#include <linux/mm_inline.h>
26
27#include "internal.h"
28
29bool can_do_mlock(void)
30{
31 if (rlimit(RLIMIT_MEMLOCK) != 0)
32 return true;
33 if (capable(CAP_IPC_LOCK))
34 return true;
35 return false;
36}
37EXPORT_SYMBOL(can_do_mlock);
38
39/*
40 * Mlocked pages are marked with PageMlocked() flag for efficient testing
41 * in vmscan and, possibly, the fault path; and to support semi-accurate
42 * statistics.
43 *
44 * An mlocked page [PageMlocked(page)] is unevictable. As such, it will
45 * be placed on the LRU "unevictable" list, rather than the [in]active lists.
46 * The unevictable list is an LRU sibling list to the [in]active lists.
47 * PageUnevictable is set to indicate the unevictable state.
48 *
49 * When lazy mlocking via vmscan, it is important to ensure that the
50 * vma's VM_LOCKED status is not concurrently being modified, otherwise we
51 * may have mlocked a page that is being munlocked. So lazy mlock must take
52 * the mmap_sem for read, and verify that the vma really is locked
53 * (see mm/rmap.c).
54 */
55
56/*
57 * LRU accounting for clear_page_mlock()
58 */
59void clear_page_mlock(struct page *page)
60{
61 if (!TestClearPageMlocked(page))
62 return;
63
64 mod_zone_page_state(page_zone(page), NR_MLOCK,
65 -hpage_nr_pages(page));
66 count_vm_event(UNEVICTABLE_PGCLEARED);
67 /*
68 * The previous TestClearPageMlocked() corresponds to the smp_mb()
69 * in __pagevec_lru_add_fn().
70 *
71 * See __pagevec_lru_add_fn for more explanation.
72 */
73 if (!isolate_lru_page(page)) {
74 putback_lru_page(page);
75 } else {
76 /*
77 * We lost the race. the page already moved to evictable list.
78 */
79 if (PageUnevictable(page))
80 count_vm_event(UNEVICTABLE_PGSTRANDED);
81 }
82}
83
84/*
85 * Mark page as mlocked if not already.
86 * If page on LRU, isolate and putback to move to unevictable list.
87 */
88void mlock_vma_page(struct page *page)
89{
90 /* Serialize with page migration */
91 BUG_ON(!PageLocked(page));
92
93 VM_BUG_ON_PAGE(PageTail(page), page);
94 VM_BUG_ON_PAGE(PageCompound(page) && PageDoubleMap(page), page);
95
96 if (!TestSetPageMlocked(page)) {
97 mod_zone_page_state(page_zone(page), NR_MLOCK,
98 hpage_nr_pages(page));
99 count_vm_event(UNEVICTABLE_PGMLOCKED);
100 if (!isolate_lru_page(page))
101 putback_lru_page(page);
102 }
103}
104
105/*
106 * Isolate a page from LRU with optional get_page() pin.
107 * Assumes lru_lock already held and page already pinned.
108 */
109static bool __munlock_isolate_lru_page(struct page *page, bool getpage)
110{
111 if (PageLRU(page)) {
112 struct lruvec *lruvec;
113
114 lruvec = mem_cgroup_page_lruvec(page, page_pgdat(page));
115 if (getpage)
116 get_page(page);
117 ClearPageLRU(page);
118 del_page_from_lru_list(page, lruvec, page_lru(page));
119 return true;
120 }
121
122 return false;
123}
124
125/*
126 * Finish munlock after successful page isolation
127 *
128 * Page must be locked. This is a wrapper for try_to_munlock()
129 * and putback_lru_page() with munlock accounting.
130 */
131static void __munlock_isolated_page(struct page *page)
132{
133 /*
134 * Optimization: if the page was mapped just once, that's our mapping
135 * and we don't need to check all the other vmas.
136 */
137 if (page_mapcount(page) > 1)
138 try_to_munlock(page);
139
140 /* Did try_to_unlock() succeed or punt? */
141 if (!PageMlocked(page))
142 count_vm_event(UNEVICTABLE_PGMUNLOCKED);
143
144 putback_lru_page(page);
145}
146
147/*
148 * Accounting for page isolation fail during munlock
149 *
150 * Performs accounting when page isolation fails in munlock. There is nothing
151 * else to do because it means some other task has already removed the page
152 * from the LRU. putback_lru_page() will take care of removing the page from
153 * the unevictable list, if necessary. vmscan [page_referenced()] will move
154 * the page back to the unevictable list if some other vma has it mlocked.
155 */
156static void __munlock_isolation_failed(struct page *page)
157{
158 if (PageUnevictable(page))
159 __count_vm_event(UNEVICTABLE_PGSTRANDED);
160 else
161 __count_vm_event(UNEVICTABLE_PGMUNLOCKED);
162}
163
164/**
165 * munlock_vma_page - munlock a vma page
166 * @page: page to be unlocked, either a normal page or THP page head
167 *
168 * returns the size of the page as a page mask (0 for normal page,
169 * HPAGE_PMD_NR - 1 for THP head page)
170 *
171 * called from munlock()/munmap() path with page supposedly on the LRU.
172 * When we munlock a page, because the vma where we found the page is being
173 * munlock()ed or munmap()ed, we want to check whether other vmas hold the
174 * page locked so that we can leave it on the unevictable lru list and not
175 * bother vmscan with it. However, to walk the page's rmap list in
176 * try_to_munlock() we must isolate the page from the LRU. If some other
177 * task has removed the page from the LRU, we won't be able to do that.
178 * So we clear the PageMlocked as we might not get another chance. If we
179 * can't isolate the page, we leave it for putback_lru_page() and vmscan
180 * [page_referenced()/try_to_unmap()] to deal with.
181 */
182unsigned int munlock_vma_page(struct page *page)
183{
184 int nr_pages;
185 pg_data_t *pgdat = page_pgdat(page);
186
187 /* For try_to_munlock() and to serialize with page migration */
188 BUG_ON(!PageLocked(page));
189
190 VM_BUG_ON_PAGE(PageTail(page), page);
191
192 /*
193 * Serialize with any parallel __split_huge_page_refcount() which
194 * might otherwise copy PageMlocked to part of the tail pages before
195 * we clear it in the head page. It also stabilizes hpage_nr_pages().
196 */
197 spin_lock_irq(&pgdat->lru_lock);
198
199 if (!TestClearPageMlocked(page)) {
200 /* Potentially, PTE-mapped THP: do not skip the rest PTEs */
201 nr_pages = 1;
202 goto unlock_out;
203 }
204
205 nr_pages = hpage_nr_pages(page);
206 __mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages);
207
208 if (__munlock_isolate_lru_page(page, true)) {
209 spin_unlock_irq(&pgdat->lru_lock);
210 __munlock_isolated_page(page);
211 goto out;
212 }
213 __munlock_isolation_failed(page);
214
215unlock_out:
216 spin_unlock_irq(&pgdat->lru_lock);
217
218out:
219 return nr_pages - 1;
220}
221
222/*
223 * convert get_user_pages() return value to posix mlock() error
224 */
225static int __mlock_posix_error_return(long retval)
226{
227 if (retval == -EFAULT)
228 retval = -ENOMEM;
229 else if (retval == -ENOMEM)
230 retval = -EAGAIN;
231 return retval;
232}
233
234/*
235 * Prepare page for fast batched LRU putback via putback_lru_evictable_pagevec()
236 *
237 * The fast path is available only for evictable pages with single mapping.
238 * Then we can bypass the per-cpu pvec and get better performance.
239 * when mapcount > 1 we need try_to_munlock() which can fail.
240 * when !page_evictable(), we need the full redo logic of putback_lru_page to
241 * avoid leaving evictable page in unevictable list.
242 *
243 * In case of success, @page is added to @pvec and @pgrescued is incremented
244 * in case that the page was previously unevictable. @page is also unlocked.
245 */
246static bool __putback_lru_fast_prepare(struct page *page, struct pagevec *pvec,
247 int *pgrescued)
248{
249 VM_BUG_ON_PAGE(PageLRU(page), page);
250 VM_BUG_ON_PAGE(!PageLocked(page), page);
251
252 if (page_mapcount(page) <= 1 && page_evictable(page)) {
253 pagevec_add(pvec, page);
254 if (TestClearPageUnevictable(page))
255 (*pgrescued)++;
256 unlock_page(page);
257 return true;
258 }
259
260 return false;
261}
262
263/*
264 * Putback multiple evictable pages to the LRU
265 *
266 * Batched putback of evictable pages that bypasses the per-cpu pvec. Some of
267 * the pages might have meanwhile become unevictable but that is OK.
268 */
269static void __putback_lru_fast(struct pagevec *pvec, int pgrescued)
270{
271 count_vm_events(UNEVICTABLE_PGMUNLOCKED, pagevec_count(pvec));
272 /*
273 *__pagevec_lru_add() calls release_pages() so we don't call
274 * put_page() explicitly
275 */
276 __pagevec_lru_add(pvec);
277 count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
278}
279
280/*
281 * Munlock a batch of pages from the same zone
282 *
283 * The work is split to two main phases. First phase clears the Mlocked flag
284 * and attempts to isolate the pages, all under a single zone lru lock.
285 * The second phase finishes the munlock only for pages where isolation
286 * succeeded.
287 *
288 * Note that the pagevec may be modified during the process.
289 */
290static void __munlock_pagevec(struct pagevec *pvec, struct zone *zone)
291{
292 int i;
293 int nr = pagevec_count(pvec);
294 int delta_munlocked = -nr;
295 struct pagevec pvec_putback;
296 int pgrescued = 0;
297
298 pagevec_init(&pvec_putback);
299
300 /* Phase 1: page isolation */
301 spin_lock_irq(&zone->zone_pgdat->lru_lock);
302 for (i = 0; i < nr; i++) {
303 struct page *page = pvec->pages[i];
304
305 if (TestClearPageMlocked(page)) {
306 /*
307 * We already have pin from follow_page_mask()
308 * so we can spare the get_page() here.
309 */
310 if (__munlock_isolate_lru_page(page, false))
311 continue;
312 else
313 __munlock_isolation_failed(page);
314 } else {
315 delta_munlocked++;
316 }
317
318 /*
319 * We won't be munlocking this page in the next phase
320 * but we still need to release the follow_page_mask()
321 * pin. We cannot do it under lru_lock however. If it's
322 * the last pin, __page_cache_release() would deadlock.
323 */
324 pagevec_add(&pvec_putback, pvec->pages[i]);
325 pvec->pages[i] = NULL;
326 }
327 __mod_zone_page_state(zone, NR_MLOCK, delta_munlocked);
328 spin_unlock_irq(&zone->zone_pgdat->lru_lock);
329
330 /* Now we can release pins of pages that we are not munlocking */
331 pagevec_release(&pvec_putback);
332
333 /* Phase 2: page munlock */
334 for (i = 0; i < nr; i++) {
335 struct page *page = pvec->pages[i];
336
337 if (page) {
338 lock_page(page);
339 if (!__putback_lru_fast_prepare(page, &pvec_putback,
340 &pgrescued)) {
341 /*
342 * Slow path. We don't want to lose the last
343 * pin before unlock_page()
344 */
345 get_page(page); /* for putback_lru_page() */
346 __munlock_isolated_page(page);
347 unlock_page(page);
348 put_page(page); /* from follow_page_mask() */
349 }
350 }
351 }
352
353 /*
354 * Phase 3: page putback for pages that qualified for the fast path
355 * This will also call put_page() to return pin from follow_page_mask()
356 */
357 if (pagevec_count(&pvec_putback))
358 __putback_lru_fast(&pvec_putback, pgrescued);
359}
360
361/*
362 * Fill up pagevec for __munlock_pagevec using pte walk
363 *
364 * The function expects that the struct page corresponding to @start address is
365 * a non-TPH page already pinned and in the @pvec, and that it belongs to @zone.
366 *
367 * The rest of @pvec is filled by subsequent pages within the same pmd and same
368 * zone, as long as the pte's are present and vm_normal_page() succeeds. These
369 * pages also get pinned.
370 *
371 * Returns the address of the next page that should be scanned. This equals
372 * @start + PAGE_SIZE when no page could be added by the pte walk.
373 */
374static unsigned long __munlock_pagevec_fill(struct pagevec *pvec,
375 struct vm_area_struct *vma, struct zone *zone,
376 unsigned long start, unsigned long end)
377{
378 pte_t *pte;
379 spinlock_t *ptl;
380
381 /*
382 * Initialize pte walk starting at the already pinned page where we
383 * are sure that there is a pte, as it was pinned under the same
384 * mmap_sem write op.
385 */
386 pte = get_locked_pte(vma->vm_mm, start, &ptl);
387 /* Make sure we do not cross the page table boundary */
388 end = pgd_addr_end(start, end);
389 end = p4d_addr_end(start, end);
390 end = pud_addr_end(start, end);
391 end = pmd_addr_end(start, end);
392
393 /* The page next to the pinned page is the first we will try to get */
394 start += PAGE_SIZE;
395 while (start < end) {
396 struct page *page = NULL;
397 pte++;
398 if (pte_present(*pte))
399 page = vm_normal_page(vma, start, *pte);
400 /*
401 * Break if page could not be obtained or the page's node+zone does not
402 * match
403 */
404 if (!page || page_zone(page) != zone)
405 break;
406
407 /*
408 * Do not use pagevec for PTE-mapped THP,
409 * munlock_vma_pages_range() will handle them.
410 */
411 if (PageTransCompound(page))
412 break;
413
414 get_page(page);
415 /*
416 * Increase the address that will be returned *before* the
417 * eventual break due to pvec becoming full by adding the page
418 */
419 start += PAGE_SIZE;
420 if (pagevec_add(pvec, page) == 0)
421 break;
422 }
423 pte_unmap_unlock(pte, ptl);
424 return start;
425}
426
427/*
428 * munlock_vma_pages_range() - munlock all pages in the vma range.'
429 * @vma - vma containing range to be munlock()ed.
430 * @start - start address in @vma of the range
431 * @end - end of range in @vma.
432 *
433 * For mremap(), munmap() and exit().
434 *
435 * Called with @vma VM_LOCKED.
436 *
437 * Returns with VM_LOCKED cleared. Callers must be prepared to
438 * deal with this.
439 *
440 * We don't save and restore VM_LOCKED here because pages are
441 * still on lru. In unmap path, pages might be scanned by reclaim
442 * and re-mlocked by try_to_{munlock|unmap} before we unmap and
443 * free them. This will result in freeing mlocked pages.
444 */
445void munlock_vma_pages_range(struct vm_area_struct *vma,
446 unsigned long start, unsigned long end)
447{
448 vma->vm_flags &= VM_LOCKED_CLEAR_MASK;
449
450 while (start < end) {
451 struct page *page;
452 unsigned int page_mask = 0;
453 unsigned long page_increm;
454 struct pagevec pvec;
455 struct zone *zone;
456
457 pagevec_init(&pvec);
458 /*
459 * Although FOLL_DUMP is intended for get_dump_page(),
460 * it just so happens that its special treatment of the
461 * ZERO_PAGE (returning an error instead of doing get_page)
462 * suits munlock very well (and if somehow an abnormal page
463 * has sneaked into the range, we won't oops here: great).
464 */
465 page = follow_page(vma, start, FOLL_GET | FOLL_DUMP);
466
467 if (page && !IS_ERR(page)) {
468 if (PageTransTail(page)) {
469 VM_BUG_ON_PAGE(PageMlocked(page), page);
470 put_page(page); /* follow_page_mask() */
471 } else if (PageTransHuge(page)) {
472 lock_page(page);
473 /*
474 * Any THP page found by follow_page_mask() may
475 * have gotten split before reaching
476 * munlock_vma_page(), so we need to compute
477 * the page_mask here instead.
478 */
479 page_mask = munlock_vma_page(page);
480 unlock_page(page);
481 put_page(page); /* follow_page_mask() */
482 } else {
483 /*
484 * Non-huge pages are handled in batches via
485 * pagevec. The pin from follow_page_mask()
486 * prevents them from collapsing by THP.
487 */
488 pagevec_add(&pvec, page);
489 zone = page_zone(page);
490
491 /*
492 * Try to fill the rest of pagevec using fast
493 * pte walk. This will also update start to
494 * the next page to process. Then munlock the
495 * pagevec.
496 */
497 start = __munlock_pagevec_fill(&pvec, vma,
498 zone, start, end);
499 __munlock_pagevec(&pvec, zone);
500 goto next;
501 }
502 }
503 page_increm = 1 + page_mask;
504 start += page_increm * PAGE_SIZE;
505next:
506 cond_resched();
507 }
508}
509
510/*
511 * mlock_fixup - handle mlock[all]/munlock[all] requests.
512 *
513 * Filters out "special" vmas -- VM_LOCKED never gets set for these, and
514 * munlock is a no-op. However, for some special vmas, we go ahead and
515 * populate the ptes.
516 *
517 * For vmas that pass the filters, merge/split as appropriate.
518 */
519static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
520 unsigned long start, unsigned long end, vm_flags_t newflags)
521{
522 struct mm_struct *mm = vma->vm_mm;
523 pgoff_t pgoff;
524 int nr_pages;
525 int ret = 0;
526 int lock = !!(newflags & VM_LOCKED);
527 vm_flags_t old_flags = vma->vm_flags;
528
529 if (newflags == vma->vm_flags || (vma->vm_flags & VM_SPECIAL) ||
530 is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm) ||
531 vma_is_dax(vma))
532 /* don't set VM_LOCKED or VM_LOCKONFAULT and don't count */
533 goto out;
534
535 pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
536 *prev = vma_merge(mm, *prev, start, end, newflags, vma->anon_vma,
537 vma->vm_file, pgoff, vma_policy(vma),
538 vma->vm_userfaultfd_ctx);
539 if (*prev) {
540 vma = *prev;
541 goto success;
542 }
543
544 if (start != vma->vm_start) {
545 ret = split_vma(mm, vma, start, 1);
546 if (ret)
547 goto out;
548 }
549
550 if (end != vma->vm_end) {
551 ret = split_vma(mm, vma, end, 0);
552 if (ret)
553 goto out;
554 }
555
556success:
557 /*
558 * Keep track of amount of locked VM.
559 */
560 nr_pages = (end - start) >> PAGE_SHIFT;
561 if (!lock)
562 nr_pages = -nr_pages;
563 else if (old_flags & VM_LOCKED)
564 nr_pages = 0;
565 mm->locked_vm += nr_pages;
566
567 /*
568 * vm_flags is protected by the mmap_sem held in write mode.
569 * It's okay if try_to_unmap_one unmaps a page just after we
570 * set VM_LOCKED, populate_vma_page_range will bring it back.
571 */
572
573 if (lock)
574 vma->vm_flags = newflags;
575 else
576 munlock_vma_pages_range(vma, start, end);
577
578out:
579 *prev = vma;
580 return ret;
581}
582
583static int apply_vma_lock_flags(unsigned long start, size_t len,
584 vm_flags_t flags)
585{
586 unsigned long nstart, end, tmp;
587 struct vm_area_struct * vma, * prev;
588 int error;
589
590 VM_BUG_ON(offset_in_page(start));
591 VM_BUG_ON(len != PAGE_ALIGN(len));
592 end = start + len;
593 if (end < start)
594 return -EINVAL;
595 if (end == start)
596 return 0;
597 vma = find_vma(current->mm, start);
598 if (!vma || vma->vm_start > start)
599 return -ENOMEM;
600
601 prev = vma->vm_prev;
602 if (start > vma->vm_start)
603 prev = vma;
604
605 for (nstart = start ; ; ) {
606 vm_flags_t newflags = vma->vm_flags & VM_LOCKED_CLEAR_MASK;
607
608 newflags |= flags;
609
610 /* Here we know that vma->vm_start <= nstart < vma->vm_end. */
611 tmp = vma->vm_end;
612 if (tmp > end)
613 tmp = end;
614 error = mlock_fixup(vma, &prev, nstart, tmp, newflags);
615 if (error)
616 break;
617 nstart = tmp;
618 if (nstart < prev->vm_end)
619 nstart = prev->vm_end;
620 if (nstart >= end)
621 break;
622
623 vma = prev->vm_next;
624 if (!vma || vma->vm_start != nstart) {
625 error = -ENOMEM;
626 break;
627 }
628 }
629 return error;
630}
631
632/*
633 * Go through vma areas and sum size of mlocked
634 * vma pages, as return value.
635 * Note deferred memory locking case(mlock2(,,MLOCK_ONFAULT)
636 * is also counted.
637 * Return value: previously mlocked page counts
638 */
639static unsigned long count_mm_mlocked_page_nr(struct mm_struct *mm,
640 unsigned long start, size_t len)
641{
642 struct vm_area_struct *vma;
643 unsigned long count = 0;
644
645 if (mm == NULL)
646 mm = current->mm;
647
648 vma = find_vma(mm, start);
649 if (vma == NULL)
650 vma = mm->mmap;
651
652 for (; vma ; vma = vma->vm_next) {
653 if (start >= vma->vm_end)
654 continue;
655 if (start + len <= vma->vm_start)
656 break;
657 if (vma->vm_flags & VM_LOCKED) {
658 if (start > vma->vm_start)
659 count -= (start - vma->vm_start);
660 if (start + len < vma->vm_end) {
661 count += start + len - vma->vm_start;
662 break;
663 }
664 count += vma->vm_end - vma->vm_start;
665 }
666 }
667
668 return count >> PAGE_SHIFT;
669}
670
671static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t flags)
672{
673 unsigned long locked;
674 unsigned long lock_limit;
675 int error = -ENOMEM;
676
677 start = untagged_addr(start);
678
679 if (!can_do_mlock())
680 return -EPERM;
681
682 len = PAGE_ALIGN(len + (offset_in_page(start)));
683 start &= PAGE_MASK;
684
685 lock_limit = rlimit(RLIMIT_MEMLOCK);
686 lock_limit >>= PAGE_SHIFT;
687 locked = len >> PAGE_SHIFT;
688
689 if (down_write_killable(¤t->mm->mmap_sem))
690 return -EINTR;
691
692 locked += current->mm->locked_vm;
693 if ((locked > lock_limit) && (!capable(CAP_IPC_LOCK))) {
694 /*
695 * It is possible that the regions requested intersect with
696 * previously mlocked areas, that part area in "mm->locked_vm"
697 * should not be counted to new mlock increment count. So check
698 * and adjust locked count if necessary.
699 */
700 locked -= count_mm_mlocked_page_nr(current->mm,
701 start, len);
702 }
703
704 /* check against resource limits */
705 if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
706 error = apply_vma_lock_flags(start, len, flags);
707
708 up_write(¤t->mm->mmap_sem);
709 if (error)
710 return error;
711
712 error = __mm_populate(start, len, 0);
713 if (error)
714 return __mlock_posix_error_return(error);
715 return 0;
716}
717
718SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
719{
720 return do_mlock(start, len, VM_LOCKED);
721}
722
723SYSCALL_DEFINE3(mlock2, unsigned long, start, size_t, len, int, flags)
724{
725 vm_flags_t vm_flags = VM_LOCKED;
726
727 if (flags & ~MLOCK_ONFAULT)
728 return -EINVAL;
729
730 if (flags & MLOCK_ONFAULT)
731 vm_flags |= VM_LOCKONFAULT;
732
733 return do_mlock(start, len, vm_flags);
734}
735
736SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
737{
738 int ret;
739
740 start = untagged_addr(start);
741
742 len = PAGE_ALIGN(len + (offset_in_page(start)));
743 start &= PAGE_MASK;
744
745 if (down_write_killable(¤t->mm->mmap_sem))
746 return -EINTR;
747 ret = apply_vma_lock_flags(start, len, 0);
748 up_write(¤t->mm->mmap_sem);
749
750 return ret;
751}
752
753/*
754 * Take the MCL_* flags passed into mlockall (or 0 if called from munlockall)
755 * and translate into the appropriate modifications to mm->def_flags and/or the
756 * flags for all current VMAs.
757 *
758 * There are a couple of subtleties with this. If mlockall() is called multiple
759 * times with different flags, the values do not necessarily stack. If mlockall
760 * is called once including the MCL_FUTURE flag and then a second time without
761 * it, VM_LOCKED and VM_LOCKONFAULT will be cleared from mm->def_flags.
762 */
763static int apply_mlockall_flags(int flags)
764{
765 struct vm_area_struct * vma, * prev = NULL;
766 vm_flags_t to_add = 0;
767
768 current->mm->def_flags &= VM_LOCKED_CLEAR_MASK;
769 if (flags & MCL_FUTURE) {
770 current->mm->def_flags |= VM_LOCKED;
771
772 if (flags & MCL_ONFAULT)
773 current->mm->def_flags |= VM_LOCKONFAULT;
774
775 if (!(flags & MCL_CURRENT))
776 goto out;
777 }
778
779 if (flags & MCL_CURRENT) {
780 to_add |= VM_LOCKED;
781 if (flags & MCL_ONFAULT)
782 to_add |= VM_LOCKONFAULT;
783 }
784
785 for (vma = current->mm->mmap; vma ; vma = prev->vm_next) {
786 vm_flags_t newflags;
787
788 newflags = vma->vm_flags & VM_LOCKED_CLEAR_MASK;
789 newflags |= to_add;
790
791 /* Ignore errors */
792 mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
793 cond_resched();
794 }
795out:
796 return 0;
797}
798
799SYSCALL_DEFINE1(mlockall, int, flags)
800{
801 unsigned long lock_limit;
802 int ret;
803
804 if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE | MCL_ONFAULT)) ||
805 flags == MCL_ONFAULT)
806 return -EINVAL;
807
808 if (!can_do_mlock())
809 return -EPERM;
810
811 lock_limit = rlimit(RLIMIT_MEMLOCK);
812 lock_limit >>= PAGE_SHIFT;
813
814 if (down_write_killable(¤t->mm->mmap_sem))
815 return -EINTR;
816
817 ret = -ENOMEM;
818 if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
819 capable(CAP_IPC_LOCK))
820 ret = apply_mlockall_flags(flags);
821 up_write(¤t->mm->mmap_sem);
822 if (!ret && (flags & MCL_CURRENT))
823 mm_populate(0, TASK_SIZE);
824
825 return ret;
826}
827
828SYSCALL_DEFINE0(munlockall)
829{
830 int ret;
831
832 if (down_write_killable(¤t->mm->mmap_sem))
833 return -EINTR;
834 ret = apply_mlockall_flags(0);
835 up_write(¤t->mm->mmap_sem);
836 return ret;
837}
838
839/*
840 * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB
841 * shm segments) get accounted against the user_struct instead.
842 */
843static DEFINE_SPINLOCK(shmlock_user_lock);
844
845int user_shm_lock(size_t size, struct user_struct *user)
846{
847 unsigned long lock_limit, locked;
848 int allowed = 0;
849
850 locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
851 lock_limit = rlimit(RLIMIT_MEMLOCK);
852 if (lock_limit == RLIM_INFINITY)
853 allowed = 1;
854 lock_limit >>= PAGE_SHIFT;
855 spin_lock(&shmlock_user_lock);
856 if (!allowed &&
857 locked + user->locked_shm > lock_limit && !capable(CAP_IPC_LOCK))
858 goto out;
859 get_uid(user);
860 user->locked_shm += locked;
861 allowed = 1;
862out:
863 spin_unlock(&shmlock_user_lock);
864 return allowed;
865}
866
867void user_shm_unlock(size_t size, struct user_struct *user)
868{
869 spin_lock(&shmlock_user_lock);
870 user->locked_shm -= (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
871 spin_unlock(&shmlock_user_lock);
872 free_uid(user);
873}
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * linux/mm/mlock.c
4 *
5 * (C) Copyright 1995 Linus Torvalds
6 * (C) Copyright 2002 Christoph Hellwig
7 */
8
9#include <linux/capability.h>
10#include <linux/mman.h>
11#include <linux/mm.h>
12#include <linux/sched/user.h>
13#include <linux/swap.h>
14#include <linux/swapops.h>
15#include <linux/pagemap.h>
16#include <linux/pagevec.h>
17#include <linux/pagewalk.h>
18#include <linux/mempolicy.h>
19#include <linux/syscalls.h>
20#include <linux/sched.h>
21#include <linux/export.h>
22#include <linux/rmap.h>
23#include <linux/mmzone.h>
24#include <linux/hugetlb.h>
25#include <linux/memcontrol.h>
26#include <linux/mm_inline.h>
27#include <linux/secretmem.h>
28
29#include "internal.h"
30
31struct mlock_fbatch {
32 local_lock_t lock;
33 struct folio_batch fbatch;
34};
35
36static DEFINE_PER_CPU(struct mlock_fbatch, mlock_fbatch) = {
37 .lock = INIT_LOCAL_LOCK(lock),
38};
39
40bool can_do_mlock(void)
41{
42 if (rlimit(RLIMIT_MEMLOCK) != 0)
43 return true;
44 if (capable(CAP_IPC_LOCK))
45 return true;
46 return false;
47}
48EXPORT_SYMBOL(can_do_mlock);
49
50/*
51 * Mlocked folios are marked with the PG_mlocked flag for efficient testing
52 * in vmscan and, possibly, the fault path; and to support semi-accurate
53 * statistics.
54 *
55 * An mlocked folio [folio_test_mlocked(folio)] is unevictable. As such, it
56 * will be ostensibly placed on the LRU "unevictable" list (actually no such
57 * list exists), rather than the [in]active lists. PG_unevictable is set to
58 * indicate the unevictable state.
59 */
60
61static struct lruvec *__mlock_folio(struct folio *folio, struct lruvec *lruvec)
62{
63 /* There is nothing more we can do while it's off LRU */
64 if (!folio_test_clear_lru(folio))
65 return lruvec;
66
67 lruvec = folio_lruvec_relock_irq(folio, lruvec);
68
69 if (unlikely(folio_evictable(folio))) {
70 /*
71 * This is a little surprising, but quite possible: PG_mlocked
72 * must have got cleared already by another CPU. Could this
73 * folio be unevictable? I'm not sure, but move it now if so.
74 */
75 if (folio_test_unevictable(folio)) {
76 lruvec_del_folio(lruvec, folio);
77 folio_clear_unevictable(folio);
78 lruvec_add_folio(lruvec, folio);
79
80 __count_vm_events(UNEVICTABLE_PGRESCUED,
81 folio_nr_pages(folio));
82 }
83 goto out;
84 }
85
86 if (folio_test_unevictable(folio)) {
87 if (folio_test_mlocked(folio))
88 folio->mlock_count++;
89 goto out;
90 }
91
92 lruvec_del_folio(lruvec, folio);
93 folio_clear_active(folio);
94 folio_set_unevictable(folio);
95 folio->mlock_count = !!folio_test_mlocked(folio);
96 lruvec_add_folio(lruvec, folio);
97 __count_vm_events(UNEVICTABLE_PGCULLED, folio_nr_pages(folio));
98out:
99 folio_set_lru(folio);
100 return lruvec;
101}
102
103static struct lruvec *__mlock_new_folio(struct folio *folio, struct lruvec *lruvec)
104{
105 VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
106
107 lruvec = folio_lruvec_relock_irq(folio, lruvec);
108
109 /* As above, this is a little surprising, but possible */
110 if (unlikely(folio_evictable(folio)))
111 goto out;
112
113 folio_set_unevictable(folio);
114 folio->mlock_count = !!folio_test_mlocked(folio);
115 __count_vm_events(UNEVICTABLE_PGCULLED, folio_nr_pages(folio));
116out:
117 lruvec_add_folio(lruvec, folio);
118 folio_set_lru(folio);
119 return lruvec;
120}
121
122static struct lruvec *__munlock_folio(struct folio *folio, struct lruvec *lruvec)
123{
124 int nr_pages = folio_nr_pages(folio);
125 bool isolated = false;
126
127 if (!folio_test_clear_lru(folio))
128 goto munlock;
129
130 isolated = true;
131 lruvec = folio_lruvec_relock_irq(folio, lruvec);
132
133 if (folio_test_unevictable(folio)) {
134 /* Then mlock_count is maintained, but might undercount */
135 if (folio->mlock_count)
136 folio->mlock_count--;
137 if (folio->mlock_count)
138 goto out;
139 }
140 /* else assume that was the last mlock: reclaim will fix it if not */
141
142munlock:
143 if (folio_test_clear_mlocked(folio)) {
144 __zone_stat_mod_folio(folio, NR_MLOCK, -nr_pages);
145 if (isolated || !folio_test_unevictable(folio))
146 __count_vm_events(UNEVICTABLE_PGMUNLOCKED, nr_pages);
147 else
148 __count_vm_events(UNEVICTABLE_PGSTRANDED, nr_pages);
149 }
150
151 /* folio_evictable() has to be checked *after* clearing Mlocked */
152 if (isolated && folio_test_unevictable(folio) && folio_evictable(folio)) {
153 lruvec_del_folio(lruvec, folio);
154 folio_clear_unevictable(folio);
155 lruvec_add_folio(lruvec, folio);
156 __count_vm_events(UNEVICTABLE_PGRESCUED, nr_pages);
157 }
158out:
159 if (isolated)
160 folio_set_lru(folio);
161 return lruvec;
162}
163
164/*
165 * Flags held in the low bits of a struct folio pointer on the mlock_fbatch.
166 */
167#define LRU_FOLIO 0x1
168#define NEW_FOLIO 0x2
169static inline struct folio *mlock_lru(struct folio *folio)
170{
171 return (struct folio *)((unsigned long)folio + LRU_FOLIO);
172}
173
174static inline struct folio *mlock_new(struct folio *folio)
175{
176 return (struct folio *)((unsigned long)folio + NEW_FOLIO);
177}
178
179/*
180 * mlock_folio_batch() is derived from folio_batch_move_lru(): perhaps that can
181 * make use of such folio pointer flags in future, but for now just keep it for
182 * mlock. We could use three separate folio batches instead, but one feels
183 * better (munlocking a full folio batch does not need to drain mlocking folio
184 * batches first).
185 */
186static void mlock_folio_batch(struct folio_batch *fbatch)
187{
188 struct lruvec *lruvec = NULL;
189 unsigned long mlock;
190 struct folio *folio;
191 int i;
192
193 for (i = 0; i < folio_batch_count(fbatch); i++) {
194 folio = fbatch->folios[i];
195 mlock = (unsigned long)folio & (LRU_FOLIO | NEW_FOLIO);
196 folio = (struct folio *)((unsigned long)folio - mlock);
197 fbatch->folios[i] = folio;
198
199 if (mlock & LRU_FOLIO)
200 lruvec = __mlock_folio(folio, lruvec);
201 else if (mlock & NEW_FOLIO)
202 lruvec = __mlock_new_folio(folio, lruvec);
203 else
204 lruvec = __munlock_folio(folio, lruvec);
205 }
206
207 if (lruvec)
208 unlock_page_lruvec_irq(lruvec);
209 folios_put(fbatch);
210}
211
212void mlock_drain_local(void)
213{
214 struct folio_batch *fbatch;
215
216 local_lock(&mlock_fbatch.lock);
217 fbatch = this_cpu_ptr(&mlock_fbatch.fbatch);
218 if (folio_batch_count(fbatch))
219 mlock_folio_batch(fbatch);
220 local_unlock(&mlock_fbatch.lock);
221}
222
223void mlock_drain_remote(int cpu)
224{
225 struct folio_batch *fbatch;
226
227 WARN_ON_ONCE(cpu_online(cpu));
228 fbatch = &per_cpu(mlock_fbatch.fbatch, cpu);
229 if (folio_batch_count(fbatch))
230 mlock_folio_batch(fbatch);
231}
232
233bool need_mlock_drain(int cpu)
234{
235 return folio_batch_count(&per_cpu(mlock_fbatch.fbatch, cpu));
236}
237
238/**
239 * mlock_folio - mlock a folio already on (or temporarily off) LRU
240 * @folio: folio to be mlocked.
241 */
242void mlock_folio(struct folio *folio)
243{
244 struct folio_batch *fbatch;
245
246 local_lock(&mlock_fbatch.lock);
247 fbatch = this_cpu_ptr(&mlock_fbatch.fbatch);
248
249 if (!folio_test_set_mlocked(folio)) {
250 int nr_pages = folio_nr_pages(folio);
251
252 zone_stat_mod_folio(folio, NR_MLOCK, nr_pages);
253 __count_vm_events(UNEVICTABLE_PGMLOCKED, nr_pages);
254 }
255
256 folio_get(folio);
257 if (!folio_batch_add(fbatch, mlock_lru(folio)) ||
258 folio_test_large(folio) || lru_cache_disabled())
259 mlock_folio_batch(fbatch);
260 local_unlock(&mlock_fbatch.lock);
261}
262
263/**
264 * mlock_new_folio - mlock a newly allocated folio not yet on LRU
265 * @folio: folio to be mlocked, either normal or a THP head.
266 */
267void mlock_new_folio(struct folio *folio)
268{
269 struct folio_batch *fbatch;
270 int nr_pages = folio_nr_pages(folio);
271
272 local_lock(&mlock_fbatch.lock);
273 fbatch = this_cpu_ptr(&mlock_fbatch.fbatch);
274 folio_set_mlocked(folio);
275
276 zone_stat_mod_folio(folio, NR_MLOCK, nr_pages);
277 __count_vm_events(UNEVICTABLE_PGMLOCKED, nr_pages);
278
279 folio_get(folio);
280 if (!folio_batch_add(fbatch, mlock_new(folio)) ||
281 folio_test_large(folio) || lru_cache_disabled())
282 mlock_folio_batch(fbatch);
283 local_unlock(&mlock_fbatch.lock);
284}
285
286/**
287 * munlock_folio - munlock a folio
288 * @folio: folio to be munlocked, either normal or a THP head.
289 */
290void munlock_folio(struct folio *folio)
291{
292 struct folio_batch *fbatch;
293
294 local_lock(&mlock_fbatch.lock);
295 fbatch = this_cpu_ptr(&mlock_fbatch.fbatch);
296 /*
297 * folio_test_clear_mlocked(folio) must be left to __munlock_folio(),
298 * which will check whether the folio is multiply mlocked.
299 */
300 folio_get(folio);
301 if (!folio_batch_add(fbatch, folio) ||
302 folio_test_large(folio) || lru_cache_disabled())
303 mlock_folio_batch(fbatch);
304 local_unlock(&mlock_fbatch.lock);
305}
306
307static inline unsigned int folio_mlock_step(struct folio *folio,
308 pte_t *pte, unsigned long addr, unsigned long end)
309{
310 unsigned int count, i, nr = folio_nr_pages(folio);
311 unsigned long pfn = folio_pfn(folio);
312 pte_t ptent = ptep_get(pte);
313
314 if (!folio_test_large(folio))
315 return 1;
316
317 count = pfn + nr - pte_pfn(ptent);
318 count = min_t(unsigned int, count, (end - addr) >> PAGE_SHIFT);
319
320 for (i = 0; i < count; i++, pte++) {
321 pte_t entry = ptep_get(pte);
322
323 if (!pte_present(entry))
324 break;
325 if (pte_pfn(entry) - pfn >= nr)
326 break;
327 }
328
329 return i;
330}
331
332static inline bool allow_mlock_munlock(struct folio *folio,
333 struct vm_area_struct *vma, unsigned long start,
334 unsigned long end, unsigned int step)
335{
336 /*
337 * For unlock, allow munlock large folio which is partially
338 * mapped to VMA. As it's possible that large folio is
339 * mlocked and VMA is split later.
340 *
341 * During memory pressure, such kind of large folio can
342 * be split. And the pages are not in VM_LOCKed VMA
343 * can be reclaimed.
344 */
345 if (!(vma->vm_flags & VM_LOCKED))
346 return true;
347
348 /* folio_within_range() cannot take KSM, but any small folio is OK */
349 if (!folio_test_large(folio))
350 return true;
351
352 /* folio not in range [start, end), skip mlock */
353 if (!folio_within_range(folio, vma, start, end))
354 return false;
355
356 /* folio is not fully mapped, skip mlock */
357 if (step != folio_nr_pages(folio))
358 return false;
359
360 return true;
361}
362
363static int mlock_pte_range(pmd_t *pmd, unsigned long addr,
364 unsigned long end, struct mm_walk *walk)
365
366{
367 struct vm_area_struct *vma = walk->vma;
368 spinlock_t *ptl;
369 pte_t *start_pte, *pte;
370 pte_t ptent;
371 struct folio *folio;
372 unsigned int step = 1;
373 unsigned long start = addr;
374
375 ptl = pmd_trans_huge_lock(pmd, vma);
376 if (ptl) {
377 if (!pmd_present(*pmd))
378 goto out;
379 if (is_huge_zero_pmd(*pmd))
380 goto out;
381 folio = page_folio(pmd_page(*pmd));
382 if (vma->vm_flags & VM_LOCKED)
383 mlock_folio(folio);
384 else
385 munlock_folio(folio);
386 goto out;
387 }
388
389 start_pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
390 if (!start_pte) {
391 walk->action = ACTION_AGAIN;
392 return 0;
393 }
394
395 for (pte = start_pte; addr != end; pte++, addr += PAGE_SIZE) {
396 ptent = ptep_get(pte);
397 if (!pte_present(ptent))
398 continue;
399 folio = vm_normal_folio(vma, addr, ptent);
400 if (!folio || folio_is_zone_device(folio))
401 continue;
402
403 step = folio_mlock_step(folio, pte, addr, end);
404 if (!allow_mlock_munlock(folio, vma, start, end, step))
405 goto next_entry;
406
407 if (vma->vm_flags & VM_LOCKED)
408 mlock_folio(folio);
409 else
410 munlock_folio(folio);
411
412next_entry:
413 pte += step - 1;
414 addr += (step - 1) << PAGE_SHIFT;
415 }
416 pte_unmap(start_pte);
417out:
418 spin_unlock(ptl);
419 cond_resched();
420 return 0;
421}
422
423/*
424 * mlock_vma_pages_range() - mlock any pages already in the range,
425 * or munlock all pages in the range.
426 * @vma - vma containing range to be mlock()ed or munlock()ed
427 * @start - start address in @vma of the range
428 * @end - end of range in @vma
429 * @newflags - the new set of flags for @vma.
430 *
431 * Called for mlock(), mlock2() and mlockall(), to set @vma VM_LOCKED;
432 * called for munlock() and munlockall(), to clear VM_LOCKED from @vma.
433 */
434static void mlock_vma_pages_range(struct vm_area_struct *vma,
435 unsigned long start, unsigned long end, vm_flags_t newflags)
436{
437 static const struct mm_walk_ops mlock_walk_ops = {
438 .pmd_entry = mlock_pte_range,
439 .walk_lock = PGWALK_WRLOCK_VERIFY,
440 };
441
442 /*
443 * There is a slight chance that concurrent page migration,
444 * or page reclaim finding a page of this now-VM_LOCKED vma,
445 * will call mlock_vma_folio() and raise page's mlock_count:
446 * double counting, leaving the page unevictable indefinitely.
447 * Communicate this danger to mlock_vma_folio() with VM_IO,
448 * which is a VM_SPECIAL flag not allowed on VM_LOCKED vmas.
449 * mmap_lock is held in write mode here, so this weird
450 * combination should not be visible to other mmap_lock users;
451 * but WRITE_ONCE so rmap walkers must see VM_IO if VM_LOCKED.
452 */
453 if (newflags & VM_LOCKED)
454 newflags |= VM_IO;
455 vma_start_write(vma);
456 vm_flags_reset_once(vma, newflags);
457
458 lru_add_drain();
459 walk_page_range(vma->vm_mm, start, end, &mlock_walk_ops, NULL);
460 lru_add_drain();
461
462 if (newflags & VM_IO) {
463 newflags &= ~VM_IO;
464 vm_flags_reset_once(vma, newflags);
465 }
466}
467
468/*
469 * mlock_fixup - handle mlock[all]/munlock[all] requests.
470 *
471 * Filters out "special" vmas -- VM_LOCKED never gets set for these, and
472 * munlock is a no-op. However, for some special vmas, we go ahead and
473 * populate the ptes.
474 *
475 * For vmas that pass the filters, merge/split as appropriate.
476 */
477static int mlock_fixup(struct vma_iterator *vmi, struct vm_area_struct *vma,
478 struct vm_area_struct **prev, unsigned long start,
479 unsigned long end, vm_flags_t newflags)
480{
481 struct mm_struct *mm = vma->vm_mm;
482 int nr_pages;
483 int ret = 0;
484 vm_flags_t oldflags = vma->vm_flags;
485
486 if (newflags == oldflags || (oldflags & VM_SPECIAL) ||
487 is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm) ||
488 vma_is_dax(vma) || vma_is_secretmem(vma))
489 /* don't set VM_LOCKED or VM_LOCKONFAULT and don't count */
490 goto out;
491
492 vma = vma_modify_flags(vmi, *prev, vma, start, end, newflags);
493 if (IS_ERR(vma)) {
494 ret = PTR_ERR(vma);
495 goto out;
496 }
497
498 /*
499 * Keep track of amount of locked VM.
500 */
501 nr_pages = (end - start) >> PAGE_SHIFT;
502 if (!(newflags & VM_LOCKED))
503 nr_pages = -nr_pages;
504 else if (oldflags & VM_LOCKED)
505 nr_pages = 0;
506 mm->locked_vm += nr_pages;
507
508 /*
509 * vm_flags is protected by the mmap_lock held in write mode.
510 * It's okay if try_to_unmap_one unmaps a page just after we
511 * set VM_LOCKED, populate_vma_page_range will bring it back.
512 */
513 if ((newflags & VM_LOCKED) && (oldflags & VM_LOCKED)) {
514 /* No work to do, and mlocking twice would be wrong */
515 vma_start_write(vma);
516 vm_flags_reset(vma, newflags);
517 } else {
518 mlock_vma_pages_range(vma, start, end, newflags);
519 }
520out:
521 *prev = vma;
522 return ret;
523}
524
525static int apply_vma_lock_flags(unsigned long start, size_t len,
526 vm_flags_t flags)
527{
528 unsigned long nstart, end, tmp;
529 struct vm_area_struct *vma, *prev;
530 VMA_ITERATOR(vmi, current->mm, start);
531
532 VM_BUG_ON(offset_in_page(start));
533 VM_BUG_ON(len != PAGE_ALIGN(len));
534 end = start + len;
535 if (end < start)
536 return -EINVAL;
537 if (end == start)
538 return 0;
539 vma = vma_iter_load(&vmi);
540 if (!vma)
541 return -ENOMEM;
542
543 prev = vma_prev(&vmi);
544 if (start > vma->vm_start)
545 prev = vma;
546
547 nstart = start;
548 tmp = vma->vm_start;
549 for_each_vma_range(vmi, vma, end) {
550 int error;
551 vm_flags_t newflags;
552
553 if (vma->vm_start != tmp)
554 return -ENOMEM;
555
556 newflags = vma->vm_flags & ~VM_LOCKED_MASK;
557 newflags |= flags;
558 /* Here we know that vma->vm_start <= nstart < vma->vm_end. */
559 tmp = vma->vm_end;
560 if (tmp > end)
561 tmp = end;
562 error = mlock_fixup(&vmi, vma, &prev, nstart, tmp, newflags);
563 if (error)
564 return error;
565 tmp = vma_iter_end(&vmi);
566 nstart = tmp;
567 }
568
569 if (tmp < end)
570 return -ENOMEM;
571
572 return 0;
573}
574
575/*
576 * Go through vma areas and sum size of mlocked
577 * vma pages, as return value.
578 * Note deferred memory locking case(mlock2(,,MLOCK_ONFAULT)
579 * is also counted.
580 * Return value: previously mlocked page counts
581 */
582static unsigned long count_mm_mlocked_page_nr(struct mm_struct *mm,
583 unsigned long start, size_t len)
584{
585 struct vm_area_struct *vma;
586 unsigned long count = 0;
587 unsigned long end;
588 VMA_ITERATOR(vmi, mm, start);
589
590 /* Don't overflow past ULONG_MAX */
591 if (unlikely(ULONG_MAX - len < start))
592 end = ULONG_MAX;
593 else
594 end = start + len;
595
596 for_each_vma_range(vmi, vma, end) {
597 if (vma->vm_flags & VM_LOCKED) {
598 if (start > vma->vm_start)
599 count -= (start - vma->vm_start);
600 if (end < vma->vm_end) {
601 count += end - vma->vm_start;
602 break;
603 }
604 count += vma->vm_end - vma->vm_start;
605 }
606 }
607
608 return count >> PAGE_SHIFT;
609}
610
611/*
612 * convert get_user_pages() return value to posix mlock() error
613 */
614static int __mlock_posix_error_return(long retval)
615{
616 if (retval == -EFAULT)
617 retval = -ENOMEM;
618 else if (retval == -ENOMEM)
619 retval = -EAGAIN;
620 return retval;
621}
622
623static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t flags)
624{
625 unsigned long locked;
626 unsigned long lock_limit;
627 int error = -ENOMEM;
628
629 start = untagged_addr(start);
630
631 if (!can_do_mlock())
632 return -EPERM;
633
634 len = PAGE_ALIGN(len + (offset_in_page(start)));
635 start &= PAGE_MASK;
636
637 lock_limit = rlimit(RLIMIT_MEMLOCK);
638 lock_limit >>= PAGE_SHIFT;
639 locked = len >> PAGE_SHIFT;
640
641 if (mmap_write_lock_killable(current->mm))
642 return -EINTR;
643
644 locked += current->mm->locked_vm;
645 if ((locked > lock_limit) && (!capable(CAP_IPC_LOCK))) {
646 /*
647 * It is possible that the regions requested intersect with
648 * previously mlocked areas, that part area in "mm->locked_vm"
649 * should not be counted to new mlock increment count. So check
650 * and adjust locked count if necessary.
651 */
652 locked -= count_mm_mlocked_page_nr(current->mm,
653 start, len);
654 }
655
656 /* check against resource limits */
657 if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
658 error = apply_vma_lock_flags(start, len, flags);
659
660 mmap_write_unlock(current->mm);
661 if (error)
662 return error;
663
664 error = __mm_populate(start, len, 0);
665 if (error)
666 return __mlock_posix_error_return(error);
667 return 0;
668}
669
670SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
671{
672 return do_mlock(start, len, VM_LOCKED);
673}
674
675SYSCALL_DEFINE3(mlock2, unsigned long, start, size_t, len, int, flags)
676{
677 vm_flags_t vm_flags = VM_LOCKED;
678
679 if (flags & ~MLOCK_ONFAULT)
680 return -EINVAL;
681
682 if (flags & MLOCK_ONFAULT)
683 vm_flags |= VM_LOCKONFAULT;
684
685 return do_mlock(start, len, vm_flags);
686}
687
688SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
689{
690 int ret;
691
692 start = untagged_addr(start);
693
694 len = PAGE_ALIGN(len + (offset_in_page(start)));
695 start &= PAGE_MASK;
696
697 if (mmap_write_lock_killable(current->mm))
698 return -EINTR;
699 ret = apply_vma_lock_flags(start, len, 0);
700 mmap_write_unlock(current->mm);
701
702 return ret;
703}
704
705/*
706 * Take the MCL_* flags passed into mlockall (or 0 if called from munlockall)
707 * and translate into the appropriate modifications to mm->def_flags and/or the
708 * flags for all current VMAs.
709 *
710 * There are a couple of subtleties with this. If mlockall() is called multiple
711 * times with different flags, the values do not necessarily stack. If mlockall
712 * is called once including the MCL_FUTURE flag and then a second time without
713 * it, VM_LOCKED and VM_LOCKONFAULT will be cleared from mm->def_flags.
714 */
715static int apply_mlockall_flags(int flags)
716{
717 VMA_ITERATOR(vmi, current->mm, 0);
718 struct vm_area_struct *vma, *prev = NULL;
719 vm_flags_t to_add = 0;
720
721 current->mm->def_flags &= ~VM_LOCKED_MASK;
722 if (flags & MCL_FUTURE) {
723 current->mm->def_flags |= VM_LOCKED;
724
725 if (flags & MCL_ONFAULT)
726 current->mm->def_flags |= VM_LOCKONFAULT;
727
728 if (!(flags & MCL_CURRENT))
729 goto out;
730 }
731
732 if (flags & MCL_CURRENT) {
733 to_add |= VM_LOCKED;
734 if (flags & MCL_ONFAULT)
735 to_add |= VM_LOCKONFAULT;
736 }
737
738 for_each_vma(vmi, vma) {
739 vm_flags_t newflags;
740
741 newflags = vma->vm_flags & ~VM_LOCKED_MASK;
742 newflags |= to_add;
743
744 /* Ignore errors */
745 mlock_fixup(&vmi, vma, &prev, vma->vm_start, vma->vm_end,
746 newflags);
747 cond_resched();
748 }
749out:
750 return 0;
751}
752
753SYSCALL_DEFINE1(mlockall, int, flags)
754{
755 unsigned long lock_limit;
756 int ret;
757
758 if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE | MCL_ONFAULT)) ||
759 flags == MCL_ONFAULT)
760 return -EINVAL;
761
762 if (!can_do_mlock())
763 return -EPERM;
764
765 lock_limit = rlimit(RLIMIT_MEMLOCK);
766 lock_limit >>= PAGE_SHIFT;
767
768 if (mmap_write_lock_killable(current->mm))
769 return -EINTR;
770
771 ret = -ENOMEM;
772 if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
773 capable(CAP_IPC_LOCK))
774 ret = apply_mlockall_flags(flags);
775 mmap_write_unlock(current->mm);
776 if (!ret && (flags & MCL_CURRENT))
777 mm_populate(0, TASK_SIZE);
778
779 return ret;
780}
781
782SYSCALL_DEFINE0(munlockall)
783{
784 int ret;
785
786 if (mmap_write_lock_killable(current->mm))
787 return -EINTR;
788 ret = apply_mlockall_flags(0);
789 mmap_write_unlock(current->mm);
790 return ret;
791}
792
793/*
794 * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB
795 * shm segments) get accounted against the user_struct instead.
796 */
797static DEFINE_SPINLOCK(shmlock_user_lock);
798
799int user_shm_lock(size_t size, struct ucounts *ucounts)
800{
801 unsigned long lock_limit, locked;
802 long memlock;
803 int allowed = 0;
804
805 locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
806 lock_limit = rlimit(RLIMIT_MEMLOCK);
807 if (lock_limit != RLIM_INFINITY)
808 lock_limit >>= PAGE_SHIFT;
809 spin_lock(&shmlock_user_lock);
810 memlock = inc_rlimit_ucounts(ucounts, UCOUNT_RLIMIT_MEMLOCK, locked);
811
812 if ((memlock == LONG_MAX || memlock > lock_limit) && !capable(CAP_IPC_LOCK)) {
813 dec_rlimit_ucounts(ucounts, UCOUNT_RLIMIT_MEMLOCK, locked);
814 goto out;
815 }
816 if (!get_ucounts(ucounts)) {
817 dec_rlimit_ucounts(ucounts, UCOUNT_RLIMIT_MEMLOCK, locked);
818 allowed = 0;
819 goto out;
820 }
821 allowed = 1;
822out:
823 spin_unlock(&shmlock_user_lock);
824 return allowed;
825}
826
827void user_shm_unlock(size_t size, struct ucounts *ucounts)
828{
829 spin_lock(&shmlock_user_lock);
830 dec_rlimit_ucounts(ucounts, UCOUNT_RLIMIT_MEMLOCK, (size + PAGE_SIZE - 1) >> PAGE_SHIFT);
831 spin_unlock(&shmlock_user_lock);
832 put_ucounts(ucounts);
833}