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1/* Guts of POSIX spawn interface. Generic POSIX.1 version.
2 Copyright (C) 2000-2019 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <http://www.gnu.org/licenses/>. */
18
19#include <spawn.h>
20#include <assert.h>
21#include <fcntl.h>
22#include <paths.h>
23#include <string.h>
24#include <sys/resource.h>
25#include <sys/wait.h>
26#include <sys/param.h>
27#include <sys/mman.h>
28#include <not-cancel.h>
29#include <local-setxid.h>
30#include <shlib-compat.h>
31#include <nptl/pthreadP.h>
32#include <dl-sysdep.h>
33#include <libc-pointer-arith.h>
34#include <ldsodefs.h>
35#include "spawn_int.h"
36
37
38/* The Unix standard contains a long explanation of the way to signal
39 an error after the fork() was successful. Since no new wait status
40 was wanted there is no way to signal an error using one of the
41 available methods. The committee chose to signal an error by a
42 normal program exit with the exit code 127. */
43#define SPAWN_ERROR 127
44
45struct posix_spawn_args
46{
47 sigset_t oldmask;
48 const char *file;
49 int (*exec) (const char *, char *const *, char *const *);
50 const posix_spawn_file_actions_t *fa;
51 const posix_spawnattr_t *restrict attr;
52 char *const *argv;
53 ptrdiff_t argc;
54 char *const *envp;
55 int xflags;
56 int pipe[2];
57};
58
59/* Older version requires that shell script without shebang definition
60 to be called explicitly using /bin/sh (_PATH_BSHELL). */
61static void
62maybe_script_execute (struct posix_spawn_args *args)
63{
64 if (SHLIB_COMPAT (libc, GLIBC_2_2, GLIBC_2_15)
65 && (args->xflags & SPAWN_XFLAGS_TRY_SHELL) && errno == ENOEXEC)
66 {
67 char *const *argv = args->argv;
68 ptrdiff_t argc = args->argc;
69
70 /* Construct an argument list for the shell. */
71 char *new_argv[argc + 2];
72 new_argv[0] = (char *) _PATH_BSHELL;
73 new_argv[1] = (char *) args->file;
74 if (argc > 1)
75 memcpy (new_argv + 2, argv + 1, argc * sizeof (char *));
76 else
77 new_argv[2] = NULL;
78
79 /* Execute the shell. */
80 args->exec (new_argv[0], new_argv, args->envp);
81 }
82}
83
84/* Function used in the clone call to setup the signals mask, posix_spawn
85 attributes, and file actions. */
86static int
87__spawni_child (void *arguments)
88{
89 struct posix_spawn_args *args = arguments;
90 const posix_spawnattr_t *restrict attr = args->attr;
91 const posix_spawn_file_actions_t *file_actions = args->fa;
92 int ret;
93
94 __close (args->pipe[0]);
95
96 /* Set signal default action. */
97 if ((attr->__flags & POSIX_SPAWN_SETSIGDEF) != 0)
98 {
99 /* We have to iterate over all signals. This could possibly be
100 done better but it requires system specific solutions since
101 the sigset_t data type can be very different on different
102 architectures. */
103 int sig;
104 struct sigaction sa;
105
106 memset (&sa, '\0', sizeof (sa));
107 sa.sa_handler = SIG_DFL;
108
109 for (sig = 1; sig <= _NSIG; ++sig)
110 if (__sigismember (&attr->__sd, sig) != 0
111 && __sigaction (sig, &sa, NULL) != 0)
112 goto fail;
113 }
114
115#ifdef _POSIX_PRIORITY_SCHEDULING
116 /* Set the scheduling algorithm and parameters. */
117 if ((attr->__flags & (POSIX_SPAWN_SETSCHEDPARAM | POSIX_SPAWN_SETSCHEDULER))
118 == POSIX_SPAWN_SETSCHEDPARAM)
119 {
120 if (__sched_setparam (0, &attr->__sp) == -1)
121 goto fail;
122 }
123 else if ((attr->__flags & POSIX_SPAWN_SETSCHEDULER) != 0)
124 {
125 if (__sched_setscheduler (0, attr->__policy, &attr->__sp) == -1)
126 goto fail;
127 }
128#endif
129
130 /* Set the process session ID. */
131 if ((attr->__flags & POSIX_SPAWN_SETSID) != 0
132 && __setsid () < 0)
133 goto fail;
134
135 /* Set the process group ID. */
136 if ((attr->__flags & POSIX_SPAWN_SETPGROUP) != 0
137 && __setpgid (0, attr->__pgrp) != 0)
138 goto fail;
139
140 /* Set the effective user and group IDs. */
141 if ((attr->__flags & POSIX_SPAWN_RESETIDS) != 0
142 && (local_seteuid (__getuid ()) != 0
143 || local_setegid (__getgid ())) != 0)
144 goto fail;
145
146 /* Execute the file actions. */
147 if (file_actions != NULL)
148 {
149 int cnt;
150 struct rlimit64 fdlimit;
151 bool have_fdlimit = false;
152
153 for (cnt = 0; cnt < file_actions->__used; ++cnt)
154 {
155 struct __spawn_action *action = &file_actions->__actions[cnt];
156
157 switch (action->tag)
158 {
159 case spawn_do_close:
160 if (__close_nocancel (action->action.close_action.fd) != 0)
161 {
162 if (have_fdlimit == 0)
163 {
164 __getrlimit64 (RLIMIT_NOFILE, &fdlimit);
165 have_fdlimit = true;
166 }
167
168 /* Only signal errors for file descriptors out of range. */
169 if (action->action.close_action.fd < 0
170 || action->action.close_action.fd >= fdlimit.rlim_cur)
171 goto fail;
172 }
173 break;
174
175 case spawn_do_open:
176 {
177 /* POSIX states that if fildes was already an open file descriptor,
178 it shall be closed before the new file is opened. This avoid
179 pontential issues when posix_spawn plus addopen action is called
180 with the process already at maximum number of file descriptor
181 opened and also for multiple actions on single-open special
182 paths (like /dev/watchdog). */
183 __close_nocancel (action->action.open_action.fd);
184
185 int new_fd = __open_nocancel (action->action.open_action.path,
186 action->action.open_action.oflag
187 | O_LARGEFILE,
188 action->action.open_action.mode);
189
190 if (new_fd == -1)
191 goto fail;
192
193 /* Make sure the desired file descriptor is used. */
194 if (new_fd != action->action.open_action.fd)
195 {
196 if (__dup2 (new_fd, action->action.open_action.fd)
197 != action->action.open_action.fd)
198 goto fail;
199
200 if (__close_nocancel (new_fd) != 0)
201 goto fail;
202 }
203 }
204 break;
205
206 case spawn_do_dup2:
207 /* Austin Group issue #411 requires adddup2 action with source
208 and destination being equal to remove close-on-exec flag. */
209 if (action->action.dup2_action.fd
210 == action->action.dup2_action.newfd)
211 {
212 int fd = action->action.dup2_action.newfd;
213 int flags = __fcntl (fd, F_GETFD, 0);
214 if (flags == -1)
215 goto fail;
216 if (__fcntl (fd, F_SETFD, flags & ~FD_CLOEXEC) == -1)
217 goto fail;
218 }
219 else if (__dup2 (action->action.dup2_action.fd,
220 action->action.dup2_action.newfd)
221 != action->action.dup2_action.newfd)
222 goto fail;
223 break;
224
225 case spawn_do_chdir:
226 if (__chdir (action->action.chdir_action.path) != 0)
227 goto fail;
228 break;
229
230 case spawn_do_fchdir:
231 if (__fchdir (action->action.fchdir_action.fd) != 0)
232 goto fail;
233 break;
234 }
235 }
236 }
237
238 /* Set the initial signal mask of the child if POSIX_SPAWN_SETSIGMASK
239 is set, otherwise restore the previous one. */
240 __sigprocmask (SIG_SETMASK, (attr->__flags & POSIX_SPAWN_SETSIGMASK)
241 ? &attr->__ss : &args->oldmask, 0);
242
243 args->exec (args->file, args->argv, args->envp);
244
245 /* This is compatibility function required to enable posix_spawn run
246 script without shebang definition for older posix_spawn versions
247 (2.15). */
248 maybe_script_execute (args);
249
250fail:
251 /* errno should have an appropriate non-zero value; otherwise,
252 there's a bug in glibc or the kernel. For lack of an error code
253 (EINTERNALBUG) describing that, use ECHILD. Another option would
254 be to set args->err to some negative sentinel and have the parent
255 abort(), but that seems needlessly harsh. */
256 ret = errno ? : ECHILD;
257 if (ret)
258 /* Since sizeof errno < PIPE_BUF, the write is atomic. */
259 while (__write_nocancel (args->pipe[1], &ret, sizeof (ret)) < 0);
260
261 _exit (SPAWN_ERROR);
262}
263
264/* Spawn a new process executing PATH with the attributes describes in *ATTRP.
265 Before running the process perform the actions described in FILE-ACTIONS. */
266int
267__spawnix (pid_t *pid, const char *file,
268 const posix_spawn_file_actions_t *file_actions,
269 const posix_spawnattr_t *attrp, char *const argv[],
270 char *const envp[], int xflags,
271 int (*exec) (const char *, char *const *, char *const *))
272{
273 struct posix_spawn_args args;
274 int ec;
275
276 if (__pipe2 (args.pipe, O_CLOEXEC))
277 return errno;
278
279 /* Disable asynchronous cancellation. */
280 int state;
281 __libc_ptf_call (__pthread_setcancelstate,
282 (PTHREAD_CANCEL_DISABLE, &state), 0);
283
284 ptrdiff_t argc = 0;
285 ptrdiff_t limit = INT_MAX - 1;
286 while (argv[argc++] != NULL)
287 if (argc == limit)
288 {
289 errno = E2BIG;
290 return errno;
291 }
292
293 args.file = file;
294 args.exec = exec;
295 args.fa = file_actions;
296 args.attr = attrp ? attrp : &(const posix_spawnattr_t) { 0 };
297 args.argv = argv;
298 args.argc = argc;
299 args.envp = envp;
300 args.xflags = xflags;
301
302 /* Generate the new process. */
303 pid_t new_pid = __fork ();
304
305 if (new_pid == 0)
306 __spawni_child (&args);
307 else if (new_pid > 0)
308 {
309 __close (args.pipe[1]);
310
311 if (__read (args.pipe[0], &ec, sizeof ec) != sizeof ec)
312 ec = 0;
313 else
314 __waitpid (new_pid, &(int) { 0 }, 0);
315 }
316 else
317 ec = errno;
318
319 __close (args.pipe[0]);
320
321 if ((ec == 0) && (pid != NULL))
322 *pid = new_pid;
323
324 __libc_ptf_call (__pthread_setcancelstate, (state, NULL), 0);
325
326 return ec;
327}
328
329int
330__spawni (pid_t * pid, const char *file,
331 const posix_spawn_file_actions_t * acts,
332 const posix_spawnattr_t * attrp, char *const argv[],
333 char *const envp[], int xflags)
334{
335 /* It uses __execvpex to avoid run ENOEXEC in non compatibility mode (it
336 will be handled by maybe_script_execute). */
337 return __spawnix (pid, file, acts, attrp, argv, envp, xflags,
338 xflags & SPAWN_XFLAGS_USE_PATH ? __execvpex : __execve);
339}
340

Warning: That file was not part of the compilation database. It may have many parsing errors.