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