1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * fs/userfaultfd.c 4 * 5 * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org> 6 * Copyright (C) 2008-2009 Red Hat, Inc. 7 * Copyright (C) 2015 Red Hat, Inc. 8 * 9 * Some part derived from fs/eventfd.c (anon inode setup) and 10 * mm/ksm.c (mm hashing). 11 */ 12 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/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> 34 35 static int sysctl_unprivileged_userfaultfd __read_mostly; 36 37 #ifdef CONFIG_SYSCTL 38 static struct ctl_table vm_userfaultfd_table[] = { 39 { 40 .procname = "unprivileged_userfaultfd", 41 .data = &sysctl_unprivileged_userfaultfd, 42 .maxlen = sizeof(sysctl_unprivileged_userfaultfd), 43 .mode = 0644, 44 .proc_handler = proc_dointvec_minmax, 45 .extra1 = SYSCTL_ZERO, 46 .extra2 = SYSCTL_ONE, 47 }, 48 }; 49 #endif 50 51 static struct kmem_cache *userfaultfd_ctx_cachep __ro_after_init; 52 53 /* 54 * Start with fault_pending_wqh and fault_wqh so they're more likely 55 * to be in the same cacheline. 56 * 57 * Locking order: 58 * fd_wqh.lock 59 * fault_pending_wqh.lock 60 * fault_wqh.lock 61 * event_wqh.lock 62 * 63 * To avoid deadlocks, IRQs must be disabled when taking any of the above locks, 64 * since fd_wqh.lock is taken by aio_poll() while it's holding a lock that's 65 * also taken in IRQ context. 66 */ 67 struct userfaultfd_ctx { 68 /* waitqueue head for the pending (i.e. not read) userfaults */ 69 wait_queue_head_t fault_pending_wqh; 70 /* waitqueue head for the userfaults */ 71 wait_queue_head_t fault_wqh; 72 /* waitqueue head for the pseudo fd to wakeup poll/read */ 73 wait_queue_head_t fd_wqh; 74 /* waitqueue head for events */ 75 wait_queue_head_t event_wqh; 76 /* a refile sequence protected by fault_pending_wqh lock */ 77 seqcount_spinlock_t refile_seq; 78 /* pseudo fd refcounting */ 79 refcount_t refcount; 80 /* userfaultfd syscall flags */ 81 unsigned int flags; 82 /* features requested from the userspace */ 83 unsigned int features; 84 /* released */ 85 bool released; 86 /* memory mappings are changing because of non-cooperative event */ 87 atomic_t mmap_changing; 88 /* mm with one ore more vmas attached to this userfaultfd_ctx */ 89 struct mm_struct *mm; 90 }; 91 92 struct userfaultfd_fork_ctx { 93 struct userfaultfd_ctx *orig; 94 struct userfaultfd_ctx *new; 95 struct list_head list; 96 }; 97 98 struct userfaultfd_unmap_ctx { 99 struct userfaultfd_ctx *ctx; 100 unsigned long start; 101 unsigned long end; 102 struct list_head list; 103 }; 104 105 struct userfaultfd_wait_queue { 106 struct uffd_msg msg; 107 wait_queue_entry_t wq; 108 struct userfaultfd_ctx *ctx; 109 bool waken; 110 }; 111 112 struct userfaultfd_wake_range { 113 unsigned long start; 114 unsigned long len; 115 }; 116 117 /* internal indication that UFFD_API ioctl was successfully executed */ 118 #define UFFD_FEATURE_INITIALIZED (1u << 31) 119 120 static bool userfaultfd_is_initialized(struct userfaultfd_ctx *ctx) 121 { 122 return ctx->features & UFFD_FEATURE_INITIALIZED; 123 } 124 125 static bool userfaultfd_wp_async_ctx(struct userfaultfd_ctx *ctx) 126 { 127 return ctx && (ctx->features & UFFD_FEATURE_WP_ASYNC); 128 } 129 130 /* 131 * Whether WP_UNPOPULATED is enabled on the uffd context. It is only 132 * meaningful when userfaultfd_wp()==true on the vma and when it's 133 * anonymous. 134 */ 135 bool userfaultfd_wp_unpopulated(struct vm_area_struct *vma) 136 { 137 struct userfaultfd_ctx *ctx = vma->vm_userfaultfd_ctx.ctx; 138 139 if (!ctx) 140 return false; 141 142 return ctx->features & UFFD_FEATURE_WP_UNPOPULATED; 143 } 144 145 static void userfaultfd_set_vm_flags(struct vm_area_struct *vma, 146 vm_flags_t flags) 147 { 148 const bool uffd_wp_changed = (vma->vm_flags ^ flags) & VM_UFFD_WP; 149 150 vm_flags_reset(vma, flags); 151 /* 152 * For shared mappings, we want to enable writenotify while 153 * userfaultfd-wp is enabled (see vma_wants_writenotify()). We'll simply 154 * recalculate vma->vm_page_prot whenever userfaultfd-wp changes. 155 */ 156 if ((vma->vm_flags & VM_SHARED) && uffd_wp_changed) 157 vma_set_page_prot(vma); 158 } 159 160 static int userfaultfd_wake_function(wait_queue_entry_t *wq, unsigned mode, 161 int wake_flags, void *key) 162 { 163 struct userfaultfd_wake_range *range = key; 164 int ret; 165 struct userfaultfd_wait_queue *uwq; 166 unsigned long start, len; 167 168 uwq = container_of(wq, struct userfaultfd_wait_queue, wq); 169 ret = 0; 170 /* len == 0 means wake all */ 171 start = range->start; 172 len = range->len; 173 if (len && (start > uwq->msg.arg.pagefault.address || 174 start + len <= uwq->msg.arg.pagefault.address)) 175 goto out; 176 WRITE_ONCE(uwq->waken, true); 177 /* 178 * The Program-Order guarantees provided by the scheduler 179 * ensure uwq->waken is visible before the task is woken. 180 */ 181 ret = wake_up_state(wq->private, mode); 182 if (ret) { 183 /* 184 * Wake only once, autoremove behavior. 185 * 186 * After the effect of list_del_init is visible to the other 187 * CPUs, the waitqueue may disappear from under us, see the 188 * !list_empty_careful() in handle_userfault(). 189 * 190 * try_to_wake_up() has an implicit smp_mb(), and the 191 * wq->private is read before calling the extern function 192 * "wake_up_state" (which in turns calls try_to_wake_up). 193 */ 194 list_del_init(&wq->entry); 195 } 196 out: 197 return ret; 198 } 199 200 /** 201 * userfaultfd_ctx_get - Acquires a reference to the internal userfaultfd 202 * context. 203 * @ctx: [in] Pointer to the userfaultfd context. 204 */ 205 static void userfaultfd_ctx_get(struct userfaultfd_ctx *ctx) 206 { 207 refcount_inc(&ctx->refcount); 208 } 209 210 /** 211 * userfaultfd_ctx_put - Releases a reference to the internal userfaultfd 212 * context. 213 * @ctx: [in] Pointer to userfaultfd context. 214 * 215 * The userfaultfd context reference must have been previously acquired either 216 * with userfaultfd_ctx_get() or userfaultfd_ctx_fdget(). 217 */ 218 static void userfaultfd_ctx_put(struct userfaultfd_ctx *ctx) 219 { 220 if (refcount_dec_and_test(&ctx->refcount)) { 221 VM_BUG_ON(spin_is_locked(&ctx->fault_pending_wqh.lock)); 222 VM_BUG_ON(waitqueue_active(&ctx->fault_pending_wqh)); 223 VM_BUG_ON(spin_is_locked(&ctx->fault_wqh.lock)); 224 VM_BUG_ON(waitqueue_active(&ctx->fault_wqh)); 225 VM_BUG_ON(spin_is_locked(&ctx->event_wqh.lock)); 226 VM_BUG_ON(waitqueue_active(&ctx->event_wqh)); 227 VM_BUG_ON(spin_is_locked(&ctx->fd_wqh.lock)); 228 VM_BUG_ON(waitqueue_active(&ctx->fd_wqh)); 229 mmdrop(ctx->mm); 230 kmem_cache_free(userfaultfd_ctx_cachep, ctx); 231 } 232 } 233 234 static inline void msg_init(struct uffd_msg *msg) 235 { 236 BUILD_BUG_ON(sizeof(struct uffd_msg) != 32); 237 /* 238 * Must use memset to zero out the paddings or kernel data is 239 * leaked to userland. 240 */ 241 memset(msg, 0, sizeof(struct uffd_msg)); 242 } 243 244 static inline struct uffd_msg userfault_msg(unsigned long address, 245 unsigned long real_address, 246 unsigned int flags, 247 unsigned long reason, 248 unsigned int features) 249 { 250 struct uffd_msg msg; 251 252 msg_init(&msg); 253 msg.event = UFFD_EVENT_PAGEFAULT; 254 255 msg.arg.pagefault.address = (features & UFFD_FEATURE_EXACT_ADDRESS) ? 256 real_address : address; 257 258 /* 259 * These flags indicate why the userfault occurred: 260 * - UFFD_PAGEFAULT_FLAG_WP indicates a write protect fault. 261 * - UFFD_PAGEFAULT_FLAG_MINOR indicates a minor fault. 262 * - Neither of these flags being set indicates a MISSING fault. 263 * 264 * Separately, UFFD_PAGEFAULT_FLAG_WRITE indicates it was a write 265 * fault. Otherwise, it was a read fault. 266 */ 267 if (flags & FAULT_FLAG_WRITE) 268 msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WRITE; 269 if (reason & VM_UFFD_WP) 270 msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WP; 271 if (reason & VM_UFFD_MINOR) 272 msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_MINOR; 273 if (features & UFFD_FEATURE_THREAD_ID) 274 msg.arg.pagefault.feat.ptid = task_pid_vnr(current); 275 return msg; 276 } 277 278 #ifdef CONFIG_HUGETLB_PAGE 279 /* 280 * Same functionality as userfaultfd_must_wait below with modifications for 281 * hugepmd ranges. 282 */ 283 static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx, 284 struct vm_fault *vmf, 285 unsigned long reason) 286 { 287 struct vm_area_struct *vma = vmf->vma; 288 pte_t *ptep, pte; 289 bool ret = true; 290 291 assert_fault_locked(vmf); 292 293 ptep = hugetlb_walk(vma, vmf->address, vma_mmu_pagesize(vma)); 294 if (!ptep) 295 goto out; 296 297 ret = false; 298 pte = huge_ptep_get(ptep); 299 300 /* 301 * Lockless access: we're in a wait_event so it's ok if it 302 * changes under us. PTE markers should be handled the same as none 303 * ptes here. 304 */ 305 if (huge_pte_none_mostly(pte)) 306 ret = true; 307 if (!huge_pte_write(pte) && (reason & VM_UFFD_WP)) 308 ret = true; 309 out: 310 return ret; 311 } 312 #else 313 static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx, 314 struct vm_fault *vmf, 315 unsigned long reason) 316 { 317 return false; /* should never get here */ 318 } 319 #endif /* CONFIG_HUGETLB_PAGE */ 320 321 /* 322 * Verify the pagetables are still not ok after having reigstered into 323 * the fault_pending_wqh to avoid userland having to UFFDIO_WAKE any 324 * userfault that has already been resolved, if userfaultfd_read and 325 * UFFDIO_COPY|ZEROPAGE are being run simultaneously on two different 326 * threads. 327 */ 328 static inline bool userfaultfd_must_wait(struct userfaultfd_ctx *ctx, 329 struct vm_fault *vmf, 330 unsigned long reason) 331 { 332 struct mm_struct *mm = ctx->mm; 333 unsigned long address = vmf->address; 334 pgd_t *pgd; 335 p4d_t *p4d; 336 pud_t *pud; 337 pmd_t *pmd, _pmd; 338 pte_t *pte; 339 pte_t ptent; 340 bool ret = true; 341 342 assert_fault_locked(vmf); 343 344 pgd = pgd_offset(mm, address); 345 if (!pgd_present(*pgd)) 346 goto out; 347 p4d = p4d_offset(pgd, address); 348 if (!p4d_present(*p4d)) 349 goto out; 350 pud = pud_offset(p4d, address); 351 if (!pud_present(*pud)) 352 goto out; 353 pmd = pmd_offset(pud, address); 354 again: 355 _pmd = pmdp_get_lockless(pmd); 356 if (pmd_none(_pmd)) 357 goto out; 358 359 ret = false; 360 if (!pmd_present(_pmd) || pmd_devmap(_pmd)) 361 goto out; 362 363 if (pmd_trans_huge(_pmd)) { 364 if (!pmd_write(_pmd) && (reason & VM_UFFD_WP)) 365 ret = true; 366 goto out; 367 } 368 369 pte = pte_offset_map(pmd, address); 370 if (!pte) { 371 ret = true; 372 goto again; 373 } 374 /* 375 * Lockless access: we're in a wait_event so it's ok if it 376 * changes under us. PTE markers should be handled the same as none 377 * ptes here. 378 */ 379 ptent = ptep_get(pte); 380 if (pte_none_mostly(ptent)) 381 ret = true; 382 if (!pte_write(ptent) && (reason & VM_UFFD_WP)) 383 ret = true; 384 pte_unmap(pte); 385 386 out: 387 return ret; 388 } 389 390 static inline unsigned int userfaultfd_get_blocking_state(unsigned int flags) 391 { 392 if (flags & FAULT_FLAG_INTERRUPTIBLE) 393 return TASK_INTERRUPTIBLE; 394 395 if (flags & FAULT_FLAG_KILLABLE) 396 return TASK_KILLABLE; 397 398 return TASK_UNINTERRUPTIBLE; 399 } 400 401 /* 402 * The locking rules involved in returning VM_FAULT_RETRY depending on 403 * FAULT_FLAG_ALLOW_RETRY, FAULT_FLAG_RETRY_NOWAIT and 404 * FAULT_FLAG_KILLABLE are not straightforward. The "Caution" 405 * recommendation in __lock_page_or_retry is not an understatement. 406 * 407 * If FAULT_FLAG_ALLOW_RETRY is set, the mmap_lock must be released 408 * before returning VM_FAULT_RETRY only if FAULT_FLAG_RETRY_NOWAIT is 409 * not set. 410 * 411 * If FAULT_FLAG_ALLOW_RETRY is set but FAULT_FLAG_KILLABLE is not 412 * set, VM_FAULT_RETRY can still be returned if and only if there are 413 * fatal_signal_pending()s, and the mmap_lock must be released before 414 * returning it. 415 */ 416 vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason) 417 { 418 struct vm_area_struct *vma = vmf->vma; 419 struct mm_struct *mm = vma->vm_mm; 420 struct userfaultfd_ctx *ctx; 421 struct userfaultfd_wait_queue uwq; 422 vm_fault_t ret = VM_FAULT_SIGBUS; 423 bool must_wait; 424 unsigned int blocking_state; 425 426 /* 427 * We don't do userfault handling for the final child pid update. 428 * 429 * We also don't do userfault handling during 430 * coredumping. hugetlbfs has the special 431 * hugetlb_follow_page_mask() to skip missing pages in the 432 * FOLL_DUMP case, anon memory also checks for FOLL_DUMP with 433 * the no_page_table() helper in follow_page_mask(), but the 434 * shmem_vm_ops->fault method is invoked even during 435 * coredumping and it ends up here. 436 */ 437 if (current->flags & (PF_EXITING|PF_DUMPCORE)) 438 goto out; 439 440 assert_fault_locked(vmf); 441 442 ctx = vma->vm_userfaultfd_ctx.ctx; 443 if (!ctx) 444 goto out; 445 446 BUG_ON(ctx->mm != mm); 447 448 /* Any unrecognized flag is a bug. */ 449 VM_BUG_ON(reason & ~__VM_UFFD_FLAGS); 450 /* 0 or > 1 flags set is a bug; we expect exactly 1. */ 451 VM_BUG_ON(!reason || (reason & (reason - 1))); 452 453 if (ctx->features & UFFD_FEATURE_SIGBUS) 454 goto out; 455 if (!(vmf->flags & FAULT_FLAG_USER) && (ctx->flags & UFFD_USER_MODE_ONLY)) 456 goto out; 457 458 /* 459 * If it's already released don't get it. This avoids to loop 460 * in __get_user_pages if userfaultfd_release waits on the 461 * caller of handle_userfault to release the mmap_lock. 462 */ 463 if (unlikely(READ_ONCE(ctx->released))) { 464 /* 465 * Don't return VM_FAULT_SIGBUS in this case, so a non 466 * cooperative manager can close the uffd after the 467 * last UFFDIO_COPY, without risking to trigger an 468 * involuntary SIGBUS if the process was starting the 469 * userfaultfd while the userfaultfd was still armed 470 * (but after the last UFFDIO_COPY). If the uffd 471 * wasn't already closed when the userfault reached 472 * this point, that would normally be solved by 473 * userfaultfd_must_wait returning 'false'. 474 * 475 * If we were to return VM_FAULT_SIGBUS here, the non 476 * cooperative manager would be instead forced to 477 * always call UFFDIO_UNREGISTER before it can safely 478 * close the uffd. 479 */ 480 ret = VM_FAULT_NOPAGE; 481 goto out; 482 } 483 484 /* 485 * Check that we can return VM_FAULT_RETRY. 486 * 487 * NOTE: it should become possible to return VM_FAULT_RETRY 488 * even if FAULT_FLAG_TRIED is set without leading to gup() 489 * -EBUSY failures, if the userfaultfd is to be extended for 490 * VM_UFFD_WP tracking and we intend to arm the userfault 491 * without first stopping userland access to the memory. For 492 * VM_UFFD_MISSING userfaults this is enough for now. 493 */ 494 if (unlikely(!(vmf->flags & FAULT_FLAG_ALLOW_RETRY))) { 495 /* 496 * Validate the invariant that nowait must allow retry 497 * to be sure not to return SIGBUS erroneously on 498 * nowait invocations. 499 */ 500 BUG_ON(vmf->flags & FAULT_FLAG_RETRY_NOWAIT); 501 #ifdef CONFIG_DEBUG_VM 502 if (printk_ratelimit()) { 503 printk(KERN_WARNING 504 "FAULT_FLAG_ALLOW_RETRY missing %x\n", 505 vmf->flags); 506 dump_stack(); 507 } 508 #endif 509 goto out; 510 } 511 512 /* 513 * Handle nowait, not much to do other than tell it to retry 514 * and wait. 515 */ 516 ret = VM_FAULT_RETRY; 517 if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT) 518 goto out; 519 520 /* take the reference before dropping the mmap_lock */ 521 userfaultfd_ctx_get(ctx); 522 523 init_waitqueue_func_entry(&uwq.wq, userfaultfd_wake_function); 524 uwq.wq.private = current; 525 uwq.msg = userfault_msg(vmf->address, vmf->real_address, vmf->flags, 526 reason, ctx->features); 527 uwq.ctx = ctx; 528 uwq.waken = false; 529 530 blocking_state = userfaultfd_get_blocking_state(vmf->flags); 531 532 /* 533 * Take the vma lock now, in order to safely call 534 * userfaultfd_huge_must_wait() later. Since acquiring the 535 * (sleepable) vma lock can modify the current task state, that 536 * must be before explicitly calling set_current_state(). 537 */ 538 if (is_vm_hugetlb_page(vma)) 539 hugetlb_vma_lock_read(vma); 540 541 spin_lock_irq(&ctx->fault_pending_wqh.lock); 542 /* 543 * After the __add_wait_queue the uwq is visible to userland 544 * through poll/read(). 545 */ 546 __add_wait_queue(&ctx->fault_pending_wqh, &uwq.wq); 547 /* 548 * The smp_mb() after __set_current_state prevents the reads 549 * following the spin_unlock to happen before the list_add in 550 * __add_wait_queue. 551 */ 552 set_current_state(blocking_state); 553 spin_unlock_irq(&ctx->fault_pending_wqh.lock); 554 555 if (!is_vm_hugetlb_page(vma)) 556 must_wait = userfaultfd_must_wait(ctx, vmf, reason); 557 else 558 must_wait = userfaultfd_huge_must_wait(ctx, vmf, reason); 559 if (is_vm_hugetlb_page(vma)) 560 hugetlb_vma_unlock_read(vma); 561 release_fault_lock(vmf); 562 563 if (likely(must_wait && !READ_ONCE(ctx->released))) { 564 wake_up_poll(&ctx->fd_wqh, EPOLLIN); 565 schedule(); 566 } 567 568 __set_current_state(TASK_RUNNING); 569 570 /* 571 * Here we race with the list_del; list_add in 572 * userfaultfd_ctx_read(), however because we don't ever run 573 * list_del_init() to refile across the two lists, the prev 574 * and next pointers will never point to self. list_add also 575 * would never let any of the two pointers to point to 576 * self. So list_empty_careful won't risk to see both pointers 577 * pointing to self at any time during the list refile. The 578 * only case where list_del_init() is called is the full 579 * removal in the wake function and there we don't re-list_add 580 * and it's fine not to block on the spinlock. The uwq on this 581 * kernel stack can be released after the list_del_init. 582 */ 583 if (!list_empty_careful(&uwq.wq.entry)) { 584 spin_lock_irq(&ctx->fault_pending_wqh.lock); 585 /* 586 * No need of list_del_init(), the uwq on the stack 587 * will be freed shortly anyway. 588 */ 589 list_del(&uwq.wq.entry); 590 spin_unlock_irq(&ctx->fault_pending_wqh.lock); 591 } 592 593 /* 594 * ctx may go away after this if the userfault pseudo fd is 595 * already released. 596 */ 597 userfaultfd_ctx_put(ctx); 598 599 out: 600 return ret; 601 } 602 603 static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx, 604 struct userfaultfd_wait_queue *ewq) 605 { 606 struct userfaultfd_ctx *release_new_ctx; 607 608 if (WARN_ON_ONCE(current->flags & PF_EXITING)) 609 goto out; 610 611 ewq->ctx = ctx; 612 init_waitqueue_entry(&ewq->wq, current); 613 release_new_ctx = NULL; 614 615 spin_lock_irq(&ctx->event_wqh.lock); 616 /* 617 * After the __add_wait_queue the uwq is visible to userland 618 * through poll/read(). 619 */ 620 __add_wait_queue(&ctx->event_wqh, &ewq->wq); 621 for (;;) { 622 set_current_state(TASK_KILLABLE); 623 if (ewq->msg.event == 0) 624 break; 625 if (READ_ONCE(ctx->released) || 626 fatal_signal_pending(current)) { 627 /* 628 * &ewq->wq may be queued in fork_event, but 629 * __remove_wait_queue ignores the head 630 * parameter. It would be a problem if it 631 * didn't. 632 */ 633 __remove_wait_queue(&ctx->event_wqh, &ewq->wq); 634 if (ewq->msg.event == UFFD_EVENT_FORK) { 635 struct userfaultfd_ctx *new; 636 637 new = (struct userfaultfd_ctx *) 638 (unsigned long) 639 ewq->msg.arg.reserved.reserved1; 640 release_new_ctx = new; 641 } 642 break; 643 } 644 645 spin_unlock_irq(&ctx->event_wqh.lock); 646 647 wake_up_poll(&ctx->fd_wqh, EPOLLIN); 648 schedule(); 649 650 spin_lock_irq(&ctx->event_wqh.lock); 651 } 652 __set_current_state(TASK_RUNNING); 653 spin_unlock_irq(&ctx->event_wqh.lock); 654 655 if (release_new_ctx) { 656 struct vm_area_struct *vma; 657 struct mm_struct *mm = release_new_ctx->mm; 658 VMA_ITERATOR(vmi, mm, 0); 659 660 /* the various vma->vm_userfaultfd_ctx still points to it */ 661 mmap_write_lock(mm); 662 for_each_vma(vmi, vma) { 663 if (vma->vm_userfaultfd_ctx.ctx == release_new_ctx) { 664 vma_start_write(vma); 665 vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; 666 userfaultfd_set_vm_flags(vma, 667 vma->vm_flags & ~__VM_UFFD_FLAGS); 668 } 669 } 670 mmap_write_unlock(mm); 671 672 userfaultfd_ctx_put(release_new_ctx); 673 } 674 675 /* 676 * ctx may go away after this if the userfault pseudo fd is 677 * already released. 678 */ 679 out: 680 atomic_dec(&ctx->mmap_changing); 681 VM_BUG_ON(atomic_read(&ctx->mmap_changing) < 0); 682 userfaultfd_ctx_put(ctx); 683 } 684 685 static void userfaultfd_event_complete(struct userfaultfd_ctx *ctx, 686 struct userfaultfd_wait_queue *ewq) 687 { 688 ewq->msg.event = 0; 689 wake_up_locked(&ctx->event_wqh); 690 __remove_wait_queue(&ctx->event_wqh, &ewq->wq); 691 } 692 693 int dup_userfaultfd(struct vm_area_struct *vma, struct list_head *fcs) 694 { 695 struct userfaultfd_ctx *ctx = NULL, *octx; 696 struct userfaultfd_fork_ctx *fctx; 697 698 octx = vma->vm_userfaultfd_ctx.ctx; 699 if (!octx || !(octx->features & UFFD_FEATURE_EVENT_FORK)) { 700 vma_start_write(vma); 701 vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; 702 userfaultfd_set_vm_flags(vma, vma->vm_flags & ~__VM_UFFD_FLAGS); 703 return 0; 704 } 705 706 list_for_each_entry(fctx, fcs, list) 707 if (fctx->orig == octx) { 708 ctx = fctx->new; 709 break; 710 } 711 712 if (!ctx) { 713 fctx = kmalloc(sizeof(*fctx), GFP_KERNEL); 714 if (!fctx) 715 return -ENOMEM; 716 717 ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL); 718 if (!ctx) { 719 kfree(fctx); 720 return -ENOMEM; 721 } 722 723 refcount_set(&ctx->refcount, 1); 724 ctx->flags = octx->flags; 725 ctx->features = octx->features; 726 ctx->released = false; 727 atomic_set(&ctx->mmap_changing, 0); 728 ctx->mm = vma->vm_mm; 729 mmgrab(ctx->mm); 730 731 userfaultfd_ctx_get(octx); 732 atomic_inc(&octx->mmap_changing); 733 fctx->orig = octx; 734 fctx->new = ctx; 735 list_add_tail(&fctx->list, fcs); 736 } 737 738 vma->vm_userfaultfd_ctx.ctx = ctx; 739 return 0; 740 } 741 742 static void dup_fctx(struct userfaultfd_fork_ctx *fctx) 743 { 744 struct userfaultfd_ctx *ctx = fctx->orig; 745 struct userfaultfd_wait_queue ewq; 746 747 msg_init(&ewq.msg); 748 749 ewq.msg.event = UFFD_EVENT_FORK; 750 ewq.msg.arg.reserved.reserved1 = (unsigned long)fctx->new; 751 752 userfaultfd_event_wait_completion(ctx, &ewq); 753 } 754 755 void dup_userfaultfd_complete(struct list_head *fcs) 756 { 757 struct userfaultfd_fork_ctx *fctx, *n; 758 759 list_for_each_entry_safe(fctx, n, fcs, list) { 760 dup_fctx(fctx); 761 list_del(&fctx->list); 762 kfree(fctx); 763 } 764 } 765 766 void mremap_userfaultfd_prep(struct vm_area_struct *vma, 767 struct vm_userfaultfd_ctx *vm_ctx) 768 { 769 struct userfaultfd_ctx *ctx; 770 771 ctx = vma->vm_userfaultfd_ctx.ctx; 772 773 if (!ctx) 774 return; 775 776 if (ctx->features & UFFD_FEATURE_EVENT_REMAP) { 777 vm_ctx->ctx = ctx; 778 userfaultfd_ctx_get(ctx); 779 atomic_inc(&ctx->mmap_changing); 780 } else { 781 /* Drop uffd context if remap feature not enabled */ 782 vma_start_write(vma); 783 vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; 784 userfaultfd_set_vm_flags(vma, vma->vm_flags & ~__VM_UFFD_FLAGS); 785 } 786 } 787 788 void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *vm_ctx, 789 unsigned long from, unsigned long to, 790 unsigned long len) 791 { 792 struct userfaultfd_ctx *ctx = vm_ctx->ctx; 793 struct userfaultfd_wait_queue ewq; 794 795 if (!ctx) 796 return; 797 798 if (to & ~PAGE_MASK) { 799 userfaultfd_ctx_put(ctx); 800 return; 801 } 802 803 msg_init(&ewq.msg); 804 805 ewq.msg.event = UFFD_EVENT_REMAP; 806 ewq.msg.arg.remap.from = from; 807 ewq.msg.arg.remap.to = to; 808 ewq.msg.arg.remap.len = len; 809 810 userfaultfd_event_wait_completion(ctx, &ewq); 811 } 812 813 bool userfaultfd_remove(struct vm_area_struct *vma, 814 unsigned long start, unsigned long end) 815 { 816 struct mm_struct *mm = vma->vm_mm; 817 struct userfaultfd_ctx *ctx; 818 struct userfaultfd_wait_queue ewq; 819 820 ctx = vma->vm_userfaultfd_ctx.ctx; 821 if (!ctx || !(ctx->features & UFFD_FEATURE_EVENT_REMOVE)) 822 return true; 823 824 userfaultfd_ctx_get(ctx); 825 atomic_inc(&ctx->mmap_changing); 826 mmap_read_unlock(mm); 827 828 msg_init(&ewq.msg); 829 830 ewq.msg.event = UFFD_EVENT_REMOVE; 831 ewq.msg.arg.remove.start = start; 832 ewq.msg.arg.remove.end = end; 833 834 userfaultfd_event_wait_completion(ctx, &ewq); 835 836 return false; 837 } 838 839 static bool has_unmap_ctx(struct userfaultfd_ctx *ctx, struct list_head *unmaps, 840 unsigned long start, unsigned long end) 841 { 842 struct userfaultfd_unmap_ctx *unmap_ctx; 843 844 list_for_each_entry(unmap_ctx, unmaps, list) 845 if (unmap_ctx->ctx == ctx && unmap_ctx->start == start && 846 unmap_ctx->end == end) 847 return true; 848 849 return false; 850 } 851 852 int userfaultfd_unmap_prep(struct vm_area_struct *vma, unsigned long start, 853 unsigned long end, struct list_head *unmaps) 854 { 855 struct userfaultfd_unmap_ctx *unmap_ctx; 856 struct userfaultfd_ctx *ctx = vma->vm_userfaultfd_ctx.ctx; 857 858 if (!ctx || !(ctx->features & UFFD_FEATURE_EVENT_UNMAP) || 859 has_unmap_ctx(ctx, unmaps, start, end)) 860 return 0; 861 862 unmap_ctx = kzalloc(sizeof(*unmap_ctx), GFP_KERNEL); 863 if (!unmap_ctx) 864 return -ENOMEM; 865 866 userfaultfd_ctx_get(ctx); 867 atomic_inc(&ctx->mmap_changing); 868 unmap_ctx->ctx = ctx; 869 unmap_ctx->start = start; 870 unmap_ctx->end = end; 871 list_add_tail(&unmap_ctx->list, unmaps); 872 873 return 0; 874 } 875 876 void userfaultfd_unmap_complete(struct mm_struct *mm, struct list_head *uf) 877 { 878 struct userfaultfd_unmap_ctx *ctx, *n; 879 struct userfaultfd_wait_queue ewq; 880 881 list_for_each_entry_safe(ctx, n, uf, list) { 882 msg_init(&ewq.msg); 883 884 ewq.msg.event = UFFD_EVENT_UNMAP; 885 ewq.msg.arg.remove.start = ctx->start; 886 ewq.msg.arg.remove.end = ctx->end; 887 888 userfaultfd_event_wait_completion(ctx->ctx, &ewq); 889 890 list_del(&ctx->list); 891 kfree(ctx); 892 } 893 } 894 895 static int userfaultfd_release(struct inode *inode, struct file *file) 896 { 897 struct userfaultfd_ctx *ctx = file->private_data; 898 struct mm_struct *mm = ctx->mm; 899 struct vm_area_struct *vma, *prev; 900 /* len == 0 means wake all */ 901 struct userfaultfd_wake_range range = { .len = 0, }; 902 unsigned long new_flags; 903 VMA_ITERATOR(vmi, mm, 0); 904 905 WRITE_ONCE(ctx->released, true); 906 907 if (!mmget_not_zero(mm)) 908 goto wakeup; 909 910 /* 911 * Flush page faults out of all CPUs. NOTE: all page faults 912 * must be retried without returning VM_FAULT_SIGBUS if 913 * userfaultfd_ctx_get() succeeds but vma->vma_userfault_ctx 914 * changes while handle_userfault released the mmap_lock. So 915 * it's critical that released is set to true (above), before 916 * taking the mmap_lock for writing. 917 */ 918 mmap_write_lock(mm); 919 prev = NULL; 920 for_each_vma(vmi, vma) { 921 cond_resched(); 922 BUG_ON(!!vma->vm_userfaultfd_ctx.ctx ^ 923 !!(vma->vm_flags & __VM_UFFD_FLAGS)); 924 if (vma->vm_userfaultfd_ctx.ctx != ctx) { 925 prev = vma; 926 continue; 927 } 928 new_flags = vma->vm_flags & ~__VM_UFFD_FLAGS; 929 vma = vma_modify_flags_uffd(&vmi, prev, vma, vma->vm_start, 930 vma->vm_end, new_flags, 931 NULL_VM_UFFD_CTX); 932 933 vma_start_write(vma); 934 userfaultfd_set_vm_flags(vma, new_flags); 935 vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; 936 937 prev = vma; 938 } 939 mmap_write_unlock(mm); 940 mmput(mm); 941 wakeup: 942 /* 943 * After no new page faults can wait on this fault_*wqh, flush 944 * the last page faults that may have been already waiting on 945 * the fault_*wqh. 946 */ 947 spin_lock_irq(&ctx->fault_pending_wqh.lock); 948 __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, &range); 949 __wake_up(&ctx->fault_wqh, TASK_NORMAL, 1, &range); 950 spin_unlock_irq(&ctx->fault_pending_wqh.lock); 951 952 /* Flush pending events that may still wait on event_wqh */ 953 wake_up_all(&ctx->event_wqh); 954 955 wake_up_poll(&ctx->fd_wqh, EPOLLHUP); 956 userfaultfd_ctx_put(ctx); 957 return 0; 958 } 959 960 /* fault_pending_wqh.lock must be hold by the caller */ 961 static inline struct userfaultfd_wait_queue *find_userfault_in( 962 wait_queue_head_t *wqh) 963 { 964 wait_queue_entry_t *wq; 965 struct userfaultfd_wait_queue *uwq; 966 967 lockdep_assert_held(&wqh->lock); 968 969 uwq = NULL; 970 if (!waitqueue_active(wqh)) 971 goto out; 972 /* walk in reverse to provide FIFO behavior to read userfaults */ 973 wq = list_last_entry(&wqh->head, typeof(*wq), entry); 974 uwq = container_of(wq, struct userfaultfd_wait_queue, wq); 975 out: 976 return uwq; 977 } 978 979 static inline struct userfaultfd_wait_queue *find_userfault( 980 struct userfaultfd_ctx *ctx) 981 { 982 return find_userfault_in(&ctx->fault_pending_wqh); 983 } 984 985 static inline struct userfaultfd_wait_queue *find_userfault_evt( 986 struct userfaultfd_ctx *ctx) 987 { 988 return find_userfault_in(&ctx->event_wqh); 989 } 990 991 static __poll_t userfaultfd_poll(struct file *file, poll_table *wait) 992 { 993 struct userfaultfd_ctx *ctx = file->private_data; 994 __poll_t ret; 995 996 poll_wait(file, &ctx->fd_wqh, wait); 997 998 if (!userfaultfd_is_initialized(ctx)) 999 return EPOLLERR; 1000 1001 /* 1002 * poll() never guarantees that read won't block. 1003 * userfaults can be waken before they're read(). 1004 */ 1005 if (unlikely(!(file->f_flags & O_NONBLOCK))) 1006 return EPOLLERR; 1007 /* 1008 * lockless access to see if there are pending faults 1009 * __pollwait last action is the add_wait_queue but 1010 * the spin_unlock would allow the waitqueue_active to 1011 * pass above the actual list_add inside 1012 * add_wait_queue critical section. So use a full 1013 * memory barrier to serialize the list_add write of 1014 * add_wait_queue() with the waitqueue_active read 1015 * below. 1016 */ 1017 ret = 0; 1018 smp_mb(); 1019 if (waitqueue_active(&ctx->fault_pending_wqh)) 1020 ret = EPOLLIN; 1021 else if (waitqueue_active(&ctx->event_wqh)) 1022 ret = EPOLLIN; 1023 1024 return ret; 1025 } 1026 1027 static const struct file_operations userfaultfd_fops; 1028 1029 static int resolve_userfault_fork(struct userfaultfd_ctx *new, 1030 struct inode *inode, 1031 struct uffd_msg *msg) 1032 { 1033 int fd; 1034 1035 fd = anon_inode_create_getfd("[userfaultfd]", &userfaultfd_fops, new, 1036 O_RDONLY | (new->flags & UFFD_SHARED_FCNTL_FLAGS), inode); 1037 if (fd < 0) 1038 return fd; 1039 1040 msg->arg.reserved.reserved1 = 0; 1041 msg->arg.fork.ufd = fd; 1042 return 0; 1043 } 1044 1045 static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait, 1046 struct uffd_msg *msg, struct inode *inode) 1047 { 1048 ssize_t ret; 1049 DECLARE_WAITQUEUE(wait, current); 1050 struct userfaultfd_wait_queue *uwq; 1051 /* 1052 * Handling fork event requires sleeping operations, so 1053 * we drop the event_wqh lock, then do these ops, then 1054 * lock it back and wake up the waiter. While the lock is 1055 * dropped the ewq may go away so we keep track of it 1056 * carefully. 1057 */ 1058 LIST_HEAD(fork_event); 1059 struct userfaultfd_ctx *fork_nctx = NULL; 1060 1061 /* always take the fd_wqh lock before the fault_pending_wqh lock */ 1062 spin_lock_irq(&ctx->fd_wqh.lock); 1063 __add_wait_queue(&ctx->fd_wqh, &wait); 1064 for (;;) { 1065 set_current_state(TASK_INTERRUPTIBLE); 1066 spin_lock(&ctx->fault_pending_wqh.lock); 1067 uwq = find_userfault(ctx); 1068 if (uwq) { 1069 /* 1070 * Use a seqcount to repeat the lockless check 1071 * in wake_userfault() to avoid missing 1072 * wakeups because during the refile both 1073 * waitqueue could become empty if this is the 1074 * only userfault. 1075 */ 1076 write_seqcount_begin(&ctx->refile_seq); 1077 1078 /* 1079 * The fault_pending_wqh.lock prevents the uwq 1080 * to disappear from under us. 1081 * 1082 * Refile this userfault from 1083 * fault_pending_wqh to fault_wqh, it's not 1084 * pending anymore after we read it. 1085 * 1086 * Use list_del() by hand (as 1087 * userfaultfd_wake_function also uses 1088 * list_del_init() by hand) to be sure nobody 1089 * changes __remove_wait_queue() to use 1090 * list_del_init() in turn breaking the 1091 * !list_empty_careful() check in 1092 * handle_userfault(). The uwq->wq.head list 1093 * must never be empty at any time during the 1094 * refile, or the waitqueue could disappear 1095 * from under us. The "wait_queue_head_t" 1096 * parameter of __remove_wait_queue() is unused 1097 * anyway. 1098 */ 1099 list_del(&uwq->wq.entry); 1100 add_wait_queue(&ctx->fault_wqh, &uwq->wq); 1101 1102 write_seqcount_end(&ctx->refile_seq); 1103 1104 /* careful to always initialize msg if ret == 0 */ 1105 *msg = uwq->msg; 1106 spin_unlock(&ctx->fault_pending_wqh.lock); 1107 ret = 0; 1108 break; 1109 } 1110 spin_unlock(&ctx->fault_pending_wqh.lock); 1111 1112 spin_lock(&ctx->event_wqh.lock); 1113 uwq = find_userfault_evt(ctx); 1114 if (uwq) { 1115 *msg = uwq->msg; 1116 1117 if (uwq->msg.event == UFFD_EVENT_FORK) { 1118 fork_nctx = (struct userfaultfd_ctx *) 1119 (unsigned long) 1120 uwq->msg.arg.reserved.reserved1; 1121 list_move(&uwq->wq.entry, &fork_event); 1122 /* 1123 * fork_nctx can be freed as soon as 1124 * we drop the lock, unless we take a 1125 * reference on it. 1126 */ 1127 userfaultfd_ctx_get(fork_nctx); 1128 spin_unlock(&ctx->event_wqh.lock); 1129 ret = 0; 1130 break; 1131 } 1132 1133 userfaultfd_event_complete(ctx, uwq); 1134 spin_unlock(&ctx->event_wqh.lock); 1135 ret = 0; 1136 break; 1137 } 1138 spin_unlock(&ctx->event_wqh.lock); 1139 1140 if (signal_pending(current)) { 1141 ret = -ERESTARTSYS; 1142 break; 1143 } 1144 if (no_wait) { 1145 ret = -EAGAIN; 1146 break; 1147 } 1148 spin_unlock_irq(&ctx->fd_wqh.lock); 1149 schedule(); 1150 spin_lock_irq(&ctx->fd_wqh.lock); 1151 } 1152 __remove_wait_queue(&ctx->fd_wqh, &wait); 1153 __set_current_state(TASK_RUNNING); 1154 spin_unlock_irq(&ctx->fd_wqh.lock); 1155 1156 if (!ret && msg->event == UFFD_EVENT_FORK) { 1157 ret = resolve_userfault_fork(fork_nctx, inode, msg); 1158 spin_lock_irq(&ctx->event_wqh.lock); 1159 if (!list_empty(&fork_event)) { 1160 /* 1161 * The fork thread didn't abort, so we can 1162 * drop the temporary refcount. 1163 */ 1164 userfaultfd_ctx_put(fork_nctx); 1165 1166 uwq = list_first_entry(&fork_event, 1167 typeof(*uwq), 1168 wq.entry); 1169 /* 1170 * If fork_event list wasn't empty and in turn 1171 * the event wasn't already released by fork 1172 * (the event is allocated on fork kernel 1173 * stack), put the event back to its place in 1174 * the event_wq. fork_event head will be freed 1175 * as soon as we return so the event cannot 1176 * stay queued there no matter the current 1177 * "ret" value. 1178 */ 1179 list_del(&uwq->wq.entry); 1180 __add_wait_queue(&ctx->event_wqh, &uwq->wq); 1181 1182 /* 1183 * Leave the event in the waitqueue and report 1184 * error to userland if we failed to resolve 1185 * the userfault fork. 1186 */ 1187 if (likely(!ret)) 1188 userfaultfd_event_complete(ctx, uwq); 1189 } else { 1190 /* 1191 * Here the fork thread aborted and the 1192 * refcount from the fork thread on fork_nctx 1193 * has already been released. We still hold 1194 * the reference we took before releasing the 1195 * lock above. If resolve_userfault_fork 1196 * failed we've to drop it because the 1197 * fork_nctx has to be freed in such case. If 1198 * it succeeded we'll hold it because the new 1199 * uffd references it. 1200 */ 1201 if (ret) 1202 userfaultfd_ctx_put(fork_nctx); 1203 } 1204 spin_unlock_irq(&ctx->event_wqh.lock); 1205 } 1206 1207 return ret; 1208 } 1209 1210 static ssize_t userfaultfd_read(struct file *file, char __user *buf, 1211 size_t count, loff_t *ppos) 1212 { 1213 struct userfaultfd_ctx *ctx = file->private_data; 1214 ssize_t _ret, ret = 0; 1215 struct uffd_msg msg; 1216 int no_wait = file->f_flags & O_NONBLOCK; 1217 struct inode *inode = file_inode(file); 1218 1219 if (!userfaultfd_is_initialized(ctx)) 1220 return -EINVAL; 1221 1222 for (;;) { 1223 if (count < sizeof(msg)) 1224 return ret ? ret : -EINVAL; 1225 _ret = userfaultfd_ctx_read(ctx, no_wait, &msg, inode); 1226 if (_ret < 0) 1227 return ret ? ret : _ret; 1228 if (copy_to_user((__u64 __user *) buf, &msg, sizeof(msg))) 1229 return ret ? ret : -EFAULT; 1230 ret += sizeof(msg); 1231 buf += sizeof(msg); 1232 count -= sizeof(msg); 1233 /* 1234 * Allow to read more than one fault at time but only 1235 * block if waiting for the very first one. 1236 */ 1237 no_wait = O_NONBLOCK; 1238 } 1239 } 1240 1241 static void __wake_userfault(struct userfaultfd_ctx *ctx, 1242 struct userfaultfd_wake_range *range) 1243 { 1244 spin_lock_irq(&ctx->fault_pending_wqh.lock); 1245 /* wake all in the range and autoremove */ 1246 if (waitqueue_active(&ctx->fault_pending_wqh)) 1247 __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, 1248 range); 1249 if (waitqueue_active(&ctx->fault_wqh)) 1250 __wake_up(&ctx->fault_wqh, TASK_NORMAL, 1, range); 1251 spin_unlock_irq(&ctx->fault_pending_wqh.lock); 1252 } 1253 1254 static __always_inline void wake_userfault(struct userfaultfd_ctx *ctx, 1255 struct userfaultfd_wake_range *range) 1256 { 1257 unsigned seq; 1258 bool need_wakeup; 1259 1260 /* 1261 * To be sure waitqueue_active() is not reordered by the CPU 1262 * before the pagetable update, use an explicit SMP memory 1263 * barrier here. PT lock release or mmap_read_unlock(mm) still 1264 * have release semantics that can allow the 1265 * waitqueue_active() to be reordered before the pte update. 1266 */ 1267 smp_mb(); 1268 1269 /* 1270 * Use waitqueue_active because it's very frequent to 1271 * change the address space atomically even if there are no 1272 * userfaults yet. So we take the spinlock only when we're 1273 * sure we've userfaults to wake. 1274 */ 1275 do { 1276 seq = read_seqcount_begin(&ctx->refile_seq); 1277 need_wakeup = waitqueue_active(&ctx->fault_pending_wqh) || 1278 waitqueue_active(&ctx->fault_wqh); 1279 cond_resched(); 1280 } while (read_seqcount_retry(&ctx->refile_seq, seq)); 1281 if (need_wakeup) 1282 __wake_userfault(ctx, range); 1283 } 1284 1285 static __always_inline int validate_unaligned_range( 1286 struct mm_struct *mm, __u64 start, __u64 len) 1287 { 1288 __u64 task_size = mm->task_size; 1289 1290 if (len & ~PAGE_MASK) 1291 return -EINVAL; 1292 if (!len) 1293 return -EINVAL; 1294 if (start < mmap_min_addr) 1295 return -EINVAL; 1296 if (start >= task_size) 1297 return -EINVAL; 1298 if (len > task_size - start) 1299 return -EINVAL; 1300 if (start + len <= start) 1301 return -EINVAL; 1302 return 0; 1303 } 1304 1305 static __always_inline int validate_range(struct mm_struct *mm, 1306 __u64 start, __u64 len) 1307 { 1308 if (start & ~PAGE_MASK) 1309 return -EINVAL; 1310 1311 return validate_unaligned_range(mm, start, len); 1312 } 1313 1314 static int userfaultfd_register(struct userfaultfd_ctx *ctx, 1315 unsigned long arg) 1316 { 1317 struct mm_struct *mm = ctx->mm; 1318 struct vm_area_struct *vma, *prev, *cur; 1319 int ret; 1320 struct uffdio_register uffdio_register; 1321 struct uffdio_register __user *user_uffdio_register; 1322 unsigned long vm_flags, new_flags; 1323 bool found; 1324 bool basic_ioctls; 1325 unsigned long start, end, vma_end; 1326 struct vma_iterator vmi; 1327 bool wp_async = userfaultfd_wp_async_ctx(ctx); 1328 1329 user_uffdio_register = (struct uffdio_register __user *) arg; 1330 1331 ret = -EFAULT; 1332 if (copy_from_user(&uffdio_register, user_uffdio_register, 1333 sizeof(uffdio_register)-sizeof(__u64))) 1334 goto out; 1335 1336 ret = -EINVAL; 1337 if (!uffdio_register.mode) 1338 goto out; 1339 if (uffdio_register.mode & ~UFFD_API_REGISTER_MODES) 1340 goto out; 1341 vm_flags = 0; 1342 if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MISSING) 1343 vm_flags |= VM_UFFD_MISSING; 1344 if (uffdio_register.mode & UFFDIO_REGISTER_MODE_WP) { 1345 #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_WP 1346 goto out; 1347 #endif 1348 vm_flags |= VM_UFFD_WP; 1349 } 1350 if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MINOR) { 1351 #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR 1352 goto out; 1353 #endif 1354 vm_flags |= VM_UFFD_MINOR; 1355 } 1356 1357 ret = validate_range(mm, uffdio_register.range.start, 1358 uffdio_register.range.len); 1359 if (ret) 1360 goto out; 1361 1362 start = uffdio_register.range.start; 1363 end = start + uffdio_register.range.len; 1364 1365 ret = -ENOMEM; 1366 if (!mmget_not_zero(mm)) 1367 goto out; 1368 1369 ret = -EINVAL; 1370 mmap_write_lock(mm); 1371 vma_iter_init(&vmi, mm, start); 1372 vma = vma_find(&vmi, end); 1373 if (!vma) 1374 goto out_unlock; 1375 1376 /* 1377 * If the first vma contains huge pages, make sure start address 1378 * is aligned to huge page size. 1379 */ 1380 if (is_vm_hugetlb_page(vma)) { 1381 unsigned long vma_hpagesize = vma_kernel_pagesize(vma); 1382 1383 if (start & (vma_hpagesize - 1)) 1384 goto out_unlock; 1385 } 1386 1387 /* 1388 * Search for not compatible vmas. 1389 */ 1390 found = false; 1391 basic_ioctls = false; 1392 cur = vma; 1393 do { 1394 cond_resched(); 1395 1396 BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^ 1397 !!(cur->vm_flags & __VM_UFFD_FLAGS)); 1398 1399 /* check not compatible vmas */ 1400 ret = -EINVAL; 1401 if (!vma_can_userfault(cur, vm_flags, wp_async)) 1402 goto out_unlock; 1403 1404 /* 1405 * UFFDIO_COPY will fill file holes even without 1406 * PROT_WRITE. This check enforces that if this is a 1407 * MAP_SHARED, the process has write permission to the backing 1408 * file. If VM_MAYWRITE is set it also enforces that on a 1409 * MAP_SHARED vma: there is no F_WRITE_SEAL and no further 1410 * F_WRITE_SEAL can be taken until the vma is destroyed. 1411 */ 1412 ret = -EPERM; 1413 if (unlikely(!(cur->vm_flags & VM_MAYWRITE))) 1414 goto out_unlock; 1415 1416 /* 1417 * If this vma contains ending address, and huge pages 1418 * check alignment. 1419 */ 1420 if (is_vm_hugetlb_page(cur) && end <= cur->vm_end && 1421 end > cur->vm_start) { 1422 unsigned long vma_hpagesize = vma_kernel_pagesize(cur); 1423 1424 ret = -EINVAL; 1425 1426 if (end & (vma_hpagesize - 1)) 1427 goto out_unlock; 1428 } 1429 if ((vm_flags & VM_UFFD_WP) && !(cur->vm_flags & VM_MAYWRITE)) 1430 goto out_unlock; 1431 1432 /* 1433 * Check that this vma isn't already owned by a 1434 * different userfaultfd. We can't allow more than one 1435 * userfaultfd to own a single vma simultaneously or we 1436 * wouldn't know which one to deliver the userfaults to. 1437 */ 1438 ret = -EBUSY; 1439 if (cur->vm_userfaultfd_ctx.ctx && 1440 cur->vm_userfaultfd_ctx.ctx != ctx) 1441 goto out_unlock; 1442 1443 /* 1444 * Note vmas containing huge pages 1445 */ 1446 if (is_vm_hugetlb_page(cur)) 1447 basic_ioctls = true; 1448 1449 found = true; 1450 } for_each_vma_range(vmi, cur, end); 1451 BUG_ON(!found); 1452 1453 vma_iter_set(&vmi, start); 1454 prev = vma_prev(&vmi); 1455 if (vma->vm_start < start) 1456 prev = vma; 1457 1458 ret = 0; 1459 for_each_vma_range(vmi, vma, end) { 1460 cond_resched(); 1461 1462 BUG_ON(!vma_can_userfault(vma, vm_flags, wp_async)); 1463 BUG_ON(vma->vm_userfaultfd_ctx.ctx && 1464 vma->vm_userfaultfd_ctx.ctx != ctx); 1465 WARN_ON(!(vma->vm_flags & VM_MAYWRITE)); 1466 1467 /* 1468 * Nothing to do: this vma is already registered into this 1469 * userfaultfd and with the right tracking mode too. 1470 */ 1471 if (vma->vm_userfaultfd_ctx.ctx == ctx && 1472 (vma->vm_flags & vm_flags) == vm_flags) 1473 goto skip; 1474 1475 if (vma->vm_start > start) 1476 start = vma->vm_start; 1477 vma_end = min(end, vma->vm_end); 1478 1479 new_flags = (vma->vm_flags & ~__VM_UFFD_FLAGS) | vm_flags; 1480 vma = vma_modify_flags_uffd(&vmi, prev, vma, start, vma_end, 1481 new_flags, 1482 (struct vm_userfaultfd_ctx){ctx}); 1483 if (IS_ERR(vma)) { 1484 ret = PTR_ERR(vma); 1485 break; 1486 } 1487 1488 /* 1489 * In the vma_merge() successful mprotect-like case 8: 1490 * the next vma was merged into the current one and 1491 * the current one has not been updated yet. 1492 */ 1493 vma_start_write(vma); 1494 userfaultfd_set_vm_flags(vma, new_flags); 1495 vma->vm_userfaultfd_ctx.ctx = ctx; 1496 1497 if (is_vm_hugetlb_page(vma) && uffd_disable_huge_pmd_share(vma)) 1498 hugetlb_unshare_all_pmds(vma); 1499 1500 skip: 1501 prev = vma; 1502 start = vma->vm_end; 1503 } 1504 1505 out_unlock: 1506 mmap_write_unlock(mm); 1507 mmput(mm); 1508 if (!ret) { 1509 __u64 ioctls_out; 1510 1511 ioctls_out = basic_ioctls ? UFFD_API_RANGE_IOCTLS_BASIC : 1512 UFFD_API_RANGE_IOCTLS; 1513 1514 /* 1515 * Declare the WP ioctl only if the WP mode is 1516 * specified and all checks passed with the range 1517 */ 1518 if (!(uffdio_register.mode & UFFDIO_REGISTER_MODE_WP)) 1519 ioctls_out &= ~((__u64)1 << _UFFDIO_WRITEPROTECT); 1520 1521 /* CONTINUE ioctl is only supported for MINOR ranges. */ 1522 if (!(uffdio_register.mode & UFFDIO_REGISTER_MODE_MINOR)) 1523 ioctls_out &= ~((__u64)1 << _UFFDIO_CONTINUE); 1524 1525 /* 1526 * Now that we scanned all vmas we can already tell 1527 * userland which ioctls methods are guaranteed to 1528 * succeed on this range. 1529 */ 1530 if (put_user(ioctls_out, &user_uffdio_register->ioctls)) 1531 ret = -EFAULT; 1532 } 1533 out: 1534 return ret; 1535 } 1536 1537 static int userfaultfd_unregister(struct userfaultfd_ctx *ctx, 1538 unsigned long arg) 1539 { 1540 struct mm_struct *mm = ctx->mm; 1541 struct vm_area_struct *vma, *prev, *cur; 1542 int ret; 1543 struct uffdio_range uffdio_unregister; 1544 unsigned long new_flags; 1545 bool found; 1546 unsigned long start, end, vma_end; 1547 const void __user *buf = (void __user *)arg; 1548 struct vma_iterator vmi; 1549 bool wp_async = userfaultfd_wp_async_ctx(ctx); 1550 1551 ret = -EFAULT; 1552 if (copy_from_user(&uffdio_unregister, buf, sizeof(uffdio_unregister))) 1553 goto out; 1554 1555 ret = validate_range(mm, uffdio_unregister.start, 1556 uffdio_unregister.len); 1557 if (ret) 1558 goto out; 1559 1560 start = uffdio_unregister.start; 1561 end = start + uffdio_unregister.len; 1562 1563 ret = -ENOMEM; 1564 if (!mmget_not_zero(mm)) 1565 goto out; 1566 1567 mmap_write_lock(mm); 1568 ret = -EINVAL; 1569 vma_iter_init(&vmi, mm, start); 1570 vma = vma_find(&vmi, end); 1571 if (!vma) 1572 goto out_unlock; 1573 1574 /* 1575 * If the first vma contains huge pages, make sure start address 1576 * is aligned to huge page size. 1577 */ 1578 if (is_vm_hugetlb_page(vma)) { 1579 unsigned long vma_hpagesize = vma_kernel_pagesize(vma); 1580 1581 if (start & (vma_hpagesize - 1)) 1582 goto out_unlock; 1583 } 1584 1585 /* 1586 * Search for not compatible vmas. 1587 */ 1588 found = false; 1589 cur = vma; 1590 do { 1591 cond_resched(); 1592 1593 BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^ 1594 !!(cur->vm_flags & __VM_UFFD_FLAGS)); 1595 1596 /* 1597 * Check not compatible vmas, not strictly required 1598 * here as not compatible vmas cannot have an 1599 * userfaultfd_ctx registered on them, but this 1600 * provides for more strict behavior to notice 1601 * unregistration errors. 1602 */ 1603 if (!vma_can_userfault(cur, cur->vm_flags, wp_async)) 1604 goto out_unlock; 1605 1606 found = true; 1607 } for_each_vma_range(vmi, cur, end); 1608 BUG_ON(!found); 1609 1610 vma_iter_set(&vmi, start); 1611 prev = vma_prev(&vmi); 1612 if (vma->vm_start < start) 1613 prev = vma; 1614 1615 ret = 0; 1616 for_each_vma_range(vmi, vma, end) { 1617 cond_resched(); 1618 1619 BUG_ON(!vma_can_userfault(vma, vma->vm_flags, wp_async)); 1620 1621 /* 1622 * Nothing to do: this vma is already registered into this 1623 * userfaultfd and with the right tracking mode too. 1624 */ 1625 if (!vma->vm_userfaultfd_ctx.ctx) 1626 goto skip; 1627 1628 WARN_ON(!(vma->vm_flags & VM_MAYWRITE)); 1629 1630 if (vma->vm_start > start) 1631 start = vma->vm_start; 1632 vma_end = min(end, vma->vm_end); 1633 1634 if (userfaultfd_missing(vma)) { 1635 /* 1636 * Wake any concurrent pending userfault while 1637 * we unregister, so they will not hang 1638 * permanently and it avoids userland to call 1639 * UFFDIO_WAKE explicitly. 1640 */ 1641 struct userfaultfd_wake_range range; 1642 range.start = start; 1643 range.len = vma_end - start; 1644 wake_userfault(vma->vm_userfaultfd_ctx.ctx, &range); 1645 } 1646 1647 /* Reset ptes for the whole vma range if wr-protected */ 1648 if (userfaultfd_wp(vma)) 1649 uffd_wp_range(vma, start, vma_end - start, false); 1650 1651 new_flags = vma->vm_flags & ~__VM_UFFD_FLAGS; 1652 vma = vma_modify_flags_uffd(&vmi, prev, vma, start, vma_end, 1653 new_flags, NULL_VM_UFFD_CTX); 1654 if (IS_ERR(vma)) { 1655 ret = PTR_ERR(vma); 1656 break; 1657 } 1658 1659 /* 1660 * In the vma_merge() successful mprotect-like case 8: 1661 * the next vma was merged into the current one and 1662 * the current one has not been updated yet. 1663 */ 1664 vma_start_write(vma); 1665 userfaultfd_set_vm_flags(vma, new_flags); 1666 vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; 1667 1668 skip: 1669 prev = vma; 1670 start = vma->vm_end; 1671 } 1672 1673 out_unlock: 1674 mmap_write_unlock(mm); 1675 mmput(mm); 1676 out: 1677 return ret; 1678 } 1679 1680 /* 1681 * userfaultfd_wake may be used in combination with the 1682 * UFFDIO_*_MODE_DONTWAKE to wakeup userfaults in batches. 1683 */ 1684 static int userfaultfd_wake(struct userfaultfd_ctx *ctx, 1685 unsigned long arg) 1686 { 1687 int ret; 1688 struct uffdio_range uffdio_wake; 1689 struct userfaultfd_wake_range range; 1690 const void __user *buf = (void __user *)arg; 1691 1692 ret = -EFAULT; 1693 if (copy_from_user(&uffdio_wake, buf, sizeof(uffdio_wake))) 1694 goto out; 1695 1696 ret = validate_range(ctx->mm, uffdio_wake.start, uffdio_wake.len); 1697 if (ret) 1698 goto out; 1699 1700 range.start = uffdio_wake.start; 1701 range.len = uffdio_wake.len; 1702 1703 /* 1704 * len == 0 means wake all and we don't want to wake all here, 1705 * so check it again to be sure. 1706 */ 1707 VM_BUG_ON(!range.len); 1708 1709 wake_userfault(ctx, &range); 1710 ret = 0; 1711 1712 out: 1713 return ret; 1714 } 1715 1716 static int userfaultfd_copy(struct userfaultfd_ctx *ctx, 1717 unsigned long arg) 1718 { 1719 __s64 ret; 1720 struct uffdio_copy uffdio_copy; 1721 struct uffdio_copy __user *user_uffdio_copy; 1722 struct userfaultfd_wake_range range; 1723 uffd_flags_t flags = 0; 1724 1725 user_uffdio_copy = (struct uffdio_copy __user *) arg; 1726 1727 ret = -EAGAIN; 1728 if (atomic_read(&ctx->mmap_changing)) 1729 goto out; 1730 1731 ret = -EFAULT; 1732 if (copy_from_user(&uffdio_copy, user_uffdio_copy, 1733 /* don't copy "copy" last field */ 1734 sizeof(uffdio_copy)-sizeof(__s64))) 1735 goto out; 1736 1737 ret = validate_unaligned_range(ctx->mm, uffdio_copy.src, 1738 uffdio_copy.len); 1739 if (ret) 1740 goto out; 1741 ret = validate_range(ctx->mm, uffdio_copy.dst, uffdio_copy.len); 1742 if (ret) 1743 goto out; 1744 1745 ret = -EINVAL; 1746 if (uffdio_copy.mode & ~(UFFDIO_COPY_MODE_DONTWAKE|UFFDIO_COPY_MODE_WP)) 1747 goto out; 1748 if (uffdio_copy.mode & UFFDIO_COPY_MODE_WP) 1749 flags |= MFILL_ATOMIC_WP; 1750 if (mmget_not_zero(ctx->mm)) { 1751 ret = mfill_atomic_copy(ctx->mm, uffdio_copy.dst, uffdio_copy.src, 1752 uffdio_copy.len, &ctx->mmap_changing, 1753 flags); 1754 mmput(ctx->mm); 1755 } else { 1756 return -ESRCH; 1757 } 1758 if (unlikely(put_user(ret, &user_uffdio_copy->copy))) 1759 return -EFAULT; 1760 if (ret < 0) 1761 goto out; 1762 BUG_ON(!ret); 1763 /* len == 0 would wake all */ 1764 range.len = ret; 1765 if (!(uffdio_copy.mode & UFFDIO_COPY_MODE_DONTWAKE)) { 1766 range.start = uffdio_copy.dst; 1767 wake_userfault(ctx, &range); 1768 } 1769 ret = range.len == uffdio_copy.len ? 0 : -EAGAIN; 1770 out: 1771 return ret; 1772 } 1773 1774 static int userfaultfd_zeropage(struct userfaultfd_ctx *ctx, 1775 unsigned long arg) 1776 { 1777 __s64 ret; 1778 struct uffdio_zeropage uffdio_zeropage; 1779 struct uffdio_zeropage __user *user_uffdio_zeropage; 1780 struct userfaultfd_wake_range range; 1781 1782 user_uffdio_zeropage = (struct uffdio_zeropage __user *) arg; 1783 1784 ret = -EAGAIN; 1785 if (atomic_read(&ctx->mmap_changing)) 1786 goto out; 1787 1788 ret = -EFAULT; 1789 if (copy_from_user(&uffdio_zeropage, user_uffdio_zeropage, 1790 /* don't copy "zeropage" last field */ 1791 sizeof(uffdio_zeropage)-sizeof(__s64))) 1792 goto out; 1793 1794 ret = validate_range(ctx->mm, uffdio_zeropage.range.start, 1795 uffdio_zeropage.range.len); 1796 if (ret) 1797 goto out; 1798 ret = -EINVAL; 1799 if (uffdio_zeropage.mode & ~UFFDIO_ZEROPAGE_MODE_DONTWAKE) 1800 goto out; 1801 1802 if (mmget_not_zero(ctx->mm)) { 1803 ret = mfill_atomic_zeropage(ctx->mm, uffdio_zeropage.range.start, 1804 uffdio_zeropage.range.len, 1805 &ctx->mmap_changing); 1806 mmput(ctx->mm); 1807 } else { 1808 return -ESRCH; 1809 } 1810 if (unlikely(put_user(ret, &user_uffdio_zeropage->zeropage))) 1811 return -EFAULT; 1812 if (ret < 0) 1813 goto out; 1814 /* len == 0 would wake all */ 1815 BUG_ON(!ret); 1816 range.len = ret; 1817 if (!(uffdio_zeropage.mode & UFFDIO_ZEROPAGE_MODE_DONTWAKE)) { 1818 range.start = uffdio_zeropage.range.start; 1819 wake_userfault(ctx, &range); 1820 } 1821 ret = range.len == uffdio_zeropage.range.len ? 0 : -EAGAIN; 1822 out: 1823 return ret; 1824 } 1825 1826 static int userfaultfd_writeprotect(struct userfaultfd_ctx *ctx, 1827 unsigned long arg) 1828 { 1829 int ret; 1830 struct uffdio_writeprotect uffdio_wp; 1831 struct uffdio_writeprotect __user *user_uffdio_wp; 1832 struct userfaultfd_wake_range range; 1833 bool mode_wp, mode_dontwake; 1834 1835 if (atomic_read(&ctx->mmap_changing)) 1836 return -EAGAIN; 1837 1838 user_uffdio_wp = (struct uffdio_writeprotect __user *) arg; 1839 1840 if (copy_from_user(&uffdio_wp, user_uffdio_wp, 1841 sizeof(struct uffdio_writeprotect))) 1842 return -EFAULT; 1843 1844 ret = validate_range(ctx->mm, uffdio_wp.range.start, 1845 uffdio_wp.range.len); 1846 if (ret) 1847 return ret; 1848 1849 if (uffdio_wp.mode & ~(UFFDIO_WRITEPROTECT_MODE_DONTWAKE | 1850 UFFDIO_WRITEPROTECT_MODE_WP)) 1851 return -EINVAL; 1852 1853 mode_wp = uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_WP; 1854 mode_dontwake = uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_DONTWAKE; 1855 1856 if (mode_wp && mode_dontwake) 1857 return -EINVAL; 1858 1859 if (mmget_not_zero(ctx->mm)) { 1860 ret = mwriteprotect_range(ctx->mm, uffdio_wp.range.start, 1861 uffdio_wp.range.len, mode_wp, 1862 &ctx->mmap_changing); 1863 mmput(ctx->mm); 1864 } else { 1865 return -ESRCH; 1866 } 1867 1868 if (ret) 1869 return ret; 1870 1871 if (!mode_wp && !mode_dontwake) { 1872 range.start = uffdio_wp.range.start; 1873 range.len = uffdio_wp.range.len; 1874 wake_userfault(ctx, &range); 1875 } 1876 return ret; 1877 } 1878 1879 static int userfaultfd_continue(struct userfaultfd_ctx *ctx, unsigned long arg) 1880 { 1881 __s64 ret; 1882 struct uffdio_continue uffdio_continue; 1883 struct uffdio_continue __user *user_uffdio_continue; 1884 struct userfaultfd_wake_range range; 1885 uffd_flags_t flags = 0; 1886 1887 user_uffdio_continue = (struct uffdio_continue __user *)arg; 1888 1889 ret = -EAGAIN; 1890 if (atomic_read(&ctx->mmap_changing)) 1891 goto out; 1892 1893 ret = -EFAULT; 1894 if (copy_from_user(&uffdio_continue, user_uffdio_continue, 1895 /* don't copy the output fields */ 1896 sizeof(uffdio_continue) - (sizeof(__s64)))) 1897 goto out; 1898 1899 ret = validate_range(ctx->mm, uffdio_continue.range.start, 1900 uffdio_continue.range.len); 1901 if (ret) 1902 goto out; 1903 1904 ret = -EINVAL; 1905 if (uffdio_continue.mode & ~(UFFDIO_CONTINUE_MODE_DONTWAKE | 1906 UFFDIO_CONTINUE_MODE_WP)) 1907 goto out; 1908 if (uffdio_continue.mode & UFFDIO_CONTINUE_MODE_WP) 1909 flags |= MFILL_ATOMIC_WP; 1910 1911 if (mmget_not_zero(ctx->mm)) { 1912 ret = mfill_atomic_continue(ctx->mm, uffdio_continue.range.start, 1913 uffdio_continue.range.len, 1914 &ctx->mmap_changing, flags); 1915 mmput(ctx->mm); 1916 } else { 1917 return -ESRCH; 1918 } 1919 1920 if (unlikely(put_user(ret, &user_uffdio_continue->mapped))) 1921 return -EFAULT; 1922 if (ret < 0) 1923 goto out; 1924 1925 /* len == 0 would wake all */ 1926 BUG_ON(!ret); 1927 range.len = ret; 1928 if (!(uffdio_continue.mode & UFFDIO_CONTINUE_MODE_DONTWAKE)) { 1929 range.start = uffdio_continue.range.start; 1930 wake_userfault(ctx, &range); 1931 } 1932 ret = range.len == uffdio_continue.range.len ? 0 : -EAGAIN; 1933 1934 out: 1935 return ret; 1936 } 1937 1938 static inline int userfaultfd_poison(struct userfaultfd_ctx *ctx, unsigned long arg) 1939 { 1940 __s64 ret; 1941 struct uffdio_poison uffdio_poison; 1942 struct uffdio_poison __user *user_uffdio_poison; 1943 struct userfaultfd_wake_range range; 1944 1945 user_uffdio_poison = (struct uffdio_poison __user *)arg; 1946 1947 ret = -EAGAIN; 1948 if (atomic_read(&ctx->mmap_changing)) 1949 goto out; 1950 1951 ret = -EFAULT; 1952 if (copy_from_user(&uffdio_poison, user_uffdio_poison, 1953 /* don't copy the output fields */ 1954 sizeof(uffdio_poison) - (sizeof(__s64)))) 1955 goto out; 1956 1957 ret = validate_range(ctx->mm, uffdio_poison.range.start, 1958 uffdio_poison.range.len); 1959 if (ret) 1960 goto out; 1961 1962 ret = -EINVAL; 1963 if (uffdio_poison.mode & ~UFFDIO_POISON_MODE_DONTWAKE) 1964 goto out; 1965 1966 if (mmget_not_zero(ctx->mm)) { 1967 ret = mfill_atomic_poison(ctx->mm, uffdio_poison.range.start, 1968 uffdio_poison.range.len, 1969 &ctx->mmap_changing, 0); 1970 mmput(ctx->mm); 1971 } else { 1972 return -ESRCH; 1973 } 1974 1975 if (unlikely(put_user(ret, &user_uffdio_poison->updated))) 1976 return -EFAULT; 1977 if (ret < 0) 1978 goto out; 1979 1980 /* len == 0 would wake all */ 1981 BUG_ON(!ret); 1982 range.len = ret; 1983 if (!(uffdio_poison.mode & UFFDIO_POISON_MODE_DONTWAKE)) { 1984 range.start = uffdio_poison.range.start; 1985 wake_userfault(ctx, &range); 1986 } 1987 ret = range.len == uffdio_poison.range.len ? 0 : -EAGAIN; 1988 1989 out: 1990 return ret; 1991 } 1992 1993 bool userfaultfd_wp_async(struct vm_area_struct *vma) 1994 { 1995 return userfaultfd_wp_async_ctx(vma->vm_userfaultfd_ctx.ctx); 1996 } 1997 1998 static inline unsigned int uffd_ctx_features(__u64 user_features) 1999 { 2000 /* 2001 * For the current set of features the bits just coincide. Set 2002 * UFFD_FEATURE_INITIALIZED to mark the features as enabled. 2003 */ 2004 return (unsigned int)user_features | UFFD_FEATURE_INITIALIZED; 2005 } 2006 2007 static int userfaultfd_move(struct userfaultfd_ctx *ctx, 2008 unsigned long arg) 2009 { 2010 __s64 ret; 2011 struct uffdio_move uffdio_move; 2012 struct uffdio_move __user *user_uffdio_move; 2013 struct userfaultfd_wake_range range; 2014 struct mm_struct *mm = ctx->mm; 2015 2016 user_uffdio_move = (struct uffdio_move __user *) arg; 2017 2018 if (atomic_read(&ctx->mmap_changing)) 2019 return -EAGAIN; 2020 2021 if (copy_from_user(&uffdio_move, user_uffdio_move, 2022 /* don't copy "move" last field */ 2023 sizeof(uffdio_move)-sizeof(__s64))) 2024 return -EFAULT; 2025 2026 /* Do not allow cross-mm moves. */ 2027 if (mm != current->mm) 2028 return -EINVAL; 2029 2030 ret = validate_range(mm, uffdio_move.dst, uffdio_move.len); 2031 if (ret) 2032 return ret; 2033 2034 ret = validate_range(mm, uffdio_move.src, uffdio_move.len); 2035 if (ret) 2036 return ret; 2037 2038 if (uffdio_move.mode & ~(UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES| 2039 UFFDIO_MOVE_MODE_DONTWAKE)) 2040 return -EINVAL; 2041 2042 if (mmget_not_zero(mm)) { 2043 mmap_read_lock(mm); 2044 2045 /* Re-check after taking mmap_lock */ 2046 if (likely(!atomic_read(&ctx->mmap_changing))) 2047 ret = move_pages(ctx, mm, uffdio_move.dst, uffdio_move.src, 2048 uffdio_move.len, uffdio_move.mode); 2049 else 2050 ret = -EINVAL; 2051 2052 mmap_read_unlock(mm); 2053 mmput(mm); 2054 } else { 2055 return -ESRCH; 2056 } 2057 2058 if (unlikely(put_user(ret, &user_uffdio_move->move))) 2059 return -EFAULT; 2060 if (ret < 0) 2061 goto out; 2062 2063 /* len == 0 would wake all */ 2064 VM_WARN_ON(!ret); 2065 range.len = ret; 2066 if (!(uffdio_move.mode & UFFDIO_MOVE_MODE_DONTWAKE)) { 2067 range.start = uffdio_move.dst; 2068 wake_userfault(ctx, &range); 2069 } 2070 ret = range.len == uffdio_move.len ? 0 : -EAGAIN; 2071 2072 out: 2073 return ret; 2074 } 2075 2076 /* 2077 * userland asks for a certain API version and we return which bits 2078 * and ioctl commands are implemented in this kernel for such API 2079 * version or -EINVAL if unknown. 2080 */ 2081 static int userfaultfd_api(struct userfaultfd_ctx *ctx, 2082 unsigned long arg) 2083 { 2084 struct uffdio_api uffdio_api; 2085 void __user *buf = (void __user *)arg; 2086 unsigned int ctx_features; 2087 int ret; 2088 __u64 features; 2089 2090 ret = -EFAULT; 2091 if (copy_from_user(&uffdio_api, buf, sizeof(uffdio_api))) 2092 goto out; 2093 features = uffdio_api.features; 2094 ret = -EINVAL; 2095 if (uffdio_api.api != UFFD_API || (features & ~UFFD_API_FEATURES)) 2096 goto err_out; 2097 ret = -EPERM; 2098 if ((features & UFFD_FEATURE_EVENT_FORK) && !capable(CAP_SYS_PTRACE)) 2099 goto err_out; 2100 2101 /* WP_ASYNC relies on WP_UNPOPULATED, choose it unconditionally */ 2102 if (features & UFFD_FEATURE_WP_ASYNC) 2103 features |= UFFD_FEATURE_WP_UNPOPULATED; 2104 2105 /* report all available features and ioctls to userland */ 2106 uffdio_api.features = UFFD_API_FEATURES; 2107 #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR 2108 uffdio_api.features &= 2109 ~(UFFD_FEATURE_MINOR_HUGETLBFS | UFFD_FEATURE_MINOR_SHMEM); 2110 #endif 2111 #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_WP 2112 uffdio_api.features &= ~UFFD_FEATURE_PAGEFAULT_FLAG_WP; 2113 #endif 2114 #ifndef CONFIG_PTE_MARKER_UFFD_WP 2115 uffdio_api.features &= ~UFFD_FEATURE_WP_HUGETLBFS_SHMEM; 2116 uffdio_api.features &= ~UFFD_FEATURE_WP_UNPOPULATED; 2117 uffdio_api.features &= ~UFFD_FEATURE_WP_ASYNC; 2118 #endif 2119 uffdio_api.ioctls = UFFD_API_IOCTLS; 2120 ret = -EFAULT; 2121 if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api))) 2122 goto out; 2123 2124 /* only enable the requested features for this uffd context */ 2125 ctx_features = uffd_ctx_features(features); 2126 ret = -EINVAL; 2127 if (cmpxchg(&ctx->features, 0, ctx_features) != 0) 2128 goto err_out; 2129 2130 ret = 0; 2131 out: 2132 return ret; 2133 err_out: 2134 memset(&uffdio_api, 0, sizeof(uffdio_api)); 2135 if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api))) 2136 ret = -EFAULT; 2137 goto out; 2138 } 2139 2140 static long userfaultfd_ioctl(struct file *file, unsigned cmd, 2141 unsigned long arg) 2142 { 2143 int ret = -EINVAL; 2144 struct userfaultfd_ctx *ctx = file->private_data; 2145 2146 if (cmd != UFFDIO_API && !userfaultfd_is_initialized(ctx)) 2147 return -EINVAL; 2148 2149 switch(cmd) { 2150 case UFFDIO_API: 2151 ret = userfaultfd_api(ctx, arg); 2152 break; 2153 case UFFDIO_REGISTER: 2154 ret = userfaultfd_register(ctx, arg); 2155 break; 2156 case UFFDIO_UNREGISTER: 2157 ret = userfaultfd_unregister(ctx, arg); 2158 break; 2159 case UFFDIO_WAKE: 2160 ret = userfaultfd_wake(ctx, arg); 2161 break; 2162 case UFFDIO_COPY: 2163 ret = userfaultfd_copy(ctx, arg); 2164 break; 2165 case UFFDIO_ZEROPAGE: 2166 ret = userfaultfd_zeropage(ctx, arg); 2167 break; 2168 case UFFDIO_MOVE: 2169 ret = userfaultfd_move(ctx, arg); 2170 break; 2171 case UFFDIO_WRITEPROTECT: 2172 ret = userfaultfd_writeprotect(ctx, arg); 2173 break; 2174 case UFFDIO_CONTINUE: 2175 ret = userfaultfd_continue(ctx, arg); 2176 break; 2177 case UFFDIO_POISON: 2178 ret = userfaultfd_poison(ctx, arg); 2179 break; 2180 } 2181 return ret; 2182 } 2183 2184 #ifdef CONFIG_PROC_FS 2185 static void userfaultfd_show_fdinfo(struct seq_file *m, struct file *f) 2186 { 2187 struct userfaultfd_ctx *ctx = f->private_data; 2188 wait_queue_entry_t *wq; 2189 unsigned long pending = 0, total = 0; 2190 2191 spin_lock_irq(&ctx->fault_pending_wqh.lock); 2192 list_for_each_entry(wq, &ctx->fault_pending_wqh.head, entry) { 2193 pending++; 2194 total++; 2195 } 2196 list_for_each_entry(wq, &ctx->fault_wqh.head, entry) { 2197 total++; 2198 } 2199 spin_unlock_irq(&ctx->fault_pending_wqh.lock); 2200 2201 /* 2202 * If more protocols will be added, there will be all shown 2203 * separated by a space. Like this: 2204 * protocols: aa:... bb:... 2205 */ 2206 seq_printf(m, "pending:\t%lu\ntotal:\t%lu\nAPI:\t%Lx:%x:%Lx\n", 2207 pending, total, UFFD_API, ctx->features, 2208 UFFD_API_IOCTLS|UFFD_API_RANGE_IOCTLS); 2209 } 2210 #endif 2211 2212 static const struct file_operations userfaultfd_fops = { 2213 #ifdef CONFIG_PROC_FS 2214 .show_fdinfo = userfaultfd_show_fdinfo, 2215 #endif 2216 .release = userfaultfd_release, 2217 .poll = userfaultfd_poll, 2218 .read = userfaultfd_read, 2219 .unlocked_ioctl = userfaultfd_ioctl, 2220 .compat_ioctl = compat_ptr_ioctl, 2221 .llseek = noop_llseek, 2222 }; 2223 2224 static void init_once_userfaultfd_ctx(void *mem) 2225 { 2226 struct userfaultfd_ctx *ctx = (struct userfaultfd_ctx *) mem; 2227 2228 init_waitqueue_head(&ctx->fault_pending_wqh); 2229 init_waitqueue_head(&ctx->fault_wqh); 2230 init_waitqueue_head(&ctx->event_wqh); 2231 init_waitqueue_head(&ctx->fd_wqh); 2232 seqcount_spinlock_init(&ctx->refile_seq, &ctx->fault_pending_wqh.lock); 2233 } 2234 2235 static int new_userfaultfd(int flags) 2236 { 2237 struct userfaultfd_ctx *ctx; 2238 int fd; 2239 2240 BUG_ON(!current->mm); 2241 2242 /* Check the UFFD_* constants for consistency. */ 2243 BUILD_BUG_ON(UFFD_USER_MODE_ONLY & UFFD_SHARED_FCNTL_FLAGS); 2244 BUILD_BUG_ON(UFFD_CLOEXEC != O_CLOEXEC); 2245 BUILD_BUG_ON(UFFD_NONBLOCK != O_NONBLOCK); 2246 2247 if (flags & ~(UFFD_SHARED_FCNTL_FLAGS | UFFD_USER_MODE_ONLY)) 2248 return -EINVAL; 2249 2250 ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL); 2251 if (!ctx) 2252 return -ENOMEM; 2253 2254 refcount_set(&ctx->refcount, 1); 2255 ctx->flags = flags; 2256 ctx->features = 0; 2257 ctx->released = false; 2258 atomic_set(&ctx->mmap_changing, 0); 2259 ctx->mm = current->mm; 2260 /* prevent the mm struct to be freed */ 2261 mmgrab(ctx->mm); 2262 2263 /* Create a new inode so that the LSM can block the creation. */ 2264 fd = anon_inode_create_getfd("[userfaultfd]", &userfaultfd_fops, ctx, 2265 O_RDONLY | (flags & UFFD_SHARED_FCNTL_FLAGS), NULL); 2266 if (fd < 0) { 2267 mmdrop(ctx->mm); 2268 kmem_cache_free(userfaultfd_ctx_cachep, ctx); 2269 } 2270 return fd; 2271 } 2272 2273 static inline bool userfaultfd_syscall_allowed(int flags) 2274 { 2275 /* Userspace-only page faults are always allowed */ 2276 if (flags & UFFD_USER_MODE_ONLY) 2277 return true; 2278 2279 /* 2280 * The user is requesting a userfaultfd which can handle kernel faults. 2281 * Privileged users are always allowed to do this. 2282 */ 2283 if (capable(CAP_SYS_PTRACE)) 2284 return true; 2285 2286 /* Otherwise, access to kernel fault handling is sysctl controlled. */ 2287 return sysctl_unprivileged_userfaultfd; 2288 } 2289 2290 SYSCALL_DEFINE1(userfaultfd, int, flags) 2291 { 2292 if (!userfaultfd_syscall_allowed(flags)) 2293 return -EPERM; 2294 2295 return new_userfaultfd(flags); 2296 } 2297 2298 static long userfaultfd_dev_ioctl(struct file *file, unsigned int cmd, unsigned long flags) 2299 { 2300 if (cmd != USERFAULTFD_IOC_NEW) 2301 return -EINVAL; 2302 2303 return new_userfaultfd(flags); 2304 } 2305 2306 static const struct file_operations userfaultfd_dev_fops = { 2307 .unlocked_ioctl = userfaultfd_dev_ioctl, 2308 .compat_ioctl = userfaultfd_dev_ioctl, 2309 .owner = THIS_MODULE, 2310 .llseek = noop_llseek, 2311 }; 2312 2313 static struct miscdevice userfaultfd_misc = { 2314 .minor = MISC_DYNAMIC_MINOR, 2315 .name = "userfaultfd", 2316 .fops = &userfaultfd_dev_fops 2317 }; 2318 2319 static int __init userfaultfd_init(void) 2320 { 2321 int ret; 2322 2323 ret = misc_register(&userfaultfd_misc); 2324 if (ret) 2325 return ret; 2326 2327 userfaultfd_ctx_cachep = kmem_cache_create("userfaultfd_ctx_cache", 2328 sizeof(struct userfaultfd_ctx), 2329 0, 2330 SLAB_HWCACHE_ALIGN|SLAB_PANIC, 2331 init_once_userfaultfd_ctx); 2332 #ifdef CONFIG_SYSCTL 2333 register_sysctl_init("vm", vm_userfaultfd_table); 2334 #endif 2335 return 0; 2336 } 2337 __initcall(userfaultfd_init); 2338