summaryrefslogtreecommitdiff
path: root/fs/exec.c
blob: 93ff1c4c7ebb1084a30741fb38495c57008baf67 (plain)
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
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
// SPDX-License-Identifier: GPL-2.0-only
/*
 *  linux/fs/exec.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

/*
 * #!-checking implemented by tytso.
 */
/*
 * Demand-loading implemented 01.12.91 - no need to read anything but
 * the header into memory. The inode of the executable is put into
 * "current->executable", and page faults do the actual loading. Clean.
 *
 * Once more I can proudly say that linux stood up to being changed: it
 * was less than 2 hours work to get demand-loading completely implemented.
 *
 * Demand loading changed July 1993 by Eric Youngdale.   Use mmap instead,
 * current->executable is only used by the procfs.  This allows a dispatch
 * table to check for several different types  of binary formats.  We keep
 * trying until we recognize the file or we run out of supported binary
 * formats.
 */

#include <linux/slab.h>
#include <linux/file.h>
#include <linux/fdtable.h>
#include <linux/mm.h>
#include <linux/vmacache.h>
#include <linux/stat.h>
#include <linux/fcntl.h>
#include <linux/swap.h>
#include <linux/string.h>
#include <linux/init.h>
#include <linux/sched/mm.h>
#include <linux/sched/coredump.h>
#include <linux/sched/signal.h>
#include <linux/sched/numa_balancing.h>
#include <linux/sched/task.h>
#include <linux/pagemap.h>
#include <linux/perf_event.h>
#include <linux/highmem.h>
#include <linux/spinlock.h>
#include <linux/key.h>
#include <linux/personality.h>
#include <linux/binfmts.h>
#include <linux/utsname.h>
#include <linux/pid_namespace.h>
#include <linux/module.h>
#include <linux/namei.h>
#include <linux/mount.h>
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/tsacct_kern.h>
#include <linux/cn_proc.h>
#include <linux/audit.h>
#include <linux/tracehook.h>
#include <linux/kmod.h>
#include <linux/fsnotify.h>
#include <linux/fs_struct.h>
#include <linux/oom.h>
#include <linux/compat.h>
#include <linux/vmalloc.h>

#include <linux/uaccess.h>
#include <asm/mmu_context.h>
#include <asm/tlb.h>

#include <trace/events/task.h>
#include "internal.h"

#include <trace/events/sched.h>

static int bprm_creds_from_file(struct linux_binprm *bprm);

int suid_dumpable = 0;

static LIST_HEAD(formats);
static DEFINE_RWLOCK(binfmt_lock);

void __register_binfmt(struct linux_binfmt * fmt, int insert)
{
	BUG_ON(!fmt);
	if (WARN_ON(!fmt->load_binary))
		return;
	write_lock(&binfmt_lock);
	insert ? list_add(&fmt->lh, &formats) :
		 list_add_tail(&fmt->lh, &formats);
	write_unlock(&binfmt_lock);
}

EXPORT_SYMBOL(__register_binfmt);

void unregister_binfmt(struct linux_binfmt * fmt)
{
	write_lock(&binfmt_lock);
	list_del(&fmt->lh);
	write_unlock(&binfmt_lock);
}

EXPORT_SYMBOL(unregister_binfmt);

static inline void put_binfmt(struct linux_binfmt * fmt)
{
	module_put(fmt->module);
}

bool path_noexec(const struct path *path)
{
	return (path->mnt->mnt_flags & MNT_NOEXEC) ||
	       (path->mnt->mnt_sb->s_iflags & SB_I_NOEXEC);
}

#ifdef CONFIG_USELIB
/*
 * Note that a shared library must be both readable and executable due to
 * security reasons.
 *
 * Also note that we take the address to load from from the file itself.
 */
SYSCALL_DEFINE1(uselib, const char __user *, library)
{
	struct linux_binfmt *fmt;
	struct file *file;
	struct filename *tmp = getname(library);
	int error = PTR_ERR(tmp);
	static const struct open_flags uselib_flags = {
		.open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
		.acc_mode = MAY_READ | MAY_EXEC,
		.intent = LOOKUP_OPEN,
		.lookup_flags = LOOKUP_FOLLOW,
	};

	if (IS_ERR(tmp))
		goto out;

	file = do_filp_open(AT_FDCWD, tmp, &uselib_flags);
	putname(tmp);
	error = PTR_ERR(file);
	if (IS_ERR(file))
		goto out;

	error = -EINVAL;
	if (!S_ISREG(file_inode(file)->i_mode))
		goto exit;

	error = -EACCES;
	if (path_noexec(&file->f_path))
		goto exit;

	fsnotify_open(file);

	error = -ENOEXEC;

	read_lock(&binfmt_lock);
	list_for_each_entry(fmt, &formats, lh) {
		if (!fmt->load_shlib)
			continue;
		if (!try_module_get(fmt->module))
			continue;
		read_unlock(&binfmt_lock);
		error = fmt->load_shlib(file);
		read_lock(&binfmt_lock);
		put_binfmt(fmt);
		if (error != -ENOEXEC)
			break;
	}
	read_unlock(&binfmt_lock);
exit:
	fput(file);
out:
  	return error;
}
#endif /* #ifdef CONFIG_USELIB */

#ifdef CONFIG_MMU
/*
 * The nascent bprm->mm is not visible until exec_mmap() but it can
 * use a lot of memory, account these pages in current->mm temporary
 * for oom_badness()->get_mm_rss(). Once exec succeeds or fails, we
 * change the counter back via acct_arg_size(0).
 */
static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
{
	struct mm_struct *mm = current->mm;
	long diff = (long)(pages - bprm->vma_pages);

	if (!mm || !diff)
		return;

	bprm->vma_pages = pages;
	add_mm_counter(mm, MM_ANONPAGES, diff);
}

static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
		int write)
{
	struct page *page;
	int ret;
	unsigned int gup_flags = FOLL_FORCE;

#ifdef CONFIG_STACK_GROWSUP
	if (write) {
		ret = expand_downwards(bprm->vma, pos);
		if (ret < 0)
			return NULL;
	}
#endif

	if (write)
		gup_flags |= FOLL_WRITE;

	/*
	 * We are doing an exec().  'current' is the process
	 * doing the exec and bprm->mm is the new process's mm.
	 */
	ret = get_user_pages_remote(current, bprm->mm, pos, 1, gup_flags,
			&page, NULL, NULL);
	if (ret <= 0)
		return NULL;

	if (write)
		acct_arg_size(bprm, vma_pages(bprm->vma));

	return page;
}

static void put_arg_page(struct page *page)
{
	put_page(page);
}

static void free_arg_pages(struct linux_binprm *bprm)
{
}

static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
		struct page *page)
{
	flush_cache_page(bprm->vma, pos, page_to_pfn(page));
}

static int __bprm_mm_init(struct linux_binprm *bprm)
{
	int err;
	struct vm_area_struct *vma = NULL;
	struct mm_struct *mm = bprm->mm;

	bprm->vma = vma = vm_area_alloc(mm);
	if (!vma)
		return -ENOMEM;
	vma_set_anonymous(vma);

	if (down_write_killable(&mm->mmap_sem)) {
		err = -EINTR;
		goto err_free;
	}

	/*
	 * Place the stack at the largest stack address the architecture
	 * supports. Later, we'll move this to an appropriate place. We don't
	 * use STACK_TOP because that can depend on attributes which aren't
	 * configured yet.
	 */
	BUILD_BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP);
	vma->vm_end = STACK_TOP_MAX;
	vma->vm_start = vma->vm_end - PAGE_SIZE;
	vma->vm_flags = VM_SOFTDIRTY | VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP;
	vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);

	err = insert_vm_struct(mm, vma);
	if (err)
		goto err;

	mm->stack_vm = mm->total_vm = 1;
	up_write(&mm->mmap_sem);
	bprm->p = vma->vm_end - sizeof(void *);
	return 0;
err:
	up_write(&mm->mmap_sem);
err_free:
	bprm->vma = NULL;
	vm_area_free(vma);
	return err;
}

static bool valid_arg_len(struct linux_binprm *bprm, long len)
{
	return len <= MAX_ARG_STRLEN;
}

#else

static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
{
}

static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
		int write)
{
	struct page *page;

	page = bprm->page[pos / PAGE_SIZE];
	if (!page && write) {
		page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
		if (!page)
			return NULL;
		bprm->page[pos / PAGE_SIZE] = page;
	}

	return page;
}

static void put_arg_page(struct page *page)
{
}

static void free_arg_page(struct linux_binprm *bprm, int i)
{
	if (bprm->page[i]) {
		__free_page(bprm->page[i]);
		bprm->page[i] = NULL;
	}
}

static void free_arg_pages(struct linux_binprm *bprm)
{
	int i;

	for (i = 0; i < MAX_ARG_PAGES; i++)
		free_arg_page(bprm, i);
}

static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
		struct page *page)
{
}

static int __bprm_mm_init(struct linux_binprm *bprm)
{
	bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
	return 0;
}

static bool valid_arg_len(struct linux_binprm *bprm, long len)
{
	return len <= bprm->p;
}

#endif /* CONFIG_MMU */

/*
 * Create a new mm_struct and populate it with a temporary stack
 * vm_area_struct.  We don't have enough context at this point to set the stack
 * flags, permissions, and offset, so we use temporary values.  We'll update
 * them later in setup_arg_pages().
 */
static int bprm_mm_init(struct linux_binprm *bprm)
{
	int err;
	struct mm_struct *mm = NULL;

	bprm->mm = mm = mm_alloc();
	err = -ENOMEM;
	if (!mm)
		goto err;

	/* Save current stack limit for all calculations made during exec. */
	task_lock(current->group_leader);
	bprm->rlim_stack = current->signal->rlim[RLIMIT_STACK];
	task_unlock(current->group_leader);

	err = __bprm_mm_init(bprm);
	if (err)
		goto err;

	return 0;

err:
	if (mm) {
		bprm->mm = NULL;
		mmdrop(mm);
	}

	return err;
}

struct user_arg_ptr {
#ifdef CONFIG_COMPAT
	bool is_compat;
#endif
	union {
		const char __user *const __user *native;
#ifdef CONFIG_COMPAT
		const compat_uptr_t __user *compat;
#endif
	} ptr;
};

static const char __user *get_user_arg_ptr(struct user_arg_ptr argv, int nr)
{
	const char __user *native;

#ifdef CONFIG_COMPAT
	if (unlikely(argv.is_compat)) {
		compat_uptr_t compat;

		if (get_user(compat, argv.ptr.compat + nr))
			return ERR_PTR(-EFAULT);

		return compat_ptr(compat);
	}
#endif

	if (get_user(native, argv.ptr.native + nr))
		return ERR_PTR(-EFAULT);

	return native;
}

/*
 * count() counts the number of strings in array ARGV.
 */
static int count(struct user_arg_ptr argv, int max)
{
	int i = 0;

	if (argv.ptr.native != NULL) {
		for (;;) {
			const char __user *p = get_user_arg_ptr(argv, i);

			if (!p)
				break;

			if (IS_ERR(p))
				return -EFAULT;

			if (i >= max)
				return -E2BIG;
			++i;

			if (fatal_signal_pending(current))
				return -ERESTARTNOHAND;
			cond_resched();
		}
	}
	return i;
}

static int prepare_arg_pages(struct linux_binprm *bprm,
			struct user_arg_ptr argv, struct user_arg_ptr envp)
{
	unsigned long limit, ptr_size;

	bprm->argc = count(argv, MAX_ARG_STRINGS);
	if (bprm->argc < 0)
		return bprm->argc;

	bprm->envc = count(envp, MAX_ARG_STRINGS);
	if (bprm->envc < 0)
		return bprm->envc;

	/*
	 * Limit to 1/4 of the max stack size or 3/4 of _STK_LIM
	 * (whichever is smaller) for the argv+env strings.
	 * This ensures that:
	 *  - the remaining binfmt code will not run out of stack space,
	 *  - the program will have a reasonable amount of stack left
	 *    to work from.
	 */
	limit = _STK_LIM / 4 * 3;
	limit = min(limit, bprm->rlim_stack.rlim_cur / 4);
	/*
	 * We've historically supported up to 32 pages (ARG_MAX)
	 * of argument strings even with small stacks
	 */
	limit = max_t(unsigned long, limit, ARG_MAX);
	/*
	 * We must account for the size of all the argv and envp pointers to
	 * the argv and envp strings, since they will also take up space in
	 * the stack. They aren't stored until much later when we can't
	 * signal to the parent that the child has run out of stack space.
	 * Instead, calculate it here so it's possible to fail gracefully.
	 */
	ptr_size = (bprm->argc + bprm->envc) * sizeof(void *);
	if (limit <= ptr_size)
		return -E2BIG;
	limit -= ptr_size;

	bprm->argmin = bprm->p - limit;
	return 0;
}

/*
 * 'copy_strings()' copies argument/environment strings from the old
 * processes's memory to the new process's stack.  The call to get_user_pages()
 * ensures the destination page is created and not swapped out.
 */
static int copy_strings(int argc, struct user_arg_ptr argv,
			struct linux_binprm *bprm)
{
	struct page *kmapped_page = NULL;
	char *kaddr = NULL;
	unsigned long kpos = 0;
	int ret;

	while (argc-- > 0) {
		const char __user *str;
		int len;
		unsigned long pos;

		ret = -EFAULT;
		str = get_user_arg_ptr(argv, argc);
		if (IS_ERR(str))
			goto out;

		len = strnlen_user(str, MAX_ARG_STRLEN);
		if (!len)
			goto out;

		ret = -E2BIG;
		if (!valid_arg_len(bprm, len))
			goto out;

		/* We're going to work our way backwords. */
		pos = bprm->p;
		str += len;
		bprm->p -= len;
#ifdef CONFIG_MMU
		if (bprm->p < bprm->argmin)
			goto out;
#endif

		while (len > 0) {
			int offset, bytes_to_copy;

			if (fatal_signal_pending(current)) {
				ret = -ERESTARTNOHAND;
				goto out;
			}
			cond_resched();

			offset = pos % PAGE_SIZE;
			if (offset == 0)
				offset = PAGE_SIZE;

			bytes_to_copy = offset;
			if (bytes_to_copy > len)
				bytes_to_copy = len;

			offset -= bytes_to_copy;
			pos -= bytes_to_copy;
			str -= bytes_to_copy;
			len -= bytes_to_copy;

			if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
				struct page *page;

				page = get_arg_page(bprm, pos, 1);
				if (!page) {
					ret = -E2BIG;
					goto out;
				}

				if (kmapped_page) {
					flush_kernel_dcache_page(kmapped_page);
					kunmap(kmapped_page);
					put_arg_page(kmapped_page);
				}
				kmapped_page = page;
				kaddr = kmap(kmapped_page);
				kpos = pos & PAGE_MASK;
				flush_arg_page(bprm, kpos, kmapped_page);
			}
			if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
				ret = -EFAULT;
				goto out;
			}
		}
	}
	ret = 0;
out:
	if (kmapped_page) {
		flush_kernel_dcache_page(kmapped_page);
		kunmap(kmapped_page);
		put_arg_page(kmapped_page);
	}
	return ret;
}

/*
 * Copy and argument/environment string from the kernel to the processes stack.
 */
int copy_string_kernel(const char *arg, struct linux_binprm *bprm)
{
	int len = strnlen(arg, MAX_ARG_STRLEN) + 1 /* terminating NUL */;
	unsigned long pos = bprm->p;

	if (len == 0)
		return -EFAULT;
	if (!valid_arg_len(bprm, len))
		return -E2BIG;

	/* We're going to work our way backwards. */
	arg += len;
	bprm->p -= len;
	if (IS_ENABLED(CONFIG_MMU) && bprm->p < bprm->argmin)
		return -E2BIG;

	while (len > 0) {
		unsigned int bytes_to_copy = min_t(unsigned int, len,
				min_not_zero(offset_in_page(pos), PAGE_SIZE));
		struct page *page;
		char *kaddr;

		pos -= bytes_to_copy;
		arg -= bytes_to_copy;
		len -= bytes_to_copy;

		page = get_arg_page(bprm, pos, 1);
		if (!page)
			return -E2BIG;
		kaddr = kmap_atomic(page);
		flush_arg_page(bprm, pos & PAGE_MASK, page);
		memcpy(kaddr + offset_in_page(pos), arg, bytes_to_copy);
		flush_kernel_dcache_page(page);
		kunmap_atomic(kaddr);
		put_arg_page(page);
	}

	return 0;
}
EXPORT_SYMBOL(copy_string_kernel);

#ifdef CONFIG_MMU

/*
 * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX.  Once
 * the binfmt code determines where the new stack should reside, we shift it to
 * its final location.  The process proceeds as follows:
 *
 * 1) Use shift to calculate the new vma endpoints.
 * 2) Extend vma to cover both the old and new ranges.  This ensures the
 *    arguments passed to subsequent functions are consistent.
 * 3) Move vma's page tables to the new range.
 * 4) Free up any cleared pgd range.
 * 5) Shrink the vma to cover only the new range.
 */
static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
{
	struct mm_struct *mm = vma->vm_mm;
	unsigned long old_start = vma->vm_start;
	unsigned long old_end = vma->vm_end;
	unsigned long length = old_end - old_start;
	unsigned long new_start = old_start - shift;
	unsigned long new_end = old_end - shift;
	struct mmu_gather tlb;

	BUG_ON(new_start > new_end);

	/*
	 * ensure there are no vmas between where we want to go
	 * and where we are
	 */
	if (vma != find_vma(mm, new_start))
		return -EFAULT;

	/*
	 * cover the whole range: [new_start, old_end)
	 */
	if (vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL))
		return -ENOMEM;

	/*
	 * move the page tables downwards, on failure we rely on
	 * process cleanup to remove whatever mess we made.
	 */
	if (length != move_page_tables(vma, old_start,
				       vma, new_start, length, false))
		return -ENOMEM;

	lru_add_drain();
	tlb_gather_mmu(&tlb, mm, old_start, old_end);
	if (new_end > old_start) {
		/*
		 * when the old and new regions overlap clear from new_end.
		 */
		free_pgd_range(&tlb, new_end, old_end, new_end,
			vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING);
	} else {
		/*
		 * otherwise, clean from old_start; this is done to not touch
		 * the address space in [new_end, old_start) some architectures
		 * have constraints on va-space that make this illegal (IA64) -
		 * for the others its just a little faster.
		 */
		free_pgd_range(&tlb, old_start, old_end, new_end,
			vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING);
	}
	tlb_finish_mmu(&tlb, old_start, old_end);

	/*
	 * Shrink the vma to just the new range.  Always succeeds.
	 */
	vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);

	return 0;
}

/*
 * Finalizes the stack vm_area_struct. The flags and permissions are updated,
 * the stack is optionally relocated, and some extra space is added.
 */
int setup_arg_pages(struct linux_binprm *bprm,
		    unsigned long stack_top,
		    int executable_stack)
{
	unsigned long ret;
	unsigned long stack_shift;
	struct mm_struct *mm = current->mm;
	struct vm_area_struct *vma = bprm->vma;
	struct vm_area_struct *prev = NULL;
	unsigned long vm_flags;
	unsigned long stack_base;
	unsigned long stack_size;
	unsigned long stack_expand;
	unsigned long rlim_stack;

#ifdef CONFIG_STACK_GROWSUP
	/* Limit stack size */
	stack_base = bprm->rlim_stack.rlim_max;
	if (stack_base > STACK_SIZE_MAX)
		stack_base = STACK_SIZE_MAX;

	/* Add space for stack randomization. */
	stack_base += (STACK_RND_MASK << PAGE_SHIFT);

	/* Make sure we didn't let the argument array grow too large. */
	if (vma->vm_end - vma->vm_start > stack_base)
		return -ENOMEM;

	stack_base = PAGE_ALIGN(stack_top - stack_base);

	stack_shift = vma->vm_start - stack_base;
	mm->arg_start = bprm->p - stack_shift;
	bprm->p = vma->vm_end - stack_shift;
#else
	stack_top = arch_align_stack(stack_top);
	stack_top = PAGE_ALIGN(stack_top);

	if (unlikely(stack_top < mmap_min_addr) ||
	    unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr))
		return -ENOMEM;

	stack_shift = vma->vm_end - stack_top;

	bprm->p -= stack_shift;
	mm->arg_start = bprm->p;
#endif

	if (bprm->loader)
		bprm->loader -= stack_shift;
	bprm->exec -= stack_shift;

	if (down_write_killable(&mm->mmap_sem))
		return -EINTR;

	vm_flags = VM_STACK_FLAGS;

	/*
	 * Adjust stack execute permissions; explicitly enable for
	 * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
	 * (arch default) otherwise.
	 */
	if (unlikely(executable_stack == EXSTACK_ENABLE_X))
		vm_flags |= VM_EXEC;
	else if (executable_stack == EXSTACK_DISABLE_X)
		vm_flags &= ~VM_EXEC;
	vm_flags |= mm->def_flags;
	vm_flags |= VM_STACK_INCOMPLETE_SETUP;

	ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end,
			vm_flags);
	if (ret)
		goto out_unlock;
	BUG_ON(prev != vma);

	if (unlikely(vm_flags & VM_EXEC)) {
		pr_warn_once("process '%pD4' started with executable stack\n",
			     bprm->file);
	}

	/* Move stack pages down in memory. */
	if (stack_shift) {
		ret = shift_arg_pages(vma, stack_shift);
		if (ret)
			goto out_unlock;
	}

	/* mprotect_fixup is overkill to remove the temporary stack flags */
	vma->vm_flags &= ~VM_STACK_INCOMPLETE_SETUP;

	stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */
	stack_size = vma->vm_end - vma->vm_start;
	/*
	 * Align this down to a page boundary as expand_stack
	 * will align it up.
	 */
	rlim_stack = bprm->rlim_stack.rlim_cur & PAGE_MASK;
#ifdef CONFIG_STACK_GROWSUP
	if (stack_size + stack_expand > rlim_stack)
		stack_base = vma->vm_start + rlim_stack;
	else
		stack_base = vma->vm_end + stack_expand;
#else
	if (stack_size + stack_expand > rlim_stack)
		stack_base = vma->vm_end - rlim_stack;
	else
		stack_base = vma->vm_start - stack_expand;
#endif
	current->mm->start_stack = bprm->p;
	ret = expand_stack(vma, stack_base);
	if (ret)
		ret = -EFAULT;

out_unlock:
	up_write(&mm->mmap_sem);
	return ret;
}
EXPORT_SYMBOL(setup_arg_pages);

#else

/*
 * Transfer the program arguments and environment from the holding pages
 * onto the stack. The provided stack pointer is adjusted accordingly.
 */
int transfer_args_to_stack(struct linux_binprm *bprm,
			   unsigned long *sp_location)
{
	unsigned long index, stop, sp;
	int ret = 0;

	stop = bprm->p >> PAGE_SHIFT;
	sp = *sp_location;

	for (index = MAX_ARG_PAGES - 1; index >= stop; index--) {
		unsigned int offset = index == stop ? bprm->p & ~PAGE_MASK : 0;
		char *src = kmap(bprm->page[index]) + offset;
		sp -= PAGE_SIZE - offset;
		if (copy_to_user((void *) sp, src, PAGE_SIZE - offset) != 0)
			ret = -EFAULT;
		kunmap(bprm->page[index]);
		if (ret)
			goto out;
	}

	*sp_location = sp;

out:
	return ret;
}
EXPORT_SYMBOL(transfer_args_to_stack);

#endif /* CONFIG_MMU */

static struct file *do_open_execat(int fd, struct filename *name, int flags)
{
	struct file *file;
	int err;
	struct open_flags open_exec_flags = {
		.open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
		.acc_mode = MAY_EXEC,
		.intent = LOOKUP_OPEN,
		.lookup_flags = LOOKUP_FOLLOW,
	};

	if ((flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
		return ERR_PTR(-EINVAL);
	if (flags & AT_SYMLINK_NOFOLLOW)
		open_exec_flags.lookup_flags &= ~LOOKUP_FOLLOW;
	if (flags & AT_EMPTY_PATH)
		open_exec_flags.lookup_flags |= LOOKUP_EMPTY;

	file = do_filp_open(fd, name, &open_exec_flags);
	if (IS_ERR(file))
		goto out;

	err = -EACCES;
	if (!S_ISREG(file_inode(file)->i_mode))
		goto exit;

	if (path_noexec(&file->f_path))
		goto exit;

	err = deny_write_access(file);
	if (err)
		goto exit;

	if (name->name[0] != '\0')
		fsnotify_open(file);

out:
	return file;

exit:
	fput(file);
	return ERR_PTR(err);
}

struct file *open_exec(const char *name)
{
	struct filename *filename = getname_kernel(name);
	struct file *f = ERR_CAST(filename);

	if (!IS_ERR(filename)) {
		f = do_open_execat(AT_FDCWD, filename, 0);
		putname(filename);
	}
	return f;
}
EXPORT_SYMBOL(open_exec);

int kernel_read_file(struct file *file, void **buf, loff_t *size,
		     loff_t max_size, enum kernel_read_file_id id)
{
	loff_t i_size, pos;
	ssize_t bytes = 0;
	int ret;

	if (!S_ISREG(file_inode(file)->i_mode) || max_size < 0)
		return -EINVAL;

	ret = deny_write_access(file);
	if (ret)
		return ret;

	ret = security_kernel_read_file(file, id);
	if (ret)
		goto out;

	i_size = i_size_read(file_inode(file));
	if (i_size <= 0) {
		ret = -EINVAL;
		goto out;
	}
	if (i_size > SIZE_MAX || (max_size > 0 && i_size > max_size)) {
		ret = -EFBIG;
		goto out;
	}

	if (id != READING_FIRMWARE_PREALLOC_BUFFER)
		*buf = vmalloc(i_size);
	if (!*buf) {
		ret = -ENOMEM;
		goto out;
	}

	pos = 0;
	while (pos < i_size) {
		bytes = kernel_read(file, *buf + pos, i_size - pos, &pos);
		if (bytes < 0) {
			ret = bytes;
			goto out_free;
		}

		if (bytes == 0)
			break;
	}

	if (pos != i_size) {
		ret = -EIO;
		goto out_free;
	}

	ret = security_kernel_post_read_file(file, *buf, i_size, id);
	if (!ret)
		*size = pos;

out_free:
	if (ret < 0) {
		if (id != READING_FIRMWARE_PREALLOC_BUFFER) {
			vfree(*buf);
			*buf = NULL;
		}
	}

out:
	allow_write_access(file);
	return ret;
}
EXPORT_SYMBOL_GPL(kernel_read_file);

int kernel_read_file_from_path(const char *path, void **buf, loff_t *size,
			       loff_t max_size, enum kernel_read_file_id id)
{
	struct file *file;
	int ret;

	if (!path || !*path)
		return -EINVAL;

	file = filp_open(path, O_RDONLY, 0);
	if (IS_ERR(file))
		return PTR_ERR(file);

	ret = kernel_read_file(file, buf, size, max_size, id);
	fput(file);
	return ret;
}
EXPORT_SYMBOL_GPL(kernel_read_file_from_path);

int kernel_read_file_from_path_initns(const char *path, void **buf,
				      loff_t *size, loff_t max_size,
				      enum kernel_read_file_id id)
{
	struct file *file;
	struct path root;
	int ret;

	if (!path || !*path)
		return -EINVAL;

	task_lock(&init_task);
	get_fs_root(init_task.fs, &root);
	task_unlock(&init_task);

	file = file_open_root(root.dentry, root.mnt, path, O_RDONLY, 0);
	path_put(&root);
	if (IS_ERR(file))
		return PTR_ERR(file);

	ret = kernel_read_file(file, buf, size, max_size, id);
	fput(file);
	return ret;
}
EXPORT_SYMBOL_GPL(kernel_read_file_from_path_initns);

int kernel_read_file_from_fd(int fd, void **buf, loff_t *size, loff_t max_size,
			     enum kernel_read_file_id id)
{
	struct fd f = fdget(fd);
	int ret = -EBADF;

	if (!f.file)
		goto out;

	ret = kernel_read_file(f.file, buf, size, max_size, id);
out:
	fdput(f);
	return ret;
}
EXPORT_SYMBOL_GPL(kernel_read_file_from_fd);

ssize_t read_code(struct file *file, unsigned long addr, loff_t pos, size_t len)
{
	ssize_t res = vfs_read(file, (void __user *)addr, len, &pos);
	if (res > 0)
		flush_icache_range(addr, addr + len);
	return res;
}
EXPORT_SYMBOL(read_code);

/*
 * Maps the mm_struct mm into the current task struct.
 * On success, this function returns with the mutex
 * exec_update_mutex locked.
 */
static int exec_mmap(struct mm_struct *mm)
{
	struct task_struct *tsk;
	struct mm_struct *old_mm, *active_mm;
	int ret;

	/* Notify parent that we're no longer interested in the old VM */
	tsk = current;
	old_mm = current->mm;
	exec_mm_release(tsk, old_mm);
	if (old_mm)
		sync_mm_rss(old_mm);

	ret = mutex_lock_killable(&tsk->signal->exec_update_mutex);
	if (ret)
		return ret;

	if (old_mm) {
		/*
		 * Make sure that if there is a core dump in progress
		 * for the old mm, we get out and die instead of going
		 * through with the exec.  We must hold mmap_sem around
		 * checking core_state and changing tsk->mm.
		 */
		down_read(&old_mm->mmap_sem);
		if (unlikely(old_mm->core_state)) {
			up_read(&old_mm->mmap_sem);
			mutex_unlock(&tsk->signal->exec_update_mutex);
			return -EINTR;
		}
	}

	task_lock(tsk);
	active_mm = tsk->active_mm;
	membarrier_exec_mmap(mm);
	tsk->mm = mm;
	tsk->active_mm = mm;
	activate_mm(active_mm, mm);
	tsk->mm->vmacache_seqnum = 0;
	vmacache_flush(tsk);
	task_unlock(tsk);
	if (old_mm) {
		up_read(&old_mm->mmap_sem);
		BUG_ON(active_mm != old_mm);
		setmax_mm_hiwater_rss(&tsk->signal->maxrss, old_mm);
		mm_update_next_owner(old_mm);
		mmput(old_mm);
		return 0;
	}
	mmdrop(active_mm);
	return 0;
}

static int de_thread(struct task_struct *tsk)
{
	struct signal_struct *sig = tsk->signal;
	struct sighand_struct *oldsighand = tsk->sighand;
	spinlock_t *lock = &oldsighand->siglock;

	if (thread_group_empty(tsk))
		goto no_thread_group;

	/*
	 * Kill all other threads in the thread group.
	 */
	spin_lock_irq(lock);
	if (signal_group_exit(sig)) {
		/*
		 * Another group action in progress, just
		 * return so that the signal is processed.
		 */
		spin_unlock_irq(lock);
		return -EAGAIN;
	}

	sig->group_exit_task = tsk;
	sig->notify_count = zap_other_threads(tsk);
	if (!thread_group_leader(tsk))
		sig->notify_count--;

	while (sig->notify_count) {
		__set_current_state(TASK_KILLABLE);
		spin_unlock_irq(lock);
		schedule();
		if (__fatal_signal_pending(tsk))
			goto killed;
		spin_lock_irq(lock);
	}
	spin_unlock_irq(lock);

	/*
	 * At this point all other threads have exited, all we have to
	 * do is to wait for the thread group leader to become inactive,
	 * and to assume its PID:
	 */
	if (!thread_group_leader(tsk)) {
		struct task_struct *leader = tsk->group_leader;

		for (;;) {
			cgroup_threadgroup_change_begin(tsk);
			write_lock_irq(&tasklist_lock);
			/*
			 * Do this under tasklist_lock to ensure that
			 * exit_notify() can't miss ->group_exit_task
			 */
			sig->notify_count = -1;
			if (likely(leader->exit_state))
				break;
			__set_current_state(TASK_KILLABLE);
			write_unlock_irq(&tasklist_lock);
			cgroup_threadgroup_change_end(tsk);
			schedule();
			if (__fatal_signal_pending(tsk))
				goto killed;
		}

		/*
		 * The only record we have of the real-time age of a
		 * process, regardless of execs it's done, is start_time.
		 * All the past CPU time is accumulated in signal_struct
		 * from sister threads now dead.  But in this non-leader
		 * exec, nothing survives from the original leader thread,
		 * whose birth marks the true age of this process now.
		 * When we take on its identity by switching to its PID, we
		 * also take its birthdate (always earlier than our own).
		 */
		tsk->start_time = leader->start_time;
		tsk->start_boottime = leader->start_boottime;

		BUG_ON(!same_thread_group(leader, tsk));
		/*
		 * An exec() starts a new thread group with the
		 * TGID of the previous thread group. Rehash the
		 * two threads with a switched PID, and release
		 * the former thread group leader:
		 */

		/* Become a process group leader with the old leader's pid.
		 * The old leader becomes a thread of the this thread group.
		 */
		exchange_tids(tsk, leader);
		transfer_pid(leader, tsk, PIDTYPE_TGID);
		transfer_pid(leader, tsk, PIDTYPE_PGID);
		transfer_pid(leader, tsk, PIDTYPE_SID);

		list_replace_rcu(&leader->tasks, &tsk->tasks);
		list_replace_init(&leader->sibling, &tsk->sibling);

		tsk->group_leader = tsk;
		leader->group_leader = tsk;

		tsk->exit_signal = SIGCHLD;
		leader->exit_signal = -1;

		BUG_ON(leader->exit_state != EXIT_ZOMBIE);
		leader->exit_state = EXIT_DEAD;

		/*
		 * We are going to release_task()->ptrace_unlink() silently,
		 * the tracer can sleep in do_wait(). EXIT_DEAD guarantees
		 * the tracer wont't block again waiting for this thread.
		 */
		if (unlikely(leader->ptrace))
			__wake_up_parent(leader, leader->parent);
		write_unlock_irq(&tasklist_lock);
		cgroup_threadgroup_change_end(tsk);

		release_task(leader);
	}

	sig->group_exit_task = NULL;
	sig->notify_count = 0;

no_thread_group:
	/* we have changed execution domain */
	tsk->exit_signal = SIGCHLD;

	BUG_ON(!thread_group_leader(tsk));
	return 0;

killed:
	/* protects against exit_notify() and __exit_signal() */
	read_lock(&tasklist_lock);
	sig->group_exit_task = NULL;
	sig->notify_count = 0;
	read_unlock(&tasklist_lock);
	return -EAGAIN;
}


/*
 * This function makes sure the current process has its own signal table,
 * so that flush_signal_handlers can later reset the handlers without
 * disturbing other processes.  (Other processes might share the signal
 * table via the CLONE_SIGHAND option to clone().)
 */
static int unshare_sighand(struct task_struct *me)
{
	struct sighand_struct *oldsighand = me->sighand;

	if (refcount_read(&oldsighand->count) != 1) {
		struct sighand_struct *newsighand;
		/*
		 * This ->sighand is shared with the CLONE_SIGHAND
		 * but not CLONE_THREAD task, switch to the new one.
		 */
		newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
		if (!newsighand)
			return -ENOMEM;

		refcount_set(&newsighand->count, 1);
		memcpy(newsighand->action, oldsighand->action,
		       sizeof(newsighand->action));

		write_lock_irq(&tasklist_lock);
		spin_lock(&oldsighand->siglock);
		rcu_assign_pointer(me->sighand, newsighand);
		spin_unlock(&oldsighand->siglock);
		write_unlock_irq(&tasklist_lock);

		__cleanup_sighand(oldsighand);
	}
	return 0;
}

char *__get_task_comm(char *buf, size_t buf_size, struct task_struct *tsk)
{
	task_lock(tsk);
	strncpy(buf, tsk->comm, buf_size);
	task_unlock(tsk);
	return buf;
}
EXPORT_SYMBOL_GPL(__get_task_comm);

/*
 * These functions flushes out all traces of the currently running executable
 * so that a new one can be started
 */

void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec)
{
	task_lock(tsk);
	trace_task_rename(tsk, buf);
	strlcpy(tsk->comm, buf, sizeof(tsk->comm));
	task_unlock(tsk);
	perf_event_comm(tsk, exec);
}

/*
 * Calling this is the point of no return. None of the failures will be
 * seen by userspace since either the process is already taking a fatal
 * signal (via de_thread() or coredump), or will have SEGV raised
 * (after exec_mmap()) by search_binary_handler (see below).
 */
int begin_new_exec(struct linux_binprm * bprm)
{
	struct task_struct *me = current;
	int retval;

	/* Once we are committed compute the creds */
	retval = bprm_creds_from_file(bprm);
	if (retval)
		return retval;

	/*
	 * Ensure all future errors are fatal.
	 */
	bprm->point_of_no_return = true;

	/*
	 * Make this the only thread in the thread group.
	 */
	retval = de_thread(me);
	if (retval)
		goto out;

	/*
	 * Must be called _before_ exec_mmap() as bprm->mm is
	 * not visibile until then. This also enables the update
	 * to be lockless.
	 */
	set_mm_exe_file(bprm->mm, bprm->file);

	/* If the binary is not readable then enforce mm->dumpable=0 */
	would_dump(bprm, bprm->file);
	if (bprm->have_execfd)
		would_dump(bprm, bprm->executable);

	/*
	 * Release all of the old mmap stuff
	 */
	acct_arg_size(bprm, 0);
	retval = exec_mmap(bprm->mm);
	if (retval)
		goto out;

	bprm->mm = NULL;

#ifdef CONFIG_POSIX_TIMERS
	exit_itimers(me->signal);
	flush_itimer_signals();
#endif

	/*
	 * Make the signal table private.
	 */
	retval = unshare_sighand(me);
	if (retval)
		goto out_unlock;

	set_fs(USER_DS);
	me->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD |
					PF_NOFREEZE | PF_NO_SETAFFINITY);
	flush_thread();
	me->personality &= ~bprm->per_clear;

	/*
	 * We have to apply CLOEXEC before we change whether the process is
	 * dumpable (in setup_new_exec) to avoid a race with a process in userspace
	 * trying to access the should-be-closed file descriptors of a process
	 * undergoing exec(2).
	 */
	do_close_on_exec(me->files);

	if (bprm->secureexec) {
		/* Make sure parent cannot signal privileged process. */
		me->pdeath_signal = 0;

		/*
		 * For secureexec, reset the stack limit to sane default to
		 * avoid bad behavior from the prior rlimits. This has to
		 * happen before arch_pick_mmap_layout(), which examines
		 * RLIMIT_STACK, but after the point of no return to avoid
		 * needing to clean up the change on failure.
		 */
		if (bprm->rlim_stack.rlim_cur > _STK_LIM)
			bprm->rlim_stack.rlim_cur = _STK_LIM;
	}

	me->sas_ss_sp = me->sas_ss_size = 0;

	/*
	 * Figure out dumpability. Note that this checking only of current
	 * is wrong, but userspace depends on it. This should be testing
	 * bprm->secureexec instead.
	 */
	if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP ||
	    !(uid_eq(current_euid(), current_uid()) &&
	      gid_eq(current_egid(), current_gid())))
		set_dumpable(current->mm, suid_dumpable);
	else
		set_dumpable(current->mm, SUID_DUMP_USER);

	perf_event_exec();
	__set_task_comm(me, kbasename(bprm->filename), true);

	/* An exec changes our domain. We are no longer part of the thread
	   group */
	WRITE_ONCE(me->self_exec_id, me->self_exec_id + 1);
	flush_signal_handlers(me, 0);

	/*
	 * install the new credentials for this executable
	 */
	security_bprm_committing_creds(bprm);

	commit_creds(bprm->cred);
	bprm->cred = NULL;

	/*
	 * Disable monitoring for regular users
	 * when executing setuid binaries. Must
	 * wait until new credentials are committed
	 * by commit_creds() above
	 */
	if (get_dumpable(me->mm) != SUID_DUMP_USER)
		perf_event_exit_task(me);
	/*
	 * cred_guard_mutex must be held at least to this point to prevent
	 * ptrace_attach() from altering our determination of the task's
	 * credentials; any time after this it may be unlocked.
	 */
	security_bprm_committed_creds(bprm);

	/* Pass the opened binary to the interpreter. */
	if (bprm->have_execfd) {
		retval = get_unused_fd_flags(0);
		if (retval < 0)
			goto out_unlock;
		fd_install(retval, bprm->executable);
		bprm->executable = NULL;
		bprm->execfd = retval;
	}
	return 0;

out_unlock:
	mutex_unlock(&me->signal->exec_update_mutex);
out:
	return retval;
}
EXPORT_SYMBOL(begin_new_exec);

void would_dump(struct linux_binprm *bprm, struct file *file)
{
	struct inode *inode = file_inode(file);
	if (inode_permission(inode, MAY_READ) < 0) {
		struct user_namespace *old, *user_ns;
		bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;

		/* Ensure mm->user_ns contains the executable */
		user_ns = old = bprm->mm->user_ns;
		while ((user_ns != &init_user_ns) &&
		       !privileged_wrt_inode_uidgid(user_ns, inode))
			user_ns = user_ns->parent;

		if (old != user_ns) {
			bprm->mm->user_ns = get_user_ns(user_ns);
			put_user_ns(old);
		}
	}
}
EXPORT_SYMBOL(would_dump);

void setup_new_exec(struct linux_binprm * bprm)
{
	/* Setup things that can depend upon the personality */
	struct task_struct *me = current;

	arch_pick_mmap_layout(me->mm, &bprm->rlim_stack);

	arch_setup_new_exec();

	/* Set the new mm task size. We have to do that late because it may
	 * depend on TIF_32BIT which is only updated in flush_thread() on
	 * some architectures like powerpc
	 */
	me->mm->task_size = TASK_SIZE;
	mutex_unlock(&me->signal->exec_update_mutex);
	mutex_unlock(&me->signal->cred_guard_mutex);
}
EXPORT_SYMBOL(setup_new_exec);

/* Runs immediately before start_thread() takes over. */
void finalize_exec(struct linux_binprm *bprm)
{
	/* Store any stack rlimit changes before starting thread. */
	task_lock(current->group_leader);
	current->signal->rlim[RLIMIT_STACK] = bprm->rlim_stack;
	task_unlock(current->group_leader);
}
EXPORT_SYMBOL(finalize_exec);

/*
 * Prepare credentials and lock ->cred_guard_mutex.
 * setup_new_exec() commits the new creds and drops the lock.
 * Or, if exec fails before, free_bprm() should release ->cred and
 * and unlock.
 */
static int prepare_bprm_creds(struct linux_binprm *bprm)
{
	if (mutex_lock_interruptible(&current->signal->cred_guard_mutex))
		return -ERESTARTNOINTR;

	bprm->cred = prepare_exec_creds();
	if (likely(bprm->cred))
		return 0;

	mutex_unlock(&current->signal->cred_guard_mutex);
	return -ENOMEM;
}

static void free_bprm(struct linux_binprm *bprm)
{
	free_arg_pages(bprm);
	if (bprm->cred) {
		mutex_unlock(&current->signal->cred_guard_mutex);
		abort_creds(bprm->cred);
	}
	if (bprm->file) {
		allow_write_access(bprm->file);
		fput(bprm->file);
	}
	if (bprm->executable)
		fput(bprm->executable);
	/* If a binfmt changed the interp, free it. */
	if (bprm->interp != bprm->filename)
		kfree(bprm->interp);
	kfree(bprm);
}

int bprm_change_interp(const char *interp, struct linux_binprm *bprm)
{
	/* If a binfmt changed the interp, free it first. */
	if (bprm->interp != bprm->filename)
		kfree(bprm->interp);
	bprm->interp = kstrdup(interp, GFP_KERNEL);
	if (!bprm->interp)
		return -ENOMEM;
	return 0;
}
EXPORT_SYMBOL(bprm_change_interp);

/*
 * determine how safe it is to execute the proposed program
 * - the caller must hold ->cred_guard_mutex to protect against
 *   PTRACE_ATTACH or seccomp thread-sync
 */
static void check_unsafe_exec(struct linux_binprm *bprm)
{
	struct task_struct *p = current, *t;
	unsigned n_fs;

	if (p->ptrace)
		bprm->unsafe |= LSM_UNSAFE_PTRACE;

	/*
	 * This isn't strictly necessary, but it makes it harder for LSMs to
	 * mess up.
	 */
	if (task_no_new_privs(current))
		bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS;

	t = p;
	n_fs = 1;
	spin_lock(&p->fs->lock);
	rcu_read_lock();
	while_each_thread(p, t) {
		if (t->fs == p->fs)
			n_fs++;
	}
	rcu_read_unlock();

	if (p->fs->users > n_fs)
		bprm->unsafe |= LSM_UNSAFE_SHARE;
	else
		p->fs->in_exec = 1;
	spin_unlock(&p->fs->lock);
}

static void bprm_fill_uid(struct linux_binprm *bprm, struct file *file)
{
	/* Handle suid and sgid on files */
	struct inode *inode;
	unsigned int mode;
	kuid_t uid;
	kgid_t gid;

	if (!mnt_may_suid(file->f_path.mnt))
		return;

	if (task_no_new_privs(current))
		return;

	inode = file->f_path.dentry->d_inode;
	mode = READ_ONCE(inode->i_mode);
	if (!(mode & (S_ISUID|S_ISGID)))
		return;

	/* Be careful if suid/sgid is set */
	inode_lock(inode);

	/* reload atomically mode/uid/gid now that lock held */
	mode = inode->i_mode;
	uid = inode->i_uid;
	gid = inode->i_gid;
	inode_unlock(inode);

	/* We ignore suid/sgid if there are no mappings for them in the ns */
	if (!kuid_has_mapping(bprm->cred->user_ns, uid) ||
		 !kgid_has_mapping(bprm->cred->user_ns, gid))
		return;

	if (mode & S_ISUID) {
		bprm->per_clear |= PER_CLEAR_ON_SETID;
		bprm->cred->euid = uid;
	}

	if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
		bprm->per_clear |= PER_CLEAR_ON_SETID;
		bprm->cred->egid = gid;
	}
}

/*
 * Compute brpm->cred based upon the final binary.
 */
static int bprm_creds_from_file(struct linux_binprm *bprm)
{
	/* Compute creds based on which file? */
	struct file *file = bprm->execfd_creds ? bprm->executable : bprm->file;

	bprm_fill_uid(bprm, file);
	return security_bprm_creds_from_file(bprm, file);
}

/*
 * Fill the binprm structure from the inode.
 * Read the first BINPRM_BUF_SIZE bytes
 *
 * This may be called multiple times for binary chains (scripts for example).
 */
static int prepare_binprm(struct linux_binprm *bprm)
{
	loff_t pos = 0;

	memset(bprm->buf, 0, BINPRM_BUF_SIZE);
	return kernel_read(bprm->file, bprm->buf, BINPRM_BUF_SIZE, &pos);
}

/*
 * Arguments are '\0' separated strings found at the location bprm->p
 * points to; chop off the first by relocating brpm->p to right after
 * the first '\0' encountered.
 */
int remove_arg_zero(struct linux_binprm *bprm)
{
	int ret = 0;
	unsigned long offset;
	char *kaddr;
	struct page *page;

	if (!bprm->argc)
		return 0;

	do {
		offset = bprm->p & ~PAGE_MASK;
		page = get_arg_page(bprm, bprm->p, 0);
		if (!page) {
			ret = -EFAULT;
			goto out;
		}
		kaddr = kmap_atomic(page);

		for (; offset < PAGE_SIZE && kaddr[offset];
				offset++, bprm->p++)
			;

		kunmap_atomic(kaddr);
		put_arg_page(page);
	} while (offset == PAGE_SIZE);

	bprm->p++;
	bprm->argc--;
	ret = 0;

out:
	return ret;
}
EXPORT_SYMBOL(remove_arg_zero);

#define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
/*
 * cycle the list of binary formats handler, until one recognizes the image
 */
static int search_binary_handler(struct linux_binprm *bprm)
{
	bool need_retry = IS_ENABLED(CONFIG_MODULES);
	struct linux_binfmt *fmt;
	int retval;

	retval = prepare_binprm(bprm);
	if (retval < 0)
		return retval;

	retval = security_bprm_check(bprm);
	if (retval)
		return retval;

	retval = -ENOENT;
 retry:
	read_lock(&binfmt_lock);
	list_for_each_entry(fmt, &formats, lh) {
		if (!try_module_get(fmt->module))
			continue;
		read_unlock(&binfmt_lock);

		retval = fmt->load_binary(bprm);

		read_lock(&binfmt_lock);
		put_binfmt(fmt);
		if (bprm->point_of_no_return || (retval != -ENOEXEC)) {
			read_unlock(&binfmt_lock);
			return retval;
		}
	}
	read_unlock(&binfmt_lock);

	if (need_retry) {
		if (printable(bprm->buf[0]) && printable(bprm->buf[1]) &&
		    printable(bprm->buf[2]) && printable(bprm->buf[3]))
			return retval;
		if (request_module("binfmt-%04x", *(ushort *)(bprm->buf + 2)) < 0)
			return retval;
		need_retry = false;
		goto retry;
	}

	return retval;
}

static int exec_binprm(struct linux_binprm *bprm)
{
	pid_t old_pid, old_vpid;
	int ret, depth;

	/* Need to fetch pid before load_binary changes it */
	old_pid = current->pid;
	rcu_read_lock();
	old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent));
	rcu_read_unlock();

	/* This allows 4 levels of binfmt rewrites before failing hard. */
	for (depth = 0;; depth++) {
		struct file *exec;
		if (depth > 5)
			return -ELOOP;

		ret = search_binary_handler(bprm);
		if (ret < 0)
			return ret;
		if (!bprm->interpreter)
			break;

		exec = bprm->file;
		bprm->file = bprm->interpreter;
		bprm->interpreter = NULL;

		allow_write_access(exec);
		if (unlikely(bprm->have_execfd)) {
			if (bprm->executable) {
				fput(exec);
				return -ENOEXEC;
			}
			bprm->executable = exec;
		} else
			fput(exec);
	}

	audit_bprm(bprm);
	trace_sched_process_exec(current, old_pid, bprm);
	ptrace_event(PTRACE_EVENT_EXEC, old_vpid);
	proc_exec_connector(current);
	return 0;
}

/*
 * sys_execve() executes a new program.
 */
static int __do_execve_file(int fd, struct filename *filename,
			    struct user_arg_ptr argv,
			    struct user_arg_ptr envp,
			    int flags, struct file *file)
{
	char *pathbuf = NULL;
	struct linux_binprm *bprm;
	struct files_struct *displaced;
	int retval;

	if (IS_ERR(filename))
		return PTR_ERR(filename);

	/*
	 * We move the actual failure in case of RLIMIT_NPROC excess from
	 * set*uid() to execve() because too many poorly written programs
	 * don't check setuid() return code.  Here we additionally recheck
	 * whether NPROC limit is still exceeded.
	 */
	if ((current->flags & PF_NPROC_EXCEEDED) &&
	    atomic_read(&current_user()->processes) > rlimit(RLIMIT_NPROC)) {
		retval = -EAGAIN;
		goto out_ret;
	}

	/* We're below the limit (still or again), so we don't want to make
	 * further execve() calls fail. */
	current->flags &= ~PF_NPROC_EXCEEDED;

	retval = unshare_files(&displaced);
	if (retval)
		goto out_ret;

	retval = -ENOMEM;
	bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
	if (!bprm)
		goto out_files;

	retval = prepare_bprm_creds(bprm);
	if (retval)
		goto out_free;

	check_unsafe_exec(bprm);
	current->in_execve = 1;

	if (!file)
		file = do_open_execat(fd, filename, flags);
	retval = PTR_ERR(file);
	if (IS_ERR(file))
		goto out_unmark;

	sched_exec();

	bprm->file = file;
	if (!filename) {
		bprm->filename = "none";
	} else if (fd == AT_FDCWD || filename->name[0] == '/') {
		bprm->filename = filename->name;
	} else {
		if (filename->name[0] == '\0')
			pathbuf = kasprintf(GFP_KERNEL, "/dev/fd/%d", fd);
		else
			pathbuf = kasprintf(GFP_KERNEL, "/dev/fd/%d/%s",
					    fd, filename->name);
		if (!pathbuf) {
			retval = -ENOMEM;
			goto out_unmark;
		}
		/*
		 * Record that a name derived from an O_CLOEXEC fd will be
		 * inaccessible after exec. Relies on having exclusive access to
		 * current->files (due to unshare_files above).
		 */
		if (close_on_exec(fd, rcu_dereference_raw(current->files->fdt)))
			bprm->interp_flags |= BINPRM_FLAGS_PATH_INACCESSIBLE;
		bprm->filename = pathbuf;
	}
	bprm->interp = bprm->filename;

	retval = bprm_mm_init(bprm);
	if (retval)
		goto out_unmark;

	retval = prepare_arg_pages(bprm, argv, envp);
	if (retval < 0)
		goto out;

	/* Set the unchanging part of bprm->cred */
	retval = security_bprm_creds_for_exec(bprm);
	if (retval)
		goto out;

	retval = copy_string_kernel(bprm->filename, bprm);
	if (retval < 0)
		goto out;

	bprm->exec = bprm->p;
	retval = copy_strings(bprm->envc, envp, bprm);
	if (retval < 0)
		goto out;

	retval = copy_strings(bprm->argc, argv, bprm);
	if (retval < 0)
		goto out;

	retval = exec_binprm(bprm);
	if (retval < 0)
		goto out;

	/* execve succeeded */
	current->fs->in_exec = 0;
	current->in_execve = 0;
	rseq_execve(current);
	acct_update_integrals(current);
	task_numa_free(current, false);
	free_bprm(bprm);
	kfree(pathbuf);
	if (filename)
		putname(filename);
	if (displaced)
		put_files_struct(displaced);
	return retval;

out:
	/*
	 * If past the point of no return ensure the the code never
	 * returns to the userspace process.  Use an existing fatal
	 * signal if present otherwise terminate the process with
	 * SIGSEGV.
	 */
	if (bprm->point_of_no_return && !fatal_signal_pending(current))
		force_sigsegv(SIGSEGV);
	if (bprm->mm) {
		acct_arg_size(bprm, 0);
		mmput(bprm->mm);
	}

out_unmark:
	current->fs->in_exec = 0;
	current->in_execve = 0;

out_free:
	free_bprm(bprm);
	kfree(pathbuf);

out_files:
	if (displaced)
		reset_files_struct(displaced);
out_ret:
	if (filename)
		putname(filename);
	return retval;
}

static int do_execveat_common(int fd, struct filename *filename,
			      struct user_arg_ptr argv,
			      struct user_arg_ptr envp,
			      int flags)
{
	return __do_execve_file(fd, filename, argv, envp, flags, NULL);
}

int do_execve_file(struct file *file, void *__argv, void *__envp)
{
	struct user_arg_ptr argv = { .ptr.native = __argv };
	struct user_arg_ptr envp = { .ptr.native = __envp };

	return __do_execve_file(AT_FDCWD, NULL, argv, envp, 0, file);
}

int do_execve(struct filename *filename,
	const char __user *const __user *__argv,
	const char __user *const __user *__envp)
{
	struct user_arg_ptr argv = { .ptr.native = __argv };
	struct user_arg_ptr envp = { .ptr.native = __envp };
	return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
}

int do_execveat(int fd, struct filename *filename,
		const char __user *const __user *__argv,
		const char __user *const __user *__envp,
		int flags)
{
	struct user_arg_ptr argv = { .ptr.native = __argv };
	struct user_arg_ptr envp = { .ptr.native = __envp };

	return do_execveat_common(fd, filename, argv, envp, flags);
}

#ifdef CONFIG_COMPAT
static int compat_do_execve(struct filename *filename,
	const compat_uptr_t __user *__argv,
	const compat_uptr_t __user *__envp)
{
	struct user_arg_ptr argv = {
		.is_compat = true,
		.ptr.compat = __argv,
	};
	struct user_arg_ptr envp = {
		.is_compat = true,
		.ptr.compat = __envp,
	};
	return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
}

static int compat_do_execveat(int fd, struct filename *filename,
			      const compat_uptr_t __user *__argv,
			      const compat_uptr_t __user *__envp,
			      int flags)
{
	struct user_arg_ptr argv = {
		.is_compat = true,
		.ptr.compat = __argv,
	};
	struct user_arg_ptr envp = {
		.is_compat = true,
		.ptr.compat = __envp,
	};
	return do_execveat_common(fd, filename, argv, envp, flags);
}
#endif

void set_binfmt(struct linux_binfmt *new)
{
	struct mm_struct *mm = current->mm;

	if (mm->binfmt)
		module_put(mm->binfmt->module);

	mm->binfmt = new;
	if (new)
		__module_get(new->module);
}
EXPORT_SYMBOL(set_binfmt);

/*
 * set_dumpable stores three-value SUID_DUMP_* into mm->flags.
 */
void set_dumpable(struct mm_struct *mm, int value)
{
	if (WARN_ON((unsigned)value > SUID_DUMP_ROOT))
		return;

	set_mask_bits(&mm->flags, MMF_DUMPABLE_MASK, value);
}

SYSCALL_DEFINE3(execve,
		const char __user *, filename,
		const char __user *const __user *, argv,
		const char __user *const __user *, envp)
{
	return do_execve(getname(filename), argv, envp);
}

SYSCALL_DEFINE5(execveat,
		int, fd, const char __user *, filename,
		const char __user *const __user *, argv,
		const char __user *const __user *, envp,
		int, flags)
{
	int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;

	return do_execveat(fd,
			   getname_flags(filename, lookup_flags, NULL),
			   argv, envp, flags);
}

#ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE3(execve, const char __user *, filename,
	const compat_uptr_t __user *, argv,
	const compat_uptr_t __user *, envp)
{
	return compat_do_execve(getname(filename), argv, envp);
}

COMPAT_SYSCALL_DEFINE5(execveat, int, fd,
		       const char __user *, filename,
		       const compat_uptr_t __user *, argv,
		       const compat_uptr_t __user *, envp,
		       int,  flags)
{
	int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;

	return compat_do_execveat(fd,
				  getname_flags(filename, lookup_flags, NULL),
				  argv, envp, flags);
}
#endif