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13#include <linux/list.h>
14#include <linux/hashtable.h>
15#include <linux/sched/signal.h>
16#include <linux/sched/mm.h>
17#include <linux/mm.h>
18#include <linux/poll.h>
19#include <linux/slab.h>
20#include <linux/seq_file.h>
21#include <linux/file.h>
22#include <linux/bug.h>
23#include <linux/anon_inodes.h>
24#include <linux/syscalls.h>
25#include <linux/userfaultfd_k.h>
26#include <linux/mempolicy.h>
27#include <linux/ioctl.h>
28#include <linux/security.h>
29#include <linux/hugetlb.h>
30
31int sysctl_unprivileged_userfaultfd __read_mostly;
32
33static struct kmem_cache *userfaultfd_ctx_cachep __read_mostly;
34
35enum userfaultfd_state {
36 UFFD_STATE_WAIT_API,
37 UFFD_STATE_RUNNING,
38};
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54struct userfaultfd_ctx {
55
56 wait_queue_head_t fault_pending_wqh;
57
58 wait_queue_head_t fault_wqh;
59
60 wait_queue_head_t fd_wqh;
61
62 wait_queue_head_t event_wqh;
63
64 seqcount_spinlock_t refile_seq;
65
66 refcount_t refcount;
67
68 unsigned int flags;
69
70 unsigned int features;
71
72 enum userfaultfd_state state;
73
74 bool released;
75
76 bool mmap_changing;
77
78 struct mm_struct *mm;
79};
80
81struct userfaultfd_fork_ctx {
82 struct userfaultfd_ctx *orig;
83 struct userfaultfd_ctx *new;
84 struct list_head list;
85};
86
87struct userfaultfd_unmap_ctx {
88 struct userfaultfd_ctx *ctx;
89 unsigned long start;
90 unsigned long end;
91 struct list_head list;
92};
93
94struct userfaultfd_wait_queue {
95 struct uffd_msg msg;
96 wait_queue_entry_t wq;
97 struct userfaultfd_ctx *ctx;
98 bool waken;
99};
100
101struct userfaultfd_wake_range {
102 unsigned long start;
103 unsigned long len;
104};
105
106static int userfaultfd_wake_function(wait_queue_entry_t *wq, unsigned mode,
107 int wake_flags, void *key)
108{
109 struct userfaultfd_wake_range *range = key;
110 int ret;
111 struct userfaultfd_wait_queue *uwq;
112 unsigned long start, len;
113
114 uwq = container_of(wq, struct userfaultfd_wait_queue, wq);
115 ret = 0;
116
117 start = range->start;
118 len = range->len;
119 if (len && (start > uwq->msg.arg.pagefault.address ||
120 start + len <= uwq->msg.arg.pagefault.address))
121 goto out;
122 WRITE_ONCE(uwq->waken, true);
123
124
125
126
127 ret = wake_up_state(wq->private, mode);
128 if (ret) {
129
130
131
132
133
134
135
136
137
138
139
140 list_del_init(&wq->entry);
141 }
142out:
143 return ret;
144}
145
146
147
148
149
150
151static void userfaultfd_ctx_get(struct userfaultfd_ctx *ctx)
152{
153 refcount_inc(&ctx->refcount);
154}
155
156
157
158
159
160
161
162
163
164static void userfaultfd_ctx_put(struct userfaultfd_ctx *ctx)
165{
166 if (refcount_dec_and_test(&ctx->refcount)) {
167 VM_BUG_ON(spin_is_locked(&ctx->fault_pending_wqh.lock));
168 VM_BUG_ON(waitqueue_active(&ctx->fault_pending_wqh));
169 VM_BUG_ON(spin_is_locked(&ctx->fault_wqh.lock));
170 VM_BUG_ON(waitqueue_active(&ctx->fault_wqh));
171 VM_BUG_ON(spin_is_locked(&ctx->event_wqh.lock));
172 VM_BUG_ON(waitqueue_active(&ctx->event_wqh));
173 VM_BUG_ON(spin_is_locked(&ctx->fd_wqh.lock));
174 VM_BUG_ON(waitqueue_active(&ctx->fd_wqh));
175 mmdrop(ctx->mm);
176 kmem_cache_free(userfaultfd_ctx_cachep, ctx);
177 }
178}
179
180static inline void msg_init(struct uffd_msg *msg)
181{
182 BUILD_BUG_ON(sizeof(struct uffd_msg) != 32);
183
184
185
186
187 memset(msg, 0, sizeof(struct uffd_msg));
188}
189
190static inline struct uffd_msg userfault_msg(unsigned long address,
191 unsigned int flags,
192 unsigned long reason,
193 unsigned int features)
194{
195 struct uffd_msg msg;
196 msg_init(&msg);
197 msg.event = UFFD_EVENT_PAGEFAULT;
198 msg.arg.pagefault.address = address;
199 if (flags & FAULT_FLAG_WRITE)
200
201
202
203
204
205
206
207 msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WRITE;
208 if (reason & VM_UFFD_WP)
209
210
211
212
213
214
215
216 msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WP;
217 if (features & UFFD_FEATURE_THREAD_ID)
218 msg.arg.pagefault.feat.ptid = task_pid_vnr(current);
219 return msg;
220}
221
222#ifdef CONFIG_HUGETLB_PAGE
223
224
225
226
227static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx,
228 struct vm_area_struct *vma,
229 unsigned long address,
230 unsigned long flags,
231 unsigned long reason)
232{
233 struct mm_struct *mm = ctx->mm;
234 pte_t *ptep, pte;
235 bool ret = true;
236
237 mmap_assert_locked(mm);
238
239 ptep = huge_pte_offset(mm, address, vma_mmu_pagesize(vma));
240
241 if (!ptep)
242 goto out;
243
244 ret = false;
245 pte = huge_ptep_get(ptep);
246
247
248
249
250
251 if (huge_pte_none(pte))
252 ret = true;
253 if (!huge_pte_write(pte) && (reason & VM_UFFD_WP))
254 ret = true;
255out:
256 return ret;
257}
258#else
259static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx,
260 struct vm_area_struct *vma,
261 unsigned long address,
262 unsigned long flags,
263 unsigned long reason)
264{
265 return false;
266}
267#endif
268
269
270
271
272
273
274
275
276static inline bool userfaultfd_must_wait(struct userfaultfd_ctx *ctx,
277 unsigned long address,
278 unsigned long flags,
279 unsigned long reason)
280{
281 struct mm_struct *mm = ctx->mm;
282 pgd_t *pgd;
283 p4d_t *p4d;
284 pud_t *pud;
285 pmd_t *pmd, _pmd;
286 pte_t *pte;
287 bool ret = true;
288
289 mmap_assert_locked(mm);
290
291 pgd = pgd_offset(mm, address);
292 if (!pgd_present(*pgd))
293 goto out;
294 p4d = p4d_offset(pgd, address);
295 if (!p4d_present(*p4d))
296 goto out;
297 pud = pud_offset(p4d, address);
298 if (!pud_present(*pud))
299 goto out;
300 pmd = pmd_offset(pud, address);
301
302
303
304
305
306
307
308
309 _pmd = READ_ONCE(*pmd);
310 if (pmd_none(_pmd))
311 goto out;
312
313 ret = false;
314 if (!pmd_present(_pmd))
315 goto out;
316
317 if (pmd_trans_huge(_pmd)) {
318 if (!pmd_write(_pmd) && (reason & VM_UFFD_WP))
319 ret = true;
320 goto out;
321 }
322
323
324
325
326
327 pte = pte_offset_map(pmd, address);
328
329
330
331
332 if (pte_none(*pte))
333 ret = true;
334 if (!pte_write(*pte) && (reason & VM_UFFD_WP))
335 ret = true;
336 pte_unmap(pte);
337
338out:
339 return ret;
340}
341
342static inline long userfaultfd_get_blocking_state(unsigned int flags)
343{
344 if (flags & FAULT_FLAG_INTERRUPTIBLE)
345 return TASK_INTERRUPTIBLE;
346
347 if (flags & FAULT_FLAG_KILLABLE)
348 return TASK_KILLABLE;
349
350 return TASK_UNINTERRUPTIBLE;
351}
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason)
369{
370 struct mm_struct *mm = vmf->vma->vm_mm;
371 struct userfaultfd_ctx *ctx;
372 struct userfaultfd_wait_queue uwq;
373 vm_fault_t ret = VM_FAULT_SIGBUS;
374 bool must_wait;
375 long blocking_state;
376
377
378
379
380
381
382
383
384
385
386
387
388 if (current->flags & (PF_EXITING|PF_DUMPCORE))
389 goto out;
390
391
392
393
394
395 mmap_assert_locked(mm);
396
397 ctx = vmf->vma->vm_userfaultfd_ctx.ctx;
398 if (!ctx)
399 goto out;
400
401 BUG_ON(ctx->mm != mm);
402
403 VM_BUG_ON(reason & ~(VM_UFFD_MISSING|VM_UFFD_WP));
404 VM_BUG_ON(!(reason & VM_UFFD_MISSING) ^ !!(reason & VM_UFFD_WP));
405
406 if (ctx->features & UFFD_FEATURE_SIGBUS)
407 goto out;
408 if ((vmf->flags & FAULT_FLAG_USER) == 0 &&
409 ctx->flags & UFFD_USER_MODE_ONLY) {
410 printk_once(KERN_WARNING "uffd: Set unprivileged_userfaultfd "
411 "sysctl knob to 1 if kernel faults must be handled "
412 "without obtaining CAP_SYS_PTRACE capability\n");
413 goto out;
414 }
415
416
417
418
419
420
421 if (unlikely(READ_ONCE(ctx->released))) {
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438 ret = VM_FAULT_NOPAGE;
439 goto out;
440 }
441
442
443
444
445
446
447
448
449
450
451
452 if (unlikely(!(vmf->flags & FAULT_FLAG_ALLOW_RETRY))) {
453
454
455
456
457
458 BUG_ON(vmf->flags & FAULT_FLAG_RETRY_NOWAIT);
459#ifdef CONFIG_DEBUG_VM
460 if (printk_ratelimit()) {
461 printk(KERN_WARNING
462 "FAULT_FLAG_ALLOW_RETRY missing %x\n",
463 vmf->flags);
464 dump_stack();
465 }
466#endif
467 goto out;
468 }
469
470
471
472
473
474 ret = VM_FAULT_RETRY;
475 if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT)
476 goto out;
477
478
479 userfaultfd_ctx_get(ctx);
480
481 init_waitqueue_func_entry(&uwq.wq, userfaultfd_wake_function);
482 uwq.wq.private = current;
483 uwq.msg = userfault_msg(vmf->address, vmf->flags, reason,
484 ctx->features);
485 uwq.ctx = ctx;
486 uwq.waken = false;
487
488 blocking_state = userfaultfd_get_blocking_state(vmf->flags);
489
490 spin_lock_irq(&ctx->fault_pending_wqh.lock);
491
492
493
494
495 __add_wait_queue(&ctx->fault_pending_wqh, &uwq.wq);
496
497
498
499
500
501 set_current_state(blocking_state);
502 spin_unlock_irq(&ctx->fault_pending_wqh.lock);
503
504 if (!is_vm_hugetlb_page(vmf->vma))
505 must_wait = userfaultfd_must_wait(ctx, vmf->address, vmf->flags,
506 reason);
507 else
508 must_wait = userfaultfd_huge_must_wait(ctx, vmf->vma,
509 vmf->address,
510 vmf->flags, reason);
511 mmap_read_unlock(mm);
512
513 if (likely(must_wait && !READ_ONCE(ctx->released))) {
514 wake_up_poll(&ctx->fd_wqh, EPOLLIN);
515 schedule();
516 }
517
518 __set_current_state(TASK_RUNNING);
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533 if (!list_empty_careful(&uwq.wq.entry)) {
534 spin_lock_irq(&ctx->fault_pending_wqh.lock);
535
536
537
538
539 list_del(&uwq.wq.entry);
540 spin_unlock_irq(&ctx->fault_pending_wqh.lock);
541 }
542
543
544
545
546
547 userfaultfd_ctx_put(ctx);
548
549out:
550 return ret;
551}
552
553static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx,
554 struct userfaultfd_wait_queue *ewq)
555{
556 struct userfaultfd_ctx *release_new_ctx;
557
558 if (WARN_ON_ONCE(current->flags & PF_EXITING))
559 goto out;
560
561 ewq->ctx = ctx;
562 init_waitqueue_entry(&ewq->wq, current);
563 release_new_ctx = NULL;
564
565 spin_lock_irq(&ctx->event_wqh.lock);
566
567
568
569
570 __add_wait_queue(&ctx->event_wqh, &ewq->wq);
571 for (;;) {
572 set_current_state(TASK_KILLABLE);
573 if (ewq->msg.event == 0)
574 break;
575 if (READ_ONCE(ctx->released) ||
576 fatal_signal_pending(current)) {
577
578
579
580
581
582
583 __remove_wait_queue(&ctx->event_wqh, &ewq->wq);
584 if (ewq->msg.event == UFFD_EVENT_FORK) {
585 struct userfaultfd_ctx *new;
586
587 new = (struct userfaultfd_ctx *)
588 (unsigned long)
589 ewq->msg.arg.reserved.reserved1;
590 release_new_ctx = new;
591 }
592 break;
593 }
594
595 spin_unlock_irq(&ctx->event_wqh.lock);
596
597 wake_up_poll(&ctx->fd_wqh, EPOLLIN);
598 schedule();
599
600 spin_lock_irq(&ctx->event_wqh.lock);
601 }
602 __set_current_state(TASK_RUNNING);
603 spin_unlock_irq(&ctx->event_wqh.lock);
604
605 if (release_new_ctx) {
606 struct vm_area_struct *vma;
607 struct mm_struct *mm = release_new_ctx->mm;
608
609
610 mmap_write_lock(mm);
611 for (vma = mm->mmap; vma; vma = vma->vm_next)
612 if (vma->vm_userfaultfd_ctx.ctx == release_new_ctx) {
613 vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
614 vma->vm_flags &= ~(VM_UFFD_WP | VM_UFFD_MISSING);
615 }
616 mmap_write_unlock(mm);
617
618 userfaultfd_ctx_put(release_new_ctx);
619 }
620
621
622
623
624
625out:
626 WRITE_ONCE(ctx->mmap_changing, false);
627 userfaultfd_ctx_put(ctx);
628}
629
630static void userfaultfd_event_complete(struct userfaultfd_ctx *ctx,
631 struct userfaultfd_wait_queue *ewq)
632{
633 ewq->msg.event = 0;
634 wake_up_locked(&ctx->event_wqh);
635 __remove_wait_queue(&ctx->event_wqh, &ewq->wq);
636}
637
638int dup_userfaultfd(struct vm_area_struct *vma, struct list_head *fcs)
639{
640 struct userfaultfd_ctx *ctx = NULL, *octx;
641 struct userfaultfd_fork_ctx *fctx;
642
643 octx = vma->vm_userfaultfd_ctx.ctx;
644 if (!octx || !(octx->features & UFFD_FEATURE_EVENT_FORK)) {
645 vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
646 vma->vm_flags &= ~(VM_UFFD_WP | VM_UFFD_MISSING);
647 return 0;
648 }
649
650 list_for_each_entry(fctx, fcs, list)
651 if (fctx->orig == octx) {
652 ctx = fctx->new;
653 break;
654 }
655
656 if (!ctx) {
657 fctx = kmalloc(sizeof(*fctx), GFP_KERNEL);
658 if (!fctx)
659 return -ENOMEM;
660
661 ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL);
662 if (!ctx) {
663 kfree(fctx);
664 return -ENOMEM;
665 }
666
667 refcount_set(&ctx->refcount, 1);
668 ctx->flags = octx->flags;
669 ctx->state = UFFD_STATE_RUNNING;
670 ctx->features = octx->features;
671 ctx->released = false;
672 ctx->mmap_changing = false;
673 ctx->mm = vma->vm_mm;
674 mmgrab(ctx->mm);
675
676 userfaultfd_ctx_get(octx);
677 WRITE_ONCE(octx->mmap_changing, true);
678 fctx->orig = octx;
679 fctx->new = ctx;
680 list_add_tail(&fctx->list, fcs);
681 }
682
683 vma->vm_userfaultfd_ctx.ctx = ctx;
684 return 0;
685}
686
687static void dup_fctx(struct userfaultfd_fork_ctx *fctx)
688{
689 struct userfaultfd_ctx *ctx = fctx->orig;
690 struct userfaultfd_wait_queue ewq;
691
692 msg_init(&ewq.msg);
693
694 ewq.msg.event = UFFD_EVENT_FORK;
695 ewq.msg.arg.reserved.reserved1 = (unsigned long)fctx->new;
696
697 userfaultfd_event_wait_completion(ctx, &ewq);
698}
699
700void dup_userfaultfd_complete(struct list_head *fcs)
701{
702 struct userfaultfd_fork_ctx *fctx, *n;
703
704 list_for_each_entry_safe(fctx, n, fcs, list) {
705 dup_fctx(fctx);
706 list_del(&fctx->list);
707 kfree(fctx);
708 }
709}
710
711void mremap_userfaultfd_prep(struct vm_area_struct *vma,
712 struct vm_userfaultfd_ctx *vm_ctx)
713{
714 struct userfaultfd_ctx *ctx;
715
716 ctx = vma->vm_userfaultfd_ctx.ctx;
717
718 if (!ctx)
719 return;
720
721 if (ctx->features & UFFD_FEATURE_EVENT_REMAP) {
722 vm_ctx->ctx = ctx;
723 userfaultfd_ctx_get(ctx);
724 WRITE_ONCE(ctx->mmap_changing, true);
725 } else {
726
727 vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
728 vma->vm_flags &= ~(VM_UFFD_WP | VM_UFFD_MISSING);
729 }
730}
731
732void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *vm_ctx,
733 unsigned long from, unsigned long to,
734 unsigned long len)
735{
736 struct userfaultfd_ctx *ctx = vm_ctx->ctx;
737 struct userfaultfd_wait_queue ewq;
738
739 if (!ctx)
740 return;
741
742 if (to & ~PAGE_MASK) {
743 userfaultfd_ctx_put(ctx);
744 return;
745 }
746
747 msg_init(&ewq.msg);
748
749 ewq.msg.event = UFFD_EVENT_REMAP;
750 ewq.msg.arg.remap.from = from;
751 ewq.msg.arg.remap.to = to;
752 ewq.msg.arg.remap.len = len;
753
754 userfaultfd_event_wait_completion(ctx, &ewq);
755}
756
757bool userfaultfd_remove(struct vm_area_struct *vma,
758 unsigned long start, unsigned long end)
759{
760 struct mm_struct *mm = vma->vm_mm;
761 struct userfaultfd_ctx *ctx;
762 struct userfaultfd_wait_queue ewq;
763
764 ctx = vma->vm_userfaultfd_ctx.ctx;
765 if (!ctx || !(ctx->features & UFFD_FEATURE_EVENT_REMOVE))
766 return true;
767
768 userfaultfd_ctx_get(ctx);
769 WRITE_ONCE(ctx->mmap_changing, true);
770 mmap_read_unlock(mm);
771
772 msg_init(&ewq.msg);
773
774 ewq.msg.event = UFFD_EVENT_REMOVE;
775 ewq.msg.arg.remove.start = start;
776 ewq.msg.arg.remove.end = end;
777
778 userfaultfd_event_wait_completion(ctx, &ewq);
779
780 return false;
781}
782
783static bool has_unmap_ctx(struct userfaultfd_ctx *ctx, struct list_head *unmaps,
784 unsigned long start, unsigned long end)
785{
786 struct userfaultfd_unmap_ctx *unmap_ctx;
787
788 list_for_each_entry(unmap_ctx, unmaps, list)
789 if (unmap_ctx->ctx == ctx && unmap_ctx->start == start &&
790 unmap_ctx->end == end)
791 return true;
792
793 return false;
794}
795
796int userfaultfd_unmap_prep(struct vm_area_struct *vma,
797 unsigned long start, unsigned long end,
798 struct list_head *unmaps)
799{
800 for ( ; vma && vma->vm_start < end; vma = vma->vm_next) {
801 struct userfaultfd_unmap_ctx *unmap_ctx;
802 struct userfaultfd_ctx *ctx = vma->vm_userfaultfd_ctx.ctx;
803
804 if (!ctx || !(ctx->features & UFFD_FEATURE_EVENT_UNMAP) ||
805 has_unmap_ctx(ctx, unmaps, start, end))
806 continue;
807
808 unmap_ctx = kzalloc(sizeof(*unmap_ctx), GFP_KERNEL);
809 if (!unmap_ctx)
810 return -ENOMEM;
811
812 userfaultfd_ctx_get(ctx);
813 WRITE_ONCE(ctx->mmap_changing, true);
814 unmap_ctx->ctx = ctx;
815 unmap_ctx->start = start;
816 unmap_ctx->end = end;
817 list_add_tail(&unmap_ctx->list, unmaps);
818 }
819
820 return 0;
821}
822
823void userfaultfd_unmap_complete(struct mm_struct *mm, struct list_head *uf)
824{
825 struct userfaultfd_unmap_ctx *ctx, *n;
826 struct userfaultfd_wait_queue ewq;
827
828 list_for_each_entry_safe(ctx, n, uf, list) {
829 msg_init(&ewq.msg);
830
831 ewq.msg.event = UFFD_EVENT_UNMAP;
832 ewq.msg.arg.remove.start = ctx->start;
833 ewq.msg.arg.remove.end = ctx->end;
834
835 userfaultfd_event_wait_completion(ctx->ctx, &ewq);
836
837 list_del(&ctx->list);
838 kfree(ctx);
839 }
840}
841
842static int userfaultfd_release(struct inode *inode, struct file *file)
843{
844 struct userfaultfd_ctx *ctx = file->private_data;
845 struct mm_struct *mm = ctx->mm;
846 struct vm_area_struct *vma, *prev;
847
848 struct userfaultfd_wake_range range = { .len = 0, };
849 unsigned long new_flags;
850
851 WRITE_ONCE(ctx->released, true);
852
853 if (!mmget_not_zero(mm))
854 goto wakeup;
855
856
857
858
859
860
861
862
863
864 mmap_write_lock(mm);
865 prev = NULL;
866 for (vma = mm->mmap; vma; vma = vma->vm_next) {
867 cond_resched();
868 BUG_ON(!!vma->vm_userfaultfd_ctx.ctx ^
869 !!(vma->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP)));
870 if (vma->vm_userfaultfd_ctx.ctx != ctx) {
871 prev = vma;
872 continue;
873 }
874 new_flags = vma->vm_flags & ~(VM_UFFD_MISSING | VM_UFFD_WP);
875 prev = vma_merge(mm, prev, vma->vm_start, vma->vm_end,
876 new_flags, vma->anon_vma,
877 vma->vm_file, vma->vm_pgoff,
878 vma_policy(vma),
879 NULL_VM_UFFD_CTX);
880 if (prev)
881 vma = prev;
882 else
883 prev = vma;
884 vma->vm_flags = new_flags;
885 vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
886 }
887 mmap_write_unlock(mm);
888 mmput(mm);
889wakeup:
890
891
892
893
894
895 spin_lock_irq(&ctx->fault_pending_wqh.lock);
896 __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, &range);
897 __wake_up(&ctx->fault_wqh, TASK_NORMAL, 1, &range);
898 spin_unlock_irq(&ctx->fault_pending_wqh.lock);
899
900
901 wake_up_all(&ctx->event_wqh);
902
903 wake_up_poll(&ctx->fd_wqh, EPOLLHUP);
904 userfaultfd_ctx_put(ctx);
905 return 0;
906}
907
908
909static inline struct userfaultfd_wait_queue *find_userfault_in(
910 wait_queue_head_t *wqh)
911{
912 wait_queue_entry_t *wq;
913 struct userfaultfd_wait_queue *uwq;
914
915 lockdep_assert_held(&wqh->lock);
916
917 uwq = NULL;
918 if (!waitqueue_active(wqh))
919 goto out;
920
921 wq = list_last_entry(&wqh->head, typeof(*wq), entry);
922 uwq = container_of(wq, struct userfaultfd_wait_queue, wq);
923out:
924 return uwq;
925}
926
927static inline struct userfaultfd_wait_queue *find_userfault(
928 struct userfaultfd_ctx *ctx)
929{
930 return find_userfault_in(&ctx->fault_pending_wqh);
931}
932
933static inline struct userfaultfd_wait_queue *find_userfault_evt(
934 struct userfaultfd_ctx *ctx)
935{
936 return find_userfault_in(&ctx->event_wqh);
937}
938
939static __poll_t userfaultfd_poll(struct file *file, poll_table *wait)
940{
941 struct userfaultfd_ctx *ctx = file->private_data;
942 __poll_t ret;
943
944 poll_wait(file, &ctx->fd_wqh, wait);
945
946 switch (ctx->state) {
947 case UFFD_STATE_WAIT_API:
948 return EPOLLERR;
949 case UFFD_STATE_RUNNING:
950
951
952
953
954 if (unlikely(!(file->f_flags & O_NONBLOCK)))
955 return EPOLLERR;
956
957
958
959
960
961
962
963
964
965
966 ret = 0;
967 smp_mb();
968 if (waitqueue_active(&ctx->fault_pending_wqh))
969 ret = EPOLLIN;
970 else if (waitqueue_active(&ctx->event_wqh))
971 ret = EPOLLIN;
972
973 return ret;
974 default:
975 WARN_ON_ONCE(1);
976 return EPOLLERR;
977 }
978}
979
980static const struct file_operations userfaultfd_fops;
981
982static int resolve_userfault_fork(struct userfaultfd_ctx *new,
983 struct inode *inode,
984 struct uffd_msg *msg)
985{
986 int fd;
987
988 fd = anon_inode_getfd_secure("[userfaultfd]", &userfaultfd_fops, new,
989 O_RDWR | (new->flags & UFFD_SHARED_FCNTL_FLAGS), inode);
990 if (fd < 0)
991 return fd;
992
993 msg->arg.reserved.reserved1 = 0;
994 msg->arg.fork.ufd = fd;
995 return 0;
996}
997
998static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait,
999 struct uffd_msg *msg, struct inode *inode)
1000{
1001 ssize_t ret;
1002 DECLARE_WAITQUEUE(wait, current);
1003 struct userfaultfd_wait_queue *uwq;
1004
1005
1006
1007
1008
1009
1010
1011 LIST_HEAD(fork_event);
1012 struct userfaultfd_ctx *fork_nctx = NULL;
1013
1014
1015 spin_lock_irq(&ctx->fd_wqh.lock);
1016 __add_wait_queue(&ctx->fd_wqh, &wait);
1017 for (;;) {
1018 set_current_state(TASK_INTERRUPTIBLE);
1019 spin_lock(&ctx->fault_pending_wqh.lock);
1020 uwq = find_userfault(ctx);
1021 if (uwq) {
1022
1023
1024
1025
1026
1027
1028
1029 write_seqcount_begin(&ctx->refile_seq);
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052 list_del(&uwq->wq.entry);
1053 add_wait_queue(&ctx->fault_wqh, &uwq->wq);
1054
1055 write_seqcount_end(&ctx->refile_seq);
1056
1057
1058 *msg = uwq->msg;
1059 spin_unlock(&ctx->fault_pending_wqh.lock);
1060 ret = 0;
1061 break;
1062 }
1063 spin_unlock(&ctx->fault_pending_wqh.lock);
1064
1065 spin_lock(&ctx->event_wqh.lock);
1066 uwq = find_userfault_evt(ctx);
1067 if (uwq) {
1068 *msg = uwq->msg;
1069
1070 if (uwq->msg.event == UFFD_EVENT_FORK) {
1071 fork_nctx = (struct userfaultfd_ctx *)
1072 (unsigned long)
1073 uwq->msg.arg.reserved.reserved1;
1074 list_move(&uwq->wq.entry, &fork_event);
1075
1076
1077
1078
1079
1080 userfaultfd_ctx_get(fork_nctx);
1081 spin_unlock(&ctx->event_wqh.lock);
1082 ret = 0;
1083 break;
1084 }
1085
1086 userfaultfd_event_complete(ctx, uwq);
1087 spin_unlock(&ctx->event_wqh.lock);
1088 ret = 0;
1089 break;
1090 }
1091 spin_unlock(&ctx->event_wqh.lock);
1092
1093 if (signal_pending(current)) {
1094 ret = -ERESTARTSYS;
1095 break;
1096 }
1097 if (no_wait) {
1098 ret = -EAGAIN;
1099 break;
1100 }
1101 spin_unlock_irq(&ctx->fd_wqh.lock);
1102 schedule();
1103 spin_lock_irq(&ctx->fd_wqh.lock);
1104 }
1105 __remove_wait_queue(&ctx->fd_wqh, &wait);
1106 __set_current_state(TASK_RUNNING);
1107 spin_unlock_irq(&ctx->fd_wqh.lock);
1108
1109 if (!ret && msg->event == UFFD_EVENT_FORK) {
1110 ret = resolve_userfault_fork(fork_nctx, inode, msg);
1111 spin_lock_irq(&ctx->event_wqh.lock);
1112 if (!list_empty(&fork_event)) {
1113
1114
1115
1116
1117 userfaultfd_ctx_put(fork_nctx);
1118
1119 uwq = list_first_entry(&fork_event,
1120 typeof(*uwq),
1121 wq.entry);
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132 list_del(&uwq->wq.entry);
1133 __add_wait_queue(&ctx->event_wqh, &uwq->wq);
1134
1135
1136
1137
1138
1139
1140 if (likely(!ret))
1141 userfaultfd_event_complete(ctx, uwq);
1142 } else {
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154 if (ret)
1155 userfaultfd_ctx_put(fork_nctx);
1156 }
1157 spin_unlock_irq(&ctx->event_wqh.lock);
1158 }
1159
1160 return ret;
1161}
1162
1163static ssize_t userfaultfd_read(struct file *file, char __user *buf,
1164 size_t count, loff_t *ppos)
1165{
1166 struct userfaultfd_ctx *ctx = file->private_data;
1167 ssize_t _ret, ret = 0;
1168 struct uffd_msg msg;
1169 int no_wait = file->f_flags & O_NONBLOCK;
1170 struct inode *inode = file_inode(file);
1171
1172 if (ctx->state == UFFD_STATE_WAIT_API)
1173 return -EINVAL;
1174
1175 for (;;) {
1176 if (count < sizeof(msg))
1177 return ret ? ret : -EINVAL;
1178 _ret = userfaultfd_ctx_read(ctx, no_wait, &msg, inode);
1179 if (_ret < 0)
1180 return ret ? ret : _ret;
1181 if (copy_to_user((__u64 __user *) buf, &msg, sizeof(msg)))
1182 return ret ? ret : -EFAULT;
1183 ret += sizeof(msg);
1184 buf += sizeof(msg);
1185 count -= sizeof(msg);
1186
1187
1188
1189
1190 no_wait = O_NONBLOCK;
1191 }
1192}
1193
1194static void __wake_userfault(struct userfaultfd_ctx *ctx,
1195 struct userfaultfd_wake_range *range)
1196{
1197 spin_lock_irq(&ctx->fault_pending_wqh.lock);
1198
1199 if (waitqueue_active(&ctx->fault_pending_wqh))
1200 __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL,
1201 range);
1202 if (waitqueue_active(&ctx->fault_wqh))
1203 __wake_up(&ctx->fault_wqh, TASK_NORMAL, 1, range);
1204 spin_unlock_irq(&ctx->fault_pending_wqh.lock);
1205}
1206
1207static __always_inline void wake_userfault(struct userfaultfd_ctx *ctx,
1208 struct userfaultfd_wake_range *range)
1209{
1210 unsigned seq;
1211 bool need_wakeup;
1212
1213
1214
1215
1216
1217
1218
1219
1220 smp_mb();
1221
1222
1223
1224
1225
1226
1227
1228 do {
1229 seq = read_seqcount_begin(&ctx->refile_seq);
1230 need_wakeup = waitqueue_active(&ctx->fault_pending_wqh) ||
1231 waitqueue_active(&ctx->fault_wqh);
1232 cond_resched();
1233 } while (read_seqcount_retry(&ctx->refile_seq, seq));
1234 if (need_wakeup)
1235 __wake_userfault(ctx, range);
1236}
1237
1238static __always_inline int validate_range(struct mm_struct *mm,
1239 __u64 *start, __u64 len)
1240{
1241 __u64 task_size = mm->task_size;
1242
1243 *start = untagged_addr(*start);
1244
1245 if (*start & ~PAGE_MASK)
1246 return -EINVAL;
1247 if (len & ~PAGE_MASK)
1248 return -EINVAL;
1249 if (!len)
1250 return -EINVAL;
1251 if (*start < mmap_min_addr)
1252 return -EINVAL;
1253 if (*start >= task_size)
1254 return -EINVAL;
1255 if (len > task_size - *start)
1256 return -EINVAL;
1257 return 0;
1258}
1259
1260static inline bool vma_can_userfault(struct vm_area_struct *vma,
1261 unsigned long vm_flags)
1262{
1263
1264 return vma_is_anonymous(vma) ||
1265 ((is_vm_hugetlb_page(vma) || vma_is_shmem(vma)) &&
1266 !(vm_flags & VM_UFFD_WP));
1267}
1268
1269static int userfaultfd_register(struct userfaultfd_ctx *ctx,
1270 unsigned long arg)
1271{
1272 struct mm_struct *mm = ctx->mm;
1273 struct vm_area_struct *vma, *prev, *cur;
1274 int ret;
1275 struct uffdio_register uffdio_register;
1276 struct uffdio_register __user *user_uffdio_register;
1277 unsigned long vm_flags, new_flags;
1278 bool found;
1279 bool basic_ioctls;
1280 unsigned long start, end, vma_end;
1281
1282 user_uffdio_register = (struct uffdio_register __user *) arg;
1283
1284 ret = -EFAULT;
1285 if (copy_from_user(&uffdio_register, user_uffdio_register,
1286 sizeof(uffdio_register)-sizeof(__u64)))
1287 goto out;
1288
1289 ret = -EINVAL;
1290 if (!uffdio_register.mode)
1291 goto out;
1292 if (uffdio_register.mode & ~(UFFDIO_REGISTER_MODE_MISSING|
1293 UFFDIO_REGISTER_MODE_WP))
1294 goto out;
1295 vm_flags = 0;
1296 if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MISSING)
1297 vm_flags |= VM_UFFD_MISSING;
1298 if (uffdio_register.mode & UFFDIO_REGISTER_MODE_WP)
1299 vm_flags |= VM_UFFD_WP;
1300
1301 ret = validate_range(mm, &uffdio_register.range.start,
1302 uffdio_register.range.len);
1303 if (ret)
1304 goto out;
1305
1306 start = uffdio_register.range.start;
1307 end = start + uffdio_register.range.len;
1308
1309 ret = -ENOMEM;
1310 if (!mmget_not_zero(mm))
1311 goto out;
1312
1313 mmap_write_lock(mm);
1314 vma = find_vma_prev(mm, start, &prev);
1315 if (!vma)
1316 goto out_unlock;
1317
1318
1319 ret = -EINVAL;
1320 if (vma->vm_start >= end)
1321 goto out_unlock;
1322
1323
1324
1325
1326
1327 if (is_vm_hugetlb_page(vma)) {
1328 unsigned long vma_hpagesize = vma_kernel_pagesize(vma);
1329
1330 if (start & (vma_hpagesize - 1))
1331 goto out_unlock;
1332 }
1333
1334
1335
1336
1337 found = false;
1338 basic_ioctls = false;
1339 for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) {
1340 cond_resched();
1341
1342 BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^
1343 !!(cur->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP)));
1344
1345
1346 ret = -EINVAL;
1347 if (!vma_can_userfault(cur, vm_flags))
1348 goto out_unlock;
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358 ret = -EPERM;
1359 if (unlikely(!(cur->vm_flags & VM_MAYWRITE)))
1360 goto out_unlock;
1361
1362
1363
1364
1365
1366 if (is_vm_hugetlb_page(cur) && end <= cur->vm_end &&
1367 end > cur->vm_start) {
1368 unsigned long vma_hpagesize = vma_kernel_pagesize(cur);
1369
1370 ret = -EINVAL;
1371
1372 if (end & (vma_hpagesize - 1))
1373 goto out_unlock;
1374 }
1375 if ((vm_flags & VM_UFFD_WP) && !(cur->vm_flags & VM_MAYWRITE))
1376 goto out_unlock;
1377
1378
1379
1380
1381
1382
1383
1384 ret = -EBUSY;
1385 if (cur->vm_userfaultfd_ctx.ctx &&
1386 cur->vm_userfaultfd_ctx.ctx != ctx)
1387 goto out_unlock;
1388
1389
1390
1391
1392 if (is_vm_hugetlb_page(cur))
1393 basic_ioctls = true;
1394
1395 found = true;
1396 }
1397 BUG_ON(!found);
1398
1399 if (vma->vm_start < start)
1400 prev = vma;
1401
1402 ret = 0;
1403 do {
1404 cond_resched();
1405
1406 BUG_ON(!vma_can_userfault(vma, vm_flags));
1407 BUG_ON(vma->vm_userfaultfd_ctx.ctx &&
1408 vma->vm_userfaultfd_ctx.ctx != ctx);
1409 WARN_ON(!(vma->vm_flags & VM_MAYWRITE));
1410
1411
1412
1413
1414
1415 if (vma->vm_userfaultfd_ctx.ctx == ctx &&
1416 (vma->vm_flags & vm_flags) == vm_flags)
1417 goto skip;
1418
1419 if (vma->vm_start > start)
1420 start = vma->vm_start;
1421 vma_end = min(end, vma->vm_end);
1422
1423 new_flags = (vma->vm_flags &
1424 ~(VM_UFFD_MISSING|VM_UFFD_WP)) | vm_flags;
1425 prev = vma_merge(mm, prev, start, vma_end, new_flags,
1426 vma->anon_vma, vma->vm_file, vma->vm_pgoff,
1427 vma_policy(vma),
1428 ((struct vm_userfaultfd_ctx){ ctx }));
1429 if (prev) {
1430 vma = prev;
1431 goto next;
1432 }
1433 if (vma->vm_start < start) {
1434 ret = split_vma(mm, vma, start, 1);
1435 if (ret)
1436 break;
1437 }
1438 if (vma->vm_end > end) {
1439 ret = split_vma(mm, vma, end, 0);
1440 if (ret)
1441 break;
1442 }
1443 next:
1444
1445
1446
1447
1448
1449 vma->vm_flags = new_flags;
1450 vma->vm_userfaultfd_ctx.ctx = ctx;
1451
1452 skip:
1453 prev = vma;
1454 start = vma->vm_end;
1455 vma = vma->vm_next;
1456 } while (vma && vma->vm_start < end);
1457out_unlock:
1458 mmap_write_unlock(mm);
1459 mmput(mm);
1460 if (!ret) {
1461 __u64 ioctls_out;
1462
1463 ioctls_out = basic_ioctls ? UFFD_API_RANGE_IOCTLS_BASIC :
1464 UFFD_API_RANGE_IOCTLS;
1465
1466
1467
1468
1469
1470 if (!(uffdio_register.mode & UFFDIO_REGISTER_MODE_WP))
1471 ioctls_out &= ~((__u64)1 << _UFFDIO_WRITEPROTECT);
1472
1473
1474
1475
1476
1477
1478 if (put_user(ioctls_out, &user_uffdio_register->ioctls))
1479 ret = -EFAULT;
1480 }
1481out:
1482 return ret;
1483}
1484
1485static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
1486 unsigned long arg)
1487{
1488 struct mm_struct *mm = ctx->mm;
1489 struct vm_area_struct *vma, *prev, *cur;
1490 int ret;
1491 struct uffdio_range uffdio_unregister;
1492 unsigned long new_flags;
1493 bool found;
1494 unsigned long start, end, vma_end;
1495 const void __user *buf = (void __user *)arg;
1496
1497 ret = -EFAULT;
1498 if (copy_from_user(&uffdio_unregister, buf, sizeof(uffdio_unregister)))
1499 goto out;
1500
1501 ret = validate_range(mm, &uffdio_unregister.start,
1502 uffdio_unregister.len);
1503 if (ret)
1504 goto out;
1505
1506 start = uffdio_unregister.start;
1507 end = start + uffdio_unregister.len;
1508
1509 ret = -ENOMEM;
1510 if (!mmget_not_zero(mm))
1511 goto out;
1512
1513 mmap_write_lock(mm);
1514 vma = find_vma_prev(mm, start, &prev);
1515 if (!vma)
1516 goto out_unlock;
1517
1518
1519 ret = -EINVAL;
1520 if (vma->vm_start >= end)
1521 goto out_unlock;
1522
1523
1524
1525
1526
1527 if (is_vm_hugetlb_page(vma)) {
1528 unsigned long vma_hpagesize = vma_kernel_pagesize(vma);
1529
1530 if (start & (vma_hpagesize - 1))
1531 goto out_unlock;
1532 }
1533
1534
1535
1536
1537 found = false;
1538 ret = -EINVAL;
1539 for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) {
1540 cond_resched();
1541
1542 BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^
1543 !!(cur->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP)));
1544
1545
1546
1547
1548
1549
1550
1551
1552 if (!vma_can_userfault(cur, cur->vm_flags))
1553 goto out_unlock;
1554
1555 found = true;
1556 }
1557 BUG_ON(!found);
1558
1559 if (vma->vm_start < start)
1560 prev = vma;
1561
1562 ret = 0;
1563 do {
1564 cond_resched();
1565
1566 BUG_ON(!vma_can_userfault(vma, vma->vm_flags));
1567
1568
1569
1570
1571
1572 if (!vma->vm_userfaultfd_ctx.ctx)
1573 goto skip;
1574
1575 WARN_ON(!(vma->vm_flags & VM_MAYWRITE));
1576
1577 if (vma->vm_start > start)
1578 start = vma->vm_start;
1579 vma_end = min(end, vma->vm_end);
1580
1581 if (userfaultfd_missing(vma)) {
1582
1583
1584
1585
1586
1587
1588 struct userfaultfd_wake_range range;
1589 range.start = start;
1590 range.len = vma_end - start;
1591 wake_userfault(vma->vm_userfaultfd_ctx.ctx, &range);
1592 }
1593
1594 new_flags = vma->vm_flags & ~(VM_UFFD_MISSING | VM_UFFD_WP);
1595 prev = vma_merge(mm, prev, start, vma_end, new_flags,
1596 vma->anon_vma, vma->vm_file, vma->vm_pgoff,
1597 vma_policy(vma),
1598 NULL_VM_UFFD_CTX);
1599 if (prev) {
1600 vma = prev;
1601 goto next;
1602 }
1603 if (vma->vm_start < start) {
1604 ret = split_vma(mm, vma, start, 1);
1605 if (ret)
1606 break;
1607 }
1608 if (vma->vm_end > end) {
1609 ret = split_vma(mm, vma, end, 0);
1610 if (ret)
1611 break;
1612 }
1613 next:
1614
1615
1616
1617
1618
1619 vma->vm_flags = new_flags;
1620 vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
1621
1622 skip:
1623 prev = vma;
1624 start = vma->vm_end;
1625 vma = vma->vm_next;
1626 } while (vma && vma->vm_start < end);
1627out_unlock:
1628 mmap_write_unlock(mm);
1629 mmput(mm);
1630out:
1631 return ret;
1632}
1633
1634
1635
1636
1637
1638static int userfaultfd_wake(struct userfaultfd_ctx *ctx,
1639 unsigned long arg)
1640{
1641 int ret;
1642 struct uffdio_range uffdio_wake;
1643 struct userfaultfd_wake_range range;
1644 const void __user *buf = (void __user *)arg;
1645
1646 ret = -EFAULT;
1647 if (copy_from_user(&uffdio_wake, buf, sizeof(uffdio_wake)))
1648 goto out;
1649
1650 ret = validate_range(ctx->mm, &uffdio_wake.start, uffdio_wake.len);
1651 if (ret)
1652 goto out;
1653
1654 range.start = uffdio_wake.start;
1655 range.len = uffdio_wake.len;
1656
1657
1658
1659
1660
1661 VM_BUG_ON(!range.len);
1662
1663 wake_userfault(ctx, &range);
1664 ret = 0;
1665
1666out:
1667 return ret;
1668}
1669
1670static int userfaultfd_copy(struct userfaultfd_ctx *ctx,
1671 unsigned long arg)
1672{
1673 __s64 ret;
1674 struct uffdio_copy uffdio_copy;
1675 struct uffdio_copy __user *user_uffdio_copy;
1676 struct userfaultfd_wake_range range;
1677
1678 user_uffdio_copy = (struct uffdio_copy __user *) arg;
1679
1680 ret = -EAGAIN;
1681 if (READ_ONCE(ctx->mmap_changing))
1682 goto out;
1683
1684 ret = -EFAULT;
1685 if (copy_from_user(&uffdio_copy, user_uffdio_copy,
1686
1687 sizeof(uffdio_copy)-sizeof(__s64)))
1688 goto out;
1689
1690 ret = validate_range(ctx->mm, &uffdio_copy.dst, uffdio_copy.len);
1691 if (ret)
1692 goto out;
1693
1694
1695
1696
1697
1698 ret = -EINVAL;
1699 if (uffdio_copy.src + uffdio_copy.len <= uffdio_copy.src)
1700 goto out;
1701 if (uffdio_copy.mode & ~(UFFDIO_COPY_MODE_DONTWAKE|UFFDIO_COPY_MODE_WP))
1702 goto out;
1703 if (mmget_not_zero(ctx->mm)) {
1704 ret = mcopy_atomic(ctx->mm, uffdio_copy.dst, uffdio_copy.src,
1705 uffdio_copy.len, &ctx->mmap_changing,
1706 uffdio_copy.mode);
1707 mmput(ctx->mm);
1708 } else {
1709 return -ESRCH;
1710 }
1711 if (unlikely(put_user(ret, &user_uffdio_copy->copy)))
1712 return -EFAULT;
1713 if (ret < 0)
1714 goto out;
1715 BUG_ON(!ret);
1716
1717 range.len = ret;
1718 if (!(uffdio_copy.mode & UFFDIO_COPY_MODE_DONTWAKE)) {
1719 range.start = uffdio_copy.dst;
1720 wake_userfault(ctx, &range);
1721 }
1722 ret = range.len == uffdio_copy.len ? 0 : -EAGAIN;
1723out:
1724 return ret;
1725}
1726
1727static int userfaultfd_zeropage(struct userfaultfd_ctx *ctx,
1728 unsigned long arg)
1729{
1730 __s64 ret;
1731 struct uffdio_zeropage uffdio_zeropage;
1732 struct uffdio_zeropage __user *user_uffdio_zeropage;
1733 struct userfaultfd_wake_range range;
1734
1735 user_uffdio_zeropage = (struct uffdio_zeropage __user *) arg;
1736
1737 ret = -EAGAIN;
1738 if (READ_ONCE(ctx->mmap_changing))
1739 goto out;
1740
1741 ret = -EFAULT;
1742 if (copy_from_user(&uffdio_zeropage, user_uffdio_zeropage,
1743
1744 sizeof(uffdio_zeropage)-sizeof(__s64)))
1745 goto out;
1746
1747 ret = validate_range(ctx->mm, &uffdio_zeropage.range.start,
1748 uffdio_zeropage.range.len);
1749 if (ret)
1750 goto out;
1751 ret = -EINVAL;
1752 if (uffdio_zeropage.mode & ~UFFDIO_ZEROPAGE_MODE_DONTWAKE)
1753 goto out;
1754
1755 if (mmget_not_zero(ctx->mm)) {
1756 ret = mfill_zeropage(ctx->mm, uffdio_zeropage.range.start,
1757 uffdio_zeropage.range.len,
1758 &ctx->mmap_changing);
1759 mmput(ctx->mm);
1760 } else {
1761 return -ESRCH;
1762 }
1763 if (unlikely(put_user(ret, &user_uffdio_zeropage->zeropage)))
1764 return -EFAULT;
1765 if (ret < 0)
1766 goto out;
1767
1768 BUG_ON(!ret);
1769 range.len = ret;
1770 if (!(uffdio_zeropage.mode & UFFDIO_ZEROPAGE_MODE_DONTWAKE)) {
1771 range.start = uffdio_zeropage.range.start;
1772 wake_userfault(ctx, &range);
1773 }
1774 ret = range.len == uffdio_zeropage.range.len ? 0 : -EAGAIN;
1775out:
1776 return ret;
1777}
1778
1779static int userfaultfd_writeprotect(struct userfaultfd_ctx *ctx,
1780 unsigned long arg)
1781{
1782 int ret;
1783 struct uffdio_writeprotect uffdio_wp;
1784 struct uffdio_writeprotect __user *user_uffdio_wp;
1785 struct userfaultfd_wake_range range;
1786 bool mode_wp, mode_dontwake;
1787
1788 if (READ_ONCE(ctx->mmap_changing))
1789 return -EAGAIN;
1790
1791 user_uffdio_wp = (struct uffdio_writeprotect __user *) arg;
1792
1793 if (copy_from_user(&uffdio_wp, user_uffdio_wp,
1794 sizeof(struct uffdio_writeprotect)))
1795 return -EFAULT;
1796
1797 ret = validate_range(ctx->mm, &uffdio_wp.range.start,
1798 uffdio_wp.range.len);
1799 if (ret)
1800 return ret;
1801
1802 if (uffdio_wp.mode & ~(UFFDIO_WRITEPROTECT_MODE_DONTWAKE |
1803 UFFDIO_WRITEPROTECT_MODE_WP))
1804 return -EINVAL;
1805
1806 mode_wp = uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_WP;
1807 mode_dontwake = uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_DONTWAKE;
1808
1809 if (mode_wp && mode_dontwake)
1810 return -EINVAL;
1811
1812 ret = mwriteprotect_range(ctx->mm, uffdio_wp.range.start,
1813 uffdio_wp.range.len, mode_wp,
1814 &ctx->mmap_changing);
1815 if (ret)
1816 return ret;
1817
1818 if (!mode_wp && !mode_dontwake) {
1819 range.start = uffdio_wp.range.start;
1820 range.len = uffdio_wp.range.len;
1821 wake_userfault(ctx, &range);
1822 }
1823 return ret;
1824}
1825
1826static inline unsigned int uffd_ctx_features(__u64 user_features)
1827{
1828
1829
1830
1831 return (unsigned int)user_features;
1832}
1833
1834
1835
1836
1837
1838
1839static int userfaultfd_api(struct userfaultfd_ctx *ctx,
1840 unsigned long arg)
1841{
1842 struct uffdio_api uffdio_api;
1843 void __user *buf = (void __user *)arg;
1844 int ret;
1845 __u64 features;
1846
1847 ret = -EINVAL;
1848 if (ctx->state != UFFD_STATE_WAIT_API)
1849 goto out;
1850 ret = -EFAULT;
1851 if (copy_from_user(&uffdio_api, buf, sizeof(uffdio_api)))
1852 goto out;
1853 features = uffdio_api.features;
1854 ret = -EINVAL;
1855 if (uffdio_api.api != UFFD_API || (features & ~UFFD_API_FEATURES))
1856 goto err_out;
1857 ret = -EPERM;
1858 if ((features & UFFD_FEATURE_EVENT_FORK) && !capable(CAP_SYS_PTRACE))
1859 goto err_out;
1860
1861 uffdio_api.features = UFFD_API_FEATURES;
1862 uffdio_api.ioctls = UFFD_API_IOCTLS;
1863 ret = -EFAULT;
1864 if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api)))
1865 goto out;
1866 ctx->state = UFFD_STATE_RUNNING;
1867
1868 ctx->features = uffd_ctx_features(features);
1869 ret = 0;
1870out:
1871 return ret;
1872err_out:
1873 memset(&uffdio_api, 0, sizeof(uffdio_api));
1874 if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api)))
1875 ret = -EFAULT;
1876 goto out;
1877}
1878
1879static long userfaultfd_ioctl(struct file *file, unsigned cmd,
1880 unsigned long arg)
1881{
1882 int ret = -EINVAL;
1883 struct userfaultfd_ctx *ctx = file->private_data;
1884
1885 if (cmd != UFFDIO_API && ctx->state == UFFD_STATE_WAIT_API)
1886 return -EINVAL;
1887
1888 switch(cmd) {
1889 case UFFDIO_API:
1890 ret = userfaultfd_api(ctx, arg);
1891 break;
1892 case UFFDIO_REGISTER:
1893 ret = userfaultfd_register(ctx, arg);
1894 break;
1895 case UFFDIO_UNREGISTER:
1896 ret = userfaultfd_unregister(ctx, arg);
1897 break;
1898 case UFFDIO_WAKE:
1899 ret = userfaultfd_wake(ctx, arg);
1900 break;
1901 case UFFDIO_COPY:
1902 ret = userfaultfd_copy(ctx, arg);
1903 break;
1904 case UFFDIO_ZEROPAGE:
1905 ret = userfaultfd_zeropage(ctx, arg);
1906 break;
1907 case UFFDIO_WRITEPROTECT:
1908 ret = userfaultfd_writeprotect(ctx, arg);
1909 break;
1910 }
1911 return ret;
1912}
1913
1914#ifdef CONFIG_PROC_FS
1915static void userfaultfd_show_fdinfo(struct seq_file *m, struct file *f)
1916{
1917 struct userfaultfd_ctx *ctx = f->private_data;
1918 wait_queue_entry_t *wq;
1919 unsigned long pending = 0, total = 0;
1920
1921 spin_lock_irq(&ctx->fault_pending_wqh.lock);
1922 list_for_each_entry(wq, &ctx->fault_pending_wqh.head, entry) {
1923 pending++;
1924 total++;
1925 }
1926 list_for_each_entry(wq, &ctx->fault_wqh.head, entry) {
1927 total++;
1928 }
1929 spin_unlock_irq(&ctx->fault_pending_wqh.lock);
1930
1931
1932
1933
1934
1935
1936 seq_printf(m, "pending:\t%lu\ntotal:\t%lu\nAPI:\t%Lx:%x:%Lx\n",
1937 pending, total, UFFD_API, ctx->features,
1938 UFFD_API_IOCTLS|UFFD_API_RANGE_IOCTLS);
1939}
1940#endif
1941
1942static const struct file_operations userfaultfd_fops = {
1943#ifdef CONFIG_PROC_FS
1944 .show_fdinfo = userfaultfd_show_fdinfo,
1945#endif
1946 .release = userfaultfd_release,
1947 .poll = userfaultfd_poll,
1948 .read = userfaultfd_read,
1949 .unlocked_ioctl = userfaultfd_ioctl,
1950 .compat_ioctl = compat_ptr_ioctl,
1951 .llseek = noop_llseek,
1952};
1953
1954static void init_once_userfaultfd_ctx(void *mem)
1955{
1956 struct userfaultfd_ctx *ctx = (struct userfaultfd_ctx *) mem;
1957
1958 init_waitqueue_head(&ctx->fault_pending_wqh);
1959 init_waitqueue_head(&ctx->fault_wqh);
1960 init_waitqueue_head(&ctx->event_wqh);
1961 init_waitqueue_head(&ctx->fd_wqh);
1962 seqcount_spinlock_init(&ctx->refile_seq, &ctx->fault_pending_wqh.lock);
1963}
1964
1965SYSCALL_DEFINE1(userfaultfd, int, flags)
1966{
1967 struct userfaultfd_ctx *ctx;
1968 int fd;
1969
1970 if (!sysctl_unprivileged_userfaultfd &&
1971 (flags & UFFD_USER_MODE_ONLY) == 0 &&
1972 !capable(CAP_SYS_PTRACE)) {
1973 printk_once(KERN_WARNING "uffd: Set unprivileged_userfaultfd "
1974 "sysctl knob to 1 if kernel faults must be handled "
1975 "without obtaining CAP_SYS_PTRACE capability\n");
1976 return -EPERM;
1977 }
1978
1979 BUG_ON(!current->mm);
1980
1981
1982 BUILD_BUG_ON(UFFD_USER_MODE_ONLY & UFFD_SHARED_FCNTL_FLAGS);
1983 BUILD_BUG_ON(UFFD_CLOEXEC != O_CLOEXEC);
1984 BUILD_BUG_ON(UFFD_NONBLOCK != O_NONBLOCK);
1985
1986 if (flags & ~(UFFD_SHARED_FCNTL_FLAGS | UFFD_USER_MODE_ONLY))
1987 return -EINVAL;
1988
1989 ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL);
1990 if (!ctx)
1991 return -ENOMEM;
1992
1993 refcount_set(&ctx->refcount, 1);
1994 ctx->flags = flags;
1995 ctx->features = 0;
1996 ctx->state = UFFD_STATE_WAIT_API;
1997 ctx->released = false;
1998 ctx->mmap_changing = false;
1999 ctx->mm = current->mm;
2000
2001 mmgrab(ctx->mm);
2002
2003 fd = anon_inode_getfd_secure("[userfaultfd]", &userfaultfd_fops, ctx,
2004 O_RDWR | (flags & UFFD_SHARED_FCNTL_FLAGS), NULL);
2005 if (fd < 0) {
2006 mmdrop(ctx->mm);
2007 kmem_cache_free(userfaultfd_ctx_cachep, ctx);
2008 }
2009 return fd;
2010}
2011
2012static int __init userfaultfd_init(void)
2013{
2014 userfaultfd_ctx_cachep = kmem_cache_create("userfaultfd_ctx_cache",
2015 sizeof(struct userfaultfd_ctx),
2016 0,
2017 SLAB_HWCACHE_ALIGN|SLAB_PANIC,
2018 init_once_userfaultfd_ctx);
2019 return 0;
2020}
2021__initcall(userfaultfd_init);
2022