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 dup_userfaultfd_fail(struct list_head *fcs) 696 { 697 struct userfaultfd_fork_ctx *fctx, *n; 698 699 /* 700 * An error has occurred on fork, we will tear memory down, but have 701 * allocated memory for fctx's and raised reference counts for both the 702 * original and child contexts (and on the mm for each as a result). 703 * 704 * These would ordinarily be taken care of by a user handling the event, 705 * but we are no longer doing so, so manually clean up here. 706 * 707 * mm tear down will take care of cleaning up VMA contexts. 708 */ 709 list_for_each_entry_safe(fctx, n, fcs, list) { 710 struct userfaultfd_ctx *octx = fctx->orig; 711 struct userfaultfd_ctx *ctx = fctx->new; 712 713 atomic_dec(&octx->mmap_changing); 714 VM_BUG_ON(atomic_read(&octx->mmap_changing) < 0); 715 userfaultfd_ctx_put(octx); 716 userfaultfd_ctx_put(ctx); 717 718 list_del(&fctx->list); 719 kfree(fctx); 720 } 721 } 722 723 void mremap_userfaultfd_prep(struct vm_area_struct *vma, 724 struct vm_userfaultfd_ctx *vm_ctx) 725 { 726 struct userfaultfd_ctx *ctx; 727 728 ctx = vma->vm_userfaultfd_ctx.ctx; 729 730 if (!ctx) 731 return; 732 733 if (ctx->features & UFFD_FEATURE_EVENT_REMAP) { 734 vm_ctx->ctx = ctx; 735 userfaultfd_ctx_get(ctx); 736 down_write(&ctx->map_changing_lock); 737 atomic_inc(&ctx->mmap_changing); 738 up_write(&ctx->map_changing_lock); 739 } else { 740 /* Drop uffd context if remap feature not enabled */ 741 userfaultfd_reset_ctx(vma); 742 } 743 } 744 745 void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *vm_ctx, 746 unsigned long from, unsigned long to, 747 unsigned long len) 748 { 749 struct userfaultfd_ctx *ctx = vm_ctx->ctx; 750 struct userfaultfd_wait_queue ewq; 751 752 if (!ctx) 753 return; 754 755 if (to & ~PAGE_MASK) { 756 userfaultfd_ctx_put(ctx); 757 return; 758 } 759 760 msg_init(&ewq.msg); 761 762 ewq.msg.event = UFFD_EVENT_REMAP; 763 ewq.msg.arg.remap.from = from; 764 ewq.msg.arg.remap.to = to; 765 ewq.msg.arg.remap.len = len; 766 767 userfaultfd_event_wait_completion(ctx, &ewq); 768 } 769 770 bool userfaultfd_remove(struct vm_area_struct *vma, 771 unsigned long start, unsigned long end) 772 { 773 struct mm_struct *mm = vma->vm_mm; 774 struct userfaultfd_ctx *ctx; 775 struct userfaultfd_wait_queue ewq; 776 777 ctx = vma->vm_userfaultfd_ctx.ctx; 778 if (!ctx || !(ctx->features & UFFD_FEATURE_EVENT_REMOVE)) 779 return true; 780 781 userfaultfd_ctx_get(ctx); 782 down_write(&ctx->map_changing_lock); 783 atomic_inc(&ctx->mmap_changing); 784 up_write(&ctx->map_changing_lock); 785 mmap_read_unlock(mm); 786 787 msg_init(&ewq.msg); 788 789 ewq.msg.event = UFFD_EVENT_REMOVE; 790 ewq.msg.arg.remove.start = start; 791 ewq.msg.arg.remove.end = end; 792 793 userfaultfd_event_wait_completion(ctx, &ewq); 794 795 return false; 796 } 797 798 static bool has_unmap_ctx(struct userfaultfd_ctx *ctx, struct list_head *unmaps, 799 unsigned long start, unsigned long end) 800 { 801 struct userfaultfd_unmap_ctx *unmap_ctx; 802 803 list_for_each_entry(unmap_ctx, unmaps, list) 804 if (unmap_ctx->ctx == ctx && unmap_ctx->start == start && 805 unmap_ctx->end == end) 806 return true; 807 808 return false; 809 } 810 811 int userfaultfd_unmap_prep(struct vm_area_struct *vma, unsigned long start, 812 unsigned long end, struct list_head *unmaps) 813 { 814 struct userfaultfd_unmap_ctx *unmap_ctx; 815 struct userfaultfd_ctx *ctx = vma->vm_userfaultfd_ctx.ctx; 816 817 if (!ctx || !(ctx->features & UFFD_FEATURE_EVENT_UNMAP) || 818 has_unmap_ctx(ctx, unmaps, start, end)) 819 return 0; 820 821 unmap_ctx = kzalloc(sizeof(*unmap_ctx), GFP_KERNEL); 822 if (!unmap_ctx) 823 return -ENOMEM; 824 825 userfaultfd_ctx_get(ctx); 826 down_write(&ctx->map_changing_lock); 827 atomic_inc(&ctx->mmap_changing); 828 up_write(&ctx->map_changing_lock); 829 unmap_ctx->ctx = ctx; 830 unmap_ctx->start = start; 831 unmap_ctx->end = end; 832 list_add_tail(&unmap_ctx->list, unmaps); 833 834 return 0; 835 } 836 837 void userfaultfd_unmap_complete(struct mm_struct *mm, struct list_head *uf) 838 { 839 struct userfaultfd_unmap_ctx *ctx, *n; 840 struct userfaultfd_wait_queue ewq; 841 842 list_for_each_entry_safe(ctx, n, uf, list) { 843 msg_init(&ewq.msg); 844 845 ewq.msg.event = UFFD_EVENT_UNMAP; 846 ewq.msg.arg.remove.start = ctx->start; 847 ewq.msg.arg.remove.end = ctx->end; 848 849 userfaultfd_event_wait_completion(ctx->ctx, &ewq); 850 851 list_del(&ctx->list); 852 kfree(ctx); 853 } 854 } 855 856 static int userfaultfd_release(struct inode *inode, struct file *file) 857 { 858 struct userfaultfd_ctx *ctx = file->private_data; 859 struct mm_struct *mm = ctx->mm; 860 /* len == 0 means wake all */ 861 struct userfaultfd_wake_range range = { .len = 0, }; 862 863 WRITE_ONCE(ctx->released, true); 864 865 userfaultfd_release_all(mm, ctx); 866 867 /* 868 * After no new page faults can wait on this fault_*wqh, flush 869 * the last page faults that may have been already waiting on 870 * the fault_*wqh. 871 */ 872 spin_lock_irq(&ctx->fault_pending_wqh.lock); 873 __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, &range); 874 __wake_up(&ctx->fault_wqh, TASK_NORMAL, 1, &range); 875 spin_unlock_irq(&ctx->fault_pending_wqh.lock); 876 877 /* Flush pending events that may still wait on event_wqh */ 878 wake_up_all(&ctx->event_wqh); 879 880 wake_up_poll(&ctx->fd_wqh, EPOLLHUP); 881 userfaultfd_ctx_put(ctx); 882 return 0; 883 } 884 885 /* fault_pending_wqh.lock must be hold by the caller */ 886 static inline struct userfaultfd_wait_queue *find_userfault_in( 887 wait_queue_head_t *wqh) 888 { 889 wait_queue_entry_t *wq; 890 struct userfaultfd_wait_queue *uwq; 891 892 lockdep_assert_held(&wqh->lock); 893 894 uwq = NULL; 895 if (!waitqueue_active(wqh)) 896 goto out; 897 /* walk in reverse to provide FIFO behavior to read userfaults */ 898 wq = list_last_entry(&wqh->head, typeof(*wq), entry); 899 uwq = container_of(wq, struct userfaultfd_wait_queue, wq); 900 out: 901 return uwq; 902 } 903 904 static inline struct userfaultfd_wait_queue *find_userfault( 905 struct userfaultfd_ctx *ctx) 906 { 907 return find_userfault_in(&ctx->fault_pending_wqh); 908 } 909 910 static inline struct userfaultfd_wait_queue *find_userfault_evt( 911 struct userfaultfd_ctx *ctx) 912 { 913 return find_userfault_in(&ctx->event_wqh); 914 } 915 916 static __poll_t userfaultfd_poll(struct file *file, poll_table *wait) 917 { 918 struct userfaultfd_ctx *ctx = file->private_data; 919 __poll_t ret; 920 921 poll_wait(file, &ctx->fd_wqh, wait); 922 923 if (!userfaultfd_is_initialized(ctx)) 924 return EPOLLERR; 925 926 /* 927 * poll() never guarantees that read won't block. 928 * userfaults can be waken before they're read(). 929 */ 930 if (unlikely(!(file->f_flags & O_NONBLOCK))) 931 return EPOLLERR; 932 /* 933 * lockless access to see if there are pending faults 934 * __pollwait last action is the add_wait_queue but 935 * the spin_unlock would allow the waitqueue_active to 936 * pass above the actual list_add inside 937 * add_wait_queue critical section. So use a full 938 * memory barrier to serialize the list_add write of 939 * add_wait_queue() with the waitqueue_active read 940 * below. 941 */ 942 ret = 0; 943 smp_mb(); 944 if (waitqueue_active(&ctx->fault_pending_wqh)) 945 ret = EPOLLIN; 946 else if (waitqueue_active(&ctx->event_wqh)) 947 ret = EPOLLIN; 948 949 return ret; 950 } 951 952 static const struct file_operations userfaultfd_fops; 953 954 static int resolve_userfault_fork(struct userfaultfd_ctx *new, 955 struct inode *inode, 956 struct uffd_msg *msg) 957 { 958 int fd; 959 960 fd = anon_inode_create_getfd("[userfaultfd]", &userfaultfd_fops, new, 961 O_RDONLY | (new->flags & UFFD_SHARED_FCNTL_FLAGS), inode); 962 if (fd < 0) 963 return fd; 964 965 msg->arg.reserved.reserved1 = 0; 966 msg->arg.fork.ufd = fd; 967 return 0; 968 } 969 970 static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait, 971 struct uffd_msg *msg, struct inode *inode) 972 { 973 ssize_t ret; 974 DECLARE_WAITQUEUE(wait, current); 975 struct userfaultfd_wait_queue *uwq; 976 /* 977 * Handling fork event requires sleeping operations, so 978 * we drop the event_wqh lock, then do these ops, then 979 * lock it back and wake up the waiter. While the lock is 980 * dropped the ewq may go away so we keep track of it 981 * carefully. 982 */ 983 LIST_HEAD(fork_event); 984 struct userfaultfd_ctx *fork_nctx = NULL; 985 986 /* always take the fd_wqh lock before the fault_pending_wqh lock */ 987 spin_lock_irq(&ctx->fd_wqh.lock); 988 __add_wait_queue(&ctx->fd_wqh, &wait); 989 for (;;) { 990 set_current_state(TASK_INTERRUPTIBLE); 991 spin_lock(&ctx->fault_pending_wqh.lock); 992 uwq = find_userfault(ctx); 993 if (uwq) { 994 /* 995 * Use a seqcount to repeat the lockless check 996 * in wake_userfault() to avoid missing 997 * wakeups because during the refile both 998 * waitqueue could become empty if this is the 999 * only userfault. 1000 */ 1001 write_seqcount_begin(&ctx->refile_seq); 1002 1003 /* 1004 * The fault_pending_wqh.lock prevents the uwq 1005 * to disappear from under us. 1006 * 1007 * Refile this userfault from 1008 * fault_pending_wqh to fault_wqh, it's not 1009 * pending anymore after we read it. 1010 * 1011 * Use list_del() by hand (as 1012 * userfaultfd_wake_function also uses 1013 * list_del_init() by hand) to be sure nobody 1014 * changes __remove_wait_queue() to use 1015 * list_del_init() in turn breaking the 1016 * !list_empty_careful() check in 1017 * handle_userfault(). The uwq->wq.head list 1018 * must never be empty at any time during the 1019 * refile, or the waitqueue could disappear 1020 * from under us. The "wait_queue_head_t" 1021 * parameter of __remove_wait_queue() is unused 1022 * anyway. 1023 */ 1024 list_del(&uwq->wq.entry); 1025 add_wait_queue(&ctx->fault_wqh, &uwq->wq); 1026 1027 write_seqcount_end(&ctx->refile_seq); 1028 1029 /* careful to always initialize msg if ret == 0 */ 1030 *msg = uwq->msg; 1031 spin_unlock(&ctx->fault_pending_wqh.lock); 1032 ret = 0; 1033 break; 1034 } 1035 spin_unlock(&ctx->fault_pending_wqh.lock); 1036 1037 spin_lock(&ctx->event_wqh.lock); 1038 uwq = find_userfault_evt(ctx); 1039 if (uwq) { 1040 *msg = uwq->msg; 1041 1042 if (uwq->msg.event == UFFD_EVENT_FORK) { 1043 fork_nctx = (struct userfaultfd_ctx *) 1044 (unsigned long) 1045 uwq->msg.arg.reserved.reserved1; 1046 list_move(&uwq->wq.entry, &fork_event); 1047 /* 1048 * fork_nctx can be freed as soon as 1049 * we drop the lock, unless we take a 1050 * reference on it. 1051 */ 1052 userfaultfd_ctx_get(fork_nctx); 1053 spin_unlock(&ctx->event_wqh.lock); 1054 ret = 0; 1055 break; 1056 } 1057 1058 userfaultfd_event_complete(ctx, uwq); 1059 spin_unlock(&ctx->event_wqh.lock); 1060 ret = 0; 1061 break; 1062 } 1063 spin_unlock(&ctx->event_wqh.lock); 1064 1065 if (signal_pending(current)) { 1066 ret = -ERESTARTSYS; 1067 break; 1068 } 1069 if (no_wait) { 1070 ret = -EAGAIN; 1071 break; 1072 } 1073 spin_unlock_irq(&ctx->fd_wqh.lock); 1074 schedule(); 1075 spin_lock_irq(&ctx->fd_wqh.lock); 1076 } 1077 __remove_wait_queue(&ctx->fd_wqh, &wait); 1078 __set_current_state(TASK_RUNNING); 1079 spin_unlock_irq(&ctx->fd_wqh.lock); 1080 1081 if (!ret && msg->event == UFFD_EVENT_FORK) { 1082 ret = resolve_userfault_fork(fork_nctx, inode, msg); 1083 spin_lock_irq(&ctx->event_wqh.lock); 1084 if (!list_empty(&fork_event)) { 1085 /* 1086 * The fork thread didn't abort, so we can 1087 * drop the temporary refcount. 1088 */ 1089 userfaultfd_ctx_put(fork_nctx); 1090 1091 uwq = list_first_entry(&fork_event, 1092 typeof(*uwq), 1093 wq.entry); 1094 /* 1095 * If fork_event list wasn't empty and in turn 1096 * the event wasn't already released by fork 1097 * (the event is allocated on fork kernel 1098 * stack), put the event back to its place in 1099 * the event_wq. fork_event head will be freed 1100 * as soon as we return so the event cannot 1101 * stay queued there no matter the current 1102 * "ret" value. 1103 */ 1104 list_del(&uwq->wq.entry); 1105 __add_wait_queue(&ctx->event_wqh, &uwq->wq); 1106 1107 /* 1108 * Leave the event in the waitqueue and report 1109 * error to userland if we failed to resolve 1110 * the userfault fork. 1111 */ 1112 if (likely(!ret)) 1113 userfaultfd_event_complete(ctx, uwq); 1114 } else { 1115 /* 1116 * Here the fork thread aborted and the 1117 * refcount from the fork thread on fork_nctx 1118 * has already been released. We still hold 1119 * the reference we took before releasing the 1120 * lock above. If resolve_userfault_fork 1121 * failed we've to drop it because the 1122 * fork_nctx has to be freed in such case. If 1123 * it succeeded we'll hold it because the new 1124 * uffd references it. 1125 */ 1126 if (ret) 1127 userfaultfd_ctx_put(fork_nctx); 1128 } 1129 spin_unlock_irq(&ctx->event_wqh.lock); 1130 } 1131 1132 return ret; 1133 } 1134 1135 static ssize_t userfaultfd_read_iter(struct kiocb *iocb, struct iov_iter *to) 1136 { 1137 struct file *file = iocb->ki_filp; 1138 struct userfaultfd_ctx *ctx = file->private_data; 1139 ssize_t _ret, ret = 0; 1140 struct uffd_msg msg; 1141 struct inode *inode = file_inode(file); 1142 bool no_wait; 1143 1144 if (!userfaultfd_is_initialized(ctx)) 1145 return -EINVAL; 1146 1147 no_wait = file->f_flags & O_NONBLOCK || iocb->ki_flags & IOCB_NOWAIT; 1148 for (;;) { 1149 if (iov_iter_count(to) < sizeof(msg)) 1150 return ret ? ret : -EINVAL; 1151 _ret = userfaultfd_ctx_read(ctx, no_wait, &msg, inode); 1152 if (_ret < 0) 1153 return ret ? ret : _ret; 1154 _ret = !copy_to_iter_full(&msg, sizeof(msg), to); 1155 if (_ret) 1156 return ret ? ret : -EFAULT; 1157 ret += sizeof(msg); 1158 /* 1159 * Allow to read more than one fault at time but only 1160 * block if waiting for the very first one. 1161 */ 1162 no_wait = true; 1163 } 1164 } 1165 1166 static void __wake_userfault(struct userfaultfd_ctx *ctx, 1167 struct userfaultfd_wake_range *range) 1168 { 1169 spin_lock_irq(&ctx->fault_pending_wqh.lock); 1170 /* wake all in the range and autoremove */ 1171 if (waitqueue_active(&ctx->fault_pending_wqh)) 1172 __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, 1173 range); 1174 if (waitqueue_active(&ctx->fault_wqh)) 1175 __wake_up(&ctx->fault_wqh, TASK_NORMAL, 1, range); 1176 spin_unlock_irq(&ctx->fault_pending_wqh.lock); 1177 } 1178 1179 static __always_inline void wake_userfault(struct userfaultfd_ctx *ctx, 1180 struct userfaultfd_wake_range *range) 1181 { 1182 unsigned seq; 1183 bool need_wakeup; 1184 1185 /* 1186 * To be sure waitqueue_active() is not reordered by the CPU 1187 * before the pagetable update, use an explicit SMP memory 1188 * barrier here. PT lock release or mmap_read_unlock(mm) still 1189 * have release semantics that can allow the 1190 * waitqueue_active() to be reordered before the pte update. 1191 */ 1192 smp_mb(); 1193 1194 /* 1195 * Use waitqueue_active because it's very frequent to 1196 * change the address space atomically even if there are no 1197 * userfaults yet. So we take the spinlock only when we're 1198 * sure we've userfaults to wake. 1199 */ 1200 do { 1201 seq = read_seqcount_begin(&ctx->refile_seq); 1202 need_wakeup = waitqueue_active(&ctx->fault_pending_wqh) || 1203 waitqueue_active(&ctx->fault_wqh); 1204 cond_resched(); 1205 } while (read_seqcount_retry(&ctx->refile_seq, seq)); 1206 if (need_wakeup) 1207 __wake_userfault(ctx, range); 1208 } 1209 1210 static __always_inline int validate_unaligned_range( 1211 struct mm_struct *mm, __u64 start, __u64 len) 1212 { 1213 __u64 task_size = mm->task_size; 1214 1215 if (len & ~PAGE_MASK) 1216 return -EINVAL; 1217 if (!len) 1218 return -EINVAL; 1219 if (start < mmap_min_addr) 1220 return -EINVAL; 1221 if (start >= task_size) 1222 return -EINVAL; 1223 if (len > task_size - start) 1224 return -EINVAL; 1225 if (start + len <= start) 1226 return -EINVAL; 1227 return 0; 1228 } 1229 1230 static __always_inline int validate_range(struct mm_struct *mm, 1231 __u64 start, __u64 len) 1232 { 1233 if (start & ~PAGE_MASK) 1234 return -EINVAL; 1235 1236 return validate_unaligned_range(mm, start, len); 1237 } 1238 1239 static int userfaultfd_register(struct userfaultfd_ctx *ctx, 1240 unsigned long arg) 1241 { 1242 struct mm_struct *mm = ctx->mm; 1243 struct vm_area_struct *vma, *cur; 1244 int ret; 1245 struct uffdio_register uffdio_register; 1246 struct uffdio_register __user *user_uffdio_register; 1247 unsigned long vm_flags; 1248 bool found; 1249 bool basic_ioctls; 1250 unsigned long start, end; 1251 struct vma_iterator vmi; 1252 bool wp_async = userfaultfd_wp_async_ctx(ctx); 1253 1254 user_uffdio_register = (struct uffdio_register __user *) arg; 1255 1256 ret = -EFAULT; 1257 if (copy_from_user(&uffdio_register, user_uffdio_register, 1258 sizeof(uffdio_register)-sizeof(__u64))) 1259 goto out; 1260 1261 ret = -EINVAL; 1262 if (!uffdio_register.mode) 1263 goto out; 1264 if (uffdio_register.mode & ~UFFD_API_REGISTER_MODES) 1265 goto out; 1266 vm_flags = 0; 1267 if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MISSING) 1268 vm_flags |= VM_UFFD_MISSING; 1269 if (uffdio_register.mode & UFFDIO_REGISTER_MODE_WP) { 1270 #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_WP 1271 goto out; 1272 #endif 1273 vm_flags |= VM_UFFD_WP; 1274 } 1275 if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MINOR) { 1276 #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR 1277 goto out; 1278 #endif 1279 vm_flags |= VM_UFFD_MINOR; 1280 } 1281 1282 ret = validate_range(mm, uffdio_register.range.start, 1283 uffdio_register.range.len); 1284 if (ret) 1285 goto out; 1286 1287 start = uffdio_register.range.start; 1288 end = start + uffdio_register.range.len; 1289 1290 ret = -ENOMEM; 1291 if (!mmget_not_zero(mm)) 1292 goto out; 1293 1294 ret = -EINVAL; 1295 mmap_write_lock(mm); 1296 vma_iter_init(&vmi, mm, start); 1297 vma = vma_find(&vmi, end); 1298 if (!vma) 1299 goto out_unlock; 1300 1301 /* 1302 * If the first vma contains huge pages, make sure start address 1303 * is aligned to huge page size. 1304 */ 1305 if (is_vm_hugetlb_page(vma)) { 1306 unsigned long vma_hpagesize = vma_kernel_pagesize(vma); 1307 1308 if (start & (vma_hpagesize - 1)) 1309 goto out_unlock; 1310 } 1311 1312 /* 1313 * Search for not compatible vmas. 1314 */ 1315 found = false; 1316 basic_ioctls = false; 1317 cur = vma; 1318 do { 1319 cond_resched(); 1320 1321 BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^ 1322 !!(cur->vm_flags & __VM_UFFD_FLAGS)); 1323 1324 /* check not compatible vmas */ 1325 ret = -EINVAL; 1326 if (!vma_can_userfault(cur, vm_flags, wp_async)) 1327 goto out_unlock; 1328 1329 /* 1330 * UFFDIO_COPY will fill file holes even without 1331 * PROT_WRITE. This check enforces that if this is a 1332 * MAP_SHARED, the process has write permission to the backing 1333 * file. If VM_MAYWRITE is set it also enforces that on a 1334 * MAP_SHARED vma: there is no F_WRITE_SEAL and no further 1335 * F_WRITE_SEAL can be taken until the vma is destroyed. 1336 */ 1337 ret = -EPERM; 1338 if (unlikely(!(cur->vm_flags & VM_MAYWRITE))) 1339 goto out_unlock; 1340 1341 /* 1342 * If this vma contains ending address, and huge pages 1343 * check alignment. 1344 */ 1345 if (is_vm_hugetlb_page(cur) && end <= cur->vm_end && 1346 end > cur->vm_start) { 1347 unsigned long vma_hpagesize = vma_kernel_pagesize(cur); 1348 1349 ret = -EINVAL; 1350 1351 if (end & (vma_hpagesize - 1)) 1352 goto out_unlock; 1353 } 1354 if ((vm_flags & VM_UFFD_WP) && !(cur->vm_flags & VM_MAYWRITE)) 1355 goto out_unlock; 1356 1357 /* 1358 * Check that this vma isn't already owned by a 1359 * different userfaultfd. We can't allow more than one 1360 * userfaultfd to own a single vma simultaneously or we 1361 * wouldn't know which one to deliver the userfaults to. 1362 */ 1363 ret = -EBUSY; 1364 if (cur->vm_userfaultfd_ctx.ctx && 1365 cur->vm_userfaultfd_ctx.ctx != ctx) 1366 goto out_unlock; 1367 1368 /* 1369 * Note vmas containing huge pages 1370 */ 1371 if (is_vm_hugetlb_page(cur)) 1372 basic_ioctls = true; 1373 1374 found = true; 1375 } for_each_vma_range(vmi, cur, end); 1376 BUG_ON(!found); 1377 1378 ret = userfaultfd_register_range(ctx, vma, vm_flags, start, end, 1379 wp_async); 1380 1381 out_unlock: 1382 mmap_write_unlock(mm); 1383 mmput(mm); 1384 if (!ret) { 1385 __u64 ioctls_out; 1386 1387 ioctls_out = basic_ioctls ? UFFD_API_RANGE_IOCTLS_BASIC : 1388 UFFD_API_RANGE_IOCTLS; 1389 1390 /* 1391 * Declare the WP ioctl only if the WP mode is 1392 * specified and all checks passed with the range 1393 */ 1394 if (!(uffdio_register.mode & UFFDIO_REGISTER_MODE_WP)) 1395 ioctls_out &= ~((__u64)1 << _UFFDIO_WRITEPROTECT); 1396 1397 /* CONTINUE ioctl is only supported for MINOR ranges. */ 1398 if (!(uffdio_register.mode & UFFDIO_REGISTER_MODE_MINOR)) 1399 ioctls_out &= ~((__u64)1 << _UFFDIO_CONTINUE); 1400 1401 /* 1402 * Now that we scanned all vmas we can already tell 1403 * userland which ioctls methods are guaranteed to 1404 * succeed on this range. 1405 */ 1406 if (put_user(ioctls_out, &user_uffdio_register->ioctls)) 1407 ret = -EFAULT; 1408 } 1409 out: 1410 return ret; 1411 } 1412 1413 static int userfaultfd_unregister(struct userfaultfd_ctx *ctx, 1414 unsigned long arg) 1415 { 1416 struct mm_struct *mm = ctx->mm; 1417 struct vm_area_struct *vma, *prev, *cur; 1418 int ret; 1419 struct uffdio_range uffdio_unregister; 1420 bool found; 1421 unsigned long start, end, vma_end; 1422 const void __user *buf = (void __user *)arg; 1423 struct vma_iterator vmi; 1424 bool wp_async = userfaultfd_wp_async_ctx(ctx); 1425 1426 ret = -EFAULT; 1427 if (copy_from_user(&uffdio_unregister, buf, sizeof(uffdio_unregister))) 1428 goto out; 1429 1430 ret = validate_range(mm, uffdio_unregister.start, 1431 uffdio_unregister.len); 1432 if (ret) 1433 goto out; 1434 1435 start = uffdio_unregister.start; 1436 end = start + uffdio_unregister.len; 1437 1438 ret = -ENOMEM; 1439 if (!mmget_not_zero(mm)) 1440 goto out; 1441 1442 mmap_write_lock(mm); 1443 ret = -EINVAL; 1444 vma_iter_init(&vmi, mm, start); 1445 vma = vma_find(&vmi, end); 1446 if (!vma) 1447 goto out_unlock; 1448 1449 /* 1450 * If the first vma contains huge pages, make sure start address 1451 * is aligned to huge page size. 1452 */ 1453 if (is_vm_hugetlb_page(vma)) { 1454 unsigned long vma_hpagesize = vma_kernel_pagesize(vma); 1455 1456 if (start & (vma_hpagesize - 1)) 1457 goto out_unlock; 1458 } 1459 1460 /* 1461 * Search for not compatible vmas. 1462 */ 1463 found = false; 1464 cur = vma; 1465 do { 1466 cond_resched(); 1467 1468 BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^ 1469 !!(cur->vm_flags & __VM_UFFD_FLAGS)); 1470 1471 /* 1472 * Check not compatible vmas, not strictly required 1473 * here as not compatible vmas cannot have an 1474 * userfaultfd_ctx registered on them, but this 1475 * provides for more strict behavior to notice 1476 * unregistration errors. 1477 */ 1478 if (!vma_can_userfault(cur, cur->vm_flags, wp_async)) 1479 goto out_unlock; 1480 1481 found = true; 1482 } for_each_vma_range(vmi, cur, end); 1483 BUG_ON(!found); 1484 1485 vma_iter_set(&vmi, start); 1486 prev = vma_prev(&vmi); 1487 if (vma->vm_start < start) 1488 prev = vma; 1489 1490 ret = 0; 1491 for_each_vma_range(vmi, vma, end) { 1492 cond_resched(); 1493 1494 BUG_ON(!vma_can_userfault(vma, vma->vm_flags, wp_async)); 1495 1496 /* 1497 * Nothing to do: this vma is already registered into this 1498 * userfaultfd and with the right tracking mode too. 1499 */ 1500 if (!vma->vm_userfaultfd_ctx.ctx) 1501 goto skip; 1502 1503 WARN_ON(!(vma->vm_flags & VM_MAYWRITE)); 1504 1505 if (vma->vm_start > start) 1506 start = vma->vm_start; 1507 vma_end = min(end, vma->vm_end); 1508 1509 if (userfaultfd_missing(vma)) { 1510 /* 1511 * Wake any concurrent pending userfault while 1512 * we unregister, so they will not hang 1513 * permanently and it avoids userland to call 1514 * UFFDIO_WAKE explicitly. 1515 */ 1516 struct userfaultfd_wake_range range; 1517 range.start = start; 1518 range.len = vma_end - start; 1519 wake_userfault(vma->vm_userfaultfd_ctx.ctx, &range); 1520 } 1521 1522 vma = userfaultfd_clear_vma(&vmi, prev, vma, 1523 start, vma_end); 1524 if (IS_ERR(vma)) { 1525 ret = PTR_ERR(vma); 1526 break; 1527 } 1528 1529 skip: 1530 prev = vma; 1531 start = vma->vm_end; 1532 } 1533 1534 out_unlock: 1535 mmap_write_unlock(mm); 1536 mmput(mm); 1537 out: 1538 return ret; 1539 } 1540 1541 /* 1542 * userfaultfd_wake may be used in combination with the 1543 * UFFDIO_*_MODE_DONTWAKE to wakeup userfaults in batches. 1544 */ 1545 static int userfaultfd_wake(struct userfaultfd_ctx *ctx, 1546 unsigned long arg) 1547 { 1548 int ret; 1549 struct uffdio_range uffdio_wake; 1550 struct userfaultfd_wake_range range; 1551 const void __user *buf = (void __user *)arg; 1552 1553 ret = -EFAULT; 1554 if (copy_from_user(&uffdio_wake, buf, sizeof(uffdio_wake))) 1555 goto out; 1556 1557 ret = validate_range(ctx->mm, uffdio_wake.start, uffdio_wake.len); 1558 if (ret) 1559 goto out; 1560 1561 range.start = uffdio_wake.start; 1562 range.len = uffdio_wake.len; 1563 1564 /* 1565 * len == 0 means wake all and we don't want to wake all here, 1566 * so check it again to be sure. 1567 */ 1568 VM_BUG_ON(!range.len); 1569 1570 wake_userfault(ctx, &range); 1571 ret = 0; 1572 1573 out: 1574 return ret; 1575 } 1576 1577 static int userfaultfd_copy(struct userfaultfd_ctx *ctx, 1578 unsigned long arg) 1579 { 1580 __s64 ret; 1581 struct uffdio_copy uffdio_copy; 1582 struct uffdio_copy __user *user_uffdio_copy; 1583 struct userfaultfd_wake_range range; 1584 uffd_flags_t flags = 0; 1585 1586 user_uffdio_copy = (struct uffdio_copy __user *) arg; 1587 1588 ret = -EAGAIN; 1589 if (atomic_read(&ctx->mmap_changing)) 1590 goto out; 1591 1592 ret = -EFAULT; 1593 if (copy_from_user(&uffdio_copy, user_uffdio_copy, 1594 /* don't copy "copy" last field */ 1595 sizeof(uffdio_copy)-sizeof(__s64))) 1596 goto out; 1597 1598 ret = validate_unaligned_range(ctx->mm, uffdio_copy.src, 1599 uffdio_copy.len); 1600 if (ret) 1601 goto out; 1602 ret = validate_range(ctx->mm, uffdio_copy.dst, uffdio_copy.len); 1603 if (ret) 1604 goto out; 1605 1606 ret = -EINVAL; 1607 if (uffdio_copy.mode & ~(UFFDIO_COPY_MODE_DONTWAKE|UFFDIO_COPY_MODE_WP)) 1608 goto out; 1609 if (uffdio_copy.mode & UFFDIO_COPY_MODE_WP) 1610 flags |= MFILL_ATOMIC_WP; 1611 if (mmget_not_zero(ctx->mm)) { 1612 ret = mfill_atomic_copy(ctx, uffdio_copy.dst, uffdio_copy.src, 1613 uffdio_copy.len, flags); 1614 mmput(ctx->mm); 1615 } else { 1616 return -ESRCH; 1617 } 1618 if (unlikely(put_user(ret, &user_uffdio_copy->copy))) 1619 return -EFAULT; 1620 if (ret < 0) 1621 goto out; 1622 BUG_ON(!ret); 1623 /* len == 0 would wake all */ 1624 range.len = ret; 1625 if (!(uffdio_copy.mode & UFFDIO_COPY_MODE_DONTWAKE)) { 1626 range.start = uffdio_copy.dst; 1627 wake_userfault(ctx, &range); 1628 } 1629 ret = range.len == uffdio_copy.len ? 0 : -EAGAIN; 1630 out: 1631 return ret; 1632 } 1633 1634 static int userfaultfd_zeropage(struct userfaultfd_ctx *ctx, 1635 unsigned long arg) 1636 { 1637 __s64 ret; 1638 struct uffdio_zeropage uffdio_zeropage; 1639 struct uffdio_zeropage __user *user_uffdio_zeropage; 1640 struct userfaultfd_wake_range range; 1641 1642 user_uffdio_zeropage = (struct uffdio_zeropage __user *) arg; 1643 1644 ret = -EAGAIN; 1645 if (atomic_read(&ctx->mmap_changing)) 1646 goto out; 1647 1648 ret = -EFAULT; 1649 if (copy_from_user(&uffdio_zeropage, user_uffdio_zeropage, 1650 /* don't copy "zeropage" last field */ 1651 sizeof(uffdio_zeropage)-sizeof(__s64))) 1652 goto out; 1653 1654 ret = validate_range(ctx->mm, uffdio_zeropage.range.start, 1655 uffdio_zeropage.range.len); 1656 if (ret) 1657 goto out; 1658 ret = -EINVAL; 1659 if (uffdio_zeropage.mode & ~UFFDIO_ZEROPAGE_MODE_DONTWAKE) 1660 goto out; 1661 1662 if (mmget_not_zero(ctx->mm)) { 1663 ret = mfill_atomic_zeropage(ctx, uffdio_zeropage.range.start, 1664 uffdio_zeropage.range.len); 1665 mmput(ctx->mm); 1666 } else { 1667 return -ESRCH; 1668 } 1669 if (unlikely(put_user(ret, &user_uffdio_zeropage->zeropage))) 1670 return -EFAULT; 1671 if (ret < 0) 1672 goto out; 1673 /* len == 0 would wake all */ 1674 BUG_ON(!ret); 1675 range.len = ret; 1676 if (!(uffdio_zeropage.mode & UFFDIO_ZEROPAGE_MODE_DONTWAKE)) { 1677 range.start = uffdio_zeropage.range.start; 1678 wake_userfault(ctx, &range); 1679 } 1680 ret = range.len == uffdio_zeropage.range.len ? 0 : -EAGAIN; 1681 out: 1682 return ret; 1683 } 1684 1685 static int userfaultfd_writeprotect(struct userfaultfd_ctx *ctx, 1686 unsigned long arg) 1687 { 1688 int ret; 1689 struct uffdio_writeprotect uffdio_wp; 1690 struct uffdio_writeprotect __user *user_uffdio_wp; 1691 struct userfaultfd_wake_range range; 1692 bool mode_wp, mode_dontwake; 1693 1694 if (atomic_read(&ctx->mmap_changing)) 1695 return -EAGAIN; 1696 1697 user_uffdio_wp = (struct uffdio_writeprotect __user *) arg; 1698 1699 if (copy_from_user(&uffdio_wp, user_uffdio_wp, 1700 sizeof(struct uffdio_writeprotect))) 1701 return -EFAULT; 1702 1703 ret = validate_range(ctx->mm, uffdio_wp.range.start, 1704 uffdio_wp.range.len); 1705 if (ret) 1706 return ret; 1707 1708 if (uffdio_wp.mode & ~(UFFDIO_WRITEPROTECT_MODE_DONTWAKE | 1709 UFFDIO_WRITEPROTECT_MODE_WP)) 1710 return -EINVAL; 1711 1712 mode_wp = uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_WP; 1713 mode_dontwake = uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_DONTWAKE; 1714 1715 if (mode_wp && mode_dontwake) 1716 return -EINVAL; 1717 1718 if (mmget_not_zero(ctx->mm)) { 1719 ret = mwriteprotect_range(ctx, uffdio_wp.range.start, 1720 uffdio_wp.range.len, mode_wp); 1721 mmput(ctx->mm); 1722 } else { 1723 return -ESRCH; 1724 } 1725 1726 if (ret) 1727 return ret; 1728 1729 if (!mode_wp && !mode_dontwake) { 1730 range.start = uffdio_wp.range.start; 1731 range.len = uffdio_wp.range.len; 1732 wake_userfault(ctx, &range); 1733 } 1734 return ret; 1735 } 1736 1737 static int userfaultfd_continue(struct userfaultfd_ctx *ctx, unsigned long arg) 1738 { 1739 __s64 ret; 1740 struct uffdio_continue uffdio_continue; 1741 struct uffdio_continue __user *user_uffdio_continue; 1742 struct userfaultfd_wake_range range; 1743 uffd_flags_t flags = 0; 1744 1745 user_uffdio_continue = (struct uffdio_continue __user *)arg; 1746 1747 ret = -EAGAIN; 1748 if (atomic_read(&ctx->mmap_changing)) 1749 goto out; 1750 1751 ret = -EFAULT; 1752 if (copy_from_user(&uffdio_continue, user_uffdio_continue, 1753 /* don't copy the output fields */ 1754 sizeof(uffdio_continue) - (sizeof(__s64)))) 1755 goto out; 1756 1757 ret = validate_range(ctx->mm, uffdio_continue.range.start, 1758 uffdio_continue.range.len); 1759 if (ret) 1760 goto out; 1761 1762 ret = -EINVAL; 1763 if (uffdio_continue.mode & ~(UFFDIO_CONTINUE_MODE_DONTWAKE | 1764 UFFDIO_CONTINUE_MODE_WP)) 1765 goto out; 1766 if (uffdio_continue.mode & UFFDIO_CONTINUE_MODE_WP) 1767 flags |= MFILL_ATOMIC_WP; 1768 1769 if (mmget_not_zero(ctx->mm)) { 1770 ret = mfill_atomic_continue(ctx, uffdio_continue.range.start, 1771 uffdio_continue.range.len, flags); 1772 mmput(ctx->mm); 1773 } else { 1774 return -ESRCH; 1775 } 1776 1777 if (unlikely(put_user(ret, &user_uffdio_continue->mapped))) 1778 return -EFAULT; 1779 if (ret < 0) 1780 goto out; 1781 1782 /* len == 0 would wake all */ 1783 BUG_ON(!ret); 1784 range.len = ret; 1785 if (!(uffdio_continue.mode & UFFDIO_CONTINUE_MODE_DONTWAKE)) { 1786 range.start = uffdio_continue.range.start; 1787 wake_userfault(ctx, &range); 1788 } 1789 ret = range.len == uffdio_continue.range.len ? 0 : -EAGAIN; 1790 1791 out: 1792 return ret; 1793 } 1794 1795 static inline int userfaultfd_poison(struct userfaultfd_ctx *ctx, unsigned long arg) 1796 { 1797 __s64 ret; 1798 struct uffdio_poison uffdio_poison; 1799 struct uffdio_poison __user *user_uffdio_poison; 1800 struct userfaultfd_wake_range range; 1801 1802 user_uffdio_poison = (struct uffdio_poison __user *)arg; 1803 1804 ret = -EAGAIN; 1805 if (atomic_read(&ctx->mmap_changing)) 1806 goto out; 1807 1808 ret = -EFAULT; 1809 if (copy_from_user(&uffdio_poison, user_uffdio_poison, 1810 /* don't copy the output fields */ 1811 sizeof(uffdio_poison) - (sizeof(__s64)))) 1812 goto out; 1813 1814 ret = validate_range(ctx->mm, uffdio_poison.range.start, 1815 uffdio_poison.range.len); 1816 if (ret) 1817 goto out; 1818 1819 ret = -EINVAL; 1820 if (uffdio_poison.mode & ~UFFDIO_POISON_MODE_DONTWAKE) 1821 goto out; 1822 1823 if (mmget_not_zero(ctx->mm)) { 1824 ret = mfill_atomic_poison(ctx, uffdio_poison.range.start, 1825 uffdio_poison.range.len, 0); 1826 mmput(ctx->mm); 1827 } else { 1828 return -ESRCH; 1829 } 1830 1831 if (unlikely(put_user(ret, &user_uffdio_poison->updated))) 1832 return -EFAULT; 1833 if (ret < 0) 1834 goto out; 1835 1836 /* len == 0 would wake all */ 1837 BUG_ON(!ret); 1838 range.len = ret; 1839 if (!(uffdio_poison.mode & UFFDIO_POISON_MODE_DONTWAKE)) { 1840 range.start = uffdio_poison.range.start; 1841 wake_userfault(ctx, &range); 1842 } 1843 ret = range.len == uffdio_poison.range.len ? 0 : -EAGAIN; 1844 1845 out: 1846 return ret; 1847 } 1848 1849 bool userfaultfd_wp_async(struct vm_area_struct *vma) 1850 { 1851 return userfaultfd_wp_async_ctx(vma->vm_userfaultfd_ctx.ctx); 1852 } 1853 1854 static inline unsigned int uffd_ctx_features(__u64 user_features) 1855 { 1856 /* 1857 * For the current set of features the bits just coincide. Set 1858 * UFFD_FEATURE_INITIALIZED to mark the features as enabled. 1859 */ 1860 return (unsigned int)user_features | UFFD_FEATURE_INITIALIZED; 1861 } 1862 1863 static int userfaultfd_move(struct userfaultfd_ctx *ctx, 1864 unsigned long arg) 1865 { 1866 __s64 ret; 1867 struct uffdio_move uffdio_move; 1868 struct uffdio_move __user *user_uffdio_move; 1869 struct userfaultfd_wake_range range; 1870 struct mm_struct *mm = ctx->mm; 1871 1872 user_uffdio_move = (struct uffdio_move __user *) arg; 1873 1874 if (atomic_read(&ctx->mmap_changing)) 1875 return -EAGAIN; 1876 1877 if (copy_from_user(&uffdio_move, user_uffdio_move, 1878 /* don't copy "move" last field */ 1879 sizeof(uffdio_move)-sizeof(__s64))) 1880 return -EFAULT; 1881 1882 /* Do not allow cross-mm moves. */ 1883 if (mm != current->mm) 1884 return -EINVAL; 1885 1886 ret = validate_range(mm, uffdio_move.dst, uffdio_move.len); 1887 if (ret) 1888 return ret; 1889 1890 ret = validate_range(mm, uffdio_move.src, uffdio_move.len); 1891 if (ret) 1892 return ret; 1893 1894 if (uffdio_move.mode & ~(UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES| 1895 UFFDIO_MOVE_MODE_DONTWAKE)) 1896 return -EINVAL; 1897 1898 if (mmget_not_zero(mm)) { 1899 ret = move_pages(ctx, uffdio_move.dst, uffdio_move.src, 1900 uffdio_move.len, uffdio_move.mode); 1901 mmput(mm); 1902 } else { 1903 return -ESRCH; 1904 } 1905 1906 if (unlikely(put_user(ret, &user_uffdio_move->move))) 1907 return -EFAULT; 1908 if (ret < 0) 1909 goto out; 1910 1911 /* len == 0 would wake all */ 1912 VM_WARN_ON(!ret); 1913 range.len = ret; 1914 if (!(uffdio_move.mode & UFFDIO_MOVE_MODE_DONTWAKE)) { 1915 range.start = uffdio_move.dst; 1916 wake_userfault(ctx, &range); 1917 } 1918 ret = range.len == uffdio_move.len ? 0 : -EAGAIN; 1919 1920 out: 1921 return ret; 1922 } 1923 1924 /* 1925 * userland asks for a certain API version and we return which bits 1926 * and ioctl commands are implemented in this kernel for such API 1927 * version or -EINVAL if unknown. 1928 */ 1929 static int userfaultfd_api(struct userfaultfd_ctx *ctx, 1930 unsigned long arg) 1931 { 1932 struct uffdio_api uffdio_api; 1933 void __user *buf = (void __user *)arg; 1934 unsigned int ctx_features; 1935 int ret; 1936 __u64 features; 1937 1938 ret = -EFAULT; 1939 if (copy_from_user(&uffdio_api, buf, sizeof(uffdio_api))) 1940 goto out; 1941 features = uffdio_api.features; 1942 ret = -EINVAL; 1943 if (uffdio_api.api != UFFD_API) 1944 goto err_out; 1945 ret = -EPERM; 1946 if ((features & UFFD_FEATURE_EVENT_FORK) && !capable(CAP_SYS_PTRACE)) 1947 goto err_out; 1948 1949 /* WP_ASYNC relies on WP_UNPOPULATED, choose it unconditionally */ 1950 if (features & UFFD_FEATURE_WP_ASYNC) 1951 features |= UFFD_FEATURE_WP_UNPOPULATED; 1952 1953 /* report all available features and ioctls to userland */ 1954 uffdio_api.features = UFFD_API_FEATURES; 1955 #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR 1956 uffdio_api.features &= 1957 ~(UFFD_FEATURE_MINOR_HUGETLBFS | UFFD_FEATURE_MINOR_SHMEM); 1958 #endif 1959 #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_WP 1960 uffdio_api.features &= ~UFFD_FEATURE_PAGEFAULT_FLAG_WP; 1961 #endif 1962 #ifndef CONFIG_PTE_MARKER_UFFD_WP 1963 uffdio_api.features &= ~UFFD_FEATURE_WP_HUGETLBFS_SHMEM; 1964 uffdio_api.features &= ~UFFD_FEATURE_WP_UNPOPULATED; 1965 uffdio_api.features &= ~UFFD_FEATURE_WP_ASYNC; 1966 #endif 1967 1968 ret = -EINVAL; 1969 if (features & ~uffdio_api.features) 1970 goto err_out; 1971 1972 uffdio_api.ioctls = UFFD_API_IOCTLS; 1973 ret = -EFAULT; 1974 if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api))) 1975 goto out; 1976 1977 /* only enable the requested features for this uffd context */ 1978 ctx_features = uffd_ctx_features(features); 1979 ret = -EINVAL; 1980 if (cmpxchg(&ctx->features, 0, ctx_features) != 0) 1981 goto err_out; 1982 1983 ret = 0; 1984 out: 1985 return ret; 1986 err_out: 1987 memset(&uffdio_api, 0, sizeof(uffdio_api)); 1988 if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api))) 1989 ret = -EFAULT; 1990 goto out; 1991 } 1992 1993 static long userfaultfd_ioctl(struct file *file, unsigned cmd, 1994 unsigned long arg) 1995 { 1996 int ret = -EINVAL; 1997 struct userfaultfd_ctx *ctx = file->private_data; 1998 1999 if (cmd != UFFDIO_API && !userfaultfd_is_initialized(ctx)) 2000 return -EINVAL; 2001 2002 switch(cmd) { 2003 case UFFDIO_API: 2004 ret = userfaultfd_api(ctx, arg); 2005 break; 2006 case UFFDIO_REGISTER: 2007 ret = userfaultfd_register(ctx, arg); 2008 break; 2009 case UFFDIO_UNREGISTER: 2010 ret = userfaultfd_unregister(ctx, arg); 2011 break; 2012 case UFFDIO_WAKE: 2013 ret = userfaultfd_wake(ctx, arg); 2014 break; 2015 case UFFDIO_COPY: 2016 ret = userfaultfd_copy(ctx, arg); 2017 break; 2018 case UFFDIO_ZEROPAGE: 2019 ret = userfaultfd_zeropage(ctx, arg); 2020 break; 2021 case UFFDIO_MOVE: 2022 ret = userfaultfd_move(ctx, arg); 2023 break; 2024 case UFFDIO_WRITEPROTECT: 2025 ret = userfaultfd_writeprotect(ctx, arg); 2026 break; 2027 case UFFDIO_CONTINUE: 2028 ret = userfaultfd_continue(ctx, arg); 2029 break; 2030 case UFFDIO_POISON: 2031 ret = userfaultfd_poison(ctx, arg); 2032 break; 2033 } 2034 return ret; 2035 } 2036 2037 #ifdef CONFIG_PROC_FS 2038 static void userfaultfd_show_fdinfo(struct seq_file *m, struct file *f) 2039 { 2040 struct userfaultfd_ctx *ctx = f->private_data; 2041 wait_queue_entry_t *wq; 2042 unsigned long pending = 0, total = 0; 2043 2044 spin_lock_irq(&ctx->fault_pending_wqh.lock); 2045 list_for_each_entry(wq, &ctx->fault_pending_wqh.head, entry) { 2046 pending++; 2047 total++; 2048 } 2049 list_for_each_entry(wq, &ctx->fault_wqh.head, entry) { 2050 total++; 2051 } 2052 spin_unlock_irq(&ctx->fault_pending_wqh.lock); 2053 2054 /* 2055 * If more protocols will be added, there will be all shown 2056 * separated by a space. Like this: 2057 * protocols: aa:... bb:... 2058 */ 2059 seq_printf(m, "pending:\t%lu\ntotal:\t%lu\nAPI:\t%Lx:%x:%Lx\n", 2060 pending, total, UFFD_API, ctx->features, 2061 UFFD_API_IOCTLS|UFFD_API_RANGE_IOCTLS); 2062 } 2063 #endif 2064 2065 static const struct file_operations userfaultfd_fops = { 2066 #ifdef CONFIG_PROC_FS 2067 .show_fdinfo = userfaultfd_show_fdinfo, 2068 #endif 2069 .release = userfaultfd_release, 2070 .poll = userfaultfd_poll, 2071 .read_iter = userfaultfd_read_iter, 2072 .unlocked_ioctl = userfaultfd_ioctl, 2073 .compat_ioctl = compat_ptr_ioctl, 2074 .llseek = noop_llseek, 2075 }; 2076 2077 static void init_once_userfaultfd_ctx(void *mem) 2078 { 2079 struct userfaultfd_ctx *ctx = (struct userfaultfd_ctx *) mem; 2080 2081 init_waitqueue_head(&ctx->fault_pending_wqh); 2082 init_waitqueue_head(&ctx->fault_wqh); 2083 init_waitqueue_head(&ctx->event_wqh); 2084 init_waitqueue_head(&ctx->fd_wqh); 2085 seqcount_spinlock_init(&ctx->refile_seq, &ctx->fault_pending_wqh.lock); 2086 } 2087 2088 static int new_userfaultfd(int flags) 2089 { 2090 struct userfaultfd_ctx *ctx; 2091 struct file *file; 2092 int fd; 2093 2094 BUG_ON(!current->mm); 2095 2096 /* Check the UFFD_* constants for consistency. */ 2097 BUILD_BUG_ON(UFFD_USER_MODE_ONLY & UFFD_SHARED_FCNTL_FLAGS); 2098 BUILD_BUG_ON(UFFD_CLOEXEC != O_CLOEXEC); 2099 BUILD_BUG_ON(UFFD_NONBLOCK != O_NONBLOCK); 2100 2101 if (flags & ~(UFFD_SHARED_FCNTL_FLAGS | UFFD_USER_MODE_ONLY)) 2102 return -EINVAL; 2103 2104 ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL); 2105 if (!ctx) 2106 return -ENOMEM; 2107 2108 refcount_set(&ctx->refcount, 1); 2109 ctx->flags = flags; 2110 ctx->features = 0; 2111 ctx->released = false; 2112 init_rwsem(&ctx->map_changing_lock); 2113 atomic_set(&ctx->mmap_changing, 0); 2114 ctx->mm = current->mm; 2115 2116 fd = get_unused_fd_flags(flags & UFFD_SHARED_FCNTL_FLAGS); 2117 if (fd < 0) 2118 goto err_out; 2119 2120 /* Create a new inode so that the LSM can block the creation. */ 2121 file = anon_inode_create_getfile("[userfaultfd]", &userfaultfd_fops, ctx, 2122 O_RDONLY | (flags & UFFD_SHARED_FCNTL_FLAGS), NULL); 2123 if (IS_ERR(file)) { 2124 put_unused_fd(fd); 2125 fd = PTR_ERR(file); 2126 goto err_out; 2127 } 2128 /* prevent the mm struct to be freed */ 2129 mmgrab(ctx->mm); 2130 file->f_mode |= FMODE_NOWAIT; 2131 fd_install(fd, file); 2132 return fd; 2133 err_out: 2134 kmem_cache_free(userfaultfd_ctx_cachep, ctx); 2135 return fd; 2136 } 2137 2138 static inline bool userfaultfd_syscall_allowed(int flags) 2139 { 2140 /* Userspace-only page faults are always allowed */ 2141 if (flags & UFFD_USER_MODE_ONLY) 2142 return true; 2143 2144 /* 2145 * The user is requesting a userfaultfd which can handle kernel faults. 2146 * Privileged users are always allowed to do this. 2147 */ 2148 if (capable(CAP_SYS_PTRACE)) 2149 return true; 2150 2151 /* Otherwise, access to kernel fault handling is sysctl controlled. */ 2152 return sysctl_unprivileged_userfaultfd; 2153 } 2154 2155 SYSCALL_DEFINE1(userfaultfd, int, flags) 2156 { 2157 if (!userfaultfd_syscall_allowed(flags)) 2158 return -EPERM; 2159 2160 return new_userfaultfd(flags); 2161 } 2162 2163 static long userfaultfd_dev_ioctl(struct file *file, unsigned int cmd, unsigned long flags) 2164 { 2165 if (cmd != USERFAULTFD_IOC_NEW) 2166 return -EINVAL; 2167 2168 return new_userfaultfd(flags); 2169 } 2170 2171 static const struct file_operations userfaultfd_dev_fops = { 2172 .unlocked_ioctl = userfaultfd_dev_ioctl, 2173 .compat_ioctl = userfaultfd_dev_ioctl, 2174 .owner = THIS_MODULE, 2175 .llseek = noop_llseek, 2176 }; 2177 2178 static struct miscdevice userfaultfd_misc = { 2179 .minor = MISC_DYNAMIC_MINOR, 2180 .name = "userfaultfd", 2181 .fops = &userfaultfd_dev_fops 2182 }; 2183 2184 static int __init userfaultfd_init(void) 2185 { 2186 int ret; 2187 2188 ret = misc_register(&userfaultfd_misc); 2189 if (ret) 2190 return ret; 2191 2192 userfaultfd_ctx_cachep = kmem_cache_create("userfaultfd_ctx_cache", 2193 sizeof(struct userfaultfd_ctx), 2194 0, 2195 SLAB_HWCACHE_ALIGN|SLAB_PANIC, 2196 init_once_userfaultfd_ctx); 2197 #ifdef CONFIG_SYSCTL 2198 register_sysctl_init("vm", vm_userfaultfd_table); 2199 #endif 2200 return 0; 2201 } 2202 __initcall(userfaultfd_init); 2203