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