1 /*
2 * Copyright (c) 1995, 2018, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 #undef _LARGEFILE64_SOURCE
27 #define _LARGEFILE64_SOURCE 1
28
29 #include "jni.h"
30 #include "jvm.h"
31 #include "jvm_md.h"
32 #include "jni_util.h"
33 #include "io_util.h"
34
35 /*
36 * Platform-specific support for java.lang.Process
37 */
38 #include <assert.h>
39 #include <stddef.h>
40 #include <stdlib.h>
41 #include <sys/types.h>
42 #include <ctype.h>
43 #include <sys/wait.h>
44 #include <signal.h>
45 #include <string.h>
46
47 #include <spawn.h>
48
49 #include "childproc.h"
50
51 /*
52 *
53 * When starting a child on Unix, we need to do three things:
54 * - fork off
55 * - in the child process, do some pre-exec work: duping/closing file
56 * descriptors to set up stdio-redirection, setting environment variables,
57 * changing paths...
58 * - then exec(2) the target binary
59 *
60 * There are three ways to fork off:
61 *
62 * A) fork(2). Portable and safe (no side effects) but may fail with ENOMEM on
63 * all Unices when invoked from a VM with a high memory footprint. On Unices
64 * with strict no-overcommit policy this problem is most visible.
65 *
66 * This is because forking the VM will first create a child process with
67 * theoretically the same memory footprint as the parent - even if you plan
68 * to follow up with exec'ing a tiny binary. In reality techniques like
69 * copy-on-write etc mitigate the problem somewhat but we still run the risk
70 * of hitting system limits.
71 *
72 * For a Linux centric description of this problem, see the documentation on
73 * /proc/sys/vm/overcommit_memory in Linux proc(5).
74 *
75 * B) vfork(2): Portable and fast but very unsafe. It bypasses the memory
76 * problems related to fork(2) by starting the child in the memory image of
77 * the parent. Things that can go wrong include:
78 * - Programming errors in the child process before the exec(2) call may
79 * trash memory in the parent process, most commonly the stack of the
80 * thread invoking vfork.
81 * - Signals received by the child before the exec(2) call may be at best
82 * misdirected to the parent, at worst immediately kill child and parent.
83 *
84 * This is mitigated by very strict rules about what one is allowed to do in
85 * the child process between vfork(2) and exec(2), which is basically nothing.
86 * However, we always broke this rule by doing the pre-exec work between
87 * vfork(2) and exec(2).
88 *
89 * Also note that vfork(2) has been deprecated by the OpenGroup, presumably
90 * because of its many dangers.
91 *
92 * C) clone(2): This is a Linux specific call which gives the caller fine
93 * grained control about how exactly the process fork is executed. It is
94 * powerful, but Linux-specific.
95 *
96 * Aside from these three possibilities there is a forth option: posix_spawn(3).
97 * Where fork/vfork/clone all fork off the process and leave pre-exec work and
98 * calling exec(2) to the user, posix_spawn(3) offers the user fork+exec-like
99 * functionality in one package, similar to CreateProcess() on Windows.
100 *
101 * It is not a system call in itself, but usually a wrapper implemented within
102 * the libc in terms of one of (fork|vfork|clone)+exec - so whether or not it
103 * has advantages over calling the naked (fork|vfork|clone) functions depends
104 * on how posix_spawn(3) is implemented.
105 *
106 * Note that when using posix_spawn(3), we exec twice: first a tiny binary called
107 * the jspawnhelper, then in the jspawnhelper we do the pre-exec work and exec a
108 * second time, this time the target binary (similar to the "exec-twice-technique"
109 * described in http://mail.openjdk.java.net/pipermail/core-libs-dev/2018-September/055333.html).
110 *
111 * This is a JDK-specific implementation detail which just happens to be
112 * implemented for jdk.lang.Process.launchMechanism=POSIX_SPAWN.
113 *
114 * --- Linux-specific ---
115 *
116 * How does glibc implement posix_spawn?
117 * (see: sysdeps/posix/spawni.c for glibc < 2.24,
118 * sysdeps/unix/sysv/linux/spawni.c for glibc >= 2.24):
119 *
120 * 1) Before glibc 2.4 (released 2006), posix_spawn(3) used just fork(2)/exec(2).
121 * This would be bad for the JDK since we would risk the known memory issues with
122 * fork(2). But since this only affects glibc variants which have long been
123 * phased out by modern distributions, this is irrelevant.
124 *
125 * 2) Between glibc 2.4 and glibc 2.23, posix_spawn uses either fork(2) or
126 * vfork(2) depending on how exactly the user called posix_spawn(3):
127 *
128 * <quote>
129 * The child process is created using vfork(2) instead of fork(2) when
130 * either of the following is true:
131 *
132 * * the spawn-flags element of the attributes object pointed to by
133 * attrp contains the GNU-specific flag POSIX_SPAWN_USEVFORK; or
134 *
135 * * file_actions is NULL and the spawn-flags element of the attributes
136 * object pointed to by attrp does not contain
137 * POSIX_SPAWN_SETSIGMASK, POSIX_SPAWN_SETSIGDEF,
138 * POSIX_SPAWN_SETSCHEDPARAM, POSIX_SPAWN_SETSCHEDULER,
139 * POSIX_SPAWN_SETPGROUP, or POSIX_SPAWN_RESETIDS.
140 * </quote>
141 *
142 * Due to the way the JDK calls posix_spawn(3), it would therefore call vfork(2).
143 * So we would avoid the fork(2) memory problems. However, there still remains the
144 * risk associated with vfork(2). But it is smaller than were we to call vfork(2)
145 * directly since we use the jspawnhelper, moving all pre-exec work off to after
146 * the first exec, thereby reducing the vulnerable time window.
147 *
148 * 3) Since glibc >= 2.24, glibc uses clone+exec:
149 *
150 * new_pid = CLONE (__spawni_child, STACK (stack, stack_size), stack_size,
151 * CLONE_VM | CLONE_VFORK | SIGCHLD, &args);
152 *
153 * This is even better than (2):
154 *
155 * CLONE_VM means we run in the parent's memory image, as with (2)
156 * CLONE_VFORK means parent waits until we exec, as with (2)
157 *
158 * However, error possibilities are further reduced since:
159 * - posix_spawn(3) passes a separate stack for the child to run on, eliminating
160 * the danger of trashing the forking thread's stack in the parent process.
161 * - posix_spawn(3) takes care to temporarily block all incoming signals to the
162 * child process until the first exec(2) has been called,
163 *
164 * TL;DR
165 * Calling posix_spawn(3) for glibc
166 * (2) < 2.24 is not perfect but still better than using plain vfork(2), since
167 * the chance of an error happening is greatly reduced
168 * (3) >= 2.24 is the best option - portable, fast and as safe as possible.
169 *
170 * ---
171 *
172 * How does muslc implement posix_spawn?
173 *
174 * They always did use the clone (.. CLONE_VM | CLONE_VFORK ...)
175 * technique. So we are safe to use posix_spawn() here regardless of muslc
176 * version.
177 *
178 * </Linux-specific>
179 *
180 *
181 * Based on the above analysis, we are currently defaulting to posix_spawn()
182 * on all Unices including Linux.
183 */
184
185 static void
186 setSIGCHLDHandler(JNIEnv *env)
187 {
188 /* There is a subtle difference between having the signal handler
189 * for SIGCHLD be SIG_DFL and SIG_IGN. We cannot obtain process
190 * termination information for child processes if the signal
191 * handler is SIG_IGN. It must be SIG_DFL.
192 *
193 * We used to set the SIGCHLD handler only on Linux, but it's
194 * safest to set it unconditionally.
195 *
196 * Consider what happens if java's parent process sets the SIGCHLD
197 * handler to SIG_IGN. Normally signal handlers are inherited by
198 * children, but SIGCHLD is a controversial case. Solaris appears
199 * to always reset it to SIG_DFL, but this behavior may be
200 * non-standard-compliant, and we shouldn't rely on it.
201 *
202 * References:
203 * http://www.opengroup.org/onlinepubs/7908799/xsh/exec.html
204 * http://www.pasc.org/interps/unofficial/db/p1003.1/pasc-1003.1-132.html
205 */
206 struct sigaction sa;
207 sa.sa_handler = SIG_DFL;
208 sigemptyset(&sa.sa_mask);
209 sa.sa_flags = SA_NOCLDSTOP | SA_RESTART;
210 if (sigaction(SIGCHLD, &sa, NULL) < 0)
211 JNU_ThrowInternalError(env, "Can't set SIGCHLD handler");
212 }
213
214 static void*
215 xmalloc(JNIEnv *env, size_t size)
216 {
217 void *p = malloc(size);
218 if (p == NULL)
219 JNU_ThrowOutOfMemoryError(env, NULL);
220 return p;
221 }
222
223 #define NEW(type, n) ((type *) xmalloc(env, (n) * sizeof(type)))
224
225 /**
226 * If PATH is not defined, the OS provides some default value.
227 * Unfortunately, there's no portable way to get this value.
228 * Fortunately, it's only needed if the child has PATH while we do not.
229 */
230 static const char*
231 defaultPath(void)
232 {
233 return ":/bin:/usr/bin";
234 }
235
236 static const char*
237 effectivePath(void)
238 {
239 const char *s = getenv("PATH");
240 return (s != NULL) ? s : defaultPath();
241 }
242
243 static int
244 countOccurrences(const char *s, char c)
245 {
246 int count;
247 for (count = 0; *s != '\0'; s++)
248 count += (*s == c);
249 return count;
250 }
251
252 static const char * const *
253 effectivePathv(JNIEnv *env)
254 {
255 char *p;
256 int i;
257 const char *path = effectivePath();
258 int count = countOccurrences(path, ':') + 1;
259 size_t pathvsize = sizeof(const char *) * (count+1);
260 size_t pathsize = strlen(path) + 1;
261 const char **pathv = (const char **) xmalloc(env, pathvsize + pathsize);
262
263 if (pathv == NULL)
264 return NULL;
265 p = (char *) pathv + pathvsize;
266 memcpy(p, path, pathsize);
267 /* split PATH by replacing ':' with NULs; empty components => "." */
268 for (i = 0; i < count; i++) {
269 char *q = p + strcspn(p, ":");
270 pathv[i] = (p == q) ? "." : p;
271 *q = '\0';
272 p = q + 1;
273 }
274 pathv[count] = NULL;
275 return pathv;
276 }
277
278 JNIEXPORT void JNICALL
279 Java_java_lang_ProcessImpl_init(JNIEnv *env, jclass clazz)
280 {
281 parentPathv = effectivePathv(env);
282 CHECK_NULL(parentPathv);
283 setSIGCHLDHandler(env);
284 }
285
286
287 #ifndef WIFEXITED
288 #define WIFEXITED(status) (((status)&0xFF) == 0)
289 #endif
290
291 #ifndef WEXITSTATUS
292 #define WEXITSTATUS(status) (((status)>>8)&0xFF)
293 #endif
294
295 #ifndef WIFSIGNALED
296 #define WIFSIGNALED(status) (((status)&0xFF) > 0 && ((status)&0xFF00) == 0)
297 #endif
298
299 #ifndef WTERMSIG
300 #define WTERMSIG(status) ((status)&0x7F)
301 #endif
302
303 static const char *
304 getBytes(JNIEnv *env, jbyteArray arr)
305 {
306 return arr == NULL ? NULL :
307 (const char*) (*env)->GetByteArrayElements(env, arr, NULL);
308 }
309
310 static void
311 releaseBytes(JNIEnv *env, jbyteArray arr, const char* parr)
312 {
313 if (parr != NULL)
314 (*env)->ReleaseByteArrayElements(env, arr, (jbyte*) parr, JNI_ABORT);
315 }
316
317 #define IOE_FORMAT "error=%d, %s"
318
319 static void
320 throwIOException(JNIEnv *env, int errnum, const char *defaultDetail)
321 {
322 const char *detail = defaultDetail;
323 char *errmsg;
324 size_t fmtsize;
325 char tmpbuf[1024];
326 jstring s;
327
328 if (errnum != 0) {
329 int ret = getErrorString(errnum, tmpbuf, sizeof(tmpbuf));
330 if (ret != EINVAL)
331 detail = tmpbuf;
332 }
333 /* ASCII Decimal representation uses 2.4 times as many bits as binary. */
334 fmtsize = sizeof(IOE_FORMAT) + strlen(detail) + 3 * sizeof(errnum);
335 errmsg = NEW(char, fmtsize);
336 if (errmsg == NULL)
337 return;
338
339 snprintf(errmsg, fmtsize, IOE_FORMAT, errnum, detail);
340 s = JNU_NewStringPlatform(env, errmsg);
341 if (s != NULL) {
342 jobject x = JNU_NewObjectByName(env, "java/io/IOException",
343 "(Ljava/lang/String;)V", s);
344 if (x != NULL)
345 (*env)->Throw(env, x);
346 }
347 free(errmsg);
348 }
349
350 /**
351 * Throws an IOException with a message composed from the result of waitpid status.
352 */
353 static void throwExitCause(JNIEnv *env, int pid, int status) {
354 char ebuf[128];
355 if (WIFEXITED(status)) {
356 snprintf(ebuf, sizeof ebuf,
357 "Failed to exec spawn helper: pid: %d, exit value: %d",
358 pid, WEXITSTATUS(status));
359 } else if (WIFSIGNALED(status)) {
360 snprintf(ebuf, sizeof ebuf,
361 "Failed to exec spawn helper: pid: %d, signal: %d",
362 pid, WTERMSIG(status));
363 } else {
364 snprintf(ebuf, sizeof ebuf,
365 "Failed to exec spawn helper: pid: %d, status: 0x%08x",
366 pid, status);
367 }
368 throwIOException(env, 0, ebuf);
369 }
370
371 #ifdef DEBUG_PROCESS
372 /* Debugging process code is difficult; where to write debug output? */
373 static void
374 debugPrint(char *format, ...)
375 {
376 FILE *tty = fopen("/dev/tty", "w");
377 va_list ap;
378 va_start(ap, format);
379 vfprintf(tty, format, ap);
380 va_end(ap);
381 fclose(tty);
382 }
383 #endif /* DEBUG_PROCESS */
384
385 static void
386 copyPipe(int from[2], int to[2])
387 {
388 to[0] = from[0];
389 to[1] = from[1];
390 }
391
392 /* arg is an array of pointers to 0 terminated strings. array is terminated
393 * by a null element.
394 *
395 * *nelems and *nbytes receive the number of elements of array (incl 0)
396 * and total number of bytes (incl. 0)
397 * Note. An empty array will have one null element
398 * But if arg is null, then *nelems set to 0, and *nbytes to 0
399 */
400 static void arraysize(const char * const *arg, int *nelems, int *nbytes)
401 {
402 int i, bytes, count;
403 const char * const *a = arg;
404 char *p;
405 int *q;
406 if (arg == 0) {
407 *nelems = 0;
408 *nbytes = 0;
409 return;
410 }
411 /* count the array elements and number of bytes */
412 for (count=0, bytes=0; *a != 0; count++, a++) {
413 bytes += strlen(*a)+1;
414 }
415 *nbytes = bytes;
416 *nelems = count+1;
417 }
418
419 /* copy the strings from arg[] into buf, starting at given offset
420 * return new offset to next free byte
421 */
422 static int copystrings(char *buf, int offset, const char * const *arg) {
423 char *p;
424 const char * const *a;
425 int count=0;
426
427 if (arg == 0) {
428 return offset;
429 }
430 for (p=buf+offset, a=arg; *a != 0; a++) {
431 int len = strlen(*a) +1;
432 memcpy(p, *a, len);
433 p += len;
434 count += len;
435 }
436 return offset+count;
437 }
438
439 /**
440 * We are unusually paranoid; use of vfork is
441 * especially likely to tickle gcc/glibc bugs.
442 */
443 #ifdef __attribute_noinline__ /* See: sys/cdefs.h */
444 __attribute_noinline__
445 #endif
446
447 /* vfork(2) is deprecated on Solaris */
448 static pid_t
449 vforkChild(ChildStuff *c) {
450 volatile pid_t resultPid;
451
452 /*
453 * We separate the call to vfork into a separate function to make
454 * very sure to keep stack of child from corrupting stack of parent,
455 * as suggested by the scary gcc warning:
456 * warning: variable 'foo' might be clobbered by 'longjmp' or 'vfork'
457 */
458 resultPid = vfork();
459
460 if (resultPid == 0) {
461 childProcess(c);
462 }
463 assert(resultPid != 0); /* childProcess never returns */
464 return resultPid;
465 }
466
467 static pid_t
468 forkChild(ChildStuff *c) {
469 pid_t resultPid;
470
471 /*
472 * From Solaris fork(2): In Solaris 10, a call to fork() is
473 * identical to a call to fork1(); only the calling thread is
474 * replicated in the child process. This is the POSIX-specified
475 * behavior for fork().
476 */
477 resultPid = fork();
478
479 if (resultPid == 0) {
480 childProcess(c);
481 }
482 assert(resultPid != 0); /* childProcess never returns */
483 return resultPid;
484 }
485
486 static pid_t
487 spawnChild(JNIEnv *env, jobject process, ChildStuff *c, const char *helperpath) {
488 pid_t resultPid;
489 jboolean isCopy;
490 int i, offset, rval, bufsize, magic;
491 char *buf, buf1[16];
492 char *hlpargs[2];
493 SpawnInfo sp;
494
495 /* need to tell helper which fd is for receiving the childstuff
496 * and which fd to send response back on
497 */
498 snprintf(buf1, sizeof(buf1), "%d:%d", c->childenv[0], c->fail[1]);
499 /* put the fd string as argument to the helper cmd */
500 hlpargs[0] = buf1;
501 hlpargs[1] = 0;
502
503 /* Following items are sent down the pipe to the helper
504 * after it is spawned.
505 * All strings are null terminated. All arrays of strings
506 * have an empty string for termination.
507 * - the ChildStuff struct
508 * - the SpawnInfo struct
509 * - the argv strings array
510 * - the envv strings array
511 * - the home directory string
512 * - the parentPath string
513 * - the parentPathv array
514 */
515 /* First calculate the sizes */
516 arraysize(c->argv, &sp.nargv, &sp.argvBytes);
517 bufsize = sp.argvBytes;
518 arraysize(c->envv, &sp.nenvv, &sp.envvBytes);
519 bufsize += sp.envvBytes;
520 sp.dirlen = c->pdir == 0 ? 0 : strlen(c->pdir)+1;
521 bufsize += sp.dirlen;
522 arraysize(parentPathv, &sp.nparentPathv, &sp.parentPathvBytes);
523 bufsize += sp.parentPathvBytes;
524 /* We need to clear FD_CLOEXEC if set in the fds[].
525 * Files are created FD_CLOEXEC in Java.
526 * Otherwise, they will be closed when the target gets exec'd */
527 for (i=0; i<3; i++) {
528 if (c->fds[i] != -1) {
529 int flags = fcntl(c->fds[i], F_GETFD);
530 if (flags & FD_CLOEXEC) {
531 fcntl(c->fds[i], F_SETFD, flags & (~1));
532 }
533 }
534 }
535
536 rval = posix_spawn(&resultPid, helperpath, 0, 0, (char * const *) hlpargs, environ);
537
538 if (rval != 0) {
539 return -1;
540 }
541
542 /* now the lengths are known, copy the data */
543 buf = NEW(char, bufsize);
544 if (buf == 0) {
545 return -1;
546 }
547 offset = copystrings(buf, 0, &c->argv[0]);
548 offset = copystrings(buf, offset, &c->envv[0]);
549 memcpy(buf+offset, c->pdir, sp.dirlen);
550 offset += sp.dirlen;
551 offset = copystrings(buf, offset, parentPathv);
552 assert(offset == bufsize);
553
554 magic = magicNumber();
555
556 /* write the two structs and the data buffer */
557 write(c->childenv[1], (char *)&magic, sizeof(magic)); // magic number first
558 write(c->childenv[1], (char *)c, sizeof(*c));
559 write(c->childenv[1], (char *)&sp, sizeof(sp));
560 write(c->childenv[1], buf, bufsize);
561 free(buf);
562
563 /* In this mode an external main() in invoked which calls back into
564 * childProcess() in this file, rather than directly
565 * via the statement below */
566 return resultPid;
567 }
568
569 /*
570 * Start a child process running function childProcess.
571 * This function only returns in the parent.
572 */
573 static pid_t
574 startChild(JNIEnv *env, jobject process, ChildStuff *c, const char *helperpath) {
575 switch (c->mode) {
576 /* vfork(2) is deprecated on Solaris */
577 case MODE_VFORK:
578 return vforkChild(c);
579 case MODE_FORK:
580 return forkChild(c);
581 case MODE_POSIX_SPAWN:
582 return spawnChild(env, process, c, helperpath);
583 default:
584 return -1;
585 }
586 }
587
588 JNIEXPORT jint JNICALL
589 Java_java_lang_ProcessImpl_forkAndExec(JNIEnv *env,
590 jobject process,
591 jint mode,
592 jbyteArray helperpath,
593 jbyteArray prog,
594 jbyteArray argBlock, jint argc,
595 jbyteArray envBlock, jint envc,
596 jbyteArray dir,
597 jintArray std_fds,
598 jboolean redirectErrorStream)
599 {
600 int errnum;
601 int resultPid = -1;
602 int in[2], out[2], err[2], fail[2], childenv[2];
603 jint *fds = NULL;
604 const char *phelperpath = NULL;
605 const char *pprog = NULL;
606 const char *pargBlock = NULL;
607 const char *penvBlock = NULL;
608 ChildStuff *c;
609
610 in[0] = in[1] = out[0] = out[1] = err[0] = err[1] = fail[0] = fail[1] = -1;
611 childenv[0] = childenv[1] = -1;
612
613 if ((c = NEW(ChildStuff, 1)) == NULL) return -1;
614 c->argv = NULL;
615 c->envv = NULL;
616 c->pdir = NULL;
617
618 /* Convert prog + argBlock into a char ** argv.
619 * Add one word room for expansion of argv for use by
620 * execve_as_traditional_shell_script.
621 * This word is also used when using posix_spawn mode
622 */
623 assert(prog != NULL && argBlock != NULL);
624 if ((phelperpath = getBytes(env, helperpath)) == NULL) goto Catch;
625 if ((pprog = getBytes(env, prog)) == NULL) goto Catch;
626 if ((pargBlock = getBytes(env, argBlock)) == NULL) goto Catch;
627 if ((c->argv = NEW(const char *, argc + 3)) == NULL) goto Catch;
628 c->argv[0] = pprog;
629 c->argc = argc + 2;
630 initVectorFromBlock(c->argv+1, pargBlock, argc);
631
632 if (envBlock != NULL) {
633 /* Convert envBlock into a char ** envv */
634 if ((penvBlock = getBytes(env, envBlock)) == NULL) goto Catch;
635 if ((c->envv = NEW(const char *, envc + 1)) == NULL) goto Catch;
636 initVectorFromBlock(c->envv, penvBlock, envc);
637 }
638
639 if (dir != NULL) {
640 if ((c->pdir = getBytes(env, dir)) == NULL) goto Catch;
641 }
642
643 assert(std_fds != NULL);
644 fds = (*env)->GetIntArrayElements(env, std_fds, NULL);
645 if (fds == NULL) goto Catch;
646
647 if ((fds[0] == -1 && pipe(in) < 0) ||
648 (fds[1] == -1 && pipe(out) < 0) ||
649 (fds[2] == -1 && pipe(err) < 0) ||
650 (pipe(childenv) < 0) ||
651 (pipe(fail) < 0)) {
652 throwIOException(env, errno, "Bad file descriptor");
653 goto Catch;
654 }
655 c->fds[0] = fds[0];
656 c->fds[1] = fds[1];
657 c->fds[2] = fds[2];
658
659 copyPipe(in, c->in);
660 copyPipe(out, c->out);
661 copyPipe(err, c->err);
662 copyPipe(fail, c->fail);
663 copyPipe(childenv, c->childenv);
664
665 c->redirectErrorStream = redirectErrorStream;
666 c->mode = mode;
667
668 /* In posix_spawn mode, require the child process to signal aliveness
669 * right after it comes up. This is because there are implementations of
670 * posix_spawn() which do not report failed exec()s back to the caller
671 * (e.g. glibc, see JDK-8223777). In those cases, the fork() will have
672 * worked and successfully started the child process, but the exec() will
673 * have failed. There is no way for us to distinguish this from a target
674 * binary just exiting right after start.
675 *
676 * Note that we could do this additional handshake in all modes but for
677 * prudence only do it when it is needed (in posix_spawn mode). */
678 c->sendAlivePing = (mode == MODE_POSIX_SPAWN) ? 1 : 0;
679
680 resultPid = startChild(env, process, c, phelperpath);
681 assert(resultPid != 0);
682
683 if (resultPid < 0) {
684 switch (c->mode) {
685 case MODE_VFORK:
686 throwIOException(env, errno, "vfork failed");
687 break;
688 case MODE_FORK:
689 throwIOException(env, errno, "fork failed");
690 break;
691 case MODE_POSIX_SPAWN:
692 throwIOException(env, errno, "posix_spawn failed");
693 break;
694 }
695 goto Catch;
696 }
697 close(fail[1]); fail[1] = -1; /* See: WhyCantJohnnyExec (childproc.c) */
698
699 /* If we expect the child to ping aliveness, wait for it. */
700 if (c->sendAlivePing) {
701 switch(readFully(fail[0], &errnum, sizeof(errnum))) {
702 case 0: /* First exec failed; */
703 {
704 int tmpStatus = 0;
705 int p = waitpid(resultPid, &tmpStatus, 0);
706 throwExitCause(env, p, tmpStatus);
707 goto Catch;
708 }
709 case sizeof(errnum):
710 assert(errnum == CHILD_IS_ALIVE);
711 if (errnum != CHILD_IS_ALIVE) {
712 /* Should never happen since the first thing the spawn
713 * helper should do is to send an alive ping to the parent,
714 * before doing any subsequent work. */
715 throwIOException(env, 0, "Bad code from spawn helper "
716 "(Failed to exec spawn helper)");
717 goto Catch;
718 }
719 break;
720 default:
721 throwIOException(env, errno, "Read failed");
722 goto Catch;
723 }
724 }
725
726 switch (readFully(fail[0], &errnum, sizeof(errnum))) {
727 case 0: break; /* Exec succeeded */
728 case sizeof(errnum):
729 waitpid(resultPid, NULL, 0);
730 throwIOException(env, errnum, "Exec failed");
731 goto Catch;
732 default:
733 throwIOException(env, errno, "Read failed");
734 goto Catch;
735 }
736
737 fds[0] = (in [1] != -1) ? in [1] : -1;
738 fds[1] = (out[0] != -1) ? out[0] : -1;
739 fds[2] = (err[0] != -1) ? err[0] : -1;
740
741 Finally:
742 /* Always clean up the child's side of the pipes */
743 closeSafely(in [0]);
744 closeSafely(out[1]);
745 closeSafely(err[1]);
746
747 /* Always clean up fail and childEnv descriptors */
748 closeSafely(fail[0]);
749 closeSafely(fail[1]);
750 closeSafely(childenv[0]);
751 closeSafely(childenv[1]);
752
753 releaseBytes(env, helperpath, phelperpath);
754 releaseBytes(env, prog, pprog);
755 releaseBytes(env, argBlock, pargBlock);
756 releaseBytes(env, envBlock, penvBlock);
757 releaseBytes(env, dir, c->pdir);
758
759 free(c->argv);
760 free(c->envv);
761 free(c);
762
763 if (fds != NULL)
764 (*env)->ReleaseIntArrayElements(env, std_fds, fds, 0);
765
766 return resultPid;
767
768 Catch:
769 /* Clean up the parent's side of the pipes in case of failure only */
770 closeSafely(in [1]); in[1] = -1;
771 closeSafely(out[0]); out[0] = -1;
772 closeSafely(err[0]); err[0] = -1;
773 goto Finally;
774 }
775