1 // SPDX-License-Identifier: GPL-2.0-only
5 * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org>
6 * Copyright (C) 2008-2009 Red Hat, Inc.
7 * Copyright (C) 2015 Red Hat, Inc.
9 * Some part derived from fs/eventfd.c (anon inode setup) and
10 * mm/ksm.c (mm hashing).
13 #include <linux/list.h>
14 #include <linux/hashtable.h>
15 #include <linux/sched/signal.h>
16 #include <linux/sched/mm.h>
18 #include <linux/mm_inline.h>
19 #include <linux/mmu_notifier.h>
20 #include <linux/poll.h>
21 #include <linux/slab.h>
22 #include <linux/seq_file.h>
23 #include <linux/file.h>
24 #include <linux/bug.h>
25 #include <linux/anon_inodes.h>
26 #include <linux/syscalls.h>
27 #include <linux/userfaultfd_k.h>
28 #include <linux/mempolicy.h>
29 #include <linux/ioctl.h>
30 #include <linux/security.h>
31 #include <linux/hugetlb.h>
32 #include <linux/swapops.h>
33 #include <linux/miscdevice.h>
35 static int sysctl_unprivileged_userfaultfd __read_mostly
;
38 static struct ctl_table vm_userfaultfd_table
[] = {
40 .procname
= "unprivileged_userfaultfd",
41 .data
= &sysctl_unprivileged_userfaultfd
,
42 .maxlen
= sizeof(sysctl_unprivileged_userfaultfd
),
44 .proc_handler
= proc_dointvec_minmax
,
45 .extra1
= SYSCTL_ZERO
,
52 static struct kmem_cache
*userfaultfd_ctx_cachep __ro_after_init
;
55 * Start with fault_pending_wqh and fault_wqh so they're more likely
56 * to be in the same cacheline.
60 * fault_pending_wqh.lock
64 * To avoid deadlocks, IRQs must be disabled when taking any of the above locks,
65 * since fd_wqh.lock is taken by aio_poll() while it's holding a lock that's
66 * also taken in IRQ context.
68 struct userfaultfd_ctx
{
69 /* waitqueue head for the pending (i.e. not read) userfaults */
70 wait_queue_head_t fault_pending_wqh
;
71 /* waitqueue head for the userfaults */
72 wait_queue_head_t fault_wqh
;
73 /* waitqueue head for the pseudo fd to wakeup poll/read */
74 wait_queue_head_t fd_wqh
;
75 /* waitqueue head for events */
76 wait_queue_head_t event_wqh
;
77 /* a refile sequence protected by fault_pending_wqh lock */
78 seqcount_spinlock_t refile_seq
;
79 /* pseudo fd refcounting */
81 /* userfaultfd syscall flags */
83 /* features requested from the userspace */
84 unsigned int features
;
87 /* memory mappings are changing because of non-cooperative event */
88 atomic_t mmap_changing
;
89 /* mm with one ore more vmas attached to this userfaultfd_ctx */
93 struct userfaultfd_fork_ctx
{
94 struct userfaultfd_ctx
*orig
;
95 struct userfaultfd_ctx
*new;
96 struct list_head list
;
99 struct userfaultfd_unmap_ctx
{
100 struct userfaultfd_ctx
*ctx
;
103 struct list_head list
;
106 struct userfaultfd_wait_queue
{
108 wait_queue_entry_t wq
;
109 struct userfaultfd_ctx
*ctx
;
113 struct userfaultfd_wake_range
{
118 /* internal indication that UFFD_API ioctl was successfully executed */
119 #define UFFD_FEATURE_INITIALIZED (1u << 31)
121 static bool userfaultfd_is_initialized(struct userfaultfd_ctx
*ctx
)
123 return ctx
->features
& UFFD_FEATURE_INITIALIZED
;
126 static bool userfaultfd_wp_async_ctx(struct userfaultfd_ctx
*ctx
)
128 return ctx
&& (ctx
->features
& UFFD_FEATURE_WP_ASYNC
);
132 * Whether WP_UNPOPULATED is enabled on the uffd context. It is only
133 * meaningful when userfaultfd_wp()==true on the vma and when it's
136 bool userfaultfd_wp_unpopulated(struct vm_area_struct
*vma
)
138 struct userfaultfd_ctx
*ctx
= vma
->vm_userfaultfd_ctx
.ctx
;
143 return ctx
->features
& UFFD_FEATURE_WP_UNPOPULATED
;
146 static void userfaultfd_set_vm_flags(struct vm_area_struct
*vma
,
149 const bool uffd_wp_changed
= (vma
->vm_flags
^ flags
) & VM_UFFD_WP
;
151 vm_flags_reset(vma
, flags
);
153 * For shared mappings, we want to enable writenotify while
154 * userfaultfd-wp is enabled (see vma_wants_writenotify()). We'll simply
155 * recalculate vma->vm_page_prot whenever userfaultfd-wp changes.
157 if ((vma
->vm_flags
& VM_SHARED
) && uffd_wp_changed
)
158 vma_set_page_prot(vma
);
161 static int userfaultfd_wake_function(wait_queue_entry_t
*wq
, unsigned mode
,
162 int wake_flags
, void *key
)
164 struct userfaultfd_wake_range
*range
= key
;
166 struct userfaultfd_wait_queue
*uwq
;
167 unsigned long start
, len
;
169 uwq
= container_of(wq
, struct userfaultfd_wait_queue
, wq
);
171 /* len == 0 means wake all */
172 start
= range
->start
;
174 if (len
&& (start
> uwq
->msg
.arg
.pagefault
.address
||
175 start
+ len
<= uwq
->msg
.arg
.pagefault
.address
))
177 WRITE_ONCE(uwq
->waken
, true);
179 * The Program-Order guarantees provided by the scheduler
180 * ensure uwq->waken is visible before the task is woken.
182 ret
= wake_up_state(wq
->private, mode
);
185 * Wake only once, autoremove behavior.
187 * After the effect of list_del_init is visible to the other
188 * CPUs, the waitqueue may disappear from under us, see the
189 * !list_empty_careful() in handle_userfault().
191 * try_to_wake_up() has an implicit smp_mb(), and the
192 * wq->private is read before calling the extern function
193 * "wake_up_state" (which in turns calls try_to_wake_up).
195 list_del_init(&wq
->entry
);
202 * userfaultfd_ctx_get - Acquires a reference to the internal userfaultfd
204 * @ctx: [in] Pointer to the userfaultfd context.
206 static void userfaultfd_ctx_get(struct userfaultfd_ctx
*ctx
)
208 refcount_inc(&ctx
->refcount
);
212 * userfaultfd_ctx_put - Releases a reference to the internal userfaultfd
214 * @ctx: [in] Pointer to userfaultfd context.
216 * The userfaultfd context reference must have been previously acquired either
217 * with userfaultfd_ctx_get() or userfaultfd_ctx_fdget().
219 static void userfaultfd_ctx_put(struct userfaultfd_ctx
*ctx
)
221 if (refcount_dec_and_test(&ctx
->refcount
)) {
222 VM_BUG_ON(spin_is_locked(&ctx
->fault_pending_wqh
.lock
));
223 VM_BUG_ON(waitqueue_active(&ctx
->fault_pending_wqh
));
224 VM_BUG_ON(spin_is_locked(&ctx
->fault_wqh
.lock
));
225 VM_BUG_ON(waitqueue_active(&ctx
->fault_wqh
));
226 VM_BUG_ON(spin_is_locked(&ctx
->event_wqh
.lock
));
227 VM_BUG_ON(waitqueue_active(&ctx
->event_wqh
));
228 VM_BUG_ON(spin_is_locked(&ctx
->fd_wqh
.lock
));
229 VM_BUG_ON(waitqueue_active(&ctx
->fd_wqh
));
231 kmem_cache_free(userfaultfd_ctx_cachep
, ctx
);
235 static inline void msg_init(struct uffd_msg
*msg
)
237 BUILD_BUG_ON(sizeof(struct uffd_msg
) != 32);
239 * Must use memset to zero out the paddings or kernel data is
240 * leaked to userland.
242 memset(msg
, 0, sizeof(struct uffd_msg
));
245 static inline struct uffd_msg
userfault_msg(unsigned long address
,
246 unsigned long real_address
,
248 unsigned long reason
,
249 unsigned int features
)
254 msg
.event
= UFFD_EVENT_PAGEFAULT
;
256 msg
.arg
.pagefault
.address
= (features
& UFFD_FEATURE_EXACT_ADDRESS
) ?
257 real_address
: address
;
260 * These flags indicate why the userfault occurred:
261 * - UFFD_PAGEFAULT_FLAG_WP indicates a write protect fault.
262 * - UFFD_PAGEFAULT_FLAG_MINOR indicates a minor fault.
263 * - Neither of these flags being set indicates a MISSING fault.
265 * Separately, UFFD_PAGEFAULT_FLAG_WRITE indicates it was a write
266 * fault. Otherwise, it was a read fault.
268 if (flags
& FAULT_FLAG_WRITE
)
269 msg
.arg
.pagefault
.flags
|= UFFD_PAGEFAULT_FLAG_WRITE
;
270 if (reason
& VM_UFFD_WP
)
271 msg
.arg
.pagefault
.flags
|= UFFD_PAGEFAULT_FLAG_WP
;
272 if (reason
& VM_UFFD_MINOR
)
273 msg
.arg
.pagefault
.flags
|= UFFD_PAGEFAULT_FLAG_MINOR
;
274 if (features
& UFFD_FEATURE_THREAD_ID
)
275 msg
.arg
.pagefault
.feat
.ptid
= task_pid_vnr(current
);
279 #ifdef CONFIG_HUGETLB_PAGE
281 * Same functionality as userfaultfd_must_wait below with modifications for
284 static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx
*ctx
,
285 struct vm_fault
*vmf
,
286 unsigned long reason
)
288 struct vm_area_struct
*vma
= vmf
->vma
;
292 assert_fault_locked(vmf
);
294 ptep
= hugetlb_walk(vma
, vmf
->address
, vma_mmu_pagesize(vma
));
299 pte
= huge_ptep_get(ptep
);
302 * Lockless access: we're in a wait_event so it's ok if it
303 * changes under us. PTE markers should be handled the same as none
306 if (huge_pte_none_mostly(pte
))
308 if (!huge_pte_write(pte
) && (reason
& VM_UFFD_WP
))
314 static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx
*ctx
,
315 struct vm_fault
*vmf
,
316 unsigned long reason
)
318 return false; /* should never get here */
320 #endif /* CONFIG_HUGETLB_PAGE */
323 * Verify the pagetables are still not ok after having reigstered into
324 * the fault_pending_wqh to avoid userland having to UFFDIO_WAKE any
325 * userfault that has already been resolved, if userfaultfd_read and
326 * UFFDIO_COPY|ZEROPAGE are being run simultaneously on two different
329 static inline bool userfaultfd_must_wait(struct userfaultfd_ctx
*ctx
,
330 struct vm_fault
*vmf
,
331 unsigned long reason
)
333 struct mm_struct
*mm
= ctx
->mm
;
334 unsigned long address
= vmf
->address
;
343 assert_fault_locked(vmf
);
345 pgd
= pgd_offset(mm
, address
);
346 if (!pgd_present(*pgd
))
348 p4d
= p4d_offset(pgd
, address
);
349 if (!p4d_present(*p4d
))
351 pud
= pud_offset(p4d
, address
);
352 if (!pud_present(*pud
))
354 pmd
= pmd_offset(pud
, address
);
356 _pmd
= pmdp_get_lockless(pmd
);
361 if (!pmd_present(_pmd
) || pmd_devmap(_pmd
))
364 if (pmd_trans_huge(_pmd
)) {
365 if (!pmd_write(_pmd
) && (reason
& VM_UFFD_WP
))
370 pte
= pte_offset_map(pmd
, address
);
376 * Lockless access: we're in a wait_event so it's ok if it
377 * changes under us. PTE markers should be handled the same as none
380 ptent
= ptep_get(pte
);
381 if (pte_none_mostly(ptent
))
383 if (!pte_write(ptent
) && (reason
& VM_UFFD_WP
))
391 static inline unsigned int userfaultfd_get_blocking_state(unsigned int flags
)
393 if (flags
& FAULT_FLAG_INTERRUPTIBLE
)
394 return TASK_INTERRUPTIBLE
;
396 if (flags
& FAULT_FLAG_KILLABLE
)
397 return TASK_KILLABLE
;
399 return TASK_UNINTERRUPTIBLE
;
403 * The locking rules involved in returning VM_FAULT_RETRY depending on
404 * FAULT_FLAG_ALLOW_RETRY, FAULT_FLAG_RETRY_NOWAIT and
405 * FAULT_FLAG_KILLABLE are not straightforward. The "Caution"
406 * recommendation in __lock_page_or_retry is not an understatement.
408 * If FAULT_FLAG_ALLOW_RETRY is set, the mmap_lock must be released
409 * before returning VM_FAULT_RETRY only if FAULT_FLAG_RETRY_NOWAIT is
412 * If FAULT_FLAG_ALLOW_RETRY is set but FAULT_FLAG_KILLABLE is not
413 * set, VM_FAULT_RETRY can still be returned if and only if there are
414 * fatal_signal_pending()s, and the mmap_lock must be released before
417 vm_fault_t
handle_userfault(struct vm_fault
*vmf
, unsigned long reason
)
419 struct vm_area_struct
*vma
= vmf
->vma
;
420 struct mm_struct
*mm
= vma
->vm_mm
;
421 struct userfaultfd_ctx
*ctx
;
422 struct userfaultfd_wait_queue uwq
;
423 vm_fault_t ret
= VM_FAULT_SIGBUS
;
425 unsigned int blocking_state
;
428 * We don't do userfault handling for the final child pid update.
430 * We also don't do userfault handling during
431 * coredumping. hugetlbfs has the special
432 * hugetlb_follow_page_mask() to skip missing pages in the
433 * FOLL_DUMP case, anon memory also checks for FOLL_DUMP with
434 * the no_page_table() helper in follow_page_mask(), but the
435 * shmem_vm_ops->fault method is invoked even during
436 * coredumping and it ends up here.
438 if (current
->flags
& (PF_EXITING
|PF_DUMPCORE
))
441 assert_fault_locked(vmf
);
443 ctx
= vma
->vm_userfaultfd_ctx
.ctx
;
447 BUG_ON(ctx
->mm
!= mm
);
449 /* Any unrecognized flag is a bug. */
450 VM_BUG_ON(reason
& ~__VM_UFFD_FLAGS
);
451 /* 0 or > 1 flags set is a bug; we expect exactly 1. */
452 VM_BUG_ON(!reason
|| (reason
& (reason
- 1)));
454 if (ctx
->features
& UFFD_FEATURE_SIGBUS
)
456 if (!(vmf
->flags
& FAULT_FLAG_USER
) && (ctx
->flags
& UFFD_USER_MODE_ONLY
))
460 * If it's already released don't get it. This avoids to loop
461 * in __get_user_pages if userfaultfd_release waits on the
462 * caller of handle_userfault to release the mmap_lock.
464 if (unlikely(READ_ONCE(ctx
->released
))) {
466 * Don't return VM_FAULT_SIGBUS in this case, so a non
467 * cooperative manager can close the uffd after the
468 * last UFFDIO_COPY, without risking to trigger an
469 * involuntary SIGBUS if the process was starting the
470 * userfaultfd while the userfaultfd was still armed
471 * (but after the last UFFDIO_COPY). If the uffd
472 * wasn't already closed when the userfault reached
473 * this point, that would normally be solved by
474 * userfaultfd_must_wait returning 'false'.
476 * If we were to return VM_FAULT_SIGBUS here, the non
477 * cooperative manager would be instead forced to
478 * always call UFFDIO_UNREGISTER before it can safely
481 ret
= VM_FAULT_NOPAGE
;
486 * Check that we can return VM_FAULT_RETRY.
488 * NOTE: it should become possible to return VM_FAULT_RETRY
489 * even if FAULT_FLAG_TRIED is set without leading to gup()
490 * -EBUSY failures, if the userfaultfd is to be extended for
491 * VM_UFFD_WP tracking and we intend to arm the userfault
492 * without first stopping userland access to the memory. For
493 * VM_UFFD_MISSING userfaults this is enough for now.
495 if (unlikely(!(vmf
->flags
& FAULT_FLAG_ALLOW_RETRY
))) {
497 * Validate the invariant that nowait must allow retry
498 * to be sure not to return SIGBUS erroneously on
499 * nowait invocations.
501 BUG_ON(vmf
->flags
& FAULT_FLAG_RETRY_NOWAIT
);
502 #ifdef CONFIG_DEBUG_VM
503 if (printk_ratelimit()) {
505 "FAULT_FLAG_ALLOW_RETRY missing %x\n",
514 * Handle nowait, not much to do other than tell it to retry
517 ret
= VM_FAULT_RETRY
;
518 if (vmf
->flags
& FAULT_FLAG_RETRY_NOWAIT
)
521 /* take the reference before dropping the mmap_lock */
522 userfaultfd_ctx_get(ctx
);
524 init_waitqueue_func_entry(&uwq
.wq
, userfaultfd_wake_function
);
525 uwq
.wq
.private = current
;
526 uwq
.msg
= userfault_msg(vmf
->address
, vmf
->real_address
, vmf
->flags
,
527 reason
, ctx
->features
);
531 blocking_state
= userfaultfd_get_blocking_state(vmf
->flags
);
534 * Take the vma lock now, in order to safely call
535 * userfaultfd_huge_must_wait() later. Since acquiring the
536 * (sleepable) vma lock can modify the current task state, that
537 * must be before explicitly calling set_current_state().
539 if (is_vm_hugetlb_page(vma
))
540 hugetlb_vma_lock_read(vma
);
542 spin_lock_irq(&ctx
->fault_pending_wqh
.lock
);
544 * After the __add_wait_queue the uwq is visible to userland
545 * through poll/read().
547 __add_wait_queue(&ctx
->fault_pending_wqh
, &uwq
.wq
);
549 * The smp_mb() after __set_current_state prevents the reads
550 * following the spin_unlock to happen before the list_add in
553 set_current_state(blocking_state
);
554 spin_unlock_irq(&ctx
->fault_pending_wqh
.lock
);
556 if (!is_vm_hugetlb_page(vma
))
557 must_wait
= userfaultfd_must_wait(ctx
, vmf
, reason
);
559 must_wait
= userfaultfd_huge_must_wait(ctx
, vmf
, reason
);
560 if (is_vm_hugetlb_page(vma
))
561 hugetlb_vma_unlock_read(vma
);
562 release_fault_lock(vmf
);
564 if (likely(must_wait
&& !READ_ONCE(ctx
->released
))) {
565 wake_up_poll(&ctx
->fd_wqh
, EPOLLIN
);
569 __set_current_state(TASK_RUNNING
);
572 * Here we race with the list_del; list_add in
573 * userfaultfd_ctx_read(), however because we don't ever run
574 * list_del_init() to refile across the two lists, the prev
575 * and next pointers will never point to self. list_add also
576 * would never let any of the two pointers to point to
577 * self. So list_empty_careful won't risk to see both pointers
578 * pointing to self at any time during the list refile. The
579 * only case where list_del_init() is called is the full
580 * removal in the wake function and there we don't re-list_add
581 * and it's fine not to block on the spinlock. The uwq on this
582 * kernel stack can be released after the list_del_init.
584 if (!list_empty_careful(&uwq
.wq
.entry
)) {
585 spin_lock_irq(&ctx
->fault_pending_wqh
.lock
);
587 * No need of list_del_init(), the uwq on the stack
588 * will be freed shortly anyway.
590 list_del(&uwq
.wq
.entry
);
591 spin_unlock_irq(&ctx
->fault_pending_wqh
.lock
);
595 * ctx may go away after this if the userfault pseudo fd is
598 userfaultfd_ctx_put(ctx
);
604 static void userfaultfd_event_wait_completion(struct userfaultfd_ctx
*ctx
,
605 struct userfaultfd_wait_queue
*ewq
)
607 struct userfaultfd_ctx
*release_new_ctx
;
609 if (WARN_ON_ONCE(current
->flags
& PF_EXITING
))
613 init_waitqueue_entry(&ewq
->wq
, current
);
614 release_new_ctx
= NULL
;
616 spin_lock_irq(&ctx
->event_wqh
.lock
);
618 * After the __add_wait_queue the uwq is visible to userland
619 * through poll/read().
621 __add_wait_queue(&ctx
->event_wqh
, &ewq
->wq
);
623 set_current_state(TASK_KILLABLE
);
624 if (ewq
->msg
.event
== 0)
626 if (READ_ONCE(ctx
->released
) ||
627 fatal_signal_pending(current
)) {
629 * &ewq->wq may be queued in fork_event, but
630 * __remove_wait_queue ignores the head
631 * parameter. It would be a problem if it
634 __remove_wait_queue(&ctx
->event_wqh
, &ewq
->wq
);
635 if (ewq
->msg
.event
== UFFD_EVENT_FORK
) {
636 struct userfaultfd_ctx
*new;
638 new = (struct userfaultfd_ctx
*)
640 ewq
->msg
.arg
.reserved
.reserved1
;
641 release_new_ctx
= new;
646 spin_unlock_irq(&ctx
->event_wqh
.lock
);
648 wake_up_poll(&ctx
->fd_wqh
, EPOLLIN
);
651 spin_lock_irq(&ctx
->event_wqh
.lock
);
653 __set_current_state(TASK_RUNNING
);
654 spin_unlock_irq(&ctx
->event_wqh
.lock
);
656 if (release_new_ctx
) {
657 struct vm_area_struct
*vma
;
658 struct mm_struct
*mm
= release_new_ctx
->mm
;
659 VMA_ITERATOR(vmi
, mm
, 0);
661 /* the various vma->vm_userfaultfd_ctx still points to it */
663 for_each_vma(vmi
, vma
) {
664 if (vma
->vm_userfaultfd_ctx
.ctx
== release_new_ctx
) {
665 vma_start_write(vma
);
666 vma
->vm_userfaultfd_ctx
= NULL_VM_UFFD_CTX
;
667 userfaultfd_set_vm_flags(vma
,
668 vma
->vm_flags
& ~__VM_UFFD_FLAGS
);
671 mmap_write_unlock(mm
);
673 userfaultfd_ctx_put(release_new_ctx
);
677 * ctx may go away after this if the userfault pseudo fd is
681 atomic_dec(&ctx
->mmap_changing
);
682 VM_BUG_ON(atomic_read(&ctx
->mmap_changing
) < 0);
683 userfaultfd_ctx_put(ctx
);
686 static void userfaultfd_event_complete(struct userfaultfd_ctx
*ctx
,
687 struct userfaultfd_wait_queue
*ewq
)
690 wake_up_locked(&ctx
->event_wqh
);
691 __remove_wait_queue(&ctx
->event_wqh
, &ewq
->wq
);
694 int dup_userfaultfd(struct vm_area_struct
*vma
, struct list_head
*fcs
)
696 struct userfaultfd_ctx
*ctx
= NULL
, *octx
;
697 struct userfaultfd_fork_ctx
*fctx
;
699 octx
= vma
->vm_userfaultfd_ctx
.ctx
;
700 if (!octx
|| !(octx
->features
& UFFD_FEATURE_EVENT_FORK
)) {
701 vma_start_write(vma
);
702 vma
->vm_userfaultfd_ctx
= NULL_VM_UFFD_CTX
;
703 userfaultfd_set_vm_flags(vma
, vma
->vm_flags
& ~__VM_UFFD_FLAGS
);
707 list_for_each_entry(fctx
, fcs
, list
)
708 if (fctx
->orig
== octx
) {
714 fctx
= kmalloc(sizeof(*fctx
), GFP_KERNEL
);
718 ctx
= kmem_cache_alloc(userfaultfd_ctx_cachep
, GFP_KERNEL
);
724 refcount_set(&ctx
->refcount
, 1);
725 ctx
->flags
= octx
->flags
;
726 ctx
->features
= octx
->features
;
727 ctx
->released
= false;
728 atomic_set(&ctx
->mmap_changing
, 0);
729 ctx
->mm
= vma
->vm_mm
;
732 userfaultfd_ctx_get(octx
);
733 atomic_inc(&octx
->mmap_changing
);
736 list_add_tail(&fctx
->list
, fcs
);
739 vma
->vm_userfaultfd_ctx
.ctx
= ctx
;
743 static void dup_fctx(struct userfaultfd_fork_ctx
*fctx
)
745 struct userfaultfd_ctx
*ctx
= fctx
->orig
;
746 struct userfaultfd_wait_queue ewq
;
750 ewq
.msg
.event
= UFFD_EVENT_FORK
;
751 ewq
.msg
.arg
.reserved
.reserved1
= (unsigned long)fctx
->new;
753 userfaultfd_event_wait_completion(ctx
, &ewq
);
756 void dup_userfaultfd_complete(struct list_head
*fcs
)
758 struct userfaultfd_fork_ctx
*fctx
, *n
;
760 list_for_each_entry_safe(fctx
, n
, fcs
, list
) {
762 list_del(&fctx
->list
);
767 void mremap_userfaultfd_prep(struct vm_area_struct
*vma
,
768 struct vm_userfaultfd_ctx
*vm_ctx
)
770 struct userfaultfd_ctx
*ctx
;
772 ctx
= vma
->vm_userfaultfd_ctx
.ctx
;
777 if (ctx
->features
& UFFD_FEATURE_EVENT_REMAP
) {
779 userfaultfd_ctx_get(ctx
);
780 atomic_inc(&ctx
->mmap_changing
);
782 /* Drop uffd context if remap feature not enabled */
783 vma_start_write(vma
);
784 vma
->vm_userfaultfd_ctx
= NULL_VM_UFFD_CTX
;
785 userfaultfd_set_vm_flags(vma
, vma
->vm_flags
& ~__VM_UFFD_FLAGS
);
789 void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx
*vm_ctx
,
790 unsigned long from
, unsigned long to
,
793 struct userfaultfd_ctx
*ctx
= vm_ctx
->ctx
;
794 struct userfaultfd_wait_queue ewq
;
799 if (to
& ~PAGE_MASK
) {
800 userfaultfd_ctx_put(ctx
);
806 ewq
.msg
.event
= UFFD_EVENT_REMAP
;
807 ewq
.msg
.arg
.remap
.from
= from
;
808 ewq
.msg
.arg
.remap
.to
= to
;
809 ewq
.msg
.arg
.remap
.len
= len
;
811 userfaultfd_event_wait_completion(ctx
, &ewq
);
814 bool userfaultfd_remove(struct vm_area_struct
*vma
,
815 unsigned long start
, unsigned long end
)
817 struct mm_struct
*mm
= vma
->vm_mm
;
818 struct userfaultfd_ctx
*ctx
;
819 struct userfaultfd_wait_queue ewq
;
821 ctx
= vma
->vm_userfaultfd_ctx
.ctx
;
822 if (!ctx
|| !(ctx
->features
& UFFD_FEATURE_EVENT_REMOVE
))
825 userfaultfd_ctx_get(ctx
);
826 atomic_inc(&ctx
->mmap_changing
);
827 mmap_read_unlock(mm
);
831 ewq
.msg
.event
= UFFD_EVENT_REMOVE
;
832 ewq
.msg
.arg
.remove
.start
= start
;
833 ewq
.msg
.arg
.remove
.end
= end
;
835 userfaultfd_event_wait_completion(ctx
, &ewq
);
840 static bool has_unmap_ctx(struct userfaultfd_ctx
*ctx
, struct list_head
*unmaps
,
841 unsigned long start
, unsigned long end
)
843 struct userfaultfd_unmap_ctx
*unmap_ctx
;
845 list_for_each_entry(unmap_ctx
, unmaps
, list
)
846 if (unmap_ctx
->ctx
== ctx
&& unmap_ctx
->start
== start
&&
847 unmap_ctx
->end
== end
)
853 int userfaultfd_unmap_prep(struct vm_area_struct
*vma
, unsigned long start
,
854 unsigned long end
, struct list_head
*unmaps
)
856 struct userfaultfd_unmap_ctx
*unmap_ctx
;
857 struct userfaultfd_ctx
*ctx
= vma
->vm_userfaultfd_ctx
.ctx
;
859 if (!ctx
|| !(ctx
->features
& UFFD_FEATURE_EVENT_UNMAP
) ||
860 has_unmap_ctx(ctx
, unmaps
, start
, end
))
863 unmap_ctx
= kzalloc(sizeof(*unmap_ctx
), GFP_KERNEL
);
867 userfaultfd_ctx_get(ctx
);
868 atomic_inc(&ctx
->mmap_changing
);
869 unmap_ctx
->ctx
= ctx
;
870 unmap_ctx
->start
= start
;
871 unmap_ctx
->end
= end
;
872 list_add_tail(&unmap_ctx
->list
, unmaps
);
877 void userfaultfd_unmap_complete(struct mm_struct
*mm
, struct list_head
*uf
)
879 struct userfaultfd_unmap_ctx
*ctx
, *n
;
880 struct userfaultfd_wait_queue ewq
;
882 list_for_each_entry_safe(ctx
, n
, uf
, list
) {
885 ewq
.msg
.event
= UFFD_EVENT_UNMAP
;
886 ewq
.msg
.arg
.remove
.start
= ctx
->start
;
887 ewq
.msg
.arg
.remove
.end
= ctx
->end
;
889 userfaultfd_event_wait_completion(ctx
->ctx
, &ewq
);
891 list_del(&ctx
->list
);
896 static int userfaultfd_release(struct inode
*inode
, struct file
*file
)
898 struct userfaultfd_ctx
*ctx
= file
->private_data
;
899 struct mm_struct
*mm
= ctx
->mm
;
900 struct vm_area_struct
*vma
, *prev
;
901 /* len == 0 means wake all */
902 struct userfaultfd_wake_range range
= { .len
= 0, };
903 unsigned long new_flags
;
904 VMA_ITERATOR(vmi
, mm
, 0);
906 WRITE_ONCE(ctx
->released
, true);
908 if (!mmget_not_zero(mm
))
912 * Flush page faults out of all CPUs. NOTE: all page faults
913 * must be retried without returning VM_FAULT_SIGBUS if
914 * userfaultfd_ctx_get() succeeds but vma->vma_userfault_ctx
915 * changes while handle_userfault released the mmap_lock. So
916 * it's critical that released is set to true (above), before
917 * taking the mmap_lock for writing.
921 for_each_vma(vmi
, vma
) {
923 BUG_ON(!!vma
->vm_userfaultfd_ctx
.ctx
^
924 !!(vma
->vm_flags
& __VM_UFFD_FLAGS
));
925 if (vma
->vm_userfaultfd_ctx
.ctx
!= ctx
) {
929 new_flags
= vma
->vm_flags
& ~__VM_UFFD_FLAGS
;
930 vma
= vma_modify_flags_uffd(&vmi
, prev
, vma
, vma
->vm_start
,
931 vma
->vm_end
, new_flags
,
934 vma_start_write(vma
);
935 userfaultfd_set_vm_flags(vma
, new_flags
);
936 vma
->vm_userfaultfd_ctx
= NULL_VM_UFFD_CTX
;
940 mmap_write_unlock(mm
);
944 * After no new page faults can wait on this fault_*wqh, flush
945 * the last page faults that may have been already waiting on
948 spin_lock_irq(&ctx
->fault_pending_wqh
.lock
);
949 __wake_up_locked_key(&ctx
->fault_pending_wqh
, TASK_NORMAL
, &range
);
950 __wake_up(&ctx
->fault_wqh
, TASK_NORMAL
, 1, &range
);
951 spin_unlock_irq(&ctx
->fault_pending_wqh
.lock
);
953 /* Flush pending events that may still wait on event_wqh */
954 wake_up_all(&ctx
->event_wqh
);
956 wake_up_poll(&ctx
->fd_wqh
, EPOLLHUP
);
957 userfaultfd_ctx_put(ctx
);
961 /* fault_pending_wqh.lock must be hold by the caller */
962 static inline struct userfaultfd_wait_queue
*find_userfault_in(
963 wait_queue_head_t
*wqh
)
965 wait_queue_entry_t
*wq
;
966 struct userfaultfd_wait_queue
*uwq
;
968 lockdep_assert_held(&wqh
->lock
);
971 if (!waitqueue_active(wqh
))
973 /* walk in reverse to provide FIFO behavior to read userfaults */
974 wq
= list_last_entry(&wqh
->head
, typeof(*wq
), entry
);
975 uwq
= container_of(wq
, struct userfaultfd_wait_queue
, wq
);
980 static inline struct userfaultfd_wait_queue
*find_userfault(
981 struct userfaultfd_ctx
*ctx
)
983 return find_userfault_in(&ctx
->fault_pending_wqh
);
986 static inline struct userfaultfd_wait_queue
*find_userfault_evt(
987 struct userfaultfd_ctx
*ctx
)
989 return find_userfault_in(&ctx
->event_wqh
);
992 static __poll_t
userfaultfd_poll(struct file
*file
, poll_table
*wait
)
994 struct userfaultfd_ctx
*ctx
= file
->private_data
;
997 poll_wait(file
, &ctx
->fd_wqh
, wait
);
999 if (!userfaultfd_is_initialized(ctx
))
1003 * poll() never guarantees that read won't block.
1004 * userfaults can be waken before they're read().
1006 if (unlikely(!(file
->f_flags
& O_NONBLOCK
)))
1009 * lockless access to see if there are pending faults
1010 * __pollwait last action is the add_wait_queue but
1011 * the spin_unlock would allow the waitqueue_active to
1012 * pass above the actual list_add inside
1013 * add_wait_queue critical section. So use a full
1014 * memory barrier to serialize the list_add write of
1015 * add_wait_queue() with the waitqueue_active read
1020 if (waitqueue_active(&ctx
->fault_pending_wqh
))
1022 else if (waitqueue_active(&ctx
->event_wqh
))
1028 static const struct file_operations userfaultfd_fops
;
1030 static int resolve_userfault_fork(struct userfaultfd_ctx
*new,
1031 struct inode
*inode
,
1032 struct uffd_msg
*msg
)
1036 fd
= anon_inode_getfd_secure("[userfaultfd]", &userfaultfd_fops
, new,
1037 O_RDONLY
| (new->flags
& UFFD_SHARED_FCNTL_FLAGS
), inode
);
1041 msg
->arg
.reserved
.reserved1
= 0;
1042 msg
->arg
.fork
.ufd
= fd
;
1046 static ssize_t
userfaultfd_ctx_read(struct userfaultfd_ctx
*ctx
, int no_wait
,
1047 struct uffd_msg
*msg
, struct inode
*inode
)
1050 DECLARE_WAITQUEUE(wait
, current
);
1051 struct userfaultfd_wait_queue
*uwq
;
1053 * Handling fork event requires sleeping operations, so
1054 * we drop the event_wqh lock, then do these ops, then
1055 * lock it back and wake up the waiter. While the lock is
1056 * dropped the ewq may go away so we keep track of it
1059 LIST_HEAD(fork_event
);
1060 struct userfaultfd_ctx
*fork_nctx
= NULL
;
1062 /* always take the fd_wqh lock before the fault_pending_wqh lock */
1063 spin_lock_irq(&ctx
->fd_wqh
.lock
);
1064 __add_wait_queue(&ctx
->fd_wqh
, &wait
);
1066 set_current_state(TASK_INTERRUPTIBLE
);
1067 spin_lock(&ctx
->fault_pending_wqh
.lock
);
1068 uwq
= find_userfault(ctx
);
1071 * Use a seqcount to repeat the lockless check
1072 * in wake_userfault() to avoid missing
1073 * wakeups because during the refile both
1074 * waitqueue could become empty if this is the
1077 write_seqcount_begin(&ctx
->refile_seq
);
1080 * The fault_pending_wqh.lock prevents the uwq
1081 * to disappear from under us.
1083 * Refile this userfault from
1084 * fault_pending_wqh to fault_wqh, it's not
1085 * pending anymore after we read it.
1087 * Use list_del() by hand (as
1088 * userfaultfd_wake_function also uses
1089 * list_del_init() by hand) to be sure nobody
1090 * changes __remove_wait_queue() to use
1091 * list_del_init() in turn breaking the
1092 * !list_empty_careful() check in
1093 * handle_userfault(). The uwq->wq.head list
1094 * must never be empty at any time during the
1095 * refile, or the waitqueue could disappear
1096 * from under us. The "wait_queue_head_t"
1097 * parameter of __remove_wait_queue() is unused
1100 list_del(&uwq
->wq
.entry
);
1101 add_wait_queue(&ctx
->fault_wqh
, &uwq
->wq
);
1103 write_seqcount_end(&ctx
->refile_seq
);
1105 /* careful to always initialize msg if ret == 0 */
1107 spin_unlock(&ctx
->fault_pending_wqh
.lock
);
1111 spin_unlock(&ctx
->fault_pending_wqh
.lock
);
1113 spin_lock(&ctx
->event_wqh
.lock
);
1114 uwq
= find_userfault_evt(ctx
);
1118 if (uwq
->msg
.event
== UFFD_EVENT_FORK
) {
1119 fork_nctx
= (struct userfaultfd_ctx
*)
1121 uwq
->msg
.arg
.reserved
.reserved1
;
1122 list_move(&uwq
->wq
.entry
, &fork_event
);
1124 * fork_nctx can be freed as soon as
1125 * we drop the lock, unless we take a
1128 userfaultfd_ctx_get(fork_nctx
);
1129 spin_unlock(&ctx
->event_wqh
.lock
);
1134 userfaultfd_event_complete(ctx
, uwq
);
1135 spin_unlock(&ctx
->event_wqh
.lock
);
1139 spin_unlock(&ctx
->event_wqh
.lock
);
1141 if (signal_pending(current
)) {
1149 spin_unlock_irq(&ctx
->fd_wqh
.lock
);
1151 spin_lock_irq(&ctx
->fd_wqh
.lock
);
1153 __remove_wait_queue(&ctx
->fd_wqh
, &wait
);
1154 __set_current_state(TASK_RUNNING
);
1155 spin_unlock_irq(&ctx
->fd_wqh
.lock
);
1157 if (!ret
&& msg
->event
== UFFD_EVENT_FORK
) {
1158 ret
= resolve_userfault_fork(fork_nctx
, inode
, msg
);
1159 spin_lock_irq(&ctx
->event_wqh
.lock
);
1160 if (!list_empty(&fork_event
)) {
1162 * The fork thread didn't abort, so we can
1163 * drop the temporary refcount.
1165 userfaultfd_ctx_put(fork_nctx
);
1167 uwq
= list_first_entry(&fork_event
,
1171 * If fork_event list wasn't empty and in turn
1172 * the event wasn't already released by fork
1173 * (the event is allocated on fork kernel
1174 * stack), put the event back to its place in
1175 * the event_wq. fork_event head will be freed
1176 * as soon as we return so the event cannot
1177 * stay queued there no matter the current
1180 list_del(&uwq
->wq
.entry
);
1181 __add_wait_queue(&ctx
->event_wqh
, &uwq
->wq
);
1184 * Leave the event in the waitqueue and report
1185 * error to userland if we failed to resolve
1186 * the userfault fork.
1189 userfaultfd_event_complete(ctx
, uwq
);
1192 * Here the fork thread aborted and the
1193 * refcount from the fork thread on fork_nctx
1194 * has already been released. We still hold
1195 * the reference we took before releasing the
1196 * lock above. If resolve_userfault_fork
1197 * failed we've to drop it because the
1198 * fork_nctx has to be freed in such case. If
1199 * it succeeded we'll hold it because the new
1200 * uffd references it.
1203 userfaultfd_ctx_put(fork_nctx
);
1205 spin_unlock_irq(&ctx
->event_wqh
.lock
);
1211 static ssize_t
userfaultfd_read(struct file
*file
, char __user
*buf
,
1212 size_t count
, loff_t
*ppos
)
1214 struct userfaultfd_ctx
*ctx
= file
->private_data
;
1215 ssize_t _ret
, ret
= 0;
1216 struct uffd_msg msg
;
1217 int no_wait
= file
->f_flags
& O_NONBLOCK
;
1218 struct inode
*inode
= file_inode(file
);
1220 if (!userfaultfd_is_initialized(ctx
))
1224 if (count
< sizeof(msg
))
1225 return ret
? ret
: -EINVAL
;
1226 _ret
= userfaultfd_ctx_read(ctx
, no_wait
, &msg
, inode
);
1228 return ret
? ret
: _ret
;
1229 if (copy_to_user((__u64 __user
*) buf
, &msg
, sizeof(msg
)))
1230 return ret
? ret
: -EFAULT
;
1233 count
-= sizeof(msg
);
1235 * Allow to read more than one fault at time but only
1236 * block if waiting for the very first one.
1238 no_wait
= O_NONBLOCK
;
1242 static void __wake_userfault(struct userfaultfd_ctx
*ctx
,
1243 struct userfaultfd_wake_range
*range
)
1245 spin_lock_irq(&ctx
->fault_pending_wqh
.lock
);
1246 /* wake all in the range and autoremove */
1247 if (waitqueue_active(&ctx
->fault_pending_wqh
))
1248 __wake_up_locked_key(&ctx
->fault_pending_wqh
, TASK_NORMAL
,
1250 if (waitqueue_active(&ctx
->fault_wqh
))
1251 __wake_up(&ctx
->fault_wqh
, TASK_NORMAL
, 1, range
);
1252 spin_unlock_irq(&ctx
->fault_pending_wqh
.lock
);
1255 static __always_inline
void wake_userfault(struct userfaultfd_ctx
*ctx
,
1256 struct userfaultfd_wake_range
*range
)
1262 * To be sure waitqueue_active() is not reordered by the CPU
1263 * before the pagetable update, use an explicit SMP memory
1264 * barrier here. PT lock release or mmap_read_unlock(mm) still
1265 * have release semantics that can allow the
1266 * waitqueue_active() to be reordered before the pte update.
1271 * Use waitqueue_active because it's very frequent to
1272 * change the address space atomically even if there are no
1273 * userfaults yet. So we take the spinlock only when we're
1274 * sure we've userfaults to wake.
1277 seq
= read_seqcount_begin(&ctx
->refile_seq
);
1278 need_wakeup
= waitqueue_active(&ctx
->fault_pending_wqh
) ||
1279 waitqueue_active(&ctx
->fault_wqh
);
1281 } while (read_seqcount_retry(&ctx
->refile_seq
, seq
));
1283 __wake_userfault(ctx
, range
);
1286 static __always_inline
int validate_unaligned_range(
1287 struct mm_struct
*mm
, __u64 start
, __u64 len
)
1289 __u64 task_size
= mm
->task_size
;
1291 if (len
& ~PAGE_MASK
)
1295 if (start
< mmap_min_addr
)
1297 if (start
>= task_size
)
1299 if (len
> task_size
- start
)
1301 if (start
+ len
<= start
)
1306 static __always_inline
int validate_range(struct mm_struct
*mm
,
1307 __u64 start
, __u64 len
)
1309 if (start
& ~PAGE_MASK
)
1312 return validate_unaligned_range(mm
, start
, len
);
1315 static int userfaultfd_register(struct userfaultfd_ctx
*ctx
,
1318 struct mm_struct
*mm
= ctx
->mm
;
1319 struct vm_area_struct
*vma
, *prev
, *cur
;
1321 struct uffdio_register uffdio_register
;
1322 struct uffdio_register __user
*user_uffdio_register
;
1323 unsigned long vm_flags
, new_flags
;
1326 unsigned long start
, end
, vma_end
;
1327 struct vma_iterator vmi
;
1328 bool wp_async
= userfaultfd_wp_async_ctx(ctx
);
1330 user_uffdio_register
= (struct uffdio_register __user
*) arg
;
1333 if (copy_from_user(&uffdio_register
, user_uffdio_register
,
1334 sizeof(uffdio_register
)-sizeof(__u64
)))
1338 if (!uffdio_register
.mode
)
1340 if (uffdio_register
.mode
& ~UFFD_API_REGISTER_MODES
)
1343 if (uffdio_register
.mode
& UFFDIO_REGISTER_MODE_MISSING
)
1344 vm_flags
|= VM_UFFD_MISSING
;
1345 if (uffdio_register
.mode
& UFFDIO_REGISTER_MODE_WP
) {
1346 #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_WP
1349 vm_flags
|= VM_UFFD_WP
;
1351 if (uffdio_register
.mode
& UFFDIO_REGISTER_MODE_MINOR
) {
1352 #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR
1355 vm_flags
|= VM_UFFD_MINOR
;
1358 ret
= validate_range(mm
, uffdio_register
.range
.start
,
1359 uffdio_register
.range
.len
);
1363 start
= uffdio_register
.range
.start
;
1364 end
= start
+ uffdio_register
.range
.len
;
1367 if (!mmget_not_zero(mm
))
1371 mmap_write_lock(mm
);
1372 vma_iter_init(&vmi
, mm
, start
);
1373 vma
= vma_find(&vmi
, end
);
1378 * If the first vma contains huge pages, make sure start address
1379 * is aligned to huge page size.
1381 if (is_vm_hugetlb_page(vma
)) {
1382 unsigned long vma_hpagesize
= vma_kernel_pagesize(vma
);
1384 if (start
& (vma_hpagesize
- 1))
1389 * Search for not compatible vmas.
1392 basic_ioctls
= false;
1397 BUG_ON(!!cur
->vm_userfaultfd_ctx
.ctx
^
1398 !!(cur
->vm_flags
& __VM_UFFD_FLAGS
));
1400 /* check not compatible vmas */
1402 if (!vma_can_userfault(cur
, vm_flags
, wp_async
))
1406 * UFFDIO_COPY will fill file holes even without
1407 * PROT_WRITE. This check enforces that if this is a
1408 * MAP_SHARED, the process has write permission to the backing
1409 * file. If VM_MAYWRITE is set it also enforces that on a
1410 * MAP_SHARED vma: there is no F_WRITE_SEAL and no further
1411 * F_WRITE_SEAL can be taken until the vma is destroyed.
1414 if (unlikely(!(cur
->vm_flags
& VM_MAYWRITE
)))
1418 * If this vma contains ending address, and huge pages
1421 if (is_vm_hugetlb_page(cur
) && end
<= cur
->vm_end
&&
1422 end
> cur
->vm_start
) {
1423 unsigned long vma_hpagesize
= vma_kernel_pagesize(cur
);
1427 if (end
& (vma_hpagesize
- 1))
1430 if ((vm_flags
& VM_UFFD_WP
) && !(cur
->vm_flags
& VM_MAYWRITE
))
1434 * Check that this vma isn't already owned by a
1435 * different userfaultfd. We can't allow more than one
1436 * userfaultfd to own a single vma simultaneously or we
1437 * wouldn't know which one to deliver the userfaults to.
1440 if (cur
->vm_userfaultfd_ctx
.ctx
&&
1441 cur
->vm_userfaultfd_ctx
.ctx
!= ctx
)
1445 * Note vmas containing huge pages
1447 if (is_vm_hugetlb_page(cur
))
1448 basic_ioctls
= true;
1451 } for_each_vma_range(vmi
, cur
, end
);
1454 vma_iter_set(&vmi
, start
);
1455 prev
= vma_prev(&vmi
);
1456 if (vma
->vm_start
< start
)
1460 for_each_vma_range(vmi
, vma
, end
) {
1463 BUG_ON(!vma_can_userfault(vma
, vm_flags
, wp_async
));
1464 BUG_ON(vma
->vm_userfaultfd_ctx
.ctx
&&
1465 vma
->vm_userfaultfd_ctx
.ctx
!= ctx
);
1466 WARN_ON(!(vma
->vm_flags
& VM_MAYWRITE
));
1469 * Nothing to do: this vma is already registered into this
1470 * userfaultfd and with the right tracking mode too.
1472 if (vma
->vm_userfaultfd_ctx
.ctx
== ctx
&&
1473 (vma
->vm_flags
& vm_flags
) == vm_flags
)
1476 if (vma
->vm_start
> start
)
1477 start
= vma
->vm_start
;
1478 vma_end
= min(end
, vma
->vm_end
);
1480 new_flags
= (vma
->vm_flags
& ~__VM_UFFD_FLAGS
) | vm_flags
;
1481 vma
= vma_modify_flags_uffd(&vmi
, prev
, vma
, start
, vma_end
,
1483 (struct vm_userfaultfd_ctx
){ctx
});
1490 * In the vma_merge() successful mprotect-like case 8:
1491 * the next vma was merged into the current one and
1492 * the current one has not been updated yet.
1494 vma_start_write(vma
);
1495 userfaultfd_set_vm_flags(vma
, new_flags
);
1496 vma
->vm_userfaultfd_ctx
.ctx
= ctx
;
1498 if (is_vm_hugetlb_page(vma
) && uffd_disable_huge_pmd_share(vma
))
1499 hugetlb_unshare_all_pmds(vma
);
1503 start
= vma
->vm_end
;
1507 mmap_write_unlock(mm
);
1512 ioctls_out
= basic_ioctls
? UFFD_API_RANGE_IOCTLS_BASIC
:
1513 UFFD_API_RANGE_IOCTLS
;
1516 * Declare the WP ioctl only if the WP mode is
1517 * specified and all checks passed with the range
1519 if (!(uffdio_register
.mode
& UFFDIO_REGISTER_MODE_WP
))
1520 ioctls_out
&= ~((__u64
)1 << _UFFDIO_WRITEPROTECT
);
1522 /* CONTINUE ioctl is only supported for MINOR ranges. */
1523 if (!(uffdio_register
.mode
& UFFDIO_REGISTER_MODE_MINOR
))
1524 ioctls_out
&= ~((__u64
)1 << _UFFDIO_CONTINUE
);
1527 * Now that we scanned all vmas we can already tell
1528 * userland which ioctls methods are guaranteed to
1529 * succeed on this range.
1531 if (put_user(ioctls_out
, &user_uffdio_register
->ioctls
))
1538 static int userfaultfd_unregister(struct userfaultfd_ctx
*ctx
,
1541 struct mm_struct
*mm
= ctx
->mm
;
1542 struct vm_area_struct
*vma
, *prev
, *cur
;
1544 struct uffdio_range uffdio_unregister
;
1545 unsigned long new_flags
;
1547 unsigned long start
, end
, vma_end
;
1548 const void __user
*buf
= (void __user
*)arg
;
1549 struct vma_iterator vmi
;
1550 bool wp_async
= userfaultfd_wp_async_ctx(ctx
);
1553 if (copy_from_user(&uffdio_unregister
, buf
, sizeof(uffdio_unregister
)))
1556 ret
= validate_range(mm
, uffdio_unregister
.start
,
1557 uffdio_unregister
.len
);
1561 start
= uffdio_unregister
.start
;
1562 end
= start
+ uffdio_unregister
.len
;
1565 if (!mmget_not_zero(mm
))
1568 mmap_write_lock(mm
);
1570 vma_iter_init(&vmi
, mm
, start
);
1571 vma
= vma_find(&vmi
, end
);
1576 * If the first vma contains huge pages, make sure start address
1577 * is aligned to huge page size.
1579 if (is_vm_hugetlb_page(vma
)) {
1580 unsigned long vma_hpagesize
= vma_kernel_pagesize(vma
);
1582 if (start
& (vma_hpagesize
- 1))
1587 * Search for not compatible vmas.
1594 BUG_ON(!!cur
->vm_userfaultfd_ctx
.ctx
^
1595 !!(cur
->vm_flags
& __VM_UFFD_FLAGS
));
1598 * Check not compatible vmas, not strictly required
1599 * here as not compatible vmas cannot have an
1600 * userfaultfd_ctx registered on them, but this
1601 * provides for more strict behavior to notice
1602 * unregistration errors.
1604 if (!vma_can_userfault(cur
, cur
->vm_flags
, wp_async
))
1608 } for_each_vma_range(vmi
, cur
, end
);
1611 vma_iter_set(&vmi
, start
);
1612 prev
= vma_prev(&vmi
);
1613 if (vma
->vm_start
< start
)
1617 for_each_vma_range(vmi
, vma
, end
) {
1620 BUG_ON(!vma_can_userfault(vma
, vma
->vm_flags
, wp_async
));
1623 * Nothing to do: this vma is already registered into this
1624 * userfaultfd and with the right tracking mode too.
1626 if (!vma
->vm_userfaultfd_ctx
.ctx
)
1629 WARN_ON(!(vma
->vm_flags
& VM_MAYWRITE
));
1631 if (vma
->vm_start
> start
)
1632 start
= vma
->vm_start
;
1633 vma_end
= min(end
, vma
->vm_end
);
1635 if (userfaultfd_missing(vma
)) {
1637 * Wake any concurrent pending userfault while
1638 * we unregister, so they will not hang
1639 * permanently and it avoids userland to call
1640 * UFFDIO_WAKE explicitly.
1642 struct userfaultfd_wake_range range
;
1643 range
.start
= start
;
1644 range
.len
= vma_end
- start
;
1645 wake_userfault(vma
->vm_userfaultfd_ctx
.ctx
, &range
);
1648 /* Reset ptes for the whole vma range if wr-protected */
1649 if (userfaultfd_wp(vma
))
1650 uffd_wp_range(vma
, start
, vma_end
- start
, false);
1652 new_flags
= vma
->vm_flags
& ~__VM_UFFD_FLAGS
;
1653 vma
= vma_modify_flags_uffd(&vmi
, prev
, vma
, start
, vma_end
,
1654 new_flags
, NULL_VM_UFFD_CTX
);
1661 * In the vma_merge() successful mprotect-like case 8:
1662 * the next vma was merged into the current one and
1663 * the current one has not been updated yet.
1665 vma_start_write(vma
);
1666 userfaultfd_set_vm_flags(vma
, new_flags
);
1667 vma
->vm_userfaultfd_ctx
= NULL_VM_UFFD_CTX
;
1671 start
= vma
->vm_end
;
1675 mmap_write_unlock(mm
);
1682 * userfaultfd_wake may be used in combination with the
1683 * UFFDIO_*_MODE_DONTWAKE to wakeup userfaults in batches.
1685 static int userfaultfd_wake(struct userfaultfd_ctx
*ctx
,
1689 struct uffdio_range uffdio_wake
;
1690 struct userfaultfd_wake_range range
;
1691 const void __user
*buf
= (void __user
*)arg
;
1694 if (copy_from_user(&uffdio_wake
, buf
, sizeof(uffdio_wake
)))
1697 ret
= validate_range(ctx
->mm
, uffdio_wake
.start
, uffdio_wake
.len
);
1701 range
.start
= uffdio_wake
.start
;
1702 range
.len
= uffdio_wake
.len
;
1705 * len == 0 means wake all and we don't want to wake all here,
1706 * so check it again to be sure.
1708 VM_BUG_ON(!range
.len
);
1710 wake_userfault(ctx
, &range
);
1717 static int userfaultfd_copy(struct userfaultfd_ctx
*ctx
,
1721 struct uffdio_copy uffdio_copy
;
1722 struct uffdio_copy __user
*user_uffdio_copy
;
1723 struct userfaultfd_wake_range range
;
1724 uffd_flags_t flags
= 0;
1726 user_uffdio_copy
= (struct uffdio_copy __user
*) arg
;
1729 if (atomic_read(&ctx
->mmap_changing
))
1733 if (copy_from_user(&uffdio_copy
, user_uffdio_copy
,
1734 /* don't copy "copy" last field */
1735 sizeof(uffdio_copy
)-sizeof(__s64
)))
1738 ret
= validate_unaligned_range(ctx
->mm
, uffdio_copy
.src
,
1742 ret
= validate_range(ctx
->mm
, uffdio_copy
.dst
, uffdio_copy
.len
);
1747 if (uffdio_copy
.mode
& ~(UFFDIO_COPY_MODE_DONTWAKE
|UFFDIO_COPY_MODE_WP
))
1749 if (uffdio_copy
.mode
& UFFDIO_COPY_MODE_WP
)
1750 flags
|= MFILL_ATOMIC_WP
;
1751 if (mmget_not_zero(ctx
->mm
)) {
1752 ret
= mfill_atomic_copy(ctx
->mm
, uffdio_copy
.dst
, uffdio_copy
.src
,
1753 uffdio_copy
.len
, &ctx
->mmap_changing
,
1759 if (unlikely(put_user(ret
, &user_uffdio_copy
->copy
)))
1764 /* len == 0 would wake all */
1766 if (!(uffdio_copy
.mode
& UFFDIO_COPY_MODE_DONTWAKE
)) {
1767 range
.start
= uffdio_copy
.dst
;
1768 wake_userfault(ctx
, &range
);
1770 ret
= range
.len
== uffdio_copy
.len
? 0 : -EAGAIN
;
1775 static int userfaultfd_zeropage(struct userfaultfd_ctx
*ctx
,
1779 struct uffdio_zeropage uffdio_zeropage
;
1780 struct uffdio_zeropage __user
*user_uffdio_zeropage
;
1781 struct userfaultfd_wake_range range
;
1783 user_uffdio_zeropage
= (struct uffdio_zeropage __user
*) arg
;
1786 if (atomic_read(&ctx
->mmap_changing
))
1790 if (copy_from_user(&uffdio_zeropage
, user_uffdio_zeropage
,
1791 /* don't copy "zeropage" last field */
1792 sizeof(uffdio_zeropage
)-sizeof(__s64
)))
1795 ret
= validate_range(ctx
->mm
, uffdio_zeropage
.range
.start
,
1796 uffdio_zeropage
.range
.len
);
1800 if (uffdio_zeropage
.mode
& ~UFFDIO_ZEROPAGE_MODE_DONTWAKE
)
1803 if (mmget_not_zero(ctx
->mm
)) {
1804 ret
= mfill_atomic_zeropage(ctx
->mm
, uffdio_zeropage
.range
.start
,
1805 uffdio_zeropage
.range
.len
,
1806 &ctx
->mmap_changing
);
1811 if (unlikely(put_user(ret
, &user_uffdio_zeropage
->zeropage
)))
1815 /* len == 0 would wake all */
1818 if (!(uffdio_zeropage
.mode
& UFFDIO_ZEROPAGE_MODE_DONTWAKE
)) {
1819 range
.start
= uffdio_zeropage
.range
.start
;
1820 wake_userfault(ctx
, &range
);
1822 ret
= range
.len
== uffdio_zeropage
.range
.len
? 0 : -EAGAIN
;
1827 static int userfaultfd_writeprotect(struct userfaultfd_ctx
*ctx
,
1831 struct uffdio_writeprotect uffdio_wp
;
1832 struct uffdio_writeprotect __user
*user_uffdio_wp
;
1833 struct userfaultfd_wake_range range
;
1834 bool mode_wp
, mode_dontwake
;
1836 if (atomic_read(&ctx
->mmap_changing
))
1839 user_uffdio_wp
= (struct uffdio_writeprotect __user
*) arg
;
1841 if (copy_from_user(&uffdio_wp
, user_uffdio_wp
,
1842 sizeof(struct uffdio_writeprotect
)))
1845 ret
= validate_range(ctx
->mm
, uffdio_wp
.range
.start
,
1846 uffdio_wp
.range
.len
);
1850 if (uffdio_wp
.mode
& ~(UFFDIO_WRITEPROTECT_MODE_DONTWAKE
|
1851 UFFDIO_WRITEPROTECT_MODE_WP
))
1854 mode_wp
= uffdio_wp
.mode
& UFFDIO_WRITEPROTECT_MODE_WP
;
1855 mode_dontwake
= uffdio_wp
.mode
& UFFDIO_WRITEPROTECT_MODE_DONTWAKE
;
1857 if (mode_wp
&& mode_dontwake
)
1860 if (mmget_not_zero(ctx
->mm
)) {
1861 ret
= mwriteprotect_range(ctx
->mm
, uffdio_wp
.range
.start
,
1862 uffdio_wp
.range
.len
, mode_wp
,
1863 &ctx
->mmap_changing
);
1872 if (!mode_wp
&& !mode_dontwake
) {
1873 range
.start
= uffdio_wp
.range
.start
;
1874 range
.len
= uffdio_wp
.range
.len
;
1875 wake_userfault(ctx
, &range
);
1880 static int userfaultfd_continue(struct userfaultfd_ctx
*ctx
, unsigned long arg
)
1883 struct uffdio_continue uffdio_continue
;
1884 struct uffdio_continue __user
*user_uffdio_continue
;
1885 struct userfaultfd_wake_range range
;
1886 uffd_flags_t flags
= 0;
1888 user_uffdio_continue
= (struct uffdio_continue __user
*)arg
;
1891 if (atomic_read(&ctx
->mmap_changing
))
1895 if (copy_from_user(&uffdio_continue
, user_uffdio_continue
,
1896 /* don't copy the output fields */
1897 sizeof(uffdio_continue
) - (sizeof(__s64
))))
1900 ret
= validate_range(ctx
->mm
, uffdio_continue
.range
.start
,
1901 uffdio_continue
.range
.len
);
1906 if (uffdio_continue
.mode
& ~(UFFDIO_CONTINUE_MODE_DONTWAKE
|
1907 UFFDIO_CONTINUE_MODE_WP
))
1909 if (uffdio_continue
.mode
& UFFDIO_CONTINUE_MODE_WP
)
1910 flags
|= MFILL_ATOMIC_WP
;
1912 if (mmget_not_zero(ctx
->mm
)) {
1913 ret
= mfill_atomic_continue(ctx
->mm
, uffdio_continue
.range
.start
,
1914 uffdio_continue
.range
.len
,
1915 &ctx
->mmap_changing
, flags
);
1921 if (unlikely(put_user(ret
, &user_uffdio_continue
->mapped
)))
1926 /* len == 0 would wake all */
1929 if (!(uffdio_continue
.mode
& UFFDIO_CONTINUE_MODE_DONTWAKE
)) {
1930 range
.start
= uffdio_continue
.range
.start
;
1931 wake_userfault(ctx
, &range
);
1933 ret
= range
.len
== uffdio_continue
.range
.len
? 0 : -EAGAIN
;
1939 static inline int userfaultfd_poison(struct userfaultfd_ctx
*ctx
, unsigned long arg
)
1942 struct uffdio_poison uffdio_poison
;
1943 struct uffdio_poison __user
*user_uffdio_poison
;
1944 struct userfaultfd_wake_range range
;
1946 user_uffdio_poison
= (struct uffdio_poison __user
*)arg
;
1949 if (atomic_read(&ctx
->mmap_changing
))
1953 if (copy_from_user(&uffdio_poison
, user_uffdio_poison
,
1954 /* don't copy the output fields */
1955 sizeof(uffdio_poison
) - (sizeof(__s64
))))
1958 ret
= validate_range(ctx
->mm
, uffdio_poison
.range
.start
,
1959 uffdio_poison
.range
.len
);
1964 if (uffdio_poison
.mode
& ~UFFDIO_POISON_MODE_DONTWAKE
)
1967 if (mmget_not_zero(ctx
->mm
)) {
1968 ret
= mfill_atomic_poison(ctx
->mm
, uffdio_poison
.range
.start
,
1969 uffdio_poison
.range
.len
,
1970 &ctx
->mmap_changing
, 0);
1976 if (unlikely(put_user(ret
, &user_uffdio_poison
->updated
)))
1981 /* len == 0 would wake all */
1984 if (!(uffdio_poison
.mode
& UFFDIO_POISON_MODE_DONTWAKE
)) {
1985 range
.start
= uffdio_poison
.range
.start
;
1986 wake_userfault(ctx
, &range
);
1988 ret
= range
.len
== uffdio_poison
.range
.len
? 0 : -EAGAIN
;
1994 bool userfaultfd_wp_async(struct vm_area_struct
*vma
)
1996 return userfaultfd_wp_async_ctx(vma
->vm_userfaultfd_ctx
.ctx
);
1999 static inline unsigned int uffd_ctx_features(__u64 user_features
)
2002 * For the current set of features the bits just coincide. Set
2003 * UFFD_FEATURE_INITIALIZED to mark the features as enabled.
2005 return (unsigned int)user_features
| UFFD_FEATURE_INITIALIZED
;
2009 * userland asks for a certain API version and we return which bits
2010 * and ioctl commands are implemented in this kernel for such API
2011 * version or -EINVAL if unknown.
2013 static int userfaultfd_api(struct userfaultfd_ctx
*ctx
,
2016 struct uffdio_api uffdio_api
;
2017 void __user
*buf
= (void __user
*)arg
;
2018 unsigned int ctx_features
;
2023 if (copy_from_user(&uffdio_api
, buf
, sizeof(uffdio_api
)))
2025 features
= uffdio_api
.features
;
2027 if (uffdio_api
.api
!= UFFD_API
|| (features
& ~UFFD_API_FEATURES
))
2030 if ((features
& UFFD_FEATURE_EVENT_FORK
) && !capable(CAP_SYS_PTRACE
))
2033 /* WP_ASYNC relies on WP_UNPOPULATED, choose it unconditionally */
2034 if (features
& UFFD_FEATURE_WP_ASYNC
)
2035 features
|= UFFD_FEATURE_WP_UNPOPULATED
;
2037 /* report all available features and ioctls to userland */
2038 uffdio_api
.features
= UFFD_API_FEATURES
;
2039 #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR
2040 uffdio_api
.features
&=
2041 ~(UFFD_FEATURE_MINOR_HUGETLBFS
| UFFD_FEATURE_MINOR_SHMEM
);
2043 #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_WP
2044 uffdio_api
.features
&= ~UFFD_FEATURE_PAGEFAULT_FLAG_WP
;
2046 #ifndef CONFIG_PTE_MARKER_UFFD_WP
2047 uffdio_api
.features
&= ~UFFD_FEATURE_WP_HUGETLBFS_SHMEM
;
2048 uffdio_api
.features
&= ~UFFD_FEATURE_WP_UNPOPULATED
;
2049 uffdio_api
.features
&= ~UFFD_FEATURE_WP_ASYNC
;
2051 uffdio_api
.ioctls
= UFFD_API_IOCTLS
;
2053 if (copy_to_user(buf
, &uffdio_api
, sizeof(uffdio_api
)))
2056 /* only enable the requested features for this uffd context */
2057 ctx_features
= uffd_ctx_features(features
);
2059 if (cmpxchg(&ctx
->features
, 0, ctx_features
) != 0)
2066 memset(&uffdio_api
, 0, sizeof(uffdio_api
));
2067 if (copy_to_user(buf
, &uffdio_api
, sizeof(uffdio_api
)))
2072 static long userfaultfd_ioctl(struct file
*file
, unsigned cmd
,
2076 struct userfaultfd_ctx
*ctx
= file
->private_data
;
2078 if (cmd
!= UFFDIO_API
&& !userfaultfd_is_initialized(ctx
))
2083 ret
= userfaultfd_api(ctx
, arg
);
2085 case UFFDIO_REGISTER
:
2086 ret
= userfaultfd_register(ctx
, arg
);
2088 case UFFDIO_UNREGISTER
:
2089 ret
= userfaultfd_unregister(ctx
, arg
);
2092 ret
= userfaultfd_wake(ctx
, arg
);
2095 ret
= userfaultfd_copy(ctx
, arg
);
2097 case UFFDIO_ZEROPAGE
:
2098 ret
= userfaultfd_zeropage(ctx
, arg
);
2100 case UFFDIO_WRITEPROTECT
:
2101 ret
= userfaultfd_writeprotect(ctx
, arg
);
2103 case UFFDIO_CONTINUE
:
2104 ret
= userfaultfd_continue(ctx
, arg
);
2107 ret
= userfaultfd_poison(ctx
, arg
);
2113 #ifdef CONFIG_PROC_FS
2114 static void userfaultfd_show_fdinfo(struct seq_file
*m
, struct file
*f
)
2116 struct userfaultfd_ctx
*ctx
= f
->private_data
;
2117 wait_queue_entry_t
*wq
;
2118 unsigned long pending
= 0, total
= 0;
2120 spin_lock_irq(&ctx
->fault_pending_wqh
.lock
);
2121 list_for_each_entry(wq
, &ctx
->fault_pending_wqh
.head
, entry
) {
2125 list_for_each_entry(wq
, &ctx
->fault_wqh
.head
, entry
) {
2128 spin_unlock_irq(&ctx
->fault_pending_wqh
.lock
);
2131 * If more protocols will be added, there will be all shown
2132 * separated by a space. Like this:
2133 * protocols: aa:... bb:...
2135 seq_printf(m
, "pending:\t%lu\ntotal:\t%lu\nAPI:\t%Lx:%x:%Lx\n",
2136 pending
, total
, UFFD_API
, ctx
->features
,
2137 UFFD_API_IOCTLS
|UFFD_API_RANGE_IOCTLS
);
2141 static const struct file_operations userfaultfd_fops
= {
2142 #ifdef CONFIG_PROC_FS
2143 .show_fdinfo
= userfaultfd_show_fdinfo
,
2145 .release
= userfaultfd_release
,
2146 .poll
= userfaultfd_poll
,
2147 .read
= userfaultfd_read
,
2148 .unlocked_ioctl
= userfaultfd_ioctl
,
2149 .compat_ioctl
= compat_ptr_ioctl
,
2150 .llseek
= noop_llseek
,
2153 static void init_once_userfaultfd_ctx(void *mem
)
2155 struct userfaultfd_ctx
*ctx
= (struct userfaultfd_ctx
*) mem
;
2157 init_waitqueue_head(&ctx
->fault_pending_wqh
);
2158 init_waitqueue_head(&ctx
->fault_wqh
);
2159 init_waitqueue_head(&ctx
->event_wqh
);
2160 init_waitqueue_head(&ctx
->fd_wqh
);
2161 seqcount_spinlock_init(&ctx
->refile_seq
, &ctx
->fault_pending_wqh
.lock
);
2164 static int new_userfaultfd(int flags
)
2166 struct userfaultfd_ctx
*ctx
;
2169 BUG_ON(!current
->mm
);
2171 /* Check the UFFD_* constants for consistency. */
2172 BUILD_BUG_ON(UFFD_USER_MODE_ONLY
& UFFD_SHARED_FCNTL_FLAGS
);
2173 BUILD_BUG_ON(UFFD_CLOEXEC
!= O_CLOEXEC
);
2174 BUILD_BUG_ON(UFFD_NONBLOCK
!= O_NONBLOCK
);
2176 if (flags
& ~(UFFD_SHARED_FCNTL_FLAGS
| UFFD_USER_MODE_ONLY
))
2179 ctx
= kmem_cache_alloc(userfaultfd_ctx_cachep
, GFP_KERNEL
);
2183 refcount_set(&ctx
->refcount
, 1);
2186 ctx
->released
= false;
2187 atomic_set(&ctx
->mmap_changing
, 0);
2188 ctx
->mm
= current
->mm
;
2189 /* prevent the mm struct to be freed */
2192 fd
= anon_inode_getfd_secure("[userfaultfd]", &userfaultfd_fops
, ctx
,
2193 O_RDONLY
| (flags
& UFFD_SHARED_FCNTL_FLAGS
), NULL
);
2196 kmem_cache_free(userfaultfd_ctx_cachep
, ctx
);
2201 static inline bool userfaultfd_syscall_allowed(int flags
)
2203 /* Userspace-only page faults are always allowed */
2204 if (flags
& UFFD_USER_MODE_ONLY
)
2208 * The user is requesting a userfaultfd which can handle kernel faults.
2209 * Privileged users are always allowed to do this.
2211 if (capable(CAP_SYS_PTRACE
))
2214 /* Otherwise, access to kernel fault handling is sysctl controlled. */
2215 return sysctl_unprivileged_userfaultfd
;
2218 SYSCALL_DEFINE1(userfaultfd
, int, flags
)
2220 if (!userfaultfd_syscall_allowed(flags
))
2223 return new_userfaultfd(flags
);
2226 static long userfaultfd_dev_ioctl(struct file
*file
, unsigned int cmd
, unsigned long flags
)
2228 if (cmd
!= USERFAULTFD_IOC_NEW
)
2231 return new_userfaultfd(flags
);
2234 static const struct file_operations userfaultfd_dev_fops
= {
2235 .unlocked_ioctl
= userfaultfd_dev_ioctl
,
2236 .compat_ioctl
= userfaultfd_dev_ioctl
,
2237 .owner
= THIS_MODULE
,
2238 .llseek
= noop_llseek
,
2241 static struct miscdevice userfaultfd_misc
= {
2242 .minor
= MISC_DYNAMIC_MINOR
,
2243 .name
= "userfaultfd",
2244 .fops
= &userfaultfd_dev_fops
2247 static int __init
userfaultfd_init(void)
2251 ret
= misc_register(&userfaultfd_misc
);
2255 userfaultfd_ctx_cachep
= kmem_cache_create("userfaultfd_ctx_cache",
2256 sizeof(struct userfaultfd_ctx
),
2258 SLAB_HWCACHE_ALIGN
|SLAB_PANIC
,
2259 init_once_userfaultfd_ctx
);
2260 #ifdef CONFIG_SYSCTL
2261 register_sysctl_init("vm", vm_userfaultfd_table
);
2265 __initcall(userfaultfd_init
);