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/mmu_notifier.h> 19 #include <linux/poll.h> 20 #include <linux/slab.h> 21 #include <linux/seq_file.h> 22 #include <linux/file.h> 23 #include <linux/bug.h> 24 #include <linux/anon_inodes.h> 25 #include <linux/syscalls.h> 26 #include <linux/userfaultfd_k.h> 27 #include <linux/mempolicy.h> 28 #include <linux/ioctl.h> 29 #include <linux/security.h> 30 #include <linux/hugetlb.h> 31 32 int sysctl_unprivileged_userfaultfd __read_mostly; 33 34 static struct kmem_cache *userfaultfd_ctx_cachep __read_mostly; 35 36 /* 37 * Start with fault_pending_wqh and fault_wqh so they're more likely 38 * to be in the same cacheline. 39 * 40 * Locking order: 41 * fd_wqh.lock 42 * fault_pending_wqh.lock 43 * fault_wqh.lock 44 * event_wqh.lock 45 * 46 * To avoid deadlocks, IRQs must be disabled when taking any of the above locks, 47 * since fd_wqh.lock is taken by aio_poll() while it's holding a lock that's 48 * also taken in IRQ context. 49 */ 50 struct userfaultfd_ctx { 51 /* waitqueue head for the pending (i.e. not read) userfaults */ 52 wait_queue_head_t fault_pending_wqh; 53 /* waitqueue head for the userfaults */ 54 wait_queue_head_t fault_wqh; 55 /* waitqueue head for the pseudo fd to wakeup poll/read */ 56 wait_queue_head_t fd_wqh; 57 /* waitqueue head for events */ 58 wait_queue_head_t event_wqh; 59 /* a refile sequence protected by fault_pending_wqh lock */ 60 seqcount_spinlock_t refile_seq; 61 /* pseudo fd refcounting */ 62 refcount_t refcount; 63 /* userfaultfd syscall flags */ 64 unsigned int flags; 65 /* features requested from the userspace */ 66 unsigned int features; 67 /* released */ 68 bool released; 69 /* memory mappings are changing because of non-cooperative event */ 70 atomic_t mmap_changing; 71 /* mm with one ore more vmas attached to this userfaultfd_ctx */ 72 struct mm_struct *mm; 73 }; 74 75 struct userfaultfd_fork_ctx { 76 struct userfaultfd_ctx *orig; 77 struct userfaultfd_ctx *new; 78 struct list_head list; 79 }; 80 81 struct userfaultfd_unmap_ctx { 82 struct userfaultfd_ctx *ctx; 83 unsigned long start; 84 unsigned long end; 85 struct list_head list; 86 }; 87 88 struct userfaultfd_wait_queue { 89 struct uffd_msg msg; 90 wait_queue_entry_t wq; 91 struct userfaultfd_ctx *ctx; 92 bool waken; 93 }; 94 95 struct userfaultfd_wake_range { 96 unsigned long start; 97 unsigned long len; 98 }; 99 100 /* internal indication that UFFD_API ioctl was successfully executed */ 101 #define UFFD_FEATURE_INITIALIZED (1u << 31) 102 103 static bool userfaultfd_is_initialized(struct userfaultfd_ctx *ctx) 104 { 105 return ctx->features & UFFD_FEATURE_INITIALIZED; 106 } 107 108 static int userfaultfd_wake_function(wait_queue_entry_t *wq, unsigned mode, 109 int wake_flags, void *key) 110 { 111 struct userfaultfd_wake_range *range = key; 112 int ret; 113 struct userfaultfd_wait_queue *uwq; 114 unsigned long start, len; 115 116 uwq = container_of(wq, struct userfaultfd_wait_queue, wq); 117 ret = 0; 118 /* len == 0 means wake all */ 119 start = range->start; 120 len = range->len; 121 if (len && (start > uwq->msg.arg.pagefault.address || 122 start + len <= uwq->msg.arg.pagefault.address)) 123 goto out; 124 WRITE_ONCE(uwq->waken, true); 125 /* 126 * The Program-Order guarantees provided by the scheduler 127 * ensure uwq->waken is visible before the task is woken. 128 */ 129 ret = wake_up_state(wq->private, mode); 130 if (ret) { 131 /* 132 * Wake only once, autoremove behavior. 133 * 134 * After the effect of list_del_init is visible to the other 135 * CPUs, the waitqueue may disappear from under us, see the 136 * !list_empty_careful() in handle_userfault(). 137 * 138 * try_to_wake_up() has an implicit smp_mb(), and the 139 * wq->private is read before calling the extern function 140 * "wake_up_state" (which in turns calls try_to_wake_up). 141 */ 142 list_del_init(&wq->entry); 143 } 144 out: 145 return ret; 146 } 147 148 /** 149 * userfaultfd_ctx_get - Acquires a reference to the internal userfaultfd 150 * context. 151 * @ctx: [in] Pointer to the userfaultfd context. 152 */ 153 static void userfaultfd_ctx_get(struct userfaultfd_ctx *ctx) 154 { 155 refcount_inc(&ctx->refcount); 156 } 157 158 /** 159 * userfaultfd_ctx_put - Releases a reference to the internal userfaultfd 160 * context. 161 * @ctx: [in] Pointer to userfaultfd context. 162 * 163 * The userfaultfd context reference must have been previously acquired either 164 * with userfaultfd_ctx_get() or userfaultfd_ctx_fdget(). 165 */ 166 static void userfaultfd_ctx_put(struct userfaultfd_ctx *ctx) 167 { 168 if (refcount_dec_and_test(&ctx->refcount)) { 169 VM_BUG_ON(spin_is_locked(&ctx->fault_pending_wqh.lock)); 170 VM_BUG_ON(waitqueue_active(&ctx->fault_pending_wqh)); 171 VM_BUG_ON(spin_is_locked(&ctx->fault_wqh.lock)); 172 VM_BUG_ON(waitqueue_active(&ctx->fault_wqh)); 173 VM_BUG_ON(spin_is_locked(&ctx->event_wqh.lock)); 174 VM_BUG_ON(waitqueue_active(&ctx->event_wqh)); 175 VM_BUG_ON(spin_is_locked(&ctx->fd_wqh.lock)); 176 VM_BUG_ON(waitqueue_active(&ctx->fd_wqh)); 177 mmdrop(ctx->mm); 178 kmem_cache_free(userfaultfd_ctx_cachep, ctx); 179 } 180 } 181 182 static inline void msg_init(struct uffd_msg *msg) 183 { 184 BUILD_BUG_ON(sizeof(struct uffd_msg) != 32); 185 /* 186 * Must use memset to zero out the paddings or kernel data is 187 * leaked to userland. 188 */ 189 memset(msg, 0, sizeof(struct uffd_msg)); 190 } 191 192 static inline struct uffd_msg userfault_msg(unsigned long address, 193 unsigned int flags, 194 unsigned long reason, 195 unsigned int features) 196 { 197 struct uffd_msg msg; 198 msg_init(&msg); 199 msg.event = UFFD_EVENT_PAGEFAULT; 200 msg.arg.pagefault.address = address; 201 /* 202 * These flags indicate why the userfault occurred: 203 * - UFFD_PAGEFAULT_FLAG_WP indicates a write protect fault. 204 * - UFFD_PAGEFAULT_FLAG_MINOR indicates a minor fault. 205 * - Neither of these flags being set indicates a MISSING fault. 206 * 207 * Separately, UFFD_PAGEFAULT_FLAG_WRITE indicates it was a write 208 * fault. Otherwise, it was a read fault. 209 */ 210 if (flags & FAULT_FLAG_WRITE) 211 msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WRITE; 212 if (reason & VM_UFFD_WP) 213 msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WP; 214 if (reason & VM_UFFD_MINOR) 215 msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_MINOR; 216 if (features & UFFD_FEATURE_THREAD_ID) 217 msg.arg.pagefault.feat.ptid = task_pid_vnr(current); 218 return msg; 219 } 220 221 #ifdef CONFIG_HUGETLB_PAGE 222 /* 223 * Same functionality as userfaultfd_must_wait below with modifications for 224 * hugepmd ranges. 225 */ 226 static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx, 227 struct vm_area_struct *vma, 228 unsigned long address, 229 unsigned long flags, 230 unsigned long reason) 231 { 232 struct mm_struct *mm = ctx->mm; 233 pte_t *ptep, pte; 234 bool ret = true; 235 236 mmap_assert_locked(mm); 237 238 ptep = huge_pte_offset(mm, address, vma_mmu_pagesize(vma)); 239 240 if (!ptep) 241 goto out; 242 243 ret = false; 244 pte = huge_ptep_get(ptep); 245 246 /* 247 * Lockless access: we're in a wait_event so it's ok if it 248 * changes under us. 249 */ 250 if (huge_pte_none(pte)) 251 ret = true; 252 if (!huge_pte_write(pte) && (reason & VM_UFFD_WP)) 253 ret = true; 254 out: 255 return ret; 256 } 257 #else 258 static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx, 259 struct vm_area_struct *vma, 260 unsigned long address, 261 unsigned long flags, 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 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 unsigned long address, 277 unsigned long flags, 278 unsigned long reason) 279 { 280 struct mm_struct *mm = ctx->mm; 281 pgd_t *pgd; 282 p4d_t *p4d; 283 pud_t *pud; 284 pmd_t *pmd, _pmd; 285 pte_t *pte; 286 bool ret = true; 287 288 mmap_assert_locked(mm); 289 290 pgd = pgd_offset(mm, address); 291 if (!pgd_present(*pgd)) 292 goto out; 293 p4d = p4d_offset(pgd, address); 294 if (!p4d_present(*p4d)) 295 goto out; 296 pud = pud_offset(p4d, address); 297 if (!pud_present(*pud)) 298 goto out; 299 pmd = pmd_offset(pud, address); 300 /* 301 * READ_ONCE must function as a barrier with narrower scope 302 * and it must be equivalent to: 303 * _pmd = *pmd; barrier(); 304 * 305 * This is to deal with the instability (as in 306 * pmd_trans_unstable) of the pmd. 307 */ 308 _pmd = READ_ONCE(*pmd); 309 if (pmd_none(_pmd)) 310 goto out; 311 312 ret = false; 313 if (!pmd_present(_pmd)) 314 goto out; 315 316 if (pmd_trans_huge(_pmd)) { 317 if (!pmd_write(_pmd) && (reason & VM_UFFD_WP)) 318 ret = true; 319 goto out; 320 } 321 322 /* 323 * the pmd is stable (as in !pmd_trans_unstable) so we can re-read it 324 * and use the standard pte_offset_map() instead of parsing _pmd. 325 */ 326 pte = pte_offset_map(pmd, address); 327 /* 328 * Lockless access: we're in a wait_event so it's ok if it 329 * changes under us. 330 */ 331 if (pte_none(*pte)) 332 ret = true; 333 if (!pte_write(*pte) && (reason & VM_UFFD_WP)) 334 ret = true; 335 pte_unmap(pte); 336 337 out: 338 return ret; 339 } 340 341 static inline unsigned int userfaultfd_get_blocking_state(unsigned int flags) 342 { 343 if (flags & FAULT_FLAG_INTERRUPTIBLE) 344 return TASK_INTERRUPTIBLE; 345 346 if (flags & FAULT_FLAG_KILLABLE) 347 return TASK_KILLABLE; 348 349 return TASK_UNINTERRUPTIBLE; 350 } 351 352 /* 353 * The locking rules involved in returning VM_FAULT_RETRY depending on 354 * FAULT_FLAG_ALLOW_RETRY, FAULT_FLAG_RETRY_NOWAIT and 355 * FAULT_FLAG_KILLABLE are not straightforward. The "Caution" 356 * recommendation in __lock_page_or_retry is not an understatement. 357 * 358 * If FAULT_FLAG_ALLOW_RETRY is set, the mmap_lock must be released 359 * before returning VM_FAULT_RETRY only if FAULT_FLAG_RETRY_NOWAIT is 360 * not set. 361 * 362 * If FAULT_FLAG_ALLOW_RETRY is set but FAULT_FLAG_KILLABLE is not 363 * set, VM_FAULT_RETRY can still be returned if and only if there are 364 * fatal_signal_pending()s, and the mmap_lock must be released before 365 * returning it. 366 */ 367 vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason) 368 { 369 struct mm_struct *mm = vmf->vma->vm_mm; 370 struct userfaultfd_ctx *ctx; 371 struct userfaultfd_wait_queue uwq; 372 vm_fault_t ret = VM_FAULT_SIGBUS; 373 bool must_wait; 374 unsigned int blocking_state; 375 376 /* 377 * We don't do userfault handling for the final child pid update. 378 * 379 * We also don't do userfault handling during 380 * coredumping. hugetlbfs has the special 381 * follow_hugetlb_page() to skip missing pages in the 382 * FOLL_DUMP case, anon memory also checks for FOLL_DUMP with 383 * the no_page_table() helper in follow_page_mask(), but the 384 * shmem_vm_ops->fault method is invoked even during 385 * coredumping without mmap_lock and it ends up here. 386 */ 387 if (current->flags & (PF_EXITING|PF_DUMPCORE)) 388 goto out; 389 390 /* 391 * Coredumping runs without mmap_lock so we can only check that 392 * the mmap_lock is held, if PF_DUMPCORE was not set. 393 */ 394 mmap_assert_locked(mm); 395 396 ctx = vmf->vma->vm_userfaultfd_ctx.ctx; 397 if (!ctx) 398 goto out; 399 400 BUG_ON(ctx->mm != mm); 401 402 /* Any unrecognized flag is a bug. */ 403 VM_BUG_ON(reason & ~__VM_UFFD_FLAGS); 404 /* 0 or > 1 flags set is a bug; we expect exactly 1. */ 405 VM_BUG_ON(!reason || (reason & (reason - 1))); 406 407 if (ctx->features & UFFD_FEATURE_SIGBUS) 408 goto out; 409 if ((vmf->flags & FAULT_FLAG_USER) == 0 && 410 ctx->flags & UFFD_USER_MODE_ONLY) { 411 printk_once(KERN_WARNING "uffd: Set unprivileged_userfaultfd " 412 "sysctl knob to 1 if kernel faults must be handled " 413 "without obtaining CAP_SYS_PTRACE capability\n"); 414 goto out; 415 } 416 417 /* 418 * If it's already released don't get it. This avoids to loop 419 * in __get_user_pages if userfaultfd_release waits on the 420 * caller of handle_userfault to release the mmap_lock. 421 */ 422 if (unlikely(READ_ONCE(ctx->released))) { 423 /* 424 * Don't return VM_FAULT_SIGBUS in this case, so a non 425 * cooperative manager can close the uffd after the 426 * last UFFDIO_COPY, without risking to trigger an 427 * involuntary SIGBUS if the process was starting the 428 * userfaultfd while the userfaultfd was still armed 429 * (but after the last UFFDIO_COPY). If the uffd 430 * wasn't already closed when the userfault reached 431 * this point, that would normally be solved by 432 * userfaultfd_must_wait returning 'false'. 433 * 434 * If we were to return VM_FAULT_SIGBUS here, the non 435 * cooperative manager would be instead forced to 436 * always call UFFDIO_UNREGISTER before it can safely 437 * close the uffd. 438 */ 439 ret = VM_FAULT_NOPAGE; 440 goto out; 441 } 442 443 /* 444 * Check that we can return VM_FAULT_RETRY. 445 * 446 * NOTE: it should become possible to return VM_FAULT_RETRY 447 * even if FAULT_FLAG_TRIED is set without leading to gup() 448 * -EBUSY failures, if the userfaultfd is to be extended for 449 * VM_UFFD_WP tracking and we intend to arm the userfault 450 * without first stopping userland access to the memory. For 451 * VM_UFFD_MISSING userfaults this is enough for now. 452 */ 453 if (unlikely(!(vmf->flags & FAULT_FLAG_ALLOW_RETRY))) { 454 /* 455 * Validate the invariant that nowait must allow retry 456 * to be sure not to return SIGBUS erroneously on 457 * nowait invocations. 458 */ 459 BUG_ON(vmf->flags & FAULT_FLAG_RETRY_NOWAIT); 460 #ifdef CONFIG_DEBUG_VM 461 if (printk_ratelimit()) { 462 printk(KERN_WARNING 463 "FAULT_FLAG_ALLOW_RETRY missing %x\n", 464 vmf->flags); 465 dump_stack(); 466 } 467 #endif 468 goto out; 469 } 470 471 /* 472 * Handle nowait, not much to do other than tell it to retry 473 * and wait. 474 */ 475 ret = VM_FAULT_RETRY; 476 if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT) 477 goto out; 478 479 /* take the reference before dropping the mmap_lock */ 480 userfaultfd_ctx_get(ctx); 481 482 init_waitqueue_func_entry(&uwq.wq, userfaultfd_wake_function); 483 uwq.wq.private = current; 484 uwq.msg = userfault_msg(vmf->address, vmf->flags, reason, 485 ctx->features); 486 uwq.ctx = ctx; 487 uwq.waken = false; 488 489 blocking_state = userfaultfd_get_blocking_state(vmf->flags); 490 491 spin_lock_irq(&ctx->fault_pending_wqh.lock); 492 /* 493 * After the __add_wait_queue the uwq is visible to userland 494 * through poll/read(). 495 */ 496 __add_wait_queue(&ctx->fault_pending_wqh, &uwq.wq); 497 /* 498 * The smp_mb() after __set_current_state prevents the reads 499 * following the spin_unlock to happen before the list_add in 500 * __add_wait_queue. 501 */ 502 set_current_state(blocking_state); 503 spin_unlock_irq(&ctx->fault_pending_wqh.lock); 504 505 if (!is_vm_hugetlb_page(vmf->vma)) 506 must_wait = userfaultfd_must_wait(ctx, vmf->address, vmf->flags, 507 reason); 508 else 509 must_wait = userfaultfd_huge_must_wait(ctx, vmf->vma, 510 vmf->address, 511 vmf->flags, reason); 512 mmap_read_unlock(mm); 513 514 if (likely(must_wait && !READ_ONCE(ctx->released))) { 515 wake_up_poll(&ctx->fd_wqh, EPOLLIN); 516 schedule(); 517 } 518 519 __set_current_state(TASK_RUNNING); 520 521 /* 522 * Here we race with the list_del; list_add in 523 * userfaultfd_ctx_read(), however because we don't ever run 524 * list_del_init() to refile across the two lists, the prev 525 * and next pointers will never point to self. list_add also 526 * would never let any of the two pointers to point to 527 * self. So list_empty_careful won't risk to see both pointers 528 * pointing to self at any time during the list refile. The 529 * only case where list_del_init() is called is the full 530 * removal in the wake function and there we don't re-list_add 531 * and it's fine not to block on the spinlock. The uwq on this 532 * kernel stack can be released after the list_del_init. 533 */ 534 if (!list_empty_careful(&uwq.wq.entry)) { 535 spin_lock_irq(&ctx->fault_pending_wqh.lock); 536 /* 537 * No need of list_del_init(), the uwq on the stack 538 * will be freed shortly anyway. 539 */ 540 list_del(&uwq.wq.entry); 541 spin_unlock_irq(&ctx->fault_pending_wqh.lock); 542 } 543 544 /* 545 * ctx may go away after this if the userfault pseudo fd is 546 * already released. 547 */ 548 userfaultfd_ctx_put(ctx); 549 550 out: 551 return ret; 552 } 553 554 static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx, 555 struct userfaultfd_wait_queue *ewq) 556 { 557 struct userfaultfd_ctx *release_new_ctx; 558 559 if (WARN_ON_ONCE(current->flags & PF_EXITING)) 560 goto out; 561 562 ewq->ctx = ctx; 563 init_waitqueue_entry(&ewq->wq, current); 564 release_new_ctx = NULL; 565 566 spin_lock_irq(&ctx->event_wqh.lock); 567 /* 568 * After the __add_wait_queue the uwq is visible to userland 569 * through poll/read(). 570 */ 571 __add_wait_queue(&ctx->event_wqh, &ewq->wq); 572 for (;;) { 573 set_current_state(TASK_KILLABLE); 574 if (ewq->msg.event == 0) 575 break; 576 if (READ_ONCE(ctx->released) || 577 fatal_signal_pending(current)) { 578 /* 579 * &ewq->wq may be queued in fork_event, but 580 * __remove_wait_queue ignores the head 581 * parameter. It would be a problem if it 582 * didn't. 583 */ 584 __remove_wait_queue(&ctx->event_wqh, &ewq->wq); 585 if (ewq->msg.event == UFFD_EVENT_FORK) { 586 struct userfaultfd_ctx *new; 587 588 new = (struct userfaultfd_ctx *) 589 (unsigned long) 590 ewq->msg.arg.reserved.reserved1; 591 release_new_ctx = new; 592 } 593 break; 594 } 595 596 spin_unlock_irq(&ctx->event_wqh.lock); 597 598 wake_up_poll(&ctx->fd_wqh, EPOLLIN); 599 schedule(); 600 601 spin_lock_irq(&ctx->event_wqh.lock); 602 } 603 __set_current_state(TASK_RUNNING); 604 spin_unlock_irq(&ctx->event_wqh.lock); 605 606 if (release_new_ctx) { 607 struct vm_area_struct *vma; 608 struct mm_struct *mm = release_new_ctx->mm; 609 610 /* the various vma->vm_userfaultfd_ctx still points to it */ 611 mmap_write_lock(mm); 612 for (vma = mm->mmap; vma; vma = vma->vm_next) 613 if (vma->vm_userfaultfd_ctx.ctx == release_new_ctx) { 614 vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; 615 vma->vm_flags &= ~__VM_UFFD_FLAGS; 616 } 617 mmap_write_unlock(mm); 618 619 userfaultfd_ctx_put(release_new_ctx); 620 } 621 622 /* 623 * ctx may go away after this if the userfault pseudo fd is 624 * already released. 625 */ 626 out: 627 atomic_dec(&ctx->mmap_changing); 628 VM_BUG_ON(atomic_read(&ctx->mmap_changing) < 0); 629 userfaultfd_ctx_put(ctx); 630 } 631 632 static void userfaultfd_event_complete(struct userfaultfd_ctx *ctx, 633 struct userfaultfd_wait_queue *ewq) 634 { 635 ewq->msg.event = 0; 636 wake_up_locked(&ctx->event_wqh); 637 __remove_wait_queue(&ctx->event_wqh, &ewq->wq); 638 } 639 640 int dup_userfaultfd(struct vm_area_struct *vma, struct list_head *fcs) 641 { 642 struct userfaultfd_ctx *ctx = NULL, *octx; 643 struct userfaultfd_fork_ctx *fctx; 644 645 octx = vma->vm_userfaultfd_ctx.ctx; 646 if (!octx || !(octx->features & UFFD_FEATURE_EVENT_FORK)) { 647 vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; 648 vma->vm_flags &= ~__VM_UFFD_FLAGS; 649 return 0; 650 } 651 652 list_for_each_entry(fctx, fcs, list) 653 if (fctx->orig == octx) { 654 ctx = fctx->new; 655 break; 656 } 657 658 if (!ctx) { 659 fctx = kmalloc(sizeof(*fctx), GFP_KERNEL); 660 if (!fctx) 661 return -ENOMEM; 662 663 ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL); 664 if (!ctx) { 665 kfree(fctx); 666 return -ENOMEM; 667 } 668 669 refcount_set(&ctx->refcount, 1); 670 ctx->flags = octx->flags; 671 ctx->features = octx->features; 672 ctx->released = false; 673 atomic_set(&ctx->mmap_changing, 0); 674 ctx->mm = vma->vm_mm; 675 mmgrab(ctx->mm); 676 677 userfaultfd_ctx_get(octx); 678 atomic_inc(&octx->mmap_changing); 679 fctx->orig = octx; 680 fctx->new = ctx; 681 list_add_tail(&fctx->list, fcs); 682 } 683 684 vma->vm_userfaultfd_ctx.ctx = ctx; 685 return 0; 686 } 687 688 static void dup_fctx(struct userfaultfd_fork_ctx *fctx) 689 { 690 struct userfaultfd_ctx *ctx = fctx->orig; 691 struct userfaultfd_wait_queue ewq; 692 693 msg_init(&ewq.msg); 694 695 ewq.msg.event = UFFD_EVENT_FORK; 696 ewq.msg.arg.reserved.reserved1 = (unsigned long)fctx->new; 697 698 userfaultfd_event_wait_completion(ctx, &ewq); 699 } 700 701 void dup_userfaultfd_complete(struct list_head *fcs) 702 { 703 struct userfaultfd_fork_ctx *fctx, *n; 704 705 list_for_each_entry_safe(fctx, n, fcs, list) { 706 dup_fctx(fctx); 707 list_del(&fctx->list); 708 kfree(fctx); 709 } 710 } 711 712 void mremap_userfaultfd_prep(struct vm_area_struct *vma, 713 struct vm_userfaultfd_ctx *vm_ctx) 714 { 715 struct userfaultfd_ctx *ctx; 716 717 ctx = vma->vm_userfaultfd_ctx.ctx; 718 719 if (!ctx) 720 return; 721 722 if (ctx->features & UFFD_FEATURE_EVENT_REMAP) { 723 vm_ctx->ctx = ctx; 724 userfaultfd_ctx_get(ctx); 725 atomic_inc(&ctx->mmap_changing); 726 } else { 727 /* Drop uffd context if remap feature not enabled */ 728 vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; 729 vma->vm_flags &= ~__VM_UFFD_FLAGS; 730 } 731 } 732 733 void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *vm_ctx, 734 unsigned long from, unsigned long to, 735 unsigned long len) 736 { 737 struct userfaultfd_ctx *ctx = vm_ctx->ctx; 738 struct userfaultfd_wait_queue ewq; 739 740 if (!ctx) 741 return; 742 743 if (to & ~PAGE_MASK) { 744 userfaultfd_ctx_put(ctx); 745 return; 746 } 747 748 msg_init(&ewq.msg); 749 750 ewq.msg.event = UFFD_EVENT_REMAP; 751 ewq.msg.arg.remap.from = from; 752 ewq.msg.arg.remap.to = to; 753 ewq.msg.arg.remap.len = len; 754 755 userfaultfd_event_wait_completion(ctx, &ewq); 756 } 757 758 bool userfaultfd_remove(struct vm_area_struct *vma, 759 unsigned long start, unsigned long end) 760 { 761 struct mm_struct *mm = vma->vm_mm; 762 struct userfaultfd_ctx *ctx; 763 struct userfaultfd_wait_queue ewq; 764 765 ctx = vma->vm_userfaultfd_ctx.ctx; 766 if (!ctx || !(ctx->features & UFFD_FEATURE_EVENT_REMOVE)) 767 return true; 768 769 userfaultfd_ctx_get(ctx); 770 atomic_inc(&ctx->mmap_changing); 771 mmap_read_unlock(mm); 772 773 msg_init(&ewq.msg); 774 775 ewq.msg.event = UFFD_EVENT_REMOVE; 776 ewq.msg.arg.remove.start = start; 777 ewq.msg.arg.remove.end = end; 778 779 userfaultfd_event_wait_completion(ctx, &ewq); 780 781 return false; 782 } 783 784 static bool has_unmap_ctx(struct userfaultfd_ctx *ctx, struct list_head *unmaps, 785 unsigned long start, unsigned long end) 786 { 787 struct userfaultfd_unmap_ctx *unmap_ctx; 788 789 list_for_each_entry(unmap_ctx, unmaps, list) 790 if (unmap_ctx->ctx == ctx && unmap_ctx->start == start && 791 unmap_ctx->end == end) 792 return true; 793 794 return false; 795 } 796 797 int userfaultfd_unmap_prep(struct vm_area_struct *vma, 798 unsigned long start, unsigned long end, 799 struct list_head *unmaps) 800 { 801 for ( ; vma && vma->vm_start < end; vma = vma->vm_next) { 802 struct userfaultfd_unmap_ctx *unmap_ctx; 803 struct userfaultfd_ctx *ctx = vma->vm_userfaultfd_ctx.ctx; 804 805 if (!ctx || !(ctx->features & UFFD_FEATURE_EVENT_UNMAP) || 806 has_unmap_ctx(ctx, unmaps, start, end)) 807 continue; 808 809 unmap_ctx = kzalloc(sizeof(*unmap_ctx), GFP_KERNEL); 810 if (!unmap_ctx) 811 return -ENOMEM; 812 813 userfaultfd_ctx_get(ctx); 814 atomic_inc(&ctx->mmap_changing); 815 unmap_ctx->ctx = ctx; 816 unmap_ctx->start = start; 817 unmap_ctx->end = end; 818 list_add_tail(&unmap_ctx->list, unmaps); 819 } 820 821 return 0; 822 } 823 824 void userfaultfd_unmap_complete(struct mm_struct *mm, struct list_head *uf) 825 { 826 struct userfaultfd_unmap_ctx *ctx, *n; 827 struct userfaultfd_wait_queue ewq; 828 829 list_for_each_entry_safe(ctx, n, uf, list) { 830 msg_init(&ewq.msg); 831 832 ewq.msg.event = UFFD_EVENT_UNMAP; 833 ewq.msg.arg.remove.start = ctx->start; 834 ewq.msg.arg.remove.end = ctx->end; 835 836 userfaultfd_event_wait_completion(ctx->ctx, &ewq); 837 838 list_del(&ctx->list); 839 kfree(ctx); 840 } 841 } 842 843 static int userfaultfd_release(struct inode *inode, struct file *file) 844 { 845 struct userfaultfd_ctx *ctx = file->private_data; 846 struct mm_struct *mm = ctx->mm; 847 struct vm_area_struct *vma, *prev; 848 /* len == 0 means wake all */ 849 struct userfaultfd_wake_range range = { .len = 0, }; 850 unsigned long new_flags; 851 852 WRITE_ONCE(ctx->released, true); 853 854 if (!mmget_not_zero(mm)) 855 goto wakeup; 856 857 /* 858 * Flush page faults out of all CPUs. NOTE: all page faults 859 * must be retried without returning VM_FAULT_SIGBUS if 860 * userfaultfd_ctx_get() succeeds but vma->vma_userfault_ctx 861 * changes while handle_userfault released the mmap_lock. So 862 * it's critical that released is set to true (above), before 863 * taking the mmap_lock for writing. 864 */ 865 mmap_write_lock(mm); 866 prev = NULL; 867 for (vma = mm->mmap; vma; vma = vma->vm_next) { 868 cond_resched(); 869 BUG_ON(!!vma->vm_userfaultfd_ctx.ctx ^ 870 !!(vma->vm_flags & __VM_UFFD_FLAGS)); 871 if (vma->vm_userfaultfd_ctx.ctx != ctx) { 872 prev = vma; 873 continue; 874 } 875 new_flags = vma->vm_flags & ~__VM_UFFD_FLAGS; 876 prev = vma_merge(mm, prev, vma->vm_start, vma->vm_end, 877 new_flags, vma->anon_vma, 878 vma->vm_file, vma->vm_pgoff, 879 vma_policy(vma), 880 NULL_VM_UFFD_CTX); 881 if (prev) 882 vma = prev; 883 else 884 prev = vma; 885 vma->vm_flags = new_flags; 886 vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; 887 } 888 mmap_write_unlock(mm); 889 mmput(mm); 890 wakeup: 891 /* 892 * After no new page faults can wait on this fault_*wqh, flush 893 * the last page faults that may have been already waiting on 894 * the fault_*wqh. 895 */ 896 spin_lock_irq(&ctx->fault_pending_wqh.lock); 897 __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, &range); 898 __wake_up(&ctx->fault_wqh, TASK_NORMAL, 1, &range); 899 spin_unlock_irq(&ctx->fault_pending_wqh.lock); 900 901 /* Flush pending events that may still wait on event_wqh */ 902 wake_up_all(&ctx->event_wqh); 903 904 wake_up_poll(&ctx->fd_wqh, EPOLLHUP); 905 userfaultfd_ctx_put(ctx); 906 return 0; 907 } 908 909 /* fault_pending_wqh.lock must be hold by the caller */ 910 static inline struct userfaultfd_wait_queue *find_userfault_in( 911 wait_queue_head_t *wqh) 912 { 913 wait_queue_entry_t *wq; 914 struct userfaultfd_wait_queue *uwq; 915 916 lockdep_assert_held(&wqh->lock); 917 918 uwq = NULL; 919 if (!waitqueue_active(wqh)) 920 goto out; 921 /* walk in reverse to provide FIFO behavior to read userfaults */ 922 wq = list_last_entry(&wqh->head, typeof(*wq), entry); 923 uwq = container_of(wq, struct userfaultfd_wait_queue, wq); 924 out: 925 return uwq; 926 } 927 928 static inline struct userfaultfd_wait_queue *find_userfault( 929 struct userfaultfd_ctx *ctx) 930 { 931 return find_userfault_in(&ctx->fault_pending_wqh); 932 } 933 934 static inline struct userfaultfd_wait_queue *find_userfault_evt( 935 struct userfaultfd_ctx *ctx) 936 { 937 return find_userfault_in(&ctx->event_wqh); 938 } 939 940 static __poll_t userfaultfd_poll(struct file *file, poll_table *wait) 941 { 942 struct userfaultfd_ctx *ctx = file->private_data; 943 __poll_t ret; 944 945 poll_wait(file, &ctx->fd_wqh, wait); 946 947 if (!userfaultfd_is_initialized(ctx)) 948 return EPOLLERR; 949 950 /* 951 * poll() never guarantees that read won't block. 952 * userfaults can be waken before they're read(). 953 */ 954 if (unlikely(!(file->f_flags & O_NONBLOCK))) 955 return EPOLLERR; 956 /* 957 * lockless access to see if there are pending faults 958 * __pollwait last action is the add_wait_queue but 959 * the spin_unlock would allow the waitqueue_active to 960 * pass above the actual list_add inside 961 * add_wait_queue critical section. So use a full 962 * memory barrier to serialize the list_add write of 963 * add_wait_queue() with the waitqueue_active read 964 * below. 965 */ 966 ret = 0; 967 smp_mb(); 968 if (waitqueue_active(&ctx->fault_pending_wqh)) 969 ret = EPOLLIN; 970 else if (waitqueue_active(&ctx->event_wqh)) 971 ret = EPOLLIN; 972 973 return ret; 974 } 975 976 static const struct file_operations userfaultfd_fops; 977 978 static int resolve_userfault_fork(struct userfaultfd_ctx *new, 979 struct inode *inode, 980 struct uffd_msg *msg) 981 { 982 int fd; 983 984 fd = anon_inode_getfd_secure("[userfaultfd]", &userfaultfd_fops, new, 985 O_RDWR | (new->flags & UFFD_SHARED_FCNTL_FLAGS), inode); 986 if (fd < 0) 987 return fd; 988 989 msg->arg.reserved.reserved1 = 0; 990 msg->arg.fork.ufd = fd; 991 return 0; 992 } 993 994 static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait, 995 struct uffd_msg *msg, struct inode *inode) 996 { 997 ssize_t ret; 998 DECLARE_WAITQUEUE(wait, current); 999 struct userfaultfd_wait_queue *uwq; 1000 /* 1001 * Handling fork event requires sleeping operations, so 1002 * we drop the event_wqh lock, then do these ops, then 1003 * lock it back and wake up the waiter. While the lock is 1004 * dropped the ewq may go away so we keep track of it 1005 * carefully. 1006 */ 1007 LIST_HEAD(fork_event); 1008 struct userfaultfd_ctx *fork_nctx = NULL; 1009 1010 /* always take the fd_wqh lock before the fault_pending_wqh lock */ 1011 spin_lock_irq(&ctx->fd_wqh.lock); 1012 __add_wait_queue(&ctx->fd_wqh, &wait); 1013 for (;;) { 1014 set_current_state(TASK_INTERRUPTIBLE); 1015 spin_lock(&ctx->fault_pending_wqh.lock); 1016 uwq = find_userfault(ctx); 1017 if (uwq) { 1018 /* 1019 * Use a seqcount to repeat the lockless check 1020 * in wake_userfault() to avoid missing 1021 * wakeups because during the refile both 1022 * waitqueue could become empty if this is the 1023 * only userfault. 1024 */ 1025 write_seqcount_begin(&ctx->refile_seq); 1026 1027 /* 1028 * The fault_pending_wqh.lock prevents the uwq 1029 * to disappear from under us. 1030 * 1031 * Refile this userfault from 1032 * fault_pending_wqh to fault_wqh, it's not 1033 * pending anymore after we read it. 1034 * 1035 * Use list_del() by hand (as 1036 * userfaultfd_wake_function also uses 1037 * list_del_init() by hand) to be sure nobody 1038 * changes __remove_wait_queue() to use 1039 * list_del_init() in turn breaking the 1040 * !list_empty_careful() check in 1041 * handle_userfault(). The uwq->wq.head list 1042 * must never be empty at any time during the 1043 * refile, or the waitqueue could disappear 1044 * from under us. The "wait_queue_head_t" 1045 * parameter of __remove_wait_queue() is unused 1046 * anyway. 1047 */ 1048 list_del(&uwq->wq.entry); 1049 add_wait_queue(&ctx->fault_wqh, &uwq->wq); 1050 1051 write_seqcount_end(&ctx->refile_seq); 1052 1053 /* careful to always initialize msg if ret == 0 */ 1054 *msg = uwq->msg; 1055 spin_unlock(&ctx->fault_pending_wqh.lock); 1056 ret = 0; 1057 break; 1058 } 1059 spin_unlock(&ctx->fault_pending_wqh.lock); 1060 1061 spin_lock(&ctx->event_wqh.lock); 1062 uwq = find_userfault_evt(ctx); 1063 if (uwq) { 1064 *msg = uwq->msg; 1065 1066 if (uwq->msg.event == UFFD_EVENT_FORK) { 1067 fork_nctx = (struct userfaultfd_ctx *) 1068 (unsigned long) 1069 uwq->msg.arg.reserved.reserved1; 1070 list_move(&uwq->wq.entry, &fork_event); 1071 /* 1072 * fork_nctx can be freed as soon as 1073 * we drop the lock, unless we take a 1074 * reference on it. 1075 */ 1076 userfaultfd_ctx_get(fork_nctx); 1077 spin_unlock(&ctx->event_wqh.lock); 1078 ret = 0; 1079 break; 1080 } 1081 1082 userfaultfd_event_complete(ctx, uwq); 1083 spin_unlock(&ctx->event_wqh.lock); 1084 ret = 0; 1085 break; 1086 } 1087 spin_unlock(&ctx->event_wqh.lock); 1088 1089 if (signal_pending(current)) { 1090 ret = -ERESTARTSYS; 1091 break; 1092 } 1093 if (no_wait) { 1094 ret = -EAGAIN; 1095 break; 1096 } 1097 spin_unlock_irq(&ctx->fd_wqh.lock); 1098 schedule(); 1099 spin_lock_irq(&ctx->fd_wqh.lock); 1100 } 1101 __remove_wait_queue(&ctx->fd_wqh, &wait); 1102 __set_current_state(TASK_RUNNING); 1103 spin_unlock_irq(&ctx->fd_wqh.lock); 1104 1105 if (!ret && msg->event == UFFD_EVENT_FORK) { 1106 ret = resolve_userfault_fork(fork_nctx, inode, msg); 1107 spin_lock_irq(&ctx->event_wqh.lock); 1108 if (!list_empty(&fork_event)) { 1109 /* 1110 * The fork thread didn't abort, so we can 1111 * drop the temporary refcount. 1112 */ 1113 userfaultfd_ctx_put(fork_nctx); 1114 1115 uwq = list_first_entry(&fork_event, 1116 typeof(*uwq), 1117 wq.entry); 1118 /* 1119 * If fork_event list wasn't empty and in turn 1120 * the event wasn't already released by fork 1121 * (the event is allocated on fork kernel 1122 * stack), put the event back to its place in 1123 * the event_wq. fork_event head will be freed 1124 * as soon as we return so the event cannot 1125 * stay queued there no matter the current 1126 * "ret" value. 1127 */ 1128 list_del(&uwq->wq.entry); 1129 __add_wait_queue(&ctx->event_wqh, &uwq->wq); 1130 1131 /* 1132 * Leave the event in the waitqueue and report 1133 * error to userland if we failed to resolve 1134 * the userfault fork. 1135 */ 1136 if (likely(!ret)) 1137 userfaultfd_event_complete(ctx, uwq); 1138 } else { 1139 /* 1140 * Here the fork thread aborted and the 1141 * refcount from the fork thread on fork_nctx 1142 * has already been released. We still hold 1143 * the reference we took before releasing the 1144 * lock above. If resolve_userfault_fork 1145 * failed we've to drop it because the 1146 * fork_nctx has to be freed in such case. If 1147 * it succeeded we'll hold it because the new 1148 * uffd references it. 1149 */ 1150 if (ret) 1151 userfaultfd_ctx_put(fork_nctx); 1152 } 1153 spin_unlock_irq(&ctx->event_wqh.lock); 1154 } 1155 1156 return ret; 1157 } 1158 1159 static ssize_t userfaultfd_read(struct file *file, char __user *buf, 1160 size_t count, loff_t *ppos) 1161 { 1162 struct userfaultfd_ctx *ctx = file->private_data; 1163 ssize_t _ret, ret = 0; 1164 struct uffd_msg msg; 1165 int no_wait = file->f_flags & O_NONBLOCK; 1166 struct inode *inode = file_inode(file); 1167 1168 if (!userfaultfd_is_initialized(ctx)) 1169 return -EINVAL; 1170 1171 for (;;) { 1172 if (count < sizeof(msg)) 1173 return ret ? ret : -EINVAL; 1174 _ret = userfaultfd_ctx_read(ctx, no_wait, &msg, inode); 1175 if (_ret < 0) 1176 return ret ? ret : _ret; 1177 if (copy_to_user((__u64 __user *) buf, &msg, sizeof(msg))) 1178 return ret ? ret : -EFAULT; 1179 ret += sizeof(msg); 1180 buf += sizeof(msg); 1181 count -= sizeof(msg); 1182 /* 1183 * Allow to read more than one fault at time but only 1184 * block if waiting for the very first one. 1185 */ 1186 no_wait = O_NONBLOCK; 1187 } 1188 } 1189 1190 static void __wake_userfault(struct userfaultfd_ctx *ctx, 1191 struct userfaultfd_wake_range *range) 1192 { 1193 spin_lock_irq(&ctx->fault_pending_wqh.lock); 1194 /* wake all in the range and autoremove */ 1195 if (waitqueue_active(&ctx->fault_pending_wqh)) 1196 __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, 1197 range); 1198 if (waitqueue_active(&ctx->fault_wqh)) 1199 __wake_up(&ctx->fault_wqh, TASK_NORMAL, 1, range); 1200 spin_unlock_irq(&ctx->fault_pending_wqh.lock); 1201 } 1202 1203 static __always_inline void wake_userfault(struct userfaultfd_ctx *ctx, 1204 struct userfaultfd_wake_range *range) 1205 { 1206 unsigned seq; 1207 bool need_wakeup; 1208 1209 /* 1210 * To be sure waitqueue_active() is not reordered by the CPU 1211 * before the pagetable update, use an explicit SMP memory 1212 * barrier here. PT lock release or mmap_read_unlock(mm) still 1213 * have release semantics that can allow the 1214 * waitqueue_active() to be reordered before the pte update. 1215 */ 1216 smp_mb(); 1217 1218 /* 1219 * Use waitqueue_active because it's very frequent to 1220 * change the address space atomically even if there are no 1221 * userfaults yet. So we take the spinlock only when we're 1222 * sure we've userfaults to wake. 1223 */ 1224 do { 1225 seq = read_seqcount_begin(&ctx->refile_seq); 1226 need_wakeup = waitqueue_active(&ctx->fault_pending_wqh) || 1227 waitqueue_active(&ctx->fault_wqh); 1228 cond_resched(); 1229 } while (read_seqcount_retry(&ctx->refile_seq, seq)); 1230 if (need_wakeup) 1231 __wake_userfault(ctx, range); 1232 } 1233 1234 static __always_inline int validate_range(struct mm_struct *mm, 1235 __u64 start, __u64 len) 1236 { 1237 __u64 task_size = mm->task_size; 1238 1239 if (start & ~PAGE_MASK) 1240 return -EINVAL; 1241 if (len & ~PAGE_MASK) 1242 return -EINVAL; 1243 if (!len) 1244 return -EINVAL; 1245 if (start < mmap_min_addr) 1246 return -EINVAL; 1247 if (start >= task_size) 1248 return -EINVAL; 1249 if (len > task_size - start) 1250 return -EINVAL; 1251 return 0; 1252 } 1253 1254 static inline bool vma_can_userfault(struct vm_area_struct *vma, 1255 unsigned long vm_flags) 1256 { 1257 /* FIXME: add WP support to hugetlbfs and shmem */ 1258 if (vm_flags & VM_UFFD_WP) { 1259 if (is_vm_hugetlb_page(vma) || vma_is_shmem(vma)) 1260 return false; 1261 } 1262 1263 if (vm_flags & VM_UFFD_MINOR) { 1264 if (!(is_vm_hugetlb_page(vma) || vma_is_shmem(vma))) 1265 return false; 1266 } 1267 1268 return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma) || 1269 vma_is_shmem(vma); 1270 } 1271 1272 static int userfaultfd_register(struct userfaultfd_ctx *ctx, 1273 unsigned long arg) 1274 { 1275 struct mm_struct *mm = ctx->mm; 1276 struct vm_area_struct *vma, *prev, *cur; 1277 int ret; 1278 struct uffdio_register uffdio_register; 1279 struct uffdio_register __user *user_uffdio_register; 1280 unsigned long vm_flags, new_flags; 1281 bool found; 1282 bool basic_ioctls; 1283 unsigned long start, end, vma_end; 1284 1285 user_uffdio_register = (struct uffdio_register __user *) arg; 1286 1287 ret = -EFAULT; 1288 if (copy_from_user(&uffdio_register, user_uffdio_register, 1289 sizeof(uffdio_register)-sizeof(__u64))) 1290 goto out; 1291 1292 ret = -EINVAL; 1293 if (!uffdio_register.mode) 1294 goto out; 1295 if (uffdio_register.mode & ~UFFD_API_REGISTER_MODES) 1296 goto out; 1297 vm_flags = 0; 1298 if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MISSING) 1299 vm_flags |= VM_UFFD_MISSING; 1300 if (uffdio_register.mode & UFFDIO_REGISTER_MODE_WP) { 1301 #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_WP 1302 goto out; 1303 #endif 1304 vm_flags |= VM_UFFD_WP; 1305 } 1306 if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MINOR) { 1307 #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR 1308 goto out; 1309 #endif 1310 vm_flags |= VM_UFFD_MINOR; 1311 } 1312 1313 ret = validate_range(mm, uffdio_register.range.start, 1314 uffdio_register.range.len); 1315 if (ret) 1316 goto out; 1317 1318 start = uffdio_register.range.start; 1319 end = start + uffdio_register.range.len; 1320 1321 ret = -ENOMEM; 1322 if (!mmget_not_zero(mm)) 1323 goto out; 1324 1325 mmap_write_lock(mm); 1326 vma = find_vma_prev(mm, start, &prev); 1327 if (!vma) 1328 goto out_unlock; 1329 1330 /* check that there's at least one vma in the range */ 1331 ret = -EINVAL; 1332 if (vma->vm_start >= end) 1333 goto out_unlock; 1334 1335 /* 1336 * If the first vma contains huge pages, make sure start address 1337 * is aligned to huge page size. 1338 */ 1339 if (is_vm_hugetlb_page(vma)) { 1340 unsigned long vma_hpagesize = vma_kernel_pagesize(vma); 1341 1342 if (start & (vma_hpagesize - 1)) 1343 goto out_unlock; 1344 } 1345 1346 /* 1347 * Search for not compatible vmas. 1348 */ 1349 found = false; 1350 basic_ioctls = false; 1351 for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) { 1352 cond_resched(); 1353 1354 BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^ 1355 !!(cur->vm_flags & __VM_UFFD_FLAGS)); 1356 1357 /* check not compatible vmas */ 1358 ret = -EINVAL; 1359 if (!vma_can_userfault(cur, vm_flags)) 1360 goto out_unlock; 1361 1362 /* 1363 * UFFDIO_COPY will fill file holes even without 1364 * PROT_WRITE. This check enforces that if this is a 1365 * MAP_SHARED, the process has write permission to the backing 1366 * file. If VM_MAYWRITE is set it also enforces that on a 1367 * MAP_SHARED vma: there is no F_WRITE_SEAL and no further 1368 * F_WRITE_SEAL can be taken until the vma is destroyed. 1369 */ 1370 ret = -EPERM; 1371 if (unlikely(!(cur->vm_flags & VM_MAYWRITE))) 1372 goto out_unlock; 1373 1374 /* 1375 * If this vma contains ending address, and huge pages 1376 * check alignment. 1377 */ 1378 if (is_vm_hugetlb_page(cur) && end <= cur->vm_end && 1379 end > cur->vm_start) { 1380 unsigned long vma_hpagesize = vma_kernel_pagesize(cur); 1381 1382 ret = -EINVAL; 1383 1384 if (end & (vma_hpagesize - 1)) 1385 goto out_unlock; 1386 } 1387 if ((vm_flags & VM_UFFD_WP) && !(cur->vm_flags & VM_MAYWRITE)) 1388 goto out_unlock; 1389 1390 /* 1391 * Check that this vma isn't already owned by a 1392 * different userfaultfd. We can't allow more than one 1393 * userfaultfd to own a single vma simultaneously or we 1394 * wouldn't know which one to deliver the userfaults to. 1395 */ 1396 ret = -EBUSY; 1397 if (cur->vm_userfaultfd_ctx.ctx && 1398 cur->vm_userfaultfd_ctx.ctx != ctx) 1399 goto out_unlock; 1400 1401 /* 1402 * Note vmas containing huge pages 1403 */ 1404 if (is_vm_hugetlb_page(cur)) 1405 basic_ioctls = true; 1406 1407 found = true; 1408 } 1409 BUG_ON(!found); 1410 1411 if (vma->vm_start < start) 1412 prev = vma; 1413 1414 ret = 0; 1415 do { 1416 cond_resched(); 1417 1418 BUG_ON(!vma_can_userfault(vma, vm_flags)); 1419 BUG_ON(vma->vm_userfaultfd_ctx.ctx && 1420 vma->vm_userfaultfd_ctx.ctx != ctx); 1421 WARN_ON(!(vma->vm_flags & VM_MAYWRITE)); 1422 1423 /* 1424 * Nothing to do: this vma is already registered into this 1425 * userfaultfd and with the right tracking mode too. 1426 */ 1427 if (vma->vm_userfaultfd_ctx.ctx == ctx && 1428 (vma->vm_flags & vm_flags) == vm_flags) 1429 goto skip; 1430 1431 if (vma->vm_start > start) 1432 start = vma->vm_start; 1433 vma_end = min(end, vma->vm_end); 1434 1435 new_flags = (vma->vm_flags & ~__VM_UFFD_FLAGS) | vm_flags; 1436 prev = vma_merge(mm, prev, start, vma_end, new_flags, 1437 vma->anon_vma, vma->vm_file, vma->vm_pgoff, 1438 vma_policy(vma), 1439 ((struct vm_userfaultfd_ctx){ ctx })); 1440 if (prev) { 1441 vma = prev; 1442 goto next; 1443 } 1444 if (vma->vm_start < start) { 1445 ret = split_vma(mm, vma, start, 1); 1446 if (ret) 1447 break; 1448 } 1449 if (vma->vm_end > end) { 1450 ret = split_vma(mm, vma, end, 0); 1451 if (ret) 1452 break; 1453 } 1454 next: 1455 /* 1456 * In the vma_merge() successful mprotect-like case 8: 1457 * the next vma was merged into the current one and 1458 * the current one has not been updated yet. 1459 */ 1460 vma->vm_flags = new_flags; 1461 vma->vm_userfaultfd_ctx.ctx = ctx; 1462 1463 if (is_vm_hugetlb_page(vma) && uffd_disable_huge_pmd_share(vma)) 1464 hugetlb_unshare_all_pmds(vma); 1465 1466 skip: 1467 prev = vma; 1468 start = vma->vm_end; 1469 vma = vma->vm_next; 1470 } while (vma && vma->vm_start < end); 1471 out_unlock: 1472 mmap_write_unlock(mm); 1473 mmput(mm); 1474 if (!ret) { 1475 __u64 ioctls_out; 1476 1477 ioctls_out = basic_ioctls ? UFFD_API_RANGE_IOCTLS_BASIC : 1478 UFFD_API_RANGE_IOCTLS; 1479 1480 /* 1481 * Declare the WP ioctl only if the WP mode is 1482 * specified and all checks passed with the range 1483 */ 1484 if (!(uffdio_register.mode & UFFDIO_REGISTER_MODE_WP)) 1485 ioctls_out &= ~((__u64)1 << _UFFDIO_WRITEPROTECT); 1486 1487 /* CONTINUE ioctl is only supported for MINOR ranges. */ 1488 if (!(uffdio_register.mode & UFFDIO_REGISTER_MODE_MINOR)) 1489 ioctls_out &= ~((__u64)1 << _UFFDIO_CONTINUE); 1490 1491 /* 1492 * Now that we scanned all vmas we can already tell 1493 * userland which ioctls methods are guaranteed to 1494 * succeed on this range. 1495 */ 1496 if (put_user(ioctls_out, &user_uffdio_register->ioctls)) 1497 ret = -EFAULT; 1498 } 1499 out: 1500 return ret; 1501 } 1502 1503 static int userfaultfd_unregister(struct userfaultfd_ctx *ctx, 1504 unsigned long arg) 1505 { 1506 struct mm_struct *mm = ctx->mm; 1507 struct vm_area_struct *vma, *prev, *cur; 1508 int ret; 1509 struct uffdio_range uffdio_unregister; 1510 unsigned long new_flags; 1511 bool found; 1512 unsigned long start, end, vma_end; 1513 const void __user *buf = (void __user *)arg; 1514 1515 ret = -EFAULT; 1516 if (copy_from_user(&uffdio_unregister, buf, sizeof(uffdio_unregister))) 1517 goto out; 1518 1519 ret = validate_range(mm, uffdio_unregister.start, 1520 uffdio_unregister.len); 1521 if (ret) 1522 goto out; 1523 1524 start = uffdio_unregister.start; 1525 end = start + uffdio_unregister.len; 1526 1527 ret = -ENOMEM; 1528 if (!mmget_not_zero(mm)) 1529 goto out; 1530 1531 mmap_write_lock(mm); 1532 vma = find_vma_prev(mm, start, &prev); 1533 if (!vma) 1534 goto out_unlock; 1535 1536 /* check that there's at least one vma in the range */ 1537 ret = -EINVAL; 1538 if (vma->vm_start >= end) 1539 goto out_unlock; 1540 1541 /* 1542 * If the first vma contains huge pages, make sure start address 1543 * is aligned to huge page size. 1544 */ 1545 if (is_vm_hugetlb_page(vma)) { 1546 unsigned long vma_hpagesize = vma_kernel_pagesize(vma); 1547 1548 if (start & (vma_hpagesize - 1)) 1549 goto out_unlock; 1550 } 1551 1552 /* 1553 * Search for not compatible vmas. 1554 */ 1555 found = false; 1556 ret = -EINVAL; 1557 for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) { 1558 cond_resched(); 1559 1560 BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^ 1561 !!(cur->vm_flags & __VM_UFFD_FLAGS)); 1562 1563 /* 1564 * Check not compatible vmas, not strictly required 1565 * here as not compatible vmas cannot have an 1566 * userfaultfd_ctx registered on them, but this 1567 * provides for more strict behavior to notice 1568 * unregistration errors. 1569 */ 1570 if (!vma_can_userfault(cur, cur->vm_flags)) 1571 goto out_unlock; 1572 1573 found = true; 1574 } 1575 BUG_ON(!found); 1576 1577 if (vma->vm_start < start) 1578 prev = vma; 1579 1580 ret = 0; 1581 do { 1582 cond_resched(); 1583 1584 BUG_ON(!vma_can_userfault(vma, vma->vm_flags)); 1585 1586 /* 1587 * Nothing to do: this vma is already registered into this 1588 * userfaultfd and with the right tracking mode too. 1589 */ 1590 if (!vma->vm_userfaultfd_ctx.ctx) 1591 goto skip; 1592 1593 WARN_ON(!(vma->vm_flags & VM_MAYWRITE)); 1594 1595 if (vma->vm_start > start) 1596 start = vma->vm_start; 1597 vma_end = min(end, vma->vm_end); 1598 1599 if (userfaultfd_missing(vma)) { 1600 /* 1601 * Wake any concurrent pending userfault while 1602 * we unregister, so they will not hang 1603 * permanently and it avoids userland to call 1604 * UFFDIO_WAKE explicitly. 1605 */ 1606 struct userfaultfd_wake_range range; 1607 range.start = start; 1608 range.len = vma_end - start; 1609 wake_userfault(vma->vm_userfaultfd_ctx.ctx, &range); 1610 } 1611 1612 new_flags = vma->vm_flags & ~__VM_UFFD_FLAGS; 1613 prev = vma_merge(mm, prev, start, vma_end, new_flags, 1614 vma->anon_vma, vma->vm_file, vma->vm_pgoff, 1615 vma_policy(vma), 1616 NULL_VM_UFFD_CTX); 1617 if (prev) { 1618 vma = prev; 1619 goto next; 1620 } 1621 if (vma->vm_start < start) { 1622 ret = split_vma(mm, vma, start, 1); 1623 if (ret) 1624 break; 1625 } 1626 if (vma->vm_end > end) { 1627 ret = split_vma(mm, vma, end, 0); 1628 if (ret) 1629 break; 1630 } 1631 next: 1632 /* 1633 * In the vma_merge() successful mprotect-like case 8: 1634 * the next vma was merged into the current one and 1635 * the current one has not been updated yet. 1636 */ 1637 vma->vm_flags = new_flags; 1638 vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; 1639 1640 skip: 1641 prev = vma; 1642 start = vma->vm_end; 1643 vma = vma->vm_next; 1644 } while (vma && vma->vm_start < end); 1645 out_unlock: 1646 mmap_write_unlock(mm); 1647 mmput(mm); 1648 out: 1649 return ret; 1650 } 1651 1652 /* 1653 * userfaultfd_wake may be used in combination with the 1654 * UFFDIO_*_MODE_DONTWAKE to wakeup userfaults in batches. 1655 */ 1656 static int userfaultfd_wake(struct userfaultfd_ctx *ctx, 1657 unsigned long arg) 1658 { 1659 int ret; 1660 struct uffdio_range uffdio_wake; 1661 struct userfaultfd_wake_range range; 1662 const void __user *buf = (void __user *)arg; 1663 1664 ret = -EFAULT; 1665 if (copy_from_user(&uffdio_wake, buf, sizeof(uffdio_wake))) 1666 goto out; 1667 1668 ret = validate_range(ctx->mm, uffdio_wake.start, uffdio_wake.len); 1669 if (ret) 1670 goto out; 1671 1672 range.start = uffdio_wake.start; 1673 range.len = uffdio_wake.len; 1674 1675 /* 1676 * len == 0 means wake all and we don't want to wake all here, 1677 * so check it again to be sure. 1678 */ 1679 VM_BUG_ON(!range.len); 1680 1681 wake_userfault(ctx, &range); 1682 ret = 0; 1683 1684 out: 1685 return ret; 1686 } 1687 1688 static int userfaultfd_copy(struct userfaultfd_ctx *ctx, 1689 unsigned long arg) 1690 { 1691 __s64 ret; 1692 struct uffdio_copy uffdio_copy; 1693 struct uffdio_copy __user *user_uffdio_copy; 1694 struct userfaultfd_wake_range range; 1695 1696 user_uffdio_copy = (struct uffdio_copy __user *) arg; 1697 1698 ret = -EAGAIN; 1699 if (atomic_read(&ctx->mmap_changing)) 1700 goto out; 1701 1702 ret = -EFAULT; 1703 if (copy_from_user(&uffdio_copy, user_uffdio_copy, 1704 /* don't copy "copy" last field */ 1705 sizeof(uffdio_copy)-sizeof(__s64))) 1706 goto out; 1707 1708 ret = validate_range(ctx->mm, uffdio_copy.dst, uffdio_copy.len); 1709 if (ret) 1710 goto out; 1711 /* 1712 * double check for wraparound just in case. copy_from_user() 1713 * will later check uffdio_copy.src + uffdio_copy.len to fit 1714 * in the userland range. 1715 */ 1716 ret = -EINVAL; 1717 if (uffdio_copy.src + uffdio_copy.len <= uffdio_copy.src) 1718 goto out; 1719 if (uffdio_copy.mode & ~(UFFDIO_COPY_MODE_DONTWAKE|UFFDIO_COPY_MODE_WP)) 1720 goto out; 1721 if (mmget_not_zero(ctx->mm)) { 1722 ret = mcopy_atomic(ctx->mm, uffdio_copy.dst, uffdio_copy.src, 1723 uffdio_copy.len, &ctx->mmap_changing, 1724 uffdio_copy.mode); 1725 mmput(ctx->mm); 1726 } else { 1727 return -ESRCH; 1728 } 1729 if (unlikely(put_user(ret, &user_uffdio_copy->copy))) 1730 return -EFAULT; 1731 if (ret < 0) 1732 goto out; 1733 BUG_ON(!ret); 1734 /* len == 0 would wake all */ 1735 range.len = ret; 1736 if (!(uffdio_copy.mode & UFFDIO_COPY_MODE_DONTWAKE)) { 1737 range.start = uffdio_copy.dst; 1738 wake_userfault(ctx, &range); 1739 } 1740 ret = range.len == uffdio_copy.len ? 0 : -EAGAIN; 1741 out: 1742 return ret; 1743 } 1744 1745 static int userfaultfd_zeropage(struct userfaultfd_ctx *ctx, 1746 unsigned long arg) 1747 { 1748 __s64 ret; 1749 struct uffdio_zeropage uffdio_zeropage; 1750 struct uffdio_zeropage __user *user_uffdio_zeropage; 1751 struct userfaultfd_wake_range range; 1752 1753 user_uffdio_zeropage = (struct uffdio_zeropage __user *) arg; 1754 1755 ret = -EAGAIN; 1756 if (atomic_read(&ctx->mmap_changing)) 1757 goto out; 1758 1759 ret = -EFAULT; 1760 if (copy_from_user(&uffdio_zeropage, user_uffdio_zeropage, 1761 /* don't copy "zeropage" last field */ 1762 sizeof(uffdio_zeropage)-sizeof(__s64))) 1763 goto out; 1764 1765 ret = validate_range(ctx->mm, uffdio_zeropage.range.start, 1766 uffdio_zeropage.range.len); 1767 if (ret) 1768 goto out; 1769 ret = -EINVAL; 1770 if (uffdio_zeropage.mode & ~UFFDIO_ZEROPAGE_MODE_DONTWAKE) 1771 goto out; 1772 1773 if (mmget_not_zero(ctx->mm)) { 1774 ret = mfill_zeropage(ctx->mm, uffdio_zeropage.range.start, 1775 uffdio_zeropage.range.len, 1776 &ctx->mmap_changing); 1777 mmput(ctx->mm); 1778 } else { 1779 return -ESRCH; 1780 } 1781 if (unlikely(put_user(ret, &user_uffdio_zeropage->zeropage))) 1782 return -EFAULT; 1783 if (ret < 0) 1784 goto out; 1785 /* len == 0 would wake all */ 1786 BUG_ON(!ret); 1787 range.len = ret; 1788 if (!(uffdio_zeropage.mode & UFFDIO_ZEROPAGE_MODE_DONTWAKE)) { 1789 range.start = uffdio_zeropage.range.start; 1790 wake_userfault(ctx, &range); 1791 } 1792 ret = range.len == uffdio_zeropage.range.len ? 0 : -EAGAIN; 1793 out: 1794 return ret; 1795 } 1796 1797 static int userfaultfd_writeprotect(struct userfaultfd_ctx *ctx, 1798 unsigned long arg) 1799 { 1800 int ret; 1801 struct uffdio_writeprotect uffdio_wp; 1802 struct uffdio_writeprotect __user *user_uffdio_wp; 1803 struct userfaultfd_wake_range range; 1804 bool mode_wp, mode_dontwake; 1805 1806 if (atomic_read(&ctx->mmap_changing)) 1807 return -EAGAIN; 1808 1809 user_uffdio_wp = (struct uffdio_writeprotect __user *) arg; 1810 1811 if (copy_from_user(&uffdio_wp, user_uffdio_wp, 1812 sizeof(struct uffdio_writeprotect))) 1813 return -EFAULT; 1814 1815 ret = validate_range(ctx->mm, uffdio_wp.range.start, 1816 uffdio_wp.range.len); 1817 if (ret) 1818 return ret; 1819 1820 if (uffdio_wp.mode & ~(UFFDIO_WRITEPROTECT_MODE_DONTWAKE | 1821 UFFDIO_WRITEPROTECT_MODE_WP)) 1822 return -EINVAL; 1823 1824 mode_wp = uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_WP; 1825 mode_dontwake = uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_DONTWAKE; 1826 1827 if (mode_wp && mode_dontwake) 1828 return -EINVAL; 1829 1830 if (mmget_not_zero(ctx->mm)) { 1831 ret = mwriteprotect_range(ctx->mm, uffdio_wp.range.start, 1832 uffdio_wp.range.len, mode_wp, 1833 &ctx->mmap_changing); 1834 mmput(ctx->mm); 1835 } else { 1836 return -ESRCH; 1837 } 1838 1839 if (ret) 1840 return ret; 1841 1842 if (!mode_wp && !mode_dontwake) { 1843 range.start = uffdio_wp.range.start; 1844 range.len = uffdio_wp.range.len; 1845 wake_userfault(ctx, &range); 1846 } 1847 return ret; 1848 } 1849 1850 static int userfaultfd_continue(struct userfaultfd_ctx *ctx, unsigned long arg) 1851 { 1852 __s64 ret; 1853 struct uffdio_continue uffdio_continue; 1854 struct uffdio_continue __user *user_uffdio_continue; 1855 struct userfaultfd_wake_range range; 1856 1857 user_uffdio_continue = (struct uffdio_continue __user *)arg; 1858 1859 ret = -EAGAIN; 1860 if (atomic_read(&ctx->mmap_changing)) 1861 goto out; 1862 1863 ret = -EFAULT; 1864 if (copy_from_user(&uffdio_continue, user_uffdio_continue, 1865 /* don't copy the output fields */ 1866 sizeof(uffdio_continue) - (sizeof(__s64)))) 1867 goto out; 1868 1869 ret = validate_range(ctx->mm, uffdio_continue.range.start, 1870 uffdio_continue.range.len); 1871 if (ret) 1872 goto out; 1873 1874 ret = -EINVAL; 1875 /* double check for wraparound just in case. */ 1876 if (uffdio_continue.range.start + uffdio_continue.range.len <= 1877 uffdio_continue.range.start) { 1878 goto out; 1879 } 1880 if (uffdio_continue.mode & ~UFFDIO_CONTINUE_MODE_DONTWAKE) 1881 goto out; 1882 1883 if (mmget_not_zero(ctx->mm)) { 1884 ret = mcopy_continue(ctx->mm, uffdio_continue.range.start, 1885 uffdio_continue.range.len, 1886 &ctx->mmap_changing); 1887 mmput(ctx->mm); 1888 } else { 1889 return -ESRCH; 1890 } 1891 1892 if (unlikely(put_user(ret, &user_uffdio_continue->mapped))) 1893 return -EFAULT; 1894 if (ret < 0) 1895 goto out; 1896 1897 /* len == 0 would wake all */ 1898 BUG_ON(!ret); 1899 range.len = ret; 1900 if (!(uffdio_continue.mode & UFFDIO_CONTINUE_MODE_DONTWAKE)) { 1901 range.start = uffdio_continue.range.start; 1902 wake_userfault(ctx, &range); 1903 } 1904 ret = range.len == uffdio_continue.range.len ? 0 : -EAGAIN; 1905 1906 out: 1907 return ret; 1908 } 1909 1910 static inline unsigned int uffd_ctx_features(__u64 user_features) 1911 { 1912 /* 1913 * For the current set of features the bits just coincide. Set 1914 * UFFD_FEATURE_INITIALIZED to mark the features as enabled. 1915 */ 1916 return (unsigned int)user_features | UFFD_FEATURE_INITIALIZED; 1917 } 1918 1919 /* 1920 * userland asks for a certain API version and we return which bits 1921 * and ioctl commands are implemented in this kernel for such API 1922 * version or -EINVAL if unknown. 1923 */ 1924 static int userfaultfd_api(struct userfaultfd_ctx *ctx, 1925 unsigned long arg) 1926 { 1927 struct uffdio_api uffdio_api; 1928 void __user *buf = (void __user *)arg; 1929 unsigned int ctx_features; 1930 int ret; 1931 __u64 features; 1932 1933 ret = -EFAULT; 1934 if (copy_from_user(&uffdio_api, buf, sizeof(uffdio_api))) 1935 goto out; 1936 features = uffdio_api.features; 1937 ret = -EINVAL; 1938 if (uffdio_api.api != UFFD_API || (features & ~UFFD_API_FEATURES)) 1939 goto err_out; 1940 ret = -EPERM; 1941 if ((features & UFFD_FEATURE_EVENT_FORK) && !capable(CAP_SYS_PTRACE)) 1942 goto err_out; 1943 /* report all available features and ioctls to userland */ 1944 uffdio_api.features = UFFD_API_FEATURES; 1945 #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR 1946 uffdio_api.features &= 1947 ~(UFFD_FEATURE_MINOR_HUGETLBFS | UFFD_FEATURE_MINOR_SHMEM); 1948 #endif 1949 #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_WP 1950 uffdio_api.features &= ~UFFD_FEATURE_PAGEFAULT_FLAG_WP; 1951 #endif 1952 uffdio_api.ioctls = UFFD_API_IOCTLS; 1953 ret = -EFAULT; 1954 if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api))) 1955 goto out; 1956 1957 /* only enable the requested features for this uffd context */ 1958 ctx_features = uffd_ctx_features(features); 1959 ret = -EINVAL; 1960 if (cmpxchg(&ctx->features, 0, ctx_features) != 0) 1961 goto err_out; 1962 1963 ret = 0; 1964 out: 1965 return ret; 1966 err_out: 1967 memset(&uffdio_api, 0, sizeof(uffdio_api)); 1968 if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api))) 1969 ret = -EFAULT; 1970 goto out; 1971 } 1972 1973 static long userfaultfd_ioctl(struct file *file, unsigned cmd, 1974 unsigned long arg) 1975 { 1976 int ret = -EINVAL; 1977 struct userfaultfd_ctx *ctx = file->private_data; 1978 1979 if (cmd != UFFDIO_API && !userfaultfd_is_initialized(ctx)) 1980 return -EINVAL; 1981 1982 switch(cmd) { 1983 case UFFDIO_API: 1984 ret = userfaultfd_api(ctx, arg); 1985 break; 1986 case UFFDIO_REGISTER: 1987 ret = userfaultfd_register(ctx, arg); 1988 break; 1989 case UFFDIO_UNREGISTER: 1990 ret = userfaultfd_unregister(ctx, arg); 1991 break; 1992 case UFFDIO_WAKE: 1993 ret = userfaultfd_wake(ctx, arg); 1994 break; 1995 case UFFDIO_COPY: 1996 ret = userfaultfd_copy(ctx, arg); 1997 break; 1998 case UFFDIO_ZEROPAGE: 1999 ret = userfaultfd_zeropage(ctx, arg); 2000 break; 2001 case UFFDIO_WRITEPROTECT: 2002 ret = userfaultfd_writeprotect(ctx, arg); 2003 break; 2004 case UFFDIO_CONTINUE: 2005 ret = userfaultfd_continue(ctx, arg); 2006 break; 2007 } 2008 return ret; 2009 } 2010 2011 #ifdef CONFIG_PROC_FS 2012 static void userfaultfd_show_fdinfo(struct seq_file *m, struct file *f) 2013 { 2014 struct userfaultfd_ctx *ctx = f->private_data; 2015 wait_queue_entry_t *wq; 2016 unsigned long pending = 0, total = 0; 2017 2018 spin_lock_irq(&ctx->fault_pending_wqh.lock); 2019 list_for_each_entry(wq, &ctx->fault_pending_wqh.head, entry) { 2020 pending++; 2021 total++; 2022 } 2023 list_for_each_entry(wq, &ctx->fault_wqh.head, entry) { 2024 total++; 2025 } 2026 spin_unlock_irq(&ctx->fault_pending_wqh.lock); 2027 2028 /* 2029 * If more protocols will be added, there will be all shown 2030 * separated by a space. Like this: 2031 * protocols: aa:... bb:... 2032 */ 2033 seq_printf(m, "pending:\t%lu\ntotal:\t%lu\nAPI:\t%Lx:%x:%Lx\n", 2034 pending, total, UFFD_API, ctx->features, 2035 UFFD_API_IOCTLS|UFFD_API_RANGE_IOCTLS); 2036 } 2037 #endif 2038 2039 static const struct file_operations userfaultfd_fops = { 2040 #ifdef CONFIG_PROC_FS 2041 .show_fdinfo = userfaultfd_show_fdinfo, 2042 #endif 2043 .release = userfaultfd_release, 2044 .poll = userfaultfd_poll, 2045 .read = userfaultfd_read, 2046 .unlocked_ioctl = userfaultfd_ioctl, 2047 .compat_ioctl = compat_ptr_ioctl, 2048 .llseek = noop_llseek, 2049 }; 2050 2051 static void init_once_userfaultfd_ctx(void *mem) 2052 { 2053 struct userfaultfd_ctx *ctx = (struct userfaultfd_ctx *) mem; 2054 2055 init_waitqueue_head(&ctx->fault_pending_wqh); 2056 init_waitqueue_head(&ctx->fault_wqh); 2057 init_waitqueue_head(&ctx->event_wqh); 2058 init_waitqueue_head(&ctx->fd_wqh); 2059 seqcount_spinlock_init(&ctx->refile_seq, &ctx->fault_pending_wqh.lock); 2060 } 2061 2062 SYSCALL_DEFINE1(userfaultfd, int, flags) 2063 { 2064 struct userfaultfd_ctx *ctx; 2065 int fd; 2066 2067 if (!sysctl_unprivileged_userfaultfd && 2068 (flags & UFFD_USER_MODE_ONLY) == 0 && 2069 !capable(CAP_SYS_PTRACE)) { 2070 printk_once(KERN_WARNING "uffd: Set unprivileged_userfaultfd " 2071 "sysctl knob to 1 if kernel faults must be handled " 2072 "without obtaining CAP_SYS_PTRACE capability\n"); 2073 return -EPERM; 2074 } 2075 2076 BUG_ON(!current->mm); 2077 2078 /* Check the UFFD_* constants for consistency. */ 2079 BUILD_BUG_ON(UFFD_USER_MODE_ONLY & UFFD_SHARED_FCNTL_FLAGS); 2080 BUILD_BUG_ON(UFFD_CLOEXEC != O_CLOEXEC); 2081 BUILD_BUG_ON(UFFD_NONBLOCK != O_NONBLOCK); 2082 2083 if (flags & ~(UFFD_SHARED_FCNTL_FLAGS | UFFD_USER_MODE_ONLY)) 2084 return -EINVAL; 2085 2086 ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL); 2087 if (!ctx) 2088 return -ENOMEM; 2089 2090 refcount_set(&ctx->refcount, 1); 2091 ctx->flags = flags; 2092 ctx->features = 0; 2093 ctx->released = false; 2094 atomic_set(&ctx->mmap_changing, 0); 2095 ctx->mm = current->mm; 2096 /* prevent the mm struct to be freed */ 2097 mmgrab(ctx->mm); 2098 2099 fd = anon_inode_getfd_secure("[userfaultfd]", &userfaultfd_fops, ctx, 2100 O_RDWR | (flags & UFFD_SHARED_FCNTL_FLAGS), NULL); 2101 if (fd < 0) { 2102 mmdrop(ctx->mm); 2103 kmem_cache_free(userfaultfd_ctx_cachep, ctx); 2104 } 2105 return fd; 2106 } 2107 2108 static int __init userfaultfd_init(void) 2109 { 2110 userfaultfd_ctx_cachep = kmem_cache_create("userfaultfd_ctx_cache", 2111 sizeof(struct userfaultfd_ctx), 2112 0, 2113 SLAB_HWCACHE_ALIGN|SLAB_PANIC, 2114 init_once_userfaultfd_ctx); 2115 return 0; 2116 } 2117 __initcall(userfaultfd_init); 2118