File: nscd_helper.c

package info (click to toggle)
glibc 2.19-18+deb8u4
  • links: PTS, VCS
  • area: main
  • in suites: jessie, jessie-backports
  • size: 204,416 kB
  • ctags: 144,800
  • sloc: ansic: 970,361; asm: 241,207; sh: 10,069; makefile: 8,475; cpp: 3,595; perl: 2,077; pascal: 1,839; awk: 1,704; yacc: 317; sed: 73
file content (588 lines) | stat: -rw-r--r-- 15,900 bytes parent folder | download | duplicates (10)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
/* Copyright (C) 1998-2014 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <http://www.gnu.org/licenses/>.  */

#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <stdbool.h>
#include <stddef.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <stdint.h>
#include <sys/mman.h>
#include <sys/poll.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/uio.h>
#include <sys/un.h>
#include <not-cancel.h>
#include <nis/rpcsvc/nis.h>
#include <kernel-features.h>

#include "nscd-client.h"


/* Extra time we wait if the socket is still receiving data.  This
   value is in milliseconds.  Note that the other side is nscd on the
   local machine and it is already transmitting data.  So the wait
   time need not be long.  */
#define EXTRA_RECEIVE_TIME 200


static int
wait_on_socket (int sock, long int usectmo)
{
  struct pollfd fds[1];
  fds[0].fd = sock;
  fds[0].events = POLLIN | POLLERR | POLLHUP;
  int n = __poll (fds, 1, usectmo);
  if (n == -1 && __builtin_expect (errno == EINTR, 0))
    {
      /* Handle the case where the poll() call is interrupted by a
	 signal.  We cannot just use TEMP_FAILURE_RETRY since it might
	 lead to infinite loops.  */
      struct timeval now;
      (void) __gettimeofday (&now, NULL);
      long int end = now.tv_sec * 1000 + usectmo + (now.tv_usec + 500) / 1000;
      long int timeout = usectmo;
      while (1)
	{
	  n = __poll (fds, 1, timeout);
	  if (n != -1 || errno != EINTR)
	    break;

	  /* Recompute the timeout time.  */
	  (void) __gettimeofday (&now, NULL);
	  timeout = end - (now.tv_sec * 1000 + (now.tv_usec + 500) / 1000);
	}
    }

  return n;
}


ssize_t
__readall (int fd, void *buf, size_t len)
{
  size_t n = len;
  ssize_t ret;
  do
    {
    again:
      ret = TEMP_FAILURE_RETRY (__read (fd, buf, n));
      if (ret <= 0)
	{
	  if (__builtin_expect (ret < 0 && errno == EAGAIN, 0)
	      /* The socket is still receiving data.  Wait a bit more.  */
	      && wait_on_socket (fd, EXTRA_RECEIVE_TIME) > 0)
	    goto again;

	  break;
	}
      buf = (char *) buf + ret;
      n -= ret;
    }
  while (n > 0);
  return ret < 0 ? ret : len - n;
}


ssize_t
__readvall (int fd, const struct iovec *iov, int iovcnt)
{
  ssize_t ret = TEMP_FAILURE_RETRY (__readv (fd, iov, iovcnt));
  if (ret <= 0)
    {
      if (__builtin_expect (ret == 0 || errno != EAGAIN, 1))
	/* A genuine error or no data to read.  */
	return ret;

      /* The data has not all yet been received.  Do as if we have not
	 read anything yet.  */
      ret = 0;
    }

  size_t total = 0;
  for (int i = 0; i < iovcnt; ++i)
    total += iov[i].iov_len;

  if (ret < total)
    {
      struct iovec iov_buf[iovcnt];
      ssize_t r = ret;

      struct iovec *iovp = memcpy (iov_buf, iov, iovcnt * sizeof (*iov));
      do
	{
	  while (iovp->iov_len <= r)
	    {
	      r -= iovp->iov_len;
	      --iovcnt;
	      ++iovp;
	    }
	  iovp->iov_base = (char *) iovp->iov_base + r;
	  iovp->iov_len -= r;
	again:
	  r = TEMP_FAILURE_RETRY (__readv (fd, iovp, iovcnt));
	  if (r <= 0)
	    {
	      if (__builtin_expect (r < 0 && errno == EAGAIN, 0)
		  /* The socket is still receiving data.  Wait a bit more.  */
		  && wait_on_socket (fd, EXTRA_RECEIVE_TIME) > 0)
		goto again;

	      break;
	    }
	  ret += r;
	}
      while (ret < total);
      if (r < 0)
	ret = r;
    }
  return ret;
}


static int
open_socket (request_type type, const char *key, size_t keylen)
{
  int sock;

#ifdef SOCK_CLOEXEC
# ifndef __ASSUME_SOCK_CLOEXEC
  if (__have_sock_cloexec >= 0)
# endif
    {
      sock = __socket (PF_UNIX, SOCK_STREAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
# ifndef __ASSUME_SOCK_CLOEXEC
      if (__have_sock_cloexec == 0)
	__have_sock_cloexec = sock != -1 || errno != EINVAL ? 1 : -1;
# endif
    }
#endif
#ifndef __ASSUME_SOCK_CLOEXEC
# ifdef SOCK_CLOEXEC
  if (__have_sock_cloexec < 0)
# endif
    sock = __socket (PF_UNIX, SOCK_STREAM, 0);
#endif
  if (sock < 0)
    return -1;

  struct
  {
    request_header req;
    char key[keylen];
  } reqdata;
  size_t real_sizeof_reqdata = sizeof (request_header) + keylen;

#ifndef __ASSUME_SOCK_CLOEXEC
# ifdef SOCK_NONBLOCK
  if (__have_sock_cloexec < 0)
# endif
    /* Make socket non-blocking.  */
    __fcntl (sock, F_SETFL, O_RDWR | O_NONBLOCK);
#endif

  struct sockaddr_un sun;
  sun.sun_family = AF_UNIX;
  strcpy (sun.sun_path, _PATH_NSCDSOCKET);
  if (__connect (sock, (struct sockaddr *) &sun, sizeof (sun)) < 0
      && errno != EINPROGRESS)
    goto out;

  reqdata.req.version = NSCD_VERSION;
  reqdata.req.type = type;
  reqdata.req.key_len = keylen;

  memcpy (reqdata.key, key, keylen);

  bool first_try = true;
  struct timeval tvend;
  /* Fake initializing tvend.  */
  asm ("" : "=m" (tvend));
  while (1)
    {
#ifndef MSG_NOSIGNAL
# define MSG_NOSIGNAL 0
#endif
      ssize_t wres = TEMP_FAILURE_RETRY (__send (sock, &reqdata,
						 real_sizeof_reqdata,
						 MSG_NOSIGNAL));
      if (__builtin_expect (wres == (ssize_t) real_sizeof_reqdata, 1))
	/* We managed to send the request.  */
	return sock;

      if (wres != -1 || errno != EAGAIN)
	/* Something is really wrong, no chance to continue.  */
	break;

      /* The daemon is busy wait for it.  */
      int to;
      struct timeval now;
      (void) __gettimeofday (&now, NULL);
      if (first_try)
	{
	  tvend.tv_usec = now.tv_usec;
	  tvend.tv_sec = now.tv_sec + 5;
	  to = 5 * 1000;
	  first_try = false;
	}
      else
	to = ((tvend.tv_sec - now.tv_sec) * 1000
	      + (tvend.tv_usec - now.tv_usec) / 1000);

      struct pollfd fds[1];
      fds[0].fd = sock;
      fds[0].events = POLLOUT | POLLERR | POLLHUP;
      if (__poll (fds, 1, to) <= 0)
	/* The connection timed out or broke down.  */
	break;

      /* We try to write again.  */
    }

 out:
  close_not_cancel_no_status (sock);

  return -1;
}


void
__nscd_unmap (struct mapped_database *mapped)
{
  assert (mapped->counter == 0);
  __munmap ((void *) mapped->head, mapped->mapsize);
  free (mapped);
}


/* Try to get a file descriptor for the shared meory segment
   containing the database.  */
struct mapped_database *
__nscd_get_mapping (request_type type, const char *key,
		    struct mapped_database **mappedp)
{
  struct mapped_database *result = NO_MAPPING;
#ifdef SCM_RIGHTS
  const size_t keylen = strlen (key) + 1;
  int saved_errno = errno;

  int mapfd = -1;
  char resdata[keylen];

  /* Open a socket and send the request.  */
  int sock = open_socket (type, key, keylen);
  if (sock < 0)
    goto out;

  /* Room for the data sent along with the file descriptor.  We expect
     the key name back.  */
  uint64_t mapsize;
  struct iovec iov[2];
  iov[0].iov_base = resdata;
  iov[0].iov_len = keylen;
  iov[1].iov_base = &mapsize;
  iov[1].iov_len = sizeof (mapsize);

  union
  {
    struct cmsghdr hdr;
    char bytes[CMSG_SPACE (sizeof (int))];
  } buf;
  struct msghdr msg = { .msg_iov = iov, .msg_iovlen = 2,
			.msg_control = buf.bytes,
			.msg_controllen = sizeof (buf) };
  struct cmsghdr *cmsg = CMSG_FIRSTHDR (&msg);

  cmsg->cmsg_level = SOL_SOCKET;
  cmsg->cmsg_type = SCM_RIGHTS;
  cmsg->cmsg_len = CMSG_LEN (sizeof (int));

  /* This access is well-aligned since BUF is correctly aligned for an
     int and CMSG_DATA preserves this alignment.  */
  memset (CMSG_DATA (cmsg), '\xff', sizeof (int));

  msg.msg_controllen = cmsg->cmsg_len;

  if (wait_on_socket (sock, 5 * 1000) <= 0)
    goto out_close2;

# ifndef MSG_CMSG_CLOEXEC
#  define MSG_CMSG_CLOEXEC 0
# endif
  ssize_t n = TEMP_FAILURE_RETRY (__recvmsg (sock, &msg, MSG_CMSG_CLOEXEC));

  if (__builtin_expect (CMSG_FIRSTHDR (&msg) == NULL
			|| (CMSG_FIRSTHDR (&msg)->cmsg_len
			    != CMSG_LEN (sizeof (int))), 0))
    goto out_close2;

  int *ip = (void *) CMSG_DATA (cmsg);
  mapfd = *ip;

  if (__builtin_expect (n != keylen && n != keylen + sizeof (mapsize), 0))
    goto out_close;

  if (__builtin_expect (strcmp (resdata, key) != 0, 0))
    goto out_close;

  if (__builtin_expect (n == keylen, 0))
    {
      struct stat64 st;
      if (__builtin_expect (fstat64 (mapfd, &st) != 0, 0)
	  || __builtin_expect (st.st_size < sizeof (struct database_pers_head),
			       0))
	goto out_close;

      mapsize = st.st_size;
    }

  /* The file is large enough, map it now.  */
  void *mapping = __mmap (NULL, mapsize, PROT_READ, MAP_SHARED, mapfd, 0);
  if (__builtin_expect (mapping != MAP_FAILED, 1))
    {
      /* Check whether the database is correct and up-to-date.  */
      struct database_pers_head *head = mapping;

      if (__builtin_expect (head->version != DB_VERSION, 0)
	  || __builtin_expect (head->header_size != sizeof (*head), 0)
	  /* Catch some misconfiguration.  The server should catch
	     them now but some older versions did not.  */
	  || __builtin_expect (head->module == 0, 0)
	  /* This really should not happen but who knows, maybe the update
	     thread got stuck.  */
	  || __builtin_expect (! head->nscd_certainly_running
			       && (head->timestamp + MAPPING_TIMEOUT
				   < time (NULL)), 0))
	{
	out_unmap:
	  __munmap (mapping, mapsize);
	  goto out_close;
	}

      size_t size = (sizeof (*head) + roundup (head->module * sizeof (ref_t),
					       ALIGN)
		     + head->data_size);

      if (__builtin_expect (mapsize < size, 0))
	goto out_unmap;

      /* Allocate a record for the mapping.  */
      struct mapped_database *newp = malloc (sizeof (*newp));
      if (newp == NULL)
	/* Ugh, after all we went through the memory allocation failed.  */
	goto out_unmap;

      newp->head = mapping;
      newp->data = ((char *) mapping + head->header_size
		    + roundup (head->module * sizeof (ref_t), ALIGN));
      newp->mapsize = size;
      newp->datasize = head->data_size;
      /* Set counter to 1 to show it is usable.  */
      newp->counter = 1;

      result = newp;
    }

 out_close:
  __close (mapfd);
 out_close2:
  __close (sock);
 out:
  __set_errno (saved_errno);
#endif	/* SCM_RIGHTS */

  struct mapped_database *oldval = *mappedp;
  *mappedp = result;

  if (oldval != NULL && atomic_decrement_val (&oldval->counter) == 0)
    __nscd_unmap (oldval);

  return result;
}

struct mapped_database *
__nscd_get_map_ref (request_type type, const char *name,
		    volatile struct locked_map_ptr *mapptr, int *gc_cyclep)
{
  struct mapped_database *cur = mapptr->mapped;
  if (cur == NO_MAPPING)
    return cur;

  if (!__nscd_acquire_maplock (mapptr))
    return NO_MAPPING;

  cur = mapptr->mapped;

  if (__builtin_expect (cur != NO_MAPPING, 1))
    {
      /* If not mapped or timestamp not updated, request new map.  */
      if (cur == NULL
	  || (cur->head->nscd_certainly_running == 0
	      && cur->head->timestamp + MAPPING_TIMEOUT < time (NULL))
	  || cur->head->data_size > cur->datasize)
	cur = __nscd_get_mapping (type, name,
				  (struct mapped_database **) &mapptr->mapped);

      if (__builtin_expect (cur != NO_MAPPING, 1))
	{
	  if (__builtin_expect (((*gc_cyclep = cur->head->gc_cycle) & 1) != 0,
				0))
	    cur = NO_MAPPING;
	  else
	    atomic_increment (&cur->counter);
	}
    }

  mapptr->lock = 0;

  return cur;
}


/* Using sizeof (hashentry) is not always correct to determine the size of
   the data structure as found in the nscd cache.  The program could be
   a 64-bit process and nscd could be a 32-bit process.  In this case
   sizeof (hashentry) would overestimate the size.  The following is
   the minimum size of such an entry, good enough for our tests here.  */
#define MINIMUM_HASHENTRY_SIZE \
  (offsetof (struct hashentry, dellist) + sizeof (int32_t))


/* Don't return const struct datahead *, as eventhough the record
   is normally constant, it can change arbitrarily during nscd
   garbage collection.  */
struct datahead *
__nscd_cache_search (request_type type, const char *key, size_t keylen,
		     const struct mapped_database *mapped, size_t datalen)
{
  unsigned long int hash = __nis_hash (key, keylen) % mapped->head->module;
  size_t datasize = mapped->datasize;

  ref_t trail = mapped->head->array[hash];
  trail = atomic_forced_read (trail);
  ref_t work = trail;
  size_t loop_cnt = datasize / (MINIMUM_HASHENTRY_SIZE
				+ offsetof (struct datahead, data) / 2);
  int tick = 0;

  while (work != ENDREF && work + MINIMUM_HASHENTRY_SIZE <= datasize)
    {
      struct hashentry *here = (struct hashentry *) (mapped->data + work);
      ref_t here_key, here_packet;

#ifndef _STRING_ARCH_unaligned
      /* Although during garbage collection when moving struct hashentry
	 records around we first copy from old to new location and then
	 adjust pointer from previous hashentry to it, there is no barrier
	 between those memory writes.  It is very unlikely to hit it,
	 so check alignment only if a misaligned load can crash the
	 application.  */
      if ((uintptr_t) here & (__alignof__ (*here) - 1))
	return NULL;
#endif

      if (type == here->type
	  && keylen == here->len
	  && (here_key = atomic_forced_read (here->key)) + keylen <= datasize
	  && memcmp (key, mapped->data + here_key, keylen) == 0
	  && ((here_packet = atomic_forced_read (here->packet))
	      + sizeof (struct datahead) <= datasize))
	{
	  /* We found the entry.  Increment the appropriate counter.  */
	  struct datahead *dh
	    = (struct datahead *) (mapped->data + here_packet);

#ifndef _STRING_ARCH_unaligned
	  if ((uintptr_t) dh & (__alignof__ (*dh) - 1))
	    return NULL;
#endif

	  /* See whether we must ignore the entry or whether something
	     is wrong because garbage collection is in progress.  */
	  if (dh->usable
	      && here_packet + dh->allocsize <= datasize
	      && (here_packet + offsetof (struct datahead, data) + datalen
		  <= datasize))
	    return dh;
	}

      work = atomic_forced_read (here->next);
      /* Prevent endless loops.  This should never happen but perhaps
	 the database got corrupted, accidentally or deliberately.  */
      if (work == trail || loop_cnt-- == 0)
	break;
      if (tick)
	{
	  struct hashentry *trailelem;
	  trailelem = (struct hashentry *) (mapped->data + trail);

#ifndef _STRING_ARCH_unaligned
	  /* We have to redo the checks.  Maybe the data changed.  */
	  if ((uintptr_t) trailelem & (__alignof__ (*trailelem) - 1))
	    return NULL;
#endif

	  if (trail + MINIMUM_HASHENTRY_SIZE > datasize)
	    return NULL;

	  trail = atomic_forced_read (trailelem->next);
	}
      tick = 1 - tick;
    }

  return NULL;
}


/* Create a socket connected to a name. */
int
__nscd_open_socket (const char *key, size_t keylen, request_type type,
		    void *response, size_t responselen)
{
  /* This should never happen and it is something the nscd daemon
     enforces, too.  He it helps to limit the amount of stack
     used.  */
  if (keylen > MAXKEYLEN)
    return -1;

  int saved_errno = errno;

  int sock = open_socket (type, key, keylen);
  if (sock >= 0)
    {
      /* Wait for data.  */
      if (wait_on_socket (sock, 5 * 1000) > 0)
	{
	  ssize_t nbytes = TEMP_FAILURE_RETRY (__read (sock, response,
						       responselen));
	  if (nbytes == (ssize_t) responselen)
	    return sock;
	}

      close_not_cancel_no_status (sock);
    }

  __set_errno (saved_errno);

  return -1;
}