fs/select.c

   1 /*
   2  * This file contains the procedures for the handling of select and poll
   3  *
   4  * Created for Linux based loosely upon Mathius Lattner's minix
   5  * patches by Peter MacDonald. Heavily edited by Linus.
   6  *
   7  *  4 February 1994
   8  *     COFF/ELF binary emulation. If the process has the STICKY_TIMEOUTS
   9  *     flag set in its personality we do *not* modify the given timeout
  10  *     parameter to reflect time remaining.
  11  *
  12  *  24 January 2000
  13  *     Changed sys_poll()/do_poll() to use PAGE_SIZE chunk-based allocation
  14  *     of fds to overcome nfds < 16390 descriptors limit (Tigran Aivazian).
  15  */
  16
  17 #include <linux/kernel.h>
  18 #include <linux/sched.h>
  19 #include <linux/syscalls.h>
  20 #include <linux/export.h>
  21 #include <linux/slab.h>
  22 #include <linux/poll.h>
  23 #include <linux/personality.h> /* for STICKY_TIMEOUTS */
  24 #include <linux/file.h>
  25 #include <linux/fdtable.h>
  26 #include <linux/fs.h>
  27 #include <linux/rcupdate.h>
  28 #include <linux/hrtimer.h>
  29 #include <linux/sched/rt.h>
  30 #include <linux/freezer.h>
  31 #include <net/busy_poll.h>
  32 #include <linux/vmalloc.h>
  33
  34 #include <asm/uaccess.h>
  35
  36
  37 /*
  38  * Estimate expected accuracy in ns from a timeval.
  39  *
  40  * After quite a bit of churning around, we've settled on
  41  * a simple thing of taking 0.1% of the timeout as the
  42  * slack, with a cap of 100 msec.
  43  * "nice" tasks get a 0.5% slack instead.
  44  *
  45  * Consider this comment an open invitation to come up with even
  46  * better solutions..
  47  */
  48
  49 #define MAX_SLACK       (100 * NSEC_PER_MSEC)
  50
  51 static long __estimate_accuracy(struct timespec64 *tv)
  52 {
  53         long slack;
  54         int divfactor = 1000;
  55
  56         if (tv->tv_sec < 0)
  57                 return 0;
  58
  59         if (task_nice(current) > 0)
  60                 divfactor = divfactor / 5;
  61
  62         if (tv->tv_sec > MAX_SLACK / (NSEC_PER_SEC/divfactor))
  63                 return MAX_SLACK;
  64
  65         slack = tv->tv_nsec / divfactor;
  66         slack += tv->tv_sec * (NSEC_PER_SEC/divfactor);
  67
  68         if (slack > MAX_SLACK)
  69                 return MAX_SLACK;
  70
  71         return slack;
  72 }
  73
  74 u64 select_estimate_accuracy(struct timespec64 *tv)
  75 {
  76         u64 ret;
  77         struct timespec64 now;
  78
  79         /*
  80          * Realtime tasks get a slack of 0 for obvious reasons.
  81          */
  82
  83         if (rt_task(current))
  84                 return 0;
  85
  86         ktime_get_ts64(&now);
  87         now = timespec64_sub(*tv, now);
  88         ret = __estimate_accuracy(&now);
  89         if (ret < current->timer_slack_ns)
  90                 return current->timer_slack_ns;
  91         return ret;
  92 }
  93
  94
  95
  96 struct poll_table_page {
  97         struct poll_table_page * next;
  98         struct poll_table_entry * entry;
  99         struct poll_table_entry entries[0];
 100 };
 101
 102 #define POLL_TABLE_FULL(table) \
 103         ((unsigned long)((table)->entry+1) > PAGE_SIZE + (unsigned long)(table))
 104
 105 /*
 106  * Ok, Peter made a complicated, but straightforward multiple_wait() function.
 107  * I have rewritten this, taking some shortcuts: This code may not be easy to
 108  * follow, but it should be free of race-conditions, and it's practical. If you
 109  * understand what I'm doing here, then you understand how the linux
 110  * sleep/wakeup mechanism works.
 111  *
 112  * Two very simple procedures, poll_wait() and poll_freewait() make all the
 113  * work.  poll_wait() is an inline-function defined in <linux/poll.h>,
 114  * as all select/poll functions have to call it to add an entry to the
 115  * poll table.
 116  */
 117 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
 118                        poll_table *p);
 119
 120 void poll_initwait(struct poll_wqueues *pwq)
 121 {
 122         init_poll_funcptr(&pwq->pt, __pollwait);
 123         pwq->polling_task = current;
 124         pwq->triggered = 0;
 125         pwq->error = 0;
 126         pwq->table = NULL;
 127         pwq->inline_index = 0;
 128 }
 129 EXPORT_SYMBOL(poll_initwait);
 130
 131 static void free_poll_entry(struct poll_table_entry *entry)
 132 {
 133         remove_wait_queue(entry->wait_address, &entry->wait);
 134         fput(entry->filp);
 135 }
 136
 137 void poll_freewait(struct poll_wqueues *pwq)
 138 {
 139         struct poll_table_page * p = pwq->table;
 140         int i;
 141         for (i = 0; i < pwq->inline_index; i++)
 142                 free_poll_entry(pwq->inline_entries + i);
 143         while (p) {
 144                 struct poll_table_entry * entry;
 145                 struct poll_table_page *old;
 146
 147                 entry = p->entry;
 148                 do {
 149                         entry--;
 150                         free_poll_entry(entry);
 151                 } while (entry > p->entries);
 152                 old = p;
 153                 p = p->next;
 154                 free_page((unsigned long) old);
 155         }
 156 }
 157 EXPORT_SYMBOL(poll_freewait);
 158
 159 static struct poll_table_entry *poll_get_entry(struct poll_wqueues *p)
 160 {
 161         struct poll_table_page *table = p->table;
 162
 163         if (p->inline_index < N_INLINE_POLL_ENTRIES)
 164                 return p->inline_entries + p->inline_index++;
 165
 166         if (!table || POLL_TABLE_FULL(table)) {
 167                 struct poll_table_page *new_table;
 168
 169                 new_table = (struct poll_table_page *) __get_free_page(GFP_KERNEL);
 170                 if (!new_table) {
 171                         p->error = -ENOMEM;
 172                         return NULL;
 173                 }
 174                 new_table->entry = new_table->entries;
 175                 new_table->next = table;
 176                 p->table = new_table;
 177                 table = new_table;
 178         }
 179
 180         return table->entry++;
 181 }
 182
 183 static int __pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key)
 184 {
 185         struct poll_wqueues *pwq = wait->private;
 186         DECLARE_WAITQUEUE(dummy_wait, pwq->polling_task);
 187
 188         /*
 189          * Although this function is called under waitqueue lock, LOCK
 190          * doesn't imply write barrier and the users expect write
 191          * barrier semantics on wakeup functions.  The following
 192          * smp_wmb() is equivalent to smp_wmb() in try_to_wake_up()
 193          * and is paired with smp_store_mb() in poll_schedule_timeout.
 194          */
 195         smp_wmb();
 196         pwq->triggered = 1;
 197
 198         /*
 199          * Perform the default wake up operation using a dummy
 200          * waitqueue.
 201          *
 202          * TODO: This is hacky but there currently is no interface to
 203          * pass in @sync.  @sync is scheduled to be removed and once
 204          * that happens, wake_up_process() can be used directly.
 205          */
 206         return default_wake_function(&dummy_wait, mode, sync, key);
 207 }
 208
 209 static int pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key)
 210 {
 211         struct poll_table_entry *entry;
 212
 213         entry = container_of(wait, struct poll_table_entry, wait);
 214         if (key && !((unsigned long)key & entry->key))
 215                 return 0;
 216         return __pollwake(wait, mode, sync, key);
 217 }
 218
 219 /* Add a new entry */
 220 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
 221                                 poll_table *p)
 222 {
 223         struct poll_wqueues *pwq = container_of(p, struct poll_wqueues, pt);
 224         struct poll_table_entry *entry = poll_get_entry(pwq);
 225         if (!entry)
 226                 return;
 227         entry->filp = get_file(filp);
 228         entry->wait_address = wait_address;
 229         entry->key = p->_key;
 230         init_waitqueue_func_entry(&entry->wait, pollwake);
 231         entry->wait.private = pwq;
 232         add_wait_queue(wait_address, &entry->wait);
 233 }
 234
 235 int poll_schedule_timeout(struct poll_wqueues *pwq, int state,
 236                           ktime_t *expires, unsigned long slack)
 237 {
 238         int rc = -EINTR;
 239
 240         set_current_state(state);
 241         if (!pwq->triggered)
 242                 rc = schedule_hrtimeout_range(expires, slack, HRTIMER_MODE_ABS);
 243         __set_current_state(TASK_RUNNING);
 244
 245         /*
 246          * Prepare for the next iteration.
 247          *
 248          * The following smp_store_mb() serves two purposes.  First, it's
 249          * the counterpart rmb of the wmb in pollwake() such that data
 250          * written before wake up is always visible after wake up.
 251          * Second, the full barrier guarantees that triggered clearing
 252          * doesn't pass event check of the next iteration.  Note that
 253          * this problem doesn't exist for the first iteration as
 254          * add_wait_queue() has full barrier semantics.
 255          */
 256         smp_store_mb(pwq->triggered, 0);
 257
 258         return rc;
 259 }
 260 EXPORT_SYMBOL(poll_schedule_timeout);
 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 static int poll_select_copy_remaining(struct timespec64 *end_time,
 291                                       void __user *p,
 292                                       int timeval, int ret)
 293 {
 294         struct timespec64 rts64;
 295         struct timespec rts;
 296         struct timeval rtv;
 297
 298         if (!p)
 299                 return ret;
 300
 301         if (current->personality & STICKY_TIMEOUTS)
 302                 goto sticky;
 303
 304         /* No update for zero timeout */
 305         if (!end_time->tv_sec && !end_time->tv_nsec)
 306                 return ret;
 307
 308         ktime_get_ts64(&rts64);
 309         rts64 = timespec64_sub(*end_time, rts64);
 310         if (rts64.tv_sec < 0)
 311                 rts64.tv_sec = rts64.tv_nsec = 0;
 312
 313         rts = timespec64_to_timespec(rts64);
 314
 315         if (timeval) {
 316                 if (sizeof(rtv) > sizeof(rtv.tv_sec) + sizeof(rtv.tv_usec))
 317                         memset(&rtv, 0, sizeof(rtv));
 318                 rtv.tv_sec = rts64.tv_sec;
 319                 rtv.tv_usec = rts64.tv_nsec / NSEC_PER_USEC;
 320
 321                 if (!copy_to_user(p, &rtv, sizeof(rtv)))
 322                         return ret;
 323
 324         } else if (!copy_to_user(p, &rts, sizeof(rts)))
 325                 return ret;
 326
 327         /*
 328          * If an application puts its timeval in read-only memory, we
 329          * don't want the Linux-specific update to the timeval to
 330          * cause a fault after the select has completed
 331          * successfully. However, because we're not updating the
 332          * timeval, we can't restart the system call.
 333          */
 334
 335 sticky:
 336         if (ret == -ERESTARTNOHAND)
 337                 ret = -EINTR;
 338         return ret;
 339 }
 340
 341 #define FDS_IN(fds, n)          (fds->in + n)
 342 #define FDS_OUT(fds, n)         (fds->out + n)
 343 #define FDS_EX(fds, n)          (fds->ex + n)
 344
 345 #define BITS(fds, n)    (*FDS_IN(fds, n)|*FDS_OUT(fds, n)|*FDS_EX(fds, n))
 346
 347 static int max_select_fd(unsigned long n, fd_set_bits *fds)
 348 {
 349         unsigned long *open_fds;
 350         unsigned long set;
 351         int max;
 352         struct fdtable *fdt;
 353
 354         /* handle last in-complete long-word first */
 355         set = ~(~0UL << (n & (BITS_PER_LONG-1)));
 356         n /= BITS_PER_LONG;
 357         fdt = files_fdtable(current->files);
 358         open_fds = fdt->open_fds + n;
 359         max = 0;
 360         if (set) {
 361                 set &= BITS(fds, n);
 362                 if (set) {
 363                         if (!(set & ~*open_fds))
 364                                 goto get_max;
 365                         return -EBADF;
 366                 }
 367         }
 368         while (n) {
 369                 open_fds--;
 370                 n--;
 371                 set = BITS(fds, n);
 372                 if (!set)
 373                         continue;
 374                 if (set & ~*open_fds)
 375                         return -EBADF;
 376                 if (max)
 377                         continue;
 378 get_max:
 379                 do {
 380                         max++;
 381                         set >>= 1;
 382                 } while (set);
 383                 max += n * BITS_PER_LONG;
 384         }
 385
 386         return max;
 387 }
 388
 389 #define POLLIN_SET (POLLRDNORM | POLLRDBAND | POLLIN | POLLHUP | POLLERR)
 390 #define POLLOUT_SET (POLLWRBAND | POLLWRNORM | POLLOUT | POLLERR)
 391 #define POLLEX_SET (POLLPRI)
 392
 393 static inline void wait_key_set(poll_table *wait, unsigned long in,
 394                                 unsigned long out, unsigned long bit,
 395                                 unsigned int ll_flag)
 396 {
 397         wait->_key = POLLEX_SET | ll_flag;
 398         if (in & bit)
 399                 wait->_key |= POLLIN_SET;
 400         if (out & bit)
 401                 wait->_key |= POLLOUT_SET;
 402 }
 403
 404 int do_select(int n, fd_set_bits *fds, struct timespec64 *end_time)
 405 {
 406         ktime_t expire, *to = NULL;
 407         struct poll_wqueues table;
 408         poll_table *wait;
 409         int retval, i, timed_out = 0;
 410         u64 slack = 0;
 411         unsigned int busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0;
 412         unsigned long busy_end = 0;
 413
 414         rcu_read_lock();
 415         retval = max_select_fd(n, fds);
 416         rcu_read_unlock();
 417
 418         if (retval < 0)
 419                 return retval;
 420         n = retval;
 421
 422         poll_initwait(&table);
 423         wait = &table.pt;
 424         if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
 425                 wait->_qproc = NULL;
 426                 timed_out = 1;
 427         }
 428
 429         if (end_time && !timed_out)
 430                 slack = select_estimate_accuracy(end_time);
 431
 432         retval = 0;
 433         for (;;) {
 434                 unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp;
 435                 bool can_busy_loop = false;
 436
 437                 inp = fds->in; outp = fds->out; exp = fds->ex;
 438                 rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex;
 439
 440                 for (i = 0; i < n; ++rinp, ++routp, ++rexp) {
 441                         unsigned long in, out, ex, all_bits, bit = 1, mask, j;
 442                         unsigned long res_in = 0, res_out = 0, res_ex = 0;
 443
 444                         in = *inp++; out = *outp++; ex = *exp++;
 445                         all_bits = in | out | ex;
 446                         if (all_bits == 0) {
 447                                 i += BITS_PER_LONG;
 448                                 continue;
 449                         }
 450
 451                         for (j = 0; j < BITS_PER_LONG; ++j, ++i, bit <<= 1) {
 452                                 struct fd f;
 453                                 if (i >= n)
 454                                         break;
 455                                 if (!(bit & all_bits))
 456                                         continue;
 457                                 f = fdget(i);
 458                                 if (f.file) {
 459                                         const struct file_operations *f_op;
 460                                         f_op = f.file->f_op;
 461                                         mask = DEFAULT_POLLMASK;
 462                                         if (f_op->poll) {
 463                                                 wait_key_set(wait, in, out,
 464                                                              bit, busy_flag);
 465                                                 mask = (*f_op->poll)(f.file, wait);
 466                                         }
 467                                         fdput(f);
 468                                         if ((mask & POLLIN_SET) && (in & bit)) {
 469                                                 res_in |= bit;
 470                                                 retval++;
 471                                                 wait->_qproc = NULL;
 472                                         }
 473                                         if ((mask & POLLOUT_SET) && (out & bit)) {
 474                                                 res_out |= bit;
 475                                                 retval++;
 476                                                 wait->_qproc = NULL;
 477                                         }
 478                                         if ((mask & POLLEX_SET) && (ex & bit)) {
 479                                                 res_ex |= bit;
 480                                                 retval++;
 481                                                 wait->_qproc = NULL;
 482                                         }
 483                                         /* got something, stop busy polling */
 484                                         if (retval) {
 485                                                 can_busy_loop = false;
 486                                                 busy_flag = 0;
 487
 488                                         /*
 489                                          * only remember a returned
 490                                          * POLL_BUSY_LOOP if we asked for it
 491                                          */
 492                                         } else if (busy_flag & mask)
 493                                                 can_busy_loop = true;
 494
 495                                 }
 496                         }
 497                         if (res_in)
 498                                 *rinp = res_in;
 499                         if (res_out)
 500                                 *routp = res_out;
 501                         if (res_ex)
 502                                 *rexp = res_ex;
 503                         cond_resched();
 504                 }
 505                 wait->_qproc = NULL;
 506                 if (retval || timed_out || signal_pending(current))
 507                         break;
 508                 if (table.error) {
 509                         retval = table.error;
 510                         break;
 511                 }
 512
 513                 /* only if found POLL_BUSY_LOOP sockets && not out of time */
 514                 if (can_busy_loop && !need_resched()) {
 515                         if (!busy_end) {
 516                                 busy_end = busy_loop_end_time();
 517                                 continue;
 518                         }
 519                         if (!busy_loop_timeout(busy_end))
 520                                 continue;
 521                 }
 522                 busy_flag = 0;
 523
 524                 /*
 525                  * If this is the first loop and we have a timeout
 526                  * given, then we convert to ktime_t and set the to
 527                  * pointer to the expiry value.
 528                  */
 529                 if (end_time && !to) {
 530                         expire = timespec64_to_ktime(*end_time);
 531                         to = &expire;
 532                 }
 533
 534                 if (!poll_schedule_timeout(&table, TASK_INTERRUPTIBLE,
 535                                            to, slack))
 536                         timed_out = 1;
 537         }
 538
 539         poll_freewait(&table);
 540
 541         return retval;
 542 }
 543
 544 /*
 545  * We can actually return ERESTARTSYS instead of EINTR, but I'd
 546  * like to be certain this leads to no problems. So I return
 547  * EINTR just for safety.
 548  *
 549  * Update: ERESTARTSYS breaks at least the xview clock binary, so
 550  * I'm trying ERESTARTNOHAND which restart only when you want to.
 551  */
 552 int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
 553                            fd_set __user *exp, struct timespec64 *end_time)
 554 {
 555         fd_set_bits fds;
 556         void *bits;
 557         int ret, max_fds;
 558         size_t size, alloc_size;
 559         struct fdtable *fdt;
 560         /* Allocate small arguments on the stack to save memory and be faster */
 561         long stack_fds[SELECT_STACK_ALLOC/sizeof(long)];
 562
 563         ret = -EINVAL;
 564         if (n < 0)
 565                 goto out_nofds;
 566
 567         /* max_fds can increase, so grab it once to avoid race */
 568         rcu_read_lock();
 569         fdt = files_fdtable(current->files);
 570         max_fds = fdt->max_fds;
 571         rcu_read_unlock();
 572         if (n > max_fds)
 573                 n = max_fds;
 574
 575         /*
 576          * We need 6 bitmaps (in/out/ex for both incoming and outgoing),
 577          * since we used fdset we need to allocate memory in units of
 578          * long-words.
 579          */
 580         size = FDS_BYTES(n);
 581         bits = stack_fds;
 582         if (size > sizeof(stack_fds) / 6) {
 583                 /* Not enough space in on-stack array; must use kmalloc */
 584                 ret = -ENOMEM;
 585                 if (size > (SIZE_MAX / 6))
 586                         goto out_nofds;
 587
 588                 alloc_size = 6 * size;
 589                 bits = kmalloc(alloc_size, GFP_KERNEL|__GFP_NOWARN);
 590                 if (!bits && alloc_size > PAGE_SIZE)
 591                         bits = vmalloc(alloc_size);
 592
 593                 if (!bits)
 594                         goto out_nofds;
 595         }
 596         fds.in      = bits;
 597         fds.out     = bits +   size;
 598         fds.ex      = bits + 2*size;
 599         fds.res_in  = bits + 3*size;
 600         fds.res_out = bits + 4*size;
 601         fds.res_ex  = bits + 5*size;
 602
 603         if ((ret = get_fd_set(n, inp, fds.in)) ||
 604             (ret = get_fd_set(n, outp, fds.out)) ||
 605             (ret = get_fd_set(n, exp, fds.ex)))
 606                 goto out;
 607         zero_fd_set(n, fds.res_in);
 608         zero_fd_set(n, fds.res_out);
 609         zero_fd_set(n, fds.res_ex);
 610
 611         ret = do_select(n, &fds, end_time);
 612
 613         if (ret < 0)
 614                 goto out;
 615         if (!ret) {
 616                 ret = -ERESTARTNOHAND;
 617                 if (signal_pending(current))
 618                         goto out;
 619                 ret = 0;
 620         }
 621
 622         if (set_fd_set(n, inp, fds.res_in) ||
 623             set_fd_set(n, outp, fds.res_out) ||
 624             set_fd_set(n, exp, fds.res_ex))
 625                 ret = -EFAULT;
 626
 627 out:
 628         if (bits != stack_fds)
 629                 kvfree(bits);
 630 out_nofds:
 631         return ret;
 632 }
 633
 634 SYSCALL_DEFINE5(select, int, n, fd_set __user *, inp, fd_set __user *, outp,
 635                 fd_set __user *, exp, struct timeval __user *, tvp)
 636 {
 637         struct timespec64 end_time, *to = NULL;
 638         struct timeval tv;
 639         int ret;
 640
 641         if (tvp) {
 642                 if (copy_from_user(&tv, tvp, sizeof(tv)))
 643                         return -EFAULT;
 644
 645                 to = &end_time;
 646                 if (poll_select_set_timeout(to,
 647                                 tv.tv_sec + (tv.tv_usec / USEC_PER_SEC),
 648                                 (tv.tv_usec % USEC_PER_SEC) * NSEC_PER_USEC))
 649                         return -EINVAL;
 650         }
 651
 652         ret = core_sys_select(n, inp, outp, exp, to);
 653         ret = poll_select_copy_remaining(&end_time, tvp, 1, ret);
 654
 655         return ret;
 656 }
 657
 658 static long do_pselect(int n, fd_set __user *inp, fd_set __user *outp,
 659                        fd_set __user *exp, struct timespec __user *tsp,
 660                        const sigset_t __user *sigmask, size_t sigsetsize)
 661 {
 662         sigset_t ksigmask, sigsaved;
 663         struct timespec ts;
 664         struct timespec64 ts64, end_time, *to = NULL;
 665         int ret;
 666
 667         if (tsp) {
 668                 if (copy_from_user(&ts, tsp, sizeof(ts)))
 669                         return -EFAULT;
 670                 ts64 = timespec_to_timespec64(ts);
 671
 672                 to = &end_time;
 673                 if (poll_select_set_timeout(to, ts64.tv_sec, ts64.tv_nsec))
 674                         return -EINVAL;
 675         }
 676
 677         if (sigmask) {
 678                 /* XXX: Don't preclude handling different sized sigset_t's.  */
 679                 if (sigsetsize != sizeof(sigset_t))
 680                         return -EINVAL;
 681                 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
 682                         return -EFAULT;
 683
 684                 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
 685                 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
 686         }
 687
 688         ret = core_sys_select(n, inp, outp, exp, to);
 689         ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);
 690
 691         if (ret == -ERESTARTNOHAND) {
 692                 /*
 693                  * Don't restore the signal mask yet. Let do_signal() deliver
 694                  * the signal on the way back to userspace, before the signal
 695                  * mask is restored.
 696                  */
 697                 if (sigmask) {
 698                         memcpy(&current->saved_sigmask, &sigsaved,
 699                                         sizeof(sigsaved));
 700                         set_restore_sigmask();
 701                 }
 702         } else if (sigmask)
 703                 sigprocmask(SIG_SETMASK, &sigsaved, NULL);
 704
 705         return ret;
 706 }
 707
 708 /*
 709  * Most architectures can't handle 7-argument syscalls. So we provide a
 710  * 6-argument version where the sixth argument is a pointer to a structure
 711  * which has a pointer to the sigset_t itself followed by a size_t containing
 712  * the sigset size.
 713  */
 714 SYSCALL_DEFINE6(pselect6, int, n, fd_set __user *, inp, fd_set __user *, outp,
 715                 fd_set __user *, exp, struct timespec __user *, tsp,
 716                 void __user *, sig)
 717 {
 718         size_t sigsetsize = 0;
 719         sigset_t __user *up = NULL;
 720
 721         if (sig) {
 722                 if (!access_ok(VERIFY_READ, sig, sizeof(void *)+sizeof(size_t))
 723                     || __get_user(up, (sigset_t __user * __user *)sig)
 724                     || __get_user(sigsetsize,
 725                                 (size_t __user *)(sig+sizeof(void *))))
 726                         return -EFAULT;
 727         }
 728
 729         return do_pselect(n, inp, outp, exp, tsp, up, sigsetsize);
 730 }
 731
 732 #ifdef __ARCH_WANT_SYS_OLD_SELECT
 733 struct sel_arg_struct {
 734         unsigned long n;
 735         fd_set __user *inp, *outp, *exp;
 736         struct timeval __user *tvp;
 737 };
 738
 739 SYSCALL_DEFINE1(old_select, struct sel_arg_struct __user *, arg)
 740 {
 741         struct sel_arg_struct a;
 742
 743         if (copy_from_user(&a, arg, sizeof(a)))
 744                 return -EFAULT;
 745         return sys_select(a.n, a.inp, a.outp, a.exp, a.tvp);
 746 }
 747 #endif
 748
 749 struct poll_list {
 750         struct poll_list *next;
 751         int len;
 752         struct pollfd entries[0];
 753 };
 754
 755 #define POLLFD_PER_PAGE  ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd))
 756
 757 /*
 758  * Fish for pollable events on the pollfd->fd file descriptor. We're only
 759  * interested in events matching the pollfd->events mask, and the result
 760  * matching that mask is both recorded in pollfd->revents and returned. The
 761  * pwait poll_table will be used by the fd-provided poll handler for waiting,
 762  * if pwait->_qproc is non-NULL.
 763  */
 764 static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait,
 765                                      bool *can_busy_poll,
 766                                      unsigned int busy_flag)
 767 {
 768         unsigned int mask;
 769         int fd;
 770
 771         mask = 0;
 772         fd = pollfd->fd;
 773         if (fd >= 0) {
 774                 struct fd f = fdget(fd);
 775                 mask = POLLNVAL;
 776                 if (f.file) {
 777                         mask = DEFAULT_POLLMASK;
 778                         if (f.file->f_op->poll) {
 779                                 pwait->_key = pollfd->events|POLLERR|POLLHUP;
 780                                 pwait->_key |= busy_flag;
 781                                 mask = f.file->f_op->poll(f.file, pwait);
 782                                 if (mask & busy_flag)
 783                                         *can_busy_poll = true;
 784                         }
 785                         /* Mask out unneeded events. */
 786                         mask &= pollfd->events | POLLERR | POLLHUP;
 787                         fdput(f);
 788                 }
 789         }
 790         pollfd->revents = mask;
 791
 792         return mask;
 793 }
 794
 795 static int do_poll(struct poll_list *list, struct poll_wqueues *wait,
 796                    struct timespec64 *end_time)
 797 {
 798         poll_table* pt = &wait->pt;
 799         ktime_t expire, *to = NULL;
 800         int timed_out = 0, count = 0;
 801         u64 slack = 0;
 802         unsigned int busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0;
 803         unsigned long busy_end = 0;
 804
 805         /* Optimise the no-wait case */
 806         if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
 807                 pt->_qproc = NULL;
 808                 timed_out = 1;
 809         }
 810
 811         if (end_time && !timed_out)
 812                 slack = select_estimate_accuracy(end_time);
 813
 814         for (;;) {
 815                 struct poll_list *walk;
 816                 bool can_busy_loop = false;
 817
 818                 for (walk = list; walk != NULL; walk = walk->next) {
 819                         struct pollfd * pfd, * pfd_end;
 820
 821                         pfd = walk->entries;
 822                         pfd_end = pfd + walk->len;
 823                         for (; pfd != pfd_end; pfd++) {
 824                                 /*
 825                                  * Fish for events. If we found one, record it
 826                                  * and kill poll_table->_qproc, so we don't
 827                                  * needlessly register any other waiters after
 828                                  * this. They'll get immediately deregistered
 829                                  * when we break out and return.
 830                                  */
 831                                 if (do_pollfd(pfd, pt, &can_busy_loop,
 832                                               busy_flag)) {
 833                                         count++;
 834                                         pt->_qproc = NULL;
 835                                         /* found something, stop busy polling */
 836                                         busy_flag = 0;
 837                                         can_busy_loop = false;
 838                                 }
 839                         }
 840                 }
 841                 /*
 842                  * All waiters have already been registered, so don't provide
 843                  * a poll_table->_qproc to them on the next loop iteration.
 844                  */
 845                 pt->_qproc = NULL;
 846                 if (!count) {
 847                         count = wait->error;
 848                         if (signal_pending(current))
 849                                 count = -EINTR;
 850                 }
 851                 if (count || timed_out)
 852                         break;
 853
 854                 /* only if found POLL_BUSY_LOOP sockets && not out of time */
 855                 if (can_busy_loop && !need_resched()) {
 856                         if (!busy_end) {
 857                                 busy_end = busy_loop_end_time();
 858                                 continue;
 859                         }
 860                         if (!busy_loop_timeout(busy_end))
 861                                 continue;
 862                 }
 863                 busy_flag = 0;
 864
 865                 /*
 866                  * If this is the first loop and we have a timeout
 867                  * given, then we convert to ktime_t and set the to
 868                  * pointer to the expiry value.
 869                  */
 870                 if (end_time && !to) {
 871                         expire = timespec64_to_ktime(*end_time);
 872                         to = &expire;
 873                 }
 874
 875                 if (!poll_schedule_timeout(wait, TASK_INTERRUPTIBLE, to, slack))
 876                         timed_out = 1;
 877         }
 878         return count;
 879 }
 880
 881 #define N_STACK_PPS ((sizeof(stack_pps) - sizeof(struct poll_list))  / \
 882                         sizeof(struct pollfd))
 883
 884 int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds,
 885                 struct timespec64 *end_time)
 886 {
 887         struct poll_wqueues table;
 888         int err = -EFAULT, fdcount, len, size;
 889         /* Allocate small arguments on the stack to save memory and be
 890            faster - use long to make sure the buffer is aligned properly
 891            on 64 bit archs to avoid unaligned access */
 892         long stack_pps[POLL_STACK_ALLOC/sizeof(long)];
 893         struct poll_list *const head = (struct poll_list *)stack_pps;
 894         struct poll_list *walk = head;
 895         unsigned long todo = nfds;
 896
 897         if (nfds > rlimit(RLIMIT_NOFILE))
 898                 return -EINVAL;
 899
 900         len = min_t(unsigned int, nfds, N_STACK_PPS);
 901         for (;;) {
 902                 walk->next = NULL;
 903                 walk->len = len;
 904                 if (!len)
 905                         break;
 906
 907                 if (copy_from_user(walk->entries, ufds + nfds-todo,
 908                                         sizeof(struct pollfd) * walk->len))
 909                         goto out_fds;
 910
 911                 todo -= walk->len;
 912                 if (!todo)
 913                         break;
 914
 915                 len = min(todo, POLLFD_PER_PAGE);
 916                 size = sizeof(struct poll_list) + sizeof(struct pollfd) * len;
 917                 walk = walk->next = kmalloc(size, GFP_KERNEL);
 918                 if (!walk) {
 919                         err = -ENOMEM;
 920                         goto out_fds;
 921                 }
 922         }
 923
 924         poll_initwait(&table);
 925         fdcount = do_poll(head, &table, end_time);
 926         poll_freewait(&table);
 927
 928         for (walk = head; walk; walk = walk->next) {
 929                 struct pollfd *fds = walk->entries;
 930                 int j;
 931
 932                 for (j = 0; j < walk->len; j++, ufds++)
 933                         if (__put_user(fds[j].revents, &ufds->revents))
 934                                 goto out_fds;
 935         }
 936
 937         err = fdcount;
 938 out_fds:
 939         walk = head->next;
 940         while (walk) {
 941                 struct poll_list *pos = walk;
 942                 walk = walk->next;
 943                 kfree(pos);
 944         }
 945
 946         return err;
 947 }
 948
 949 static long do_restart_poll(struct restart_block *restart_block)
 950 {
 951         struct pollfd __user *ufds = restart_block->poll.ufds;
 952         int nfds = restart_block->poll.nfds;
 953         struct timespec64 *to = NULL, end_time;
 954         int ret;
 955
 956         if (restart_block->poll.has_timeout) {
 957                 end_time.tv_sec = restart_block->poll.tv_sec;
 958                 end_time.tv_nsec = restart_block->poll.tv_nsec;
 959                 to = &end_time;
 960         }
 961
 962         ret = do_sys_poll(ufds, nfds, to);
 963
 964         if (ret == -EINTR) {
 965                 restart_block->fn = do_restart_poll;
 966                 ret = -ERESTART_RESTARTBLOCK;
 967         }
 968         return ret;
 969 }
 970
 971 SYSCALL_DEFINE3(poll, struct pollfd __user *, ufds, unsigned int, nfds,
 972                 int, timeout_msecs)
 973 {
 974         struct timespec64 end_time, *to = NULL;
 975         int ret;
 976
 977         if (timeout_msecs >= 0) {
 978                 to = &end_time;
 979                 poll_select_set_timeout(to, timeout_msecs / MSEC_PER_SEC,
 980                         NSEC_PER_MSEC * (timeout_msecs % MSEC_PER_SEC));
 981         }
 982
 983         ret = do_sys_poll(ufds, nfds, to);
 984
 985         if (ret == -EINTR) {
 986                 struct restart_block *restart_block;
 987
 988                 restart_block = &current->restart_block;
 989                 restart_block->fn = do_restart_poll;
 990                 restart_block->poll.ufds = ufds;
 991                 restart_block->poll.nfds = nfds;
 992
 993                 if (timeout_msecs >= 0) {
 994                         restart_block->poll.tv_sec = end_time.tv_sec;
 995                         restart_block->poll.tv_nsec = end_time.tv_nsec;
 996                         restart_block->poll.has_timeout = 1;
 997                 } else
 998                         restart_block->poll.has_timeout = 0;
 999
1000                 ret = -ERESTART_RESTARTBLOCK;
1001         }
1002         return ret;
1003 }
1004
1005 SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds, unsigned int, nfds,
1006                 struct timespec __user *, tsp, const sigset_t __user *, sigmask,
1007                 size_t, sigsetsize)
1008 {
1009         sigset_t ksigmask, sigsaved;
1010         struct timespec ts;
1011         struct timespec64 end_time, *to = NULL;
1012         int ret;
1013
1014         if (tsp) {
1015                 if (copy_from_user(&ts, tsp, sizeof(ts)))
1016                         return -EFAULT;
1017
1018                 to = &end_time;
1019                 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
1020                         return -EINVAL;
1021         }
1022
1023         if (sigmask) {
1024                 /* XXX: Don't preclude handling different sized sigset_t's.  */
1025                 if (sigsetsize != sizeof(sigset_t))
1026                         return -EINVAL;
1027                 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
1028                         return -EFAULT;
1029
1030                 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
1031                 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
1032         }
1033
1034         ret = do_sys_poll(ufds, nfds, to);
1035
1036         /* We can restart this syscall, usually */
1037         if (ret == -EINTR) {
1038                 /*
1039                  * Don't restore the signal mask yet. Let do_signal() deliver
1040                  * the signal on the way back to userspace, before the signal
1041                  * mask is restored.
1042                  */
1043                 if (sigmask) {
1044                         memcpy(&current->saved_sigmask, &sigsaved,
1045                                         sizeof(sigsaved));
1046                         set_restore_sigmask();
1047                 }
1048                 ret = -ERESTARTNOHAND;
1049         } else if (sigmask)
1050                 sigprocmask(SIG_SETMASK, &sigsaved, NULL);
1051
1052         ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);
1053
1054         return ret;
1055 }