1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * This file contains the procedures for the handling of select and poll 4 * 5 * Created for Linux based loosely upon Mathius Lattner's minix 6 * patches by Peter MacDonald. Heavily edited by Linus. 7 * 8 * 4 February 1994 9 * COFF/ELF binary emulation. If the process has the STICKY_TIMEOUTS 10 * flag set in its personality we do *not* modify the given timeout 11 * parameter to reflect time remaining. 12 * 13 * 24 January 2000 14 * Changed sys_poll()/do_poll() to use PAGE_SIZE chunk-based allocation 15 * of fds to overcome nfds < 16390 descriptors limit (Tigran Aivazian). 16 */ 17 18 #include <linux/kernel.h> 19 #include <linux/sched/signal.h> 20 #include <linux/sched/rt.h> 21 #include <linux/syscalls.h> 22 #include <linux/export.h> 23 #include <linux/slab.h> 24 #include <linux/poll.h> 25 #include <linux/personality.h> /* for STICKY_TIMEOUTS */ 26 #include <linux/file.h> 27 #include <linux/fdtable.h> 28 #include <linux/fs.h> 29 #include <linux/rcupdate.h> 30 #include <linux/hrtimer.h> 31 #include <linux/freezer.h> 32 #include <net/busy_poll.h> 33 #include <linux/vmalloc.h> 34 35 #include <linux/uaccess.h> 36 37 38 /* 39 * Estimate expected accuracy in ns from a timeval. 40 * 41 * After quite a bit of churning around, we've settled on 42 * a simple thing of taking 0.1% of the timeout as the 43 * slack, with a cap of 100 msec. 44 * "nice" tasks get a 0.5% slack instead. 45 * 46 * Consider this comment an open invitation to come up with even 47 * better solutions.. 48 */ 49 50 #define MAX_SLACK (100 * NSEC_PER_MSEC) 51 52 static long __estimate_accuracy(struct timespec64 *tv) 53 { 54 long slack; 55 int divfactor = 1000; 56 57 if (tv->tv_sec < 0) 58 return 0; 59 60 if (task_nice(current) > 0) 61 divfactor = divfactor / 5; 62 63 if (tv->tv_sec > MAX_SLACK / (NSEC_PER_SEC/divfactor)) 64 return MAX_SLACK; 65 66 slack = tv->tv_nsec / divfactor; 67 slack += tv->tv_sec * (NSEC_PER_SEC/divfactor); 68 69 if (slack > MAX_SLACK) 70 return MAX_SLACK; 71 72 return slack; 73 } 74 75 u64 select_estimate_accuracy(struct timespec64 *tv) 76 { 77 u64 ret; 78 struct timespec64 now; 79 80 /* 81 * Realtime tasks get a slack of 0 for obvious reasons. 82 */ 83 84 if (rt_task(current)) 85 return 0; 86 87 ktime_get_ts64(&now); 88 now = timespec64_sub(*tv, now); 89 ret = __estimate_accuracy(&now); 90 if (ret < current->timer_slack_ns) 91 return current->timer_slack_ns; 92 return ret; 93 } 94 95 96 97 struct poll_table_page { 98 struct poll_table_page * next; 99 struct poll_table_entry * entry; 100 struct poll_table_entry entries[0]; 101 }; 102 103 #define POLL_TABLE_FULL(table) \ 104 ((unsigned long)((table)->entry+1) > PAGE_SIZE + (unsigned long)(table)) 105 106 /* 107 * Ok, Peter made a complicated, but straightforward multiple_wait() function. 108 * I have rewritten this, taking some shortcuts: This code may not be easy to 109 * follow, but it should be free of race-conditions, and it's practical. If you 110 * understand what I'm doing here, then you understand how the linux 111 * sleep/wakeup mechanism works. 112 * 113 * Two very simple procedures, poll_wait() and poll_freewait() make all the 114 * work. poll_wait() is an inline-function defined in <linux/poll.h>, 115 * as all select/poll functions have to call it to add an entry to the 116 * poll table. 117 */ 118 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address, 119 poll_table *p); 120 121 void poll_initwait(struct poll_wqueues *pwq) 122 { 123 init_poll_funcptr(&pwq->pt, __pollwait); 124 pwq->polling_task = current; 125 pwq->triggered = 0; 126 pwq->error = 0; 127 pwq->table = NULL; 128 pwq->inline_index = 0; 129 } 130 EXPORT_SYMBOL(poll_initwait); 131 132 static void free_poll_entry(struct poll_table_entry *entry) 133 { 134 remove_wait_queue(entry->wait_address, &entry->wait); 135 fput(entry->filp); 136 } 137 138 void poll_freewait(struct poll_wqueues *pwq) 139 { 140 struct poll_table_page * p = pwq->table; 141 int i; 142 for (i = 0; i < pwq->inline_index; i++) 143 free_poll_entry(pwq->inline_entries + i); 144 while (p) { 145 struct poll_table_entry * entry; 146 struct poll_table_page *old; 147 148 entry = p->entry; 149 do { 150 entry--; 151 free_poll_entry(entry); 152 } while (entry > p->entries); 153 old = p; 154 p = p->next; 155 free_page((unsigned long) old); 156 } 157 } 158 EXPORT_SYMBOL(poll_freewait); 159 160 static struct poll_table_entry *poll_get_entry(struct poll_wqueues *p) 161 { 162 struct poll_table_page *table = p->table; 163 164 if (p->inline_index < N_INLINE_POLL_ENTRIES) 165 return p->inline_entries + p->inline_index++; 166 167 if (!table || POLL_TABLE_FULL(table)) { 168 struct poll_table_page *new_table; 169 170 new_table = (struct poll_table_page *) __get_free_page(GFP_KERNEL); 171 if (!new_table) { 172 p->error = -ENOMEM; 173 return NULL; 174 } 175 new_table->entry = new_table->entries; 176 new_table->next = table; 177 p->table = new_table; 178 table = new_table; 179 } 180 181 return table->entry++; 182 } 183 184 static int __pollwake(wait_queue_entry_t *wait, unsigned mode, int sync, void *key) 185 { 186 struct poll_wqueues *pwq = wait->private; 187 DECLARE_WAITQUEUE(dummy_wait, pwq->polling_task); 188 189 /* 190 * Although this function is called under waitqueue lock, LOCK 191 * doesn't imply write barrier and the users expect write 192 * barrier semantics on wakeup functions. The following 193 * smp_wmb() is equivalent to smp_wmb() in try_to_wake_up() 194 * and is paired with smp_store_mb() in poll_schedule_timeout. 195 */ 196 smp_wmb(); 197 pwq->triggered = 1; 198 199 /* 200 * Perform the default wake up operation using a dummy 201 * waitqueue. 202 * 203 * TODO: This is hacky but there currently is no interface to 204 * pass in @sync. @sync is scheduled to be removed and once 205 * that happens, wake_up_process() can be used directly. 206 */ 207 return default_wake_function(&dummy_wait, mode, sync, key); 208 } 209 210 static int pollwake(wait_queue_entry_t *wait, unsigned mode, int sync, void *key) 211 { 212 struct poll_table_entry *entry; 213 214 entry = container_of(wait, struct poll_table_entry, wait); 215 if (key && !(key_to_poll(key) & entry->key)) 216 return 0; 217 return __pollwake(wait, mode, sync, key); 218 } 219 220 /* Add a new entry */ 221 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address, 222 poll_table *p) 223 { 224 struct poll_wqueues *pwq = container_of(p, struct poll_wqueues, pt); 225 struct poll_table_entry *entry = poll_get_entry(pwq); 226 if (!entry) 227 return; 228 entry->filp = get_file(filp); 229 entry->wait_address = wait_address; 230 entry->key = p->_key; 231 init_waitqueue_func_entry(&entry->wait, pollwake); 232 entry->wait.private = pwq; 233 add_wait_queue(wait_address, &entry->wait); 234 } 235 236 static int poll_schedule_timeout(struct poll_wqueues *pwq, int state, 237 ktime_t *expires, unsigned long slack) 238 { 239 int rc = -EINTR; 240 241 set_current_state(state); 242 if (!pwq->triggered) 243 rc = schedule_hrtimeout_range(expires, slack, HRTIMER_MODE_ABS); 244 __set_current_state(TASK_RUNNING); 245 246 /* 247 * Prepare for the next iteration. 248 * 249 * The following smp_store_mb() serves two purposes. First, it's 250 * the counterpart rmb of the wmb in pollwake() such that data 251 * written before wake up is always visible after wake up. 252 * Second, the full barrier guarantees that triggered clearing 253 * doesn't pass event check of the next iteration. Note that 254 * this problem doesn't exist for the first iteration as 255 * add_wait_queue() has full barrier semantics. 256 */ 257 smp_store_mb(pwq->triggered, 0); 258 259 return rc; 260 } 261 262 /** 263 * poll_select_set_timeout - helper function to setup the timeout value 264 * @to: pointer to timespec64 variable for the final timeout 265 * @sec: seconds (from user space) 266 * @nsec: nanoseconds (from user space) 267 * 268 * Note, we do not use a timespec for the user space value here, That 269 * way we can use the function for timeval and compat interfaces as well. 270 * 271 * Returns -EINVAL if sec/nsec are not normalized. Otherwise 0. 272 */ 273 int poll_select_set_timeout(struct timespec64 *to, time64_t sec, long nsec) 274 { 275 struct timespec64 ts = {.tv_sec = sec, .tv_nsec = nsec}; 276 277 if (!timespec64_valid(&ts)) 278 return -EINVAL; 279 280 /* Optimize for the zero timeout value here */ 281 if (!sec && !nsec) { 282 to->tv_sec = to->tv_nsec = 0; 283 } else { 284 ktime_get_ts64(to); 285 *to = timespec64_add_safe(*to, ts); 286 } 287 return 0; 288 } 289 290 enum poll_time_type { 291 PT_TIMEVAL = 0, 292 PT_OLD_TIMEVAL = 1, 293 PT_TIMESPEC = 2, 294 PT_OLD_TIMESPEC = 3, 295 }; 296 297 static int poll_select_finish(struct timespec64 *end_time, 298 void __user *p, 299 enum poll_time_type pt_type, int ret) 300 { 301 struct timespec64 rts; 302 303 restore_saved_sigmask_unless(ret == -ERESTARTNOHAND); 304 305 if (!p) 306 return ret; 307 308 if (current->personality & STICKY_TIMEOUTS) 309 goto sticky; 310 311 /* No update for zero timeout */ 312 if (!end_time->tv_sec && !end_time->tv_nsec) 313 return ret; 314 315 ktime_get_ts64(&rts); 316 rts = timespec64_sub(*end_time, rts); 317 if (rts.tv_sec < 0) 318 rts.tv_sec = rts.tv_nsec = 0; 319 320 321 switch (pt_type) { 322 case PT_TIMEVAL: 323 { 324 struct timeval rtv; 325 326 if (sizeof(rtv) > sizeof(rtv.tv_sec) + sizeof(rtv.tv_usec)) 327 memset(&rtv, 0, sizeof(rtv)); 328 rtv.tv_sec = rts.tv_sec; 329 rtv.tv_usec = rts.tv_nsec / NSEC_PER_USEC; 330 if (!copy_to_user(p, &rtv, sizeof(rtv))) 331 return ret; 332 } 333 break; 334 case PT_OLD_TIMEVAL: 335 { 336 struct old_timeval32 rtv; 337 338 rtv.tv_sec = rts.tv_sec; 339 rtv.tv_usec = rts.tv_nsec / NSEC_PER_USEC; 340 if (!copy_to_user(p, &rtv, sizeof(rtv))) 341 return ret; 342 } 343 break; 344 case PT_TIMESPEC: 345 if (!put_timespec64(&rts, p)) 346 return ret; 347 break; 348 case PT_OLD_TIMESPEC: 349 if (!put_old_timespec32(&rts, p)) 350 return ret; 351 break; 352 default: 353 BUG(); 354 } 355 /* 356 * If an application puts its timeval in read-only memory, we 357 * don't want the Linux-specific update to the timeval to 358 * cause a fault after the select has completed 359 * successfully. However, because we're not updating the 360 * timeval, we can't restart the system call. 361 */ 362 363 sticky: 364 if (ret == -ERESTARTNOHAND) 365 ret = -EINTR; 366 return ret; 367 } 368 369 /* 370 * Scalable version of the fd_set. 371 */ 372 373 typedef struct { 374 unsigned long *in, *out, *ex; 375 unsigned long *res_in, *res_out, *res_ex; 376 } fd_set_bits; 377 378 /* 379 * How many longwords for "nr" bits? 380 */ 381 #define FDS_BITPERLONG (8*sizeof(long)) 382 #define FDS_LONGS(nr) (((nr)+FDS_BITPERLONG-1)/FDS_BITPERLONG) 383 #define FDS_BYTES(nr) (FDS_LONGS(nr)*sizeof(long)) 384 385 /* 386 * Use "unsigned long" accesses to let user-mode fd_set's be long-aligned. 387 */ 388 static inline 389 int get_fd_set(unsigned long nr, void __user *ufdset, unsigned long *fdset) 390 { 391 nr = FDS_BYTES(nr); 392 if (ufdset) 393 return copy_from_user(fdset, ufdset, nr) ? -EFAULT : 0; 394 395 memset(fdset, 0, nr); 396 return 0; 397 } 398 399 static inline unsigned long __must_check 400 set_fd_set(unsigned long nr, void __user *ufdset, unsigned long *fdset) 401 { 402 if (ufdset) 403 return __copy_to_user(ufdset, fdset, FDS_BYTES(nr)); 404 return 0; 405 } 406 407 static inline 408 void zero_fd_set(unsigned long nr, unsigned long *fdset) 409 { 410 memset(fdset, 0, FDS_BYTES(nr)); 411 } 412 413 #define FDS_IN(fds, n) (fds->in + n) 414 #define FDS_OUT(fds, n) (fds->out + n) 415 #define FDS_EX(fds, n) (fds->ex + n) 416 417 #define BITS(fds, n) (*FDS_IN(fds, n)|*FDS_OUT(fds, n)|*FDS_EX(fds, n)) 418 419 static int max_select_fd(unsigned long n, fd_set_bits *fds) 420 { 421 unsigned long *open_fds; 422 unsigned long set; 423 int max; 424 struct fdtable *fdt; 425 426 /* handle last in-complete long-word first */ 427 set = ~(~0UL << (n & (BITS_PER_LONG-1))); 428 n /= BITS_PER_LONG; 429 fdt = files_fdtable(current->files); 430 open_fds = fdt->open_fds + n; 431 max = 0; 432 if (set) { 433 set &= BITS(fds, n); 434 if (set) { 435 if (!(set & ~*open_fds)) 436 goto get_max; 437 return -EBADF; 438 } 439 } 440 while (n) { 441 open_fds--; 442 n--; 443 set = BITS(fds, n); 444 if (!set) 445 continue; 446 if (set & ~*open_fds) 447 return -EBADF; 448 if (max) 449 continue; 450 get_max: 451 do { 452 max++; 453 set >>= 1; 454 } while (set); 455 max += n * BITS_PER_LONG; 456 } 457 458 return max; 459 } 460 461 #define POLLIN_SET (EPOLLRDNORM | EPOLLRDBAND | EPOLLIN | EPOLLHUP | EPOLLERR) 462 #define POLLOUT_SET (EPOLLWRBAND | EPOLLWRNORM | EPOLLOUT | EPOLLERR) 463 #define POLLEX_SET (EPOLLPRI) 464 465 static inline void wait_key_set(poll_table *wait, unsigned long in, 466 unsigned long out, unsigned long bit, 467 __poll_t ll_flag) 468 { 469 wait->_key = POLLEX_SET | ll_flag; 470 if (in & bit) 471 wait->_key |= POLLIN_SET; 472 if (out & bit) 473 wait->_key |= POLLOUT_SET; 474 } 475 476 static int do_select(int n, fd_set_bits *fds, struct timespec64 *end_time) 477 { 478 ktime_t expire, *to = NULL; 479 struct poll_wqueues table; 480 poll_table *wait; 481 int retval, i, timed_out = 0; 482 u64 slack = 0; 483 __poll_t busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0; 484 unsigned long busy_start = 0; 485 486 rcu_read_lock(); 487 retval = max_select_fd(n, fds); 488 rcu_read_unlock(); 489 490 if (retval < 0) 491 return retval; 492 n = retval; 493 494 poll_initwait(&table); 495 wait = &table.pt; 496 if (end_time && !end_time->tv_sec && !end_time->tv_nsec) { 497 wait->_qproc = NULL; 498 timed_out = 1; 499 } 500 501 if (end_time && !timed_out) 502 slack = select_estimate_accuracy(end_time); 503 504 retval = 0; 505 for (;;) { 506 unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp; 507 bool can_busy_loop = false; 508 509 inp = fds->in; outp = fds->out; exp = fds->ex; 510 rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex; 511 512 for (i = 0; i < n; ++rinp, ++routp, ++rexp) { 513 unsigned long in, out, ex, all_bits, bit = 1, j; 514 unsigned long res_in = 0, res_out = 0, res_ex = 0; 515 __poll_t mask; 516 517 in = *inp++; out = *outp++; ex = *exp++; 518 all_bits = in | out | ex; 519 if (all_bits == 0) { 520 i += BITS_PER_LONG; 521 continue; 522 } 523 524 for (j = 0; j < BITS_PER_LONG; ++j, ++i, bit <<= 1) { 525 struct fd f; 526 if (i >= n) 527 break; 528 if (!(bit & all_bits)) 529 continue; 530 f = fdget(i); 531 if (f.file) { 532 wait_key_set(wait, in, out, bit, 533 busy_flag); 534 mask = vfs_poll(f.file, wait); 535 536 fdput(f); 537 if ((mask & POLLIN_SET) && (in & bit)) { 538 res_in |= bit; 539 retval++; 540 wait->_qproc = NULL; 541 } 542 if ((mask & POLLOUT_SET) && (out & bit)) { 543 res_out |= bit; 544 retval++; 545 wait->_qproc = NULL; 546 } 547 if ((mask & POLLEX_SET) && (ex & bit)) { 548 res_ex |= bit; 549 retval++; 550 wait->_qproc = NULL; 551 } 552 /* got something, stop busy polling */ 553 if (retval) { 554 can_busy_loop = false; 555 busy_flag = 0; 556 557 /* 558 * only remember a returned 559 * POLL_BUSY_LOOP if we asked for it 560 */ 561 } else if (busy_flag & mask) 562 can_busy_loop = true; 563 564 } 565 } 566 if (res_in) 567 *rinp = res_in; 568 if (res_out) 569 *routp = res_out; 570 if (res_ex) 571 *rexp = res_ex; 572 cond_resched(); 573 } 574 wait->_qproc = NULL; 575 if (retval || timed_out || signal_pending(current)) 576 break; 577 if (table.error) { 578 retval = table.error; 579 break; 580 } 581 582 /* only if found POLL_BUSY_LOOP sockets && not out of time */ 583 if (can_busy_loop && !need_resched()) { 584 if (!busy_start) { 585 busy_start = busy_loop_current_time(); 586 continue; 587 } 588 if (!busy_loop_timeout(busy_start)) 589 continue; 590 } 591 busy_flag = 0; 592 593 /* 594 * If this is the first loop and we have a timeout 595 * given, then we convert to ktime_t and set the to 596 * pointer to the expiry value. 597 */ 598 if (end_time && !to) { 599 expire = timespec64_to_ktime(*end_time); 600 to = &expire; 601 } 602 603 if (!poll_schedule_timeout(&table, TASK_INTERRUPTIBLE, 604 to, slack)) 605 timed_out = 1; 606 } 607 608 poll_freewait(&table); 609 610 return retval; 611 } 612 613 /* 614 * We can actually return ERESTARTSYS instead of EINTR, but I'd 615 * like to be certain this leads to no problems. So I return 616 * EINTR just for safety. 617 * 618 * Update: ERESTARTSYS breaks at least the xview clock binary, so 619 * I'm trying ERESTARTNOHAND which restart only when you want to. 620 */ 621 int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp, 622 fd_set __user *exp, struct timespec64 *end_time) 623 { 624 fd_set_bits fds; 625 void *bits; 626 int ret, max_fds; 627 size_t size, alloc_size; 628 struct fdtable *fdt; 629 /* Allocate small arguments on the stack to save memory and be faster */ 630 long stack_fds[SELECT_STACK_ALLOC/sizeof(long)]; 631 632 ret = -EINVAL; 633 if (n < 0) 634 goto out_nofds; 635 636 /* max_fds can increase, so grab it once to avoid race */ 637 rcu_read_lock(); 638 fdt = files_fdtable(current->files); 639 max_fds = fdt->max_fds; 640 rcu_read_unlock(); 641 if (n > max_fds) 642 n = max_fds; 643 644 /* 645 * We need 6 bitmaps (in/out/ex for both incoming and outgoing), 646 * since we used fdset we need to allocate memory in units of 647 * long-words. 648 */ 649 size = FDS_BYTES(n); 650 bits = stack_fds; 651 if (size > sizeof(stack_fds) / 6) { 652 /* Not enough space in on-stack array; must use kmalloc */ 653 ret = -ENOMEM; 654 if (size > (SIZE_MAX / 6)) 655 goto out_nofds; 656 657 alloc_size = 6 * size; 658 bits = kvmalloc(alloc_size, GFP_KERNEL); 659 if (!bits) 660 goto out_nofds; 661 } 662 fds.in = bits; 663 fds.out = bits + size; 664 fds.ex = bits + 2*size; 665 fds.res_in = bits + 3*size; 666 fds.res_out = bits + 4*size; 667 fds.res_ex = bits + 5*size; 668 669 if ((ret = get_fd_set(n, inp, fds.in)) || 670 (ret = get_fd_set(n, outp, fds.out)) || 671 (ret = get_fd_set(n, exp, fds.ex))) 672 goto out; 673 zero_fd_set(n, fds.res_in); 674 zero_fd_set(n, fds.res_out); 675 zero_fd_set(n, fds.res_ex); 676 677 ret = do_select(n, &fds, end_time); 678 679 if (ret < 0) 680 goto out; 681 if (!ret) { 682 ret = -ERESTARTNOHAND; 683 if (signal_pending(current)) 684 goto out; 685 ret = 0; 686 } 687 688 if (set_fd_set(n, inp, fds.res_in) || 689 set_fd_set(n, outp, fds.res_out) || 690 set_fd_set(n, exp, fds.res_ex)) 691 ret = -EFAULT; 692 693 out: 694 if (bits != stack_fds) 695 kvfree(bits); 696 out_nofds: 697 return ret; 698 } 699 700 static int kern_select(int n, fd_set __user *inp, fd_set __user *outp, 701 fd_set __user *exp, struct timeval __user *tvp) 702 { 703 struct timespec64 end_time, *to = NULL; 704 struct timeval tv; 705 int ret; 706 707 if (tvp) { 708 if (copy_from_user(&tv, tvp, sizeof(tv))) 709 return -EFAULT; 710 711 to = &end_time; 712 if (poll_select_set_timeout(to, 713 tv.tv_sec + (tv.tv_usec / USEC_PER_SEC), 714 (tv.tv_usec % USEC_PER_SEC) * NSEC_PER_USEC)) 715 return -EINVAL; 716 } 717 718 ret = core_sys_select(n, inp, outp, exp, to); 719 return poll_select_finish(&end_time, tvp, PT_TIMEVAL, ret); 720 } 721 722 SYSCALL_DEFINE5(select, int, n, fd_set __user *, inp, fd_set __user *, outp, 723 fd_set __user *, exp, struct timeval __user *, tvp) 724 { 725 return kern_select(n, inp, outp, exp, tvp); 726 } 727 728 static long do_pselect(int n, fd_set __user *inp, fd_set __user *outp, 729 fd_set __user *exp, void __user *tsp, 730 const sigset_t __user *sigmask, size_t sigsetsize, 731 enum poll_time_type type) 732 { 733 struct timespec64 ts, end_time, *to = NULL; 734 int ret; 735 736 if (tsp) { 737 switch (type) { 738 case PT_TIMESPEC: 739 if (get_timespec64(&ts, tsp)) 740 return -EFAULT; 741 break; 742 case PT_OLD_TIMESPEC: 743 if (get_old_timespec32(&ts, tsp)) 744 return -EFAULT; 745 break; 746 default: 747 BUG(); 748 } 749 750 to = &end_time; 751 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec)) 752 return -EINVAL; 753 } 754 755 ret = set_user_sigmask(sigmask, sigsetsize); 756 if (ret) 757 return ret; 758 759 ret = core_sys_select(n, inp, outp, exp, to); 760 return poll_select_finish(&end_time, tsp, type, ret); 761 } 762 763 /* 764 * Most architectures can't handle 7-argument syscalls. So we provide a 765 * 6-argument version where the sixth argument is a pointer to a structure 766 * which has a pointer to the sigset_t itself followed by a size_t containing 767 * the sigset size. 768 */ 769 SYSCALL_DEFINE6(pselect6, int, n, fd_set __user *, inp, fd_set __user *, outp, 770 fd_set __user *, exp, struct __kernel_timespec __user *, tsp, 771 void __user *, sig) 772 { 773 size_t sigsetsize = 0; 774 sigset_t __user *up = NULL; 775 776 if (sig) { 777 if (!access_ok(sig, sizeof(void *)+sizeof(size_t)) 778 || __get_user(up, (sigset_t __user * __user *)sig) 779 || __get_user(sigsetsize, 780 (size_t __user *)(sig+sizeof(void *)))) 781 return -EFAULT; 782 } 783 784 return do_pselect(n, inp, outp, exp, tsp, up, sigsetsize, PT_TIMESPEC); 785 } 786 787 #if defined(CONFIG_COMPAT_32BIT_TIME) && !defined(CONFIG_64BIT) 788 789 SYSCALL_DEFINE6(pselect6_time32, int, n, fd_set __user *, inp, fd_set __user *, outp, 790 fd_set __user *, exp, struct old_timespec32 __user *, tsp, 791 void __user *, sig) 792 { 793 size_t sigsetsize = 0; 794 sigset_t __user *up = NULL; 795 796 if (sig) { 797 if (!access_ok(sig, sizeof(void *)+sizeof(size_t)) 798 || __get_user(up, (sigset_t __user * __user *)sig) 799 || __get_user(sigsetsize, 800 (size_t __user *)(sig+sizeof(void *)))) 801 return -EFAULT; 802 } 803 804 return do_pselect(n, inp, outp, exp, tsp, up, sigsetsize, PT_OLD_TIMESPEC); 805 } 806 807 #endif 808 809 #ifdef __ARCH_WANT_SYS_OLD_SELECT 810 struct sel_arg_struct { 811 unsigned long n; 812 fd_set __user *inp, *outp, *exp; 813 struct timeval __user *tvp; 814 }; 815 816 SYSCALL_DEFINE1(old_select, struct sel_arg_struct __user *, arg) 817 { 818 struct sel_arg_struct a; 819 820 if (copy_from_user(&a, arg, sizeof(a))) 821 return -EFAULT; 822 return kern_select(a.n, a.inp, a.outp, a.exp, a.tvp); 823 } 824 #endif 825 826 struct poll_list { 827 struct poll_list *next; 828 int len; 829 struct pollfd entries[0]; 830 }; 831 832 #define POLLFD_PER_PAGE ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd)) 833 834 /* 835 * Fish for pollable events on the pollfd->fd file descriptor. We're only 836 * interested in events matching the pollfd->events mask, and the result 837 * matching that mask is both recorded in pollfd->revents and returned. The 838 * pwait poll_table will be used by the fd-provided poll handler for waiting, 839 * if pwait->_qproc is non-NULL. 840 */ 841 static inline __poll_t do_pollfd(struct pollfd *pollfd, poll_table *pwait, 842 bool *can_busy_poll, 843 __poll_t busy_flag) 844 { 845 int fd = pollfd->fd; 846 __poll_t mask = 0, filter; 847 struct fd f; 848 849 if (fd < 0) 850 goto out; 851 mask = EPOLLNVAL; 852 f = fdget(fd); 853 if (!f.file) 854 goto out; 855 856 /* userland u16 ->events contains POLL... bitmap */ 857 filter = demangle_poll(pollfd->events) | EPOLLERR | EPOLLHUP; 858 pwait->_key = filter | busy_flag; 859 mask = vfs_poll(f.file, pwait); 860 if (mask & busy_flag) 861 *can_busy_poll = true; 862 mask &= filter; /* Mask out unneeded events. */ 863 fdput(f); 864 865 out: 866 /* ... and so does ->revents */ 867 pollfd->revents = mangle_poll(mask); 868 return mask; 869 } 870 871 static int do_poll(struct poll_list *list, struct poll_wqueues *wait, 872 struct timespec64 *end_time) 873 { 874 poll_table* pt = &wait->pt; 875 ktime_t expire, *to = NULL; 876 int timed_out = 0, count = 0; 877 u64 slack = 0; 878 __poll_t busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0; 879 unsigned long busy_start = 0; 880 881 /* Optimise the no-wait case */ 882 if (end_time && !end_time->tv_sec && !end_time->tv_nsec) { 883 pt->_qproc = NULL; 884 timed_out = 1; 885 } 886 887 if (end_time && !timed_out) 888 slack = select_estimate_accuracy(end_time); 889 890 for (;;) { 891 struct poll_list *walk; 892 bool can_busy_loop = false; 893 894 for (walk = list; walk != NULL; walk = walk->next) { 895 struct pollfd * pfd, * pfd_end; 896 897 pfd = walk->entries; 898 pfd_end = pfd + walk->len; 899 for (; pfd != pfd_end; pfd++) { 900 /* 901 * Fish for events. If we found one, record it 902 * and kill poll_table->_qproc, so we don't 903 * needlessly register any other waiters after 904 * this. They'll get immediately deregistered 905 * when we break out and return. 906 */ 907 if (do_pollfd(pfd, pt, &can_busy_loop, 908 busy_flag)) { 909 count++; 910 pt->_qproc = NULL; 911 /* found something, stop busy polling */ 912 busy_flag = 0; 913 can_busy_loop = false; 914 } 915 } 916 } 917 /* 918 * All waiters have already been registered, so don't provide 919 * a poll_table->_qproc to them on the next loop iteration. 920 */ 921 pt->_qproc = NULL; 922 if (!count) { 923 count = wait->error; 924 if (signal_pending(current)) 925 count = -ERESTARTNOHAND; 926 } 927 if (count || timed_out) 928 break; 929 930 /* only if found POLL_BUSY_LOOP sockets && not out of time */ 931 if (can_busy_loop && !need_resched()) { 932 if (!busy_start) { 933 busy_start = busy_loop_current_time(); 934 continue; 935 } 936 if (!busy_loop_timeout(busy_start)) 937 continue; 938 } 939 busy_flag = 0; 940 941 /* 942 * If this is the first loop and we have a timeout 943 * given, then we convert to ktime_t and set the to 944 * pointer to the expiry value. 945 */ 946 if (end_time && !to) { 947 expire = timespec64_to_ktime(*end_time); 948 to = &expire; 949 } 950 951 if (!poll_schedule_timeout(wait, TASK_INTERRUPTIBLE, to, slack)) 952 timed_out = 1; 953 } 954 return count; 955 } 956 957 #define N_STACK_PPS ((sizeof(stack_pps) - sizeof(struct poll_list)) / \ 958 sizeof(struct pollfd)) 959 960 static int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds, 961 struct timespec64 *end_time) 962 { 963 struct poll_wqueues table; 964 int err = -EFAULT, fdcount, len; 965 /* Allocate small arguments on the stack to save memory and be 966 faster - use long to make sure the buffer is aligned properly 967 on 64 bit archs to avoid unaligned access */ 968 long stack_pps[POLL_STACK_ALLOC/sizeof(long)]; 969 struct poll_list *const head = (struct poll_list *)stack_pps; 970 struct poll_list *walk = head; 971 unsigned long todo = nfds; 972 973 if (nfds > rlimit(RLIMIT_NOFILE)) 974 return -EINVAL; 975 976 len = min_t(unsigned int, nfds, N_STACK_PPS); 977 for (;;) { 978 walk->next = NULL; 979 walk->len = len; 980 if (!len) 981 break; 982 983 if (copy_from_user(walk->entries, ufds + nfds-todo, 984 sizeof(struct pollfd) * walk->len)) 985 goto out_fds; 986 987 todo -= walk->len; 988 if (!todo) 989 break; 990 991 len = min(todo, POLLFD_PER_PAGE); 992 walk = walk->next = kmalloc(struct_size(walk, entries, len), 993 GFP_KERNEL); 994 if (!walk) { 995 err = -ENOMEM; 996 goto out_fds; 997 } 998 } 999 1000 poll_initwait(&table); 1001 fdcount = do_poll(head, &table, end_time); 1002 poll_freewait(&table); 1003 1004 for (walk = head; walk; walk = walk->next) { 1005 struct pollfd *fds = walk->entries; 1006 int j; 1007 1008 for (j = 0; j < walk->len; j++, ufds++) 1009 if (__put_user(fds[j].revents, &ufds->revents)) 1010 goto out_fds; 1011 } 1012 1013 err = fdcount; 1014 out_fds: 1015 walk = head->next; 1016 while (walk) { 1017 struct poll_list *pos = walk; 1018 walk = walk->next; 1019 kfree(pos); 1020 } 1021 1022 return err; 1023 } 1024 1025 static long do_restart_poll(struct restart_block *restart_block) 1026 { 1027 struct pollfd __user *ufds = restart_block->poll.ufds; 1028 int nfds = restart_block->poll.nfds; 1029 struct timespec64 *to = NULL, end_time; 1030 int ret; 1031 1032 if (restart_block->poll.has_timeout) { 1033 end_time.tv_sec = restart_block->poll.tv_sec; 1034 end_time.tv_nsec = restart_block->poll.tv_nsec; 1035 to = &end_time; 1036 } 1037 1038 ret = do_sys_poll(ufds, nfds, to); 1039 1040 if (ret == -ERESTARTNOHAND) { 1041 restart_block->fn = do_restart_poll; 1042 ret = -ERESTART_RESTARTBLOCK; 1043 } 1044 return ret; 1045 } 1046 1047 SYSCALL_DEFINE3(poll, struct pollfd __user *, ufds, unsigned int, nfds, 1048 int, timeout_msecs) 1049 { 1050 struct timespec64 end_time, *to = NULL; 1051 int ret; 1052 1053 if (timeout_msecs >= 0) { 1054 to = &end_time; 1055 poll_select_set_timeout(to, timeout_msecs / MSEC_PER_SEC, 1056 NSEC_PER_MSEC * (timeout_msecs % MSEC_PER_SEC)); 1057 } 1058 1059 ret = do_sys_poll(ufds, nfds, to); 1060 1061 if (ret == -ERESTARTNOHAND) { 1062 struct restart_block *restart_block; 1063 1064 restart_block = ¤t->restart_block; 1065 restart_block->fn = do_restart_poll; 1066 restart_block->poll.ufds = ufds; 1067 restart_block->poll.nfds = nfds; 1068 1069 if (timeout_msecs >= 0) { 1070 restart_block->poll.tv_sec = end_time.tv_sec; 1071 restart_block->poll.tv_nsec = end_time.tv_nsec; 1072 restart_block->poll.has_timeout = 1; 1073 } else 1074 restart_block->poll.has_timeout = 0; 1075 1076 ret = -ERESTART_RESTARTBLOCK; 1077 } 1078 return ret; 1079 } 1080 1081 SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds, unsigned int, nfds, 1082 struct __kernel_timespec __user *, tsp, const sigset_t __user *, sigmask, 1083 size_t, sigsetsize) 1084 { 1085 struct timespec64 ts, end_time, *to = NULL; 1086 int ret; 1087 1088 if (tsp) { 1089 if (get_timespec64(&ts, tsp)) 1090 return -EFAULT; 1091 1092 to = &end_time; 1093 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec)) 1094 return -EINVAL; 1095 } 1096 1097 ret = set_user_sigmask(sigmask, sigsetsize); 1098 if (ret) 1099 return ret; 1100 1101 ret = do_sys_poll(ufds, nfds, to); 1102 return poll_select_finish(&end_time, tsp, PT_TIMESPEC, ret); 1103 } 1104 1105 #if defined(CONFIG_COMPAT_32BIT_TIME) && !defined(CONFIG_64BIT) 1106 1107 SYSCALL_DEFINE5(ppoll_time32, struct pollfd __user *, ufds, unsigned int, nfds, 1108 struct old_timespec32 __user *, tsp, const sigset_t __user *, sigmask, 1109 size_t, sigsetsize) 1110 { 1111 struct timespec64 ts, end_time, *to = NULL; 1112 int ret; 1113 1114 if (tsp) { 1115 if (get_old_timespec32(&ts, tsp)) 1116 return -EFAULT; 1117 1118 to = &end_time; 1119 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec)) 1120 return -EINVAL; 1121 } 1122 1123 ret = set_user_sigmask(sigmask, sigsetsize); 1124 if (ret) 1125 return ret; 1126 1127 ret = do_sys_poll(ufds, nfds, to); 1128 return poll_select_finish(&end_time, tsp, PT_OLD_TIMESPEC, ret); 1129 } 1130 #endif 1131 1132 #ifdef CONFIG_COMPAT 1133 #define __COMPAT_NFDBITS (8 * sizeof(compat_ulong_t)) 1134 1135 /* 1136 * Ooo, nasty. We need here to frob 32-bit unsigned longs to 1137 * 64-bit unsigned longs. 1138 */ 1139 static 1140 int compat_get_fd_set(unsigned long nr, compat_ulong_t __user *ufdset, 1141 unsigned long *fdset) 1142 { 1143 if (ufdset) { 1144 return compat_get_bitmap(fdset, ufdset, nr); 1145 } else { 1146 zero_fd_set(nr, fdset); 1147 return 0; 1148 } 1149 } 1150 1151 static 1152 int compat_set_fd_set(unsigned long nr, compat_ulong_t __user *ufdset, 1153 unsigned long *fdset) 1154 { 1155 if (!ufdset) 1156 return 0; 1157 return compat_put_bitmap(ufdset, fdset, nr); 1158 } 1159 1160 1161 /* 1162 * This is a virtual copy of sys_select from fs/select.c and probably 1163 * should be compared to it from time to time 1164 */ 1165 1166 /* 1167 * We can actually return ERESTARTSYS instead of EINTR, but I'd 1168 * like to be certain this leads to no problems. So I return 1169 * EINTR just for safety. 1170 * 1171 * Update: ERESTARTSYS breaks at least the xview clock binary, so 1172 * I'm trying ERESTARTNOHAND which restart only when you want to. 1173 */ 1174 static int compat_core_sys_select(int n, compat_ulong_t __user *inp, 1175 compat_ulong_t __user *outp, compat_ulong_t __user *exp, 1176 struct timespec64 *end_time) 1177 { 1178 fd_set_bits fds; 1179 void *bits; 1180 int size, max_fds, ret = -EINVAL; 1181 struct fdtable *fdt; 1182 long stack_fds[SELECT_STACK_ALLOC/sizeof(long)]; 1183 1184 if (n < 0) 1185 goto out_nofds; 1186 1187 /* max_fds can increase, so grab it once to avoid race */ 1188 rcu_read_lock(); 1189 fdt = files_fdtable(current->files); 1190 max_fds = fdt->max_fds; 1191 rcu_read_unlock(); 1192 if (n > max_fds) 1193 n = max_fds; 1194 1195 /* 1196 * We need 6 bitmaps (in/out/ex for both incoming and outgoing), 1197 * since we used fdset we need to allocate memory in units of 1198 * long-words. 1199 */ 1200 size = FDS_BYTES(n); 1201 bits = stack_fds; 1202 if (size > sizeof(stack_fds) / 6) { 1203 bits = kmalloc_array(6, size, GFP_KERNEL); 1204 ret = -ENOMEM; 1205 if (!bits) 1206 goto out_nofds; 1207 } 1208 fds.in = (unsigned long *) bits; 1209 fds.out = (unsigned long *) (bits + size); 1210 fds.ex = (unsigned long *) (bits + 2*size); 1211 fds.res_in = (unsigned long *) (bits + 3*size); 1212 fds.res_out = (unsigned long *) (bits + 4*size); 1213 fds.res_ex = (unsigned long *) (bits + 5*size); 1214 1215 if ((ret = compat_get_fd_set(n, inp, fds.in)) || 1216 (ret = compat_get_fd_set(n, outp, fds.out)) || 1217 (ret = compat_get_fd_set(n, exp, fds.ex))) 1218 goto out; 1219 zero_fd_set(n, fds.res_in); 1220 zero_fd_set(n, fds.res_out); 1221 zero_fd_set(n, fds.res_ex); 1222 1223 ret = do_select(n, &fds, end_time); 1224 1225 if (ret < 0) 1226 goto out; 1227 if (!ret) { 1228 ret = -ERESTARTNOHAND; 1229 if (signal_pending(current)) 1230 goto out; 1231 ret = 0; 1232 } 1233 1234 if (compat_set_fd_set(n, inp, fds.res_in) || 1235 compat_set_fd_set(n, outp, fds.res_out) || 1236 compat_set_fd_set(n, exp, fds.res_ex)) 1237 ret = -EFAULT; 1238 out: 1239 if (bits != stack_fds) 1240 kfree(bits); 1241 out_nofds: 1242 return ret; 1243 } 1244 1245 static int do_compat_select(int n, compat_ulong_t __user *inp, 1246 compat_ulong_t __user *outp, compat_ulong_t __user *exp, 1247 struct old_timeval32 __user *tvp) 1248 { 1249 struct timespec64 end_time, *to = NULL; 1250 struct old_timeval32 tv; 1251 int ret; 1252 1253 if (tvp) { 1254 if (copy_from_user(&tv, tvp, sizeof(tv))) 1255 return -EFAULT; 1256 1257 to = &end_time; 1258 if (poll_select_set_timeout(to, 1259 tv.tv_sec + (tv.tv_usec / USEC_PER_SEC), 1260 (tv.tv_usec % USEC_PER_SEC) * NSEC_PER_USEC)) 1261 return -EINVAL; 1262 } 1263 1264 ret = compat_core_sys_select(n, inp, outp, exp, to); 1265 return poll_select_finish(&end_time, tvp, PT_OLD_TIMEVAL, ret); 1266 } 1267 1268 COMPAT_SYSCALL_DEFINE5(select, int, n, compat_ulong_t __user *, inp, 1269 compat_ulong_t __user *, outp, compat_ulong_t __user *, exp, 1270 struct old_timeval32 __user *, tvp) 1271 { 1272 return do_compat_select(n, inp, outp, exp, tvp); 1273 } 1274 1275 struct compat_sel_arg_struct { 1276 compat_ulong_t n; 1277 compat_uptr_t inp; 1278 compat_uptr_t outp; 1279 compat_uptr_t exp; 1280 compat_uptr_t tvp; 1281 }; 1282 1283 COMPAT_SYSCALL_DEFINE1(old_select, struct compat_sel_arg_struct __user *, arg) 1284 { 1285 struct compat_sel_arg_struct a; 1286 1287 if (copy_from_user(&a, arg, sizeof(a))) 1288 return -EFAULT; 1289 return do_compat_select(a.n, compat_ptr(a.inp), compat_ptr(a.outp), 1290 compat_ptr(a.exp), compat_ptr(a.tvp)); 1291 } 1292 1293 static long do_compat_pselect(int n, compat_ulong_t __user *inp, 1294 compat_ulong_t __user *outp, compat_ulong_t __user *exp, 1295 void __user *tsp, compat_sigset_t __user *sigmask, 1296 compat_size_t sigsetsize, enum poll_time_type type) 1297 { 1298 struct timespec64 ts, end_time, *to = NULL; 1299 int ret; 1300 1301 if (tsp) { 1302 switch (type) { 1303 case PT_OLD_TIMESPEC: 1304 if (get_old_timespec32(&ts, tsp)) 1305 return -EFAULT; 1306 break; 1307 case PT_TIMESPEC: 1308 if (get_timespec64(&ts, tsp)) 1309 return -EFAULT; 1310 break; 1311 default: 1312 BUG(); 1313 } 1314 1315 to = &end_time; 1316 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec)) 1317 return -EINVAL; 1318 } 1319 1320 ret = set_compat_user_sigmask(sigmask, sigsetsize); 1321 if (ret) 1322 return ret; 1323 1324 ret = compat_core_sys_select(n, inp, outp, exp, to); 1325 return poll_select_finish(&end_time, tsp, type, ret); 1326 } 1327 1328 COMPAT_SYSCALL_DEFINE6(pselect6_time64, int, n, compat_ulong_t __user *, inp, 1329 compat_ulong_t __user *, outp, compat_ulong_t __user *, exp, 1330 struct __kernel_timespec __user *, tsp, void __user *, sig) 1331 { 1332 compat_size_t sigsetsize = 0; 1333 compat_uptr_t up = 0; 1334 1335 if (sig) { 1336 if (!access_ok(sig, 1337 sizeof(compat_uptr_t)+sizeof(compat_size_t)) || 1338 __get_user(up, (compat_uptr_t __user *)sig) || 1339 __get_user(sigsetsize, 1340 (compat_size_t __user *)(sig+sizeof(up)))) 1341 return -EFAULT; 1342 } 1343 1344 return do_compat_pselect(n, inp, outp, exp, tsp, compat_ptr(up), 1345 sigsetsize, PT_TIMESPEC); 1346 } 1347 1348 #if defined(CONFIG_COMPAT_32BIT_TIME) 1349 1350 COMPAT_SYSCALL_DEFINE6(pselect6_time32, int, n, compat_ulong_t __user *, inp, 1351 compat_ulong_t __user *, outp, compat_ulong_t __user *, exp, 1352 struct old_timespec32 __user *, tsp, void __user *, sig) 1353 { 1354 compat_size_t sigsetsize = 0; 1355 compat_uptr_t up = 0; 1356 1357 if (sig) { 1358 if (!access_ok(sig, 1359 sizeof(compat_uptr_t)+sizeof(compat_size_t)) || 1360 __get_user(up, (compat_uptr_t __user *)sig) || 1361 __get_user(sigsetsize, 1362 (compat_size_t __user *)(sig+sizeof(up)))) 1363 return -EFAULT; 1364 } 1365 1366 return do_compat_pselect(n, inp, outp, exp, tsp, compat_ptr(up), 1367 sigsetsize, PT_OLD_TIMESPEC); 1368 } 1369 1370 #endif 1371 1372 #if defined(CONFIG_COMPAT_32BIT_TIME) 1373 COMPAT_SYSCALL_DEFINE5(ppoll_time32, struct pollfd __user *, ufds, 1374 unsigned int, nfds, struct old_timespec32 __user *, tsp, 1375 const compat_sigset_t __user *, sigmask, compat_size_t, sigsetsize) 1376 { 1377 struct timespec64 ts, end_time, *to = NULL; 1378 int ret; 1379 1380 if (tsp) { 1381 if (get_old_timespec32(&ts, tsp)) 1382 return -EFAULT; 1383 1384 to = &end_time; 1385 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec)) 1386 return -EINVAL; 1387 } 1388 1389 ret = set_compat_user_sigmask(sigmask, sigsetsize); 1390 if (ret) 1391 return ret; 1392 1393 ret = do_sys_poll(ufds, nfds, to); 1394 return poll_select_finish(&end_time, tsp, PT_OLD_TIMESPEC, ret); 1395 } 1396 #endif 1397 1398 /* New compat syscall for 64 bit time_t*/ 1399 COMPAT_SYSCALL_DEFINE5(ppoll_time64, struct pollfd __user *, ufds, 1400 unsigned int, nfds, struct __kernel_timespec __user *, tsp, 1401 const compat_sigset_t __user *, sigmask, compat_size_t, sigsetsize) 1402 { 1403 struct timespec64 ts, end_time, *to = NULL; 1404 int ret; 1405 1406 if (tsp) { 1407 if (get_timespec64(&ts, tsp)) 1408 return -EFAULT; 1409 1410 to = &end_time; 1411 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec)) 1412 return -EINVAL; 1413 } 1414 1415 ret = set_compat_user_sigmask(sigmask, sigsetsize); 1416 if (ret) 1417 return ret; 1418 1419 ret = do_sys_poll(ufds, nfds, to); 1420 return poll_select_finish(&end_time, tsp, PT_TIMESPEC, ret); 1421 } 1422 1423 #endif 1424