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
can_do_mlock(void)29 bool 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 }
37 EXPORT_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_lock 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 */
clear_page_mlock(struct page * page)59 void clear_page_mlock(struct page *page)
60 {
61 int nr_pages;
62
63 if (!TestClearPageMlocked(page))
64 return;
65
66 nr_pages = thp_nr_pages(page);
67 mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages);
68 count_vm_events(UNEVICTABLE_PGCLEARED, nr_pages);
69 /*
70 * The previous TestClearPageMlocked() corresponds to the smp_mb()
71 * in __pagevec_lru_add_fn().
72 *
73 * See __pagevec_lru_add_fn for more explanation.
74 */
75 if (!isolate_lru_page(page)) {
76 putback_lru_page(page);
77 } else {
78 /*
79 * We lost the race. the page already moved to evictable list.
80 */
81 if (PageUnevictable(page))
82 count_vm_events(UNEVICTABLE_PGSTRANDED, nr_pages);
83 }
84 }
85
86 /*
87 * Mark page as mlocked if not already.
88 * If page on LRU, isolate and putback to move to unevictable list.
89 */
mlock_vma_page(struct page * page)90 void mlock_vma_page(struct page *page)
91 {
92 /* Serialize with page migration */
93 BUG_ON(!PageLocked(page));
94
95 VM_BUG_ON_PAGE(PageTail(page), page);
96 VM_BUG_ON_PAGE(PageCompound(page) && PageDoubleMap(page), page);
97
98 if (!TestSetPageMlocked(page)) {
99 int nr_pages = thp_nr_pages(page);
100
101 mod_zone_page_state(page_zone(page), NR_MLOCK, nr_pages);
102 count_vm_events(UNEVICTABLE_PGMLOCKED, nr_pages);
103 if (!isolate_lru_page(page))
104 putback_lru_page(page);
105 }
106 }
107
108 /*
109 * Isolate a page from LRU with optional get_page() pin.
110 * Assumes lru_lock already held and page already pinned.
111 */
__munlock_isolate_lru_page(struct page * page,bool getpage)112 static bool __munlock_isolate_lru_page(struct page *page, bool getpage)
113 {
114 if (PageLRU(page)) {
115 struct lruvec *lruvec;
116
117 lruvec = mem_cgroup_page_lruvec(page, page_pgdat(page));
118 if (getpage)
119 get_page(page);
120 ClearPageLRU(page);
121 del_page_from_lru_list(page, lruvec, page_lru(page));
122 return true;
123 }
124
125 return false;
126 }
127
128 /*
129 * Finish munlock after successful page isolation
130 *
131 * Page must be locked. This is a wrapper for try_to_munlock()
132 * and putback_lru_page() with munlock accounting.
133 */
__munlock_isolated_page(struct page * page)134 static void __munlock_isolated_page(struct page *page)
135 {
136 /*
137 * Optimization: if the page was mapped just once, that's our mapping
138 * and we don't need to check all the other vmas.
139 */
140 if (page_mapcount(page) > 1)
141 try_to_munlock(page);
142
143 /* Did try_to_unlock() succeed or punt? */
144 if (!PageMlocked(page))
145 count_vm_events(UNEVICTABLE_PGMUNLOCKED, thp_nr_pages(page));
146
147 putback_lru_page(page);
148 }
149
150 /*
151 * Accounting for page isolation fail during munlock
152 *
153 * Performs accounting when page isolation fails in munlock. There is nothing
154 * else to do because it means some other task has already removed the page
155 * from the LRU. putback_lru_page() will take care of removing the page from
156 * the unevictable list, if necessary. vmscan [page_referenced()] will move
157 * the page back to the unevictable list if some other vma has it mlocked.
158 */
__munlock_isolation_failed(struct page * page)159 static void __munlock_isolation_failed(struct page *page)
160 {
161 int nr_pages = thp_nr_pages(page);
162
163 if (PageUnevictable(page))
164 __count_vm_events(UNEVICTABLE_PGSTRANDED, nr_pages);
165 else
166 __count_vm_events(UNEVICTABLE_PGMUNLOCKED, nr_pages);
167 }
168
169 /**
170 * munlock_vma_page - munlock a vma page
171 * @page: page to be unlocked, either a normal page or THP page head
172 *
173 * returns the size of the page as a page mask (0 for normal page,
174 * HPAGE_PMD_NR - 1 for THP head page)
175 *
176 * called from munlock()/munmap() path with page supposedly on the LRU.
177 * When we munlock a page, because the vma where we found the page is being
178 * munlock()ed or munmap()ed, we want to check whether other vmas hold the
179 * page locked so that we can leave it on the unevictable lru list and not
180 * bother vmscan with it. However, to walk the page's rmap list in
181 * try_to_munlock() we must isolate the page from the LRU. If some other
182 * task has removed the page from the LRU, we won't be able to do that.
183 * So we clear the PageMlocked as we might not get another chance. If we
184 * can't isolate the page, we leave it for putback_lru_page() and vmscan
185 * [page_referenced()/try_to_unmap()] to deal with.
186 */
munlock_vma_page(struct page * page)187 unsigned int munlock_vma_page(struct page *page)
188 {
189 int nr_pages;
190 pg_data_t *pgdat = page_pgdat(page);
191
192 /* For try_to_munlock() and to serialize with page migration */
193 BUG_ON(!PageLocked(page));
194
195 VM_BUG_ON_PAGE(PageTail(page), page);
196
197 /*
198 * Serialize with any parallel __split_huge_page_refcount() which
199 * might otherwise copy PageMlocked to part of the tail pages before
200 * we clear it in the head page. It also stabilizes thp_nr_pages().
201 */
202 spin_lock_irq(&pgdat->lru_lock);
203
204 if (!TestClearPageMlocked(page)) {
205 /* Potentially, PTE-mapped THP: do not skip the rest PTEs */
206 nr_pages = 1;
207 goto unlock_out;
208 }
209
210 nr_pages = thp_nr_pages(page);
211 __mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages);
212
213 if (__munlock_isolate_lru_page(page, true)) {
214 spin_unlock_irq(&pgdat->lru_lock);
215 __munlock_isolated_page(page);
216 goto out;
217 }
218 __munlock_isolation_failed(page);
219
220 unlock_out:
221 spin_unlock_irq(&pgdat->lru_lock);
222
223 out:
224 return nr_pages - 1;
225 }
226
227 /*
228 * convert get_user_pages() return value to posix mlock() error
229 */
__mlock_posix_error_return(long retval)230 static int __mlock_posix_error_return(long retval)
231 {
232 if (retval == -EFAULT)
233 retval = -ENOMEM;
234 else if (retval == -ENOMEM)
235 retval = -EAGAIN;
236 return retval;
237 }
238
239 /*
240 * Prepare page for fast batched LRU putback via putback_lru_evictable_pagevec()
241 *
242 * The fast path is available only for evictable pages with single mapping.
243 * Then we can bypass the per-cpu pvec and get better performance.
244 * when mapcount > 1 we need try_to_munlock() which can fail.
245 * when !page_evictable(), we need the full redo logic of putback_lru_page to
246 * avoid leaving evictable page in unevictable list.
247 *
248 * In case of success, @page is added to @pvec and @pgrescued is incremented
249 * in case that the page was previously unevictable. @page is also unlocked.
250 */
__putback_lru_fast_prepare(struct page * page,struct pagevec * pvec,int * pgrescued)251 static bool __putback_lru_fast_prepare(struct page *page, struct pagevec *pvec,
252 int *pgrescued)
253 {
254 VM_BUG_ON_PAGE(PageLRU(page), page);
255 VM_BUG_ON_PAGE(!PageLocked(page), page);
256
257 if (page_mapcount(page) <= 1 && page_evictable(page)) {
258 pagevec_add(pvec, page);
259 if (TestClearPageUnevictable(page))
260 (*pgrescued)++;
261 unlock_page(page);
262 return true;
263 }
264
265 return false;
266 }
267
268 /*
269 * Putback multiple evictable pages to the LRU
270 *
271 * Batched putback of evictable pages that bypasses the per-cpu pvec. Some of
272 * the pages might have meanwhile become unevictable but that is OK.
273 */
__putback_lru_fast(struct pagevec * pvec,int pgrescued)274 static void __putback_lru_fast(struct pagevec *pvec, int pgrescued)
275 {
276 count_vm_events(UNEVICTABLE_PGMUNLOCKED, pagevec_count(pvec));
277 /*
278 *__pagevec_lru_add() calls release_pages() so we don't call
279 * put_page() explicitly
280 */
281 __pagevec_lru_add(pvec);
282 count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
283 }
284
285 /*
286 * Munlock a batch of pages from the same zone
287 *
288 * The work is split to two main phases. First phase clears the Mlocked flag
289 * and attempts to isolate the pages, all under a single zone lru lock.
290 * The second phase finishes the munlock only for pages where isolation
291 * succeeded.
292 *
293 * Note that the pagevec may be modified during the process.
294 */
__munlock_pagevec(struct pagevec * pvec,struct zone * zone)295 static void __munlock_pagevec(struct pagevec *pvec, struct zone *zone)
296 {
297 int i;
298 int nr = pagevec_count(pvec);
299 int delta_munlocked = -nr;
300 struct pagevec pvec_putback;
301 int pgrescued = 0;
302
303 pagevec_init(&pvec_putback);
304
305 /* Phase 1: page isolation */
306 spin_lock_irq(&zone->zone_pgdat->lru_lock);
307 for (i = 0; i < nr; i++) {
308 struct page *page = pvec->pages[i];
309
310 if (TestClearPageMlocked(page)) {
311 /*
312 * We already have pin from follow_page_mask()
313 * so we can spare the get_page() here.
314 */
315 if (__munlock_isolate_lru_page(page, false))
316 continue;
317 else
318 __munlock_isolation_failed(page);
319 } else {
320 delta_munlocked++;
321 }
322
323 /*
324 * We won't be munlocking this page in the next phase
325 * but we still need to release the follow_page_mask()
326 * pin. We cannot do it under lru_lock however. If it's
327 * the last pin, __page_cache_release() would deadlock.
328 */
329 pagevec_add(&pvec_putback, pvec->pages[i]);
330 pvec->pages[i] = NULL;
331 }
332 __mod_zone_page_state(zone, NR_MLOCK, delta_munlocked);
333 spin_unlock_irq(&zone->zone_pgdat->lru_lock);
334
335 /* Now we can release pins of pages that we are not munlocking */
336 pagevec_release(&pvec_putback);
337
338 /* Phase 2: page munlock */
339 for (i = 0; i < nr; i++) {
340 struct page *page = pvec->pages[i];
341
342 if (page) {
343 lock_page(page);
344 if (!__putback_lru_fast_prepare(page, &pvec_putback,
345 &pgrescued)) {
346 /*
347 * Slow path. We don't want to lose the last
348 * pin before unlock_page()
349 */
350 get_page(page); /* for putback_lru_page() */
351 __munlock_isolated_page(page);
352 unlock_page(page);
353 put_page(page); /* from follow_page_mask() */
354 }
355 }
356 }
357
358 /*
359 * Phase 3: page putback for pages that qualified for the fast path
360 * This will also call put_page() to return pin from follow_page_mask()
361 */
362 if (pagevec_count(&pvec_putback))
363 __putback_lru_fast(&pvec_putback, pgrescued);
364 }
365
366 /*
367 * Fill up pagevec for __munlock_pagevec using pte walk
368 *
369 * The function expects that the struct page corresponding to @start address is
370 * a non-TPH page already pinned and in the @pvec, and that it belongs to @zone.
371 *
372 * The rest of @pvec is filled by subsequent pages within the same pmd and same
373 * zone, as long as the pte's are present and vm_normal_page() succeeds. These
374 * pages also get pinned.
375 *
376 * Returns the address of the next page that should be scanned. This equals
377 * @start + PAGE_SIZE when no page could be added by the pte walk.
378 */
__munlock_pagevec_fill(struct pagevec * pvec,struct vm_area_struct * vma,struct zone * zone,unsigned long start,unsigned long end)379 static unsigned long __munlock_pagevec_fill(struct pagevec *pvec,
380 struct vm_area_struct *vma, struct zone *zone,
381 unsigned long start, unsigned long end)
382 {
383 pte_t *pte;
384 spinlock_t *ptl;
385
386 /*
387 * Initialize pte walk starting at the already pinned page where we
388 * are sure that there is a pte, as it was pinned under the same
389 * mmap_lock write op.
390 */
391 pte = get_locked_pte(vma->vm_mm, start, &ptl);
392 /* Make sure we do not cross the page table boundary */
393 end = pgd_addr_end(start, end);
394 end = p4d_addr_end(start, end);
395 end = pud_addr_end(start, end);
396 end = pmd_addr_end(start, end);
397
398 /* The page next to the pinned page is the first we will try to get */
399 start += PAGE_SIZE;
400 while (start < end) {
401 struct page *page = NULL;
402 pte++;
403 if (pte_present(*pte))
404 page = vm_normal_page(vma, start, *pte);
405 /*
406 * Break if page could not be obtained or the page's node+zone does not
407 * match
408 */
409 if (!page || page_zone(page) != zone)
410 break;
411
412 /*
413 * Do not use pagevec for PTE-mapped THP,
414 * munlock_vma_pages_range() will handle them.
415 */
416 if (PageTransCompound(page))
417 break;
418
419 get_page(page);
420 /*
421 * Increase the address that will be returned *before* the
422 * eventual break due to pvec becoming full by adding the page
423 */
424 start += PAGE_SIZE;
425 if (pagevec_add(pvec, page) == 0)
426 break;
427 }
428 pte_unmap_unlock(pte, ptl);
429 return start;
430 }
431
432 /*
433 * munlock_vma_pages_range() - munlock all pages in the vma range.'
434 * @vma - vma containing range to be munlock()ed.
435 * @start - start address in @vma of the range
436 * @end - end of range in @vma.
437 *
438 * For mremap(), munmap() and exit().
439 *
440 * Called with @vma VM_LOCKED.
441 *
442 * Returns with VM_LOCKED cleared. Callers must be prepared to
443 * deal with this.
444 *
445 * We don't save and restore VM_LOCKED here because pages are
446 * still on lru. In unmap path, pages might be scanned by reclaim
447 * and re-mlocked by try_to_{munlock|unmap} before we unmap and
448 * free them. This will result in freeing mlocked pages.
449 */
munlock_vma_pages_range(struct vm_area_struct * vma,unsigned long start,unsigned long end)450 void munlock_vma_pages_range(struct vm_area_struct *vma,
451 unsigned long start, unsigned long end)
452 {
453 vma->vm_flags &= VM_LOCKED_CLEAR_MASK;
454
455 while (start < end) {
456 struct page *page;
457 unsigned int page_mask = 0;
458 unsigned long page_increm;
459 struct pagevec pvec;
460 struct zone *zone;
461
462 pagevec_init(&pvec);
463 /*
464 * Although FOLL_DUMP is intended for get_dump_page(),
465 * it just so happens that its special treatment of the
466 * ZERO_PAGE (returning an error instead of doing get_page)
467 * suits munlock very well (and if somehow an abnormal page
468 * has sneaked into the range, we won't oops here: great).
469 */
470 page = follow_page(vma, start, FOLL_GET | FOLL_DUMP);
471
472 if (page && !IS_ERR(page)) {
473 if (PageTransTail(page)) {
474 VM_BUG_ON_PAGE(PageMlocked(page), page);
475 put_page(page); /* follow_page_mask() */
476 } else if (PageTransHuge(page)) {
477 lock_page(page);
478 /*
479 * Any THP page found by follow_page_mask() may
480 * have gotten split before reaching
481 * munlock_vma_page(), so we need to compute
482 * the page_mask here instead.
483 */
484 page_mask = munlock_vma_page(page);
485 unlock_page(page);
486 put_page(page); /* follow_page_mask() */
487 } else {
488 /*
489 * Non-huge pages are handled in batches via
490 * pagevec. The pin from follow_page_mask()
491 * prevents them from collapsing by THP.
492 */
493 pagevec_add(&pvec, page);
494 zone = page_zone(page);
495
496 /*
497 * Try to fill the rest of pagevec using fast
498 * pte walk. This will also update start to
499 * the next page to process. Then munlock the
500 * pagevec.
501 */
502 start = __munlock_pagevec_fill(&pvec, vma,
503 zone, start, end);
504 __munlock_pagevec(&pvec, zone);
505 goto next;
506 }
507 }
508 page_increm = 1 + page_mask;
509 start += page_increm * PAGE_SIZE;
510 next:
511 cond_resched();
512 }
513 }
514
515 /*
516 * mlock_fixup - handle mlock[all]/munlock[all] requests.
517 *
518 * Filters out "special" vmas -- VM_LOCKED never gets set for these, and
519 * munlock is a no-op. However, for some special vmas, we go ahead and
520 * populate the ptes.
521 *
522 * For vmas that pass the filters, merge/split as appropriate.
523 */
mlock_fixup(struct vm_area_struct * vma,struct vm_area_struct ** prev,unsigned long start,unsigned long end,vm_flags_t newflags)524 static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
525 unsigned long start, unsigned long end, vm_flags_t newflags)
526 {
527 struct mm_struct *mm = vma->vm_mm;
528 pgoff_t pgoff;
529 int nr_pages;
530 int ret = 0;
531 int lock = !!(newflags & VM_LOCKED);
532 vm_flags_t old_flags = vma->vm_flags;
533
534 if (newflags == vma->vm_flags || (vma->vm_flags & VM_SPECIAL) ||
535 is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm) ||
536 vma_is_dax(vma))
537 /* don't set VM_LOCKED or VM_LOCKONFAULT and don't count */
538 goto out;
539
540 pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
541 *prev = vma_merge(mm, *prev, start, end, newflags, vma->anon_vma,
542 vma->vm_file, pgoff, vma_policy(vma),
543 vma->vm_userfaultfd_ctx);
544 if (*prev) {
545 vma = *prev;
546 goto success;
547 }
548
549 if (start != vma->vm_start) {
550 ret = split_vma(mm, vma, start, 1);
551 if (ret)
552 goto out;
553 }
554
555 if (end != vma->vm_end) {
556 ret = split_vma(mm, vma, end, 0);
557 if (ret)
558 goto out;
559 }
560
561 success:
562 /*
563 * Keep track of amount of locked VM.
564 */
565 nr_pages = (end - start) >> PAGE_SHIFT;
566 if (!lock)
567 nr_pages = -nr_pages;
568 else if (old_flags & VM_LOCKED)
569 nr_pages = 0;
570 mm->locked_vm += nr_pages;
571
572 /*
573 * vm_flags is protected by the mmap_lock held in write mode.
574 * It's okay if try_to_unmap_one unmaps a page just after we
575 * set VM_LOCKED, populate_vma_page_range will bring it back.
576 */
577
578 if (lock)
579 vma->vm_flags = newflags;
580 else
581 munlock_vma_pages_range(vma, start, end);
582
583 out:
584 *prev = vma;
585 return ret;
586 }
587
apply_vma_lock_flags(unsigned long start,size_t len,vm_flags_t flags)588 static int apply_vma_lock_flags(unsigned long start, size_t len,
589 vm_flags_t flags)
590 {
591 unsigned long nstart, end, tmp;
592 struct vm_area_struct * vma, * prev;
593 int error;
594
595 VM_BUG_ON(offset_in_page(start));
596 VM_BUG_ON(len != PAGE_ALIGN(len));
597 end = start + len;
598 if (end < start)
599 return -EINVAL;
600 if (end == start)
601 return 0;
602 vma = find_vma(current->mm, start);
603 if (!vma || vma->vm_start > start)
604 return -ENOMEM;
605
606 prev = vma->vm_prev;
607 if (start > vma->vm_start)
608 prev = vma;
609
610 for (nstart = start ; ; ) {
611 vm_flags_t newflags = vma->vm_flags & VM_LOCKED_CLEAR_MASK;
612
613 newflags |= flags;
614
615 /* Here we know that vma->vm_start <= nstart < vma->vm_end. */
616 tmp = vma->vm_end;
617 if (tmp > end)
618 tmp = end;
619 error = mlock_fixup(vma, &prev, nstart, tmp, newflags);
620 if (error)
621 break;
622 nstart = tmp;
623 if (nstart < prev->vm_end)
624 nstart = prev->vm_end;
625 if (nstart >= end)
626 break;
627
628 vma = prev->vm_next;
629 if (!vma || vma->vm_start != nstart) {
630 error = -ENOMEM;
631 break;
632 }
633 }
634 return error;
635 }
636
637 /*
638 * Go through vma areas and sum size of mlocked
639 * vma pages, as return value.
640 * Note deferred memory locking case(mlock2(,,MLOCK_ONFAULT)
641 * is also counted.
642 * Return value: previously mlocked page counts
643 */
count_mm_mlocked_page_nr(struct mm_struct * mm,unsigned long start,size_t len)644 static unsigned long count_mm_mlocked_page_nr(struct mm_struct *mm,
645 unsigned long start, size_t len)
646 {
647 struct vm_area_struct *vma;
648 unsigned long count = 0;
649
650 if (mm == NULL)
651 mm = current->mm;
652
653 vma = find_vma(mm, start);
654 if (vma == NULL)
655 vma = mm->mmap;
656
657 for (; vma ; vma = vma->vm_next) {
658 if (start >= vma->vm_end)
659 continue;
660 if (start + len <= vma->vm_start)
661 break;
662 if (vma->vm_flags & VM_LOCKED) {
663 if (start > vma->vm_start)
664 count -= (start - vma->vm_start);
665 if (start + len < vma->vm_end) {
666 count += start + len - vma->vm_start;
667 break;
668 }
669 count += vma->vm_end - vma->vm_start;
670 }
671 }
672
673 return count >> PAGE_SHIFT;
674 }
675
do_mlock(unsigned long start,size_t len,vm_flags_t flags)676 static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t flags)
677 {
678 unsigned long locked;
679 unsigned long lock_limit;
680 int error = -ENOMEM;
681
682 start = untagged_addr(start);
683
684 if (!can_do_mlock())
685 return -EPERM;
686
687 len = PAGE_ALIGN(len + (offset_in_page(start)));
688 start &= PAGE_MASK;
689
690 lock_limit = rlimit(RLIMIT_MEMLOCK);
691 lock_limit >>= PAGE_SHIFT;
692 locked = len >> PAGE_SHIFT;
693
694 if (mmap_write_lock_killable(current->mm))
695 return -EINTR;
696
697 locked += current->mm->locked_vm;
698 if ((locked > lock_limit) && (!capable(CAP_IPC_LOCK))) {
699 /*
700 * It is possible that the regions requested intersect with
701 * previously mlocked areas, that part area in "mm->locked_vm"
702 * should not be counted to new mlock increment count. So check
703 * and adjust locked count if necessary.
704 */
705 locked -= count_mm_mlocked_page_nr(current->mm,
706 start, len);
707 }
708
709 /* check against resource limits */
710 if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
711 error = apply_vma_lock_flags(start, len, flags);
712
713 mmap_write_unlock(current->mm);
714 if (error)
715 return error;
716
717 error = __mm_populate(start, len, 0);
718 if (error)
719 return __mlock_posix_error_return(error);
720 return 0;
721 }
722
SYSCALL_DEFINE2(mlock,unsigned long,start,size_t,len)723 SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
724 {
725 return do_mlock(start, len, VM_LOCKED);
726 }
727
SYSCALL_DEFINE3(mlock2,unsigned long,start,size_t,len,int,flags)728 SYSCALL_DEFINE3(mlock2, unsigned long, start, size_t, len, int, flags)
729 {
730 vm_flags_t vm_flags = VM_LOCKED;
731
732 if (flags & ~MLOCK_ONFAULT)
733 return -EINVAL;
734
735 if (flags & MLOCK_ONFAULT)
736 vm_flags |= VM_LOCKONFAULT;
737
738 return do_mlock(start, len, vm_flags);
739 }
740
SYSCALL_DEFINE2(munlock,unsigned long,start,size_t,len)741 SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
742 {
743 int ret;
744
745 start = untagged_addr(start);
746
747 len = PAGE_ALIGN(len + (offset_in_page(start)));
748 start &= PAGE_MASK;
749
750 if (mmap_write_lock_killable(current->mm))
751 return -EINTR;
752 ret = apply_vma_lock_flags(start, len, 0);
753 mmap_write_unlock(current->mm);
754
755 return ret;
756 }
757
758 /*
759 * Take the MCL_* flags passed into mlockall (or 0 if called from munlockall)
760 * and translate into the appropriate modifications to mm->def_flags and/or the
761 * flags for all current VMAs.
762 *
763 * There are a couple of subtleties with this. If mlockall() is called multiple
764 * times with different flags, the values do not necessarily stack. If mlockall
765 * is called once including the MCL_FUTURE flag and then a second time without
766 * it, VM_LOCKED and VM_LOCKONFAULT will be cleared from mm->def_flags.
767 */
apply_mlockall_flags(int flags)768 static int apply_mlockall_flags(int flags)
769 {
770 struct vm_area_struct * vma, * prev = NULL;
771 vm_flags_t to_add = 0;
772
773 current->mm->def_flags &= VM_LOCKED_CLEAR_MASK;
774 if (flags & MCL_FUTURE) {
775 current->mm->def_flags |= VM_LOCKED;
776
777 if (flags & MCL_ONFAULT)
778 current->mm->def_flags |= VM_LOCKONFAULT;
779
780 if (!(flags & MCL_CURRENT))
781 goto out;
782 }
783
784 if (flags & MCL_CURRENT) {
785 to_add |= VM_LOCKED;
786 if (flags & MCL_ONFAULT)
787 to_add |= VM_LOCKONFAULT;
788 }
789
790 for (vma = current->mm->mmap; vma ; vma = prev->vm_next) {
791 vm_flags_t newflags;
792
793 newflags = vma->vm_flags & VM_LOCKED_CLEAR_MASK;
794 newflags |= to_add;
795
796 /* Ignore errors */
797 mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
798 cond_resched();
799 }
800 out:
801 return 0;
802 }
803
SYSCALL_DEFINE1(mlockall,int,flags)804 SYSCALL_DEFINE1(mlockall, int, flags)
805 {
806 unsigned long lock_limit;
807 int ret;
808
809 if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE | MCL_ONFAULT)) ||
810 flags == MCL_ONFAULT)
811 return -EINVAL;
812
813 if (!can_do_mlock())
814 return -EPERM;
815
816 lock_limit = rlimit(RLIMIT_MEMLOCK);
817 lock_limit >>= PAGE_SHIFT;
818
819 if (mmap_write_lock_killable(current->mm))
820 return -EINTR;
821
822 ret = -ENOMEM;
823 if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
824 capable(CAP_IPC_LOCK))
825 ret = apply_mlockall_flags(flags);
826 mmap_write_unlock(current->mm);
827 if (!ret && (flags & MCL_CURRENT))
828 mm_populate(0, TASK_SIZE);
829
830 return ret;
831 }
832
SYSCALL_DEFINE0(munlockall)833 SYSCALL_DEFINE0(munlockall)
834 {
835 int ret;
836
837 if (mmap_write_lock_killable(current->mm))
838 return -EINTR;
839 ret = apply_mlockall_flags(0);
840 mmap_write_unlock(current->mm);
841 return ret;
842 }
843
844 /*
845 * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB
846 * shm segments) get accounted against the user_struct instead.
847 */
848 static DEFINE_SPINLOCK(shmlock_user_lock);
849
user_shm_lock(size_t size,struct user_struct * user)850 int user_shm_lock(size_t size, struct user_struct *user)
851 {
852 unsigned long lock_limit, locked;
853 int allowed = 0;
854
855 locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
856 lock_limit = rlimit(RLIMIT_MEMLOCK);
857 if (lock_limit == RLIM_INFINITY)
858 allowed = 1;
859 lock_limit >>= PAGE_SHIFT;
860 spin_lock(&shmlock_user_lock);
861 if (!allowed &&
862 locked + user->locked_shm > lock_limit && !capable(CAP_IPC_LOCK))
863 goto out;
864 get_uid(user);
865 user->locked_shm += locked;
866 allowed = 1;
867 out:
868 spin_unlock(&shmlock_user_lock);
869 return allowed;
870 }
871
user_shm_unlock(size_t size,struct user_struct * user)872 void user_shm_unlock(size_t size, struct user_struct *user)
873 {
874 spin_lock(&shmlock_user_lock);
875 user->locked_shm -= (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
876 spin_unlock(&shmlock_user_lock);
877 free_uid(user);
878 }
879
