1/* Copyright (C) 1993-2019 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3 Written by Per Bothner <bothner@cygnus.com>.
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 As a special exception, if you link the code in this file with
20 files compiled with a GNU compiler to produce an executable,
21 that does not cause the resulting executable to be covered by
22 the GNU Lesser General Public License. This exception does not
23 however invalidate any other reasons why the executable file
24 might be covered by the GNU Lesser General Public License.
25 This exception applies to code released by its copyright holders
26 in files containing the exception. */
27
28#include "libioP.h"
29#include <fcntl.h>
30#include <signal.h>
31#include <unistd.h>
32#include <stdlib.h>
33#include <shlib-compat.h>
34#include <not-cancel.h>
35#include <sys/types.h>
36#include <sys/wait.h>
37#include <spawn.h>
38#include <paths.h>
39
40struct _IO_proc_file
41{
42 struct _IO_FILE_plus file;
43 /* Following fields must match those in class procbuf (procbuf.h) */
44 pid_t pid;
45 struct _IO_proc_file *next;
46};
47typedef struct _IO_proc_file _IO_proc_file;
48
49static const struct _IO_jump_t _IO_proc_jumps;
50
51static struct _IO_proc_file *proc_file_chain;
52
53#ifdef _IO_MTSAFE_IO
54static _IO_lock_t proc_file_chain_lock = _IO_lock_initializer;
55
56static void
57unlock (void *not_used)
58{
59 _IO_lock_unlock (proc_file_chain_lock);
60}
61#endif
62
63/* POSIX states popen shall ensure that any streams from previous popen()
64 calls that remain open in the parent process should be closed in the new
65 child process.
66 To avoid a race-condition between checking which file descriptors need to
67 be close (by transversing the proc_file_chain list) and the insertion of a
68 new one after a successful posix_spawn this function should be called
69 with proc_file_chain_lock acquired. */
70static bool
71spawn_process (posix_spawn_file_actions_t *fa, FILE *fp, const char *command,
72 int do_cloexec, int pipe_fds[2], int parent_end, int child_end,
73 int child_pipe_fd)
74{
75
76 for (struct _IO_proc_file *p = proc_file_chain; p; p = p->next)
77 {
78 int fd = _IO_fileno ((FILE *) p);
79
80 /* If any stream from previous popen() calls has fileno
81 child_pipe_fd, it has been already closed by the adddup2 action
82 above. */
83 if (fd != child_pipe_fd
84 && __posix_spawn_file_actions_addclose (fa, fd) != 0)
85 return false;
86 }
87
88 if (__posix_spawn (&((_IO_proc_file *) fp)->pid, _PATH_BSHELL, fa, 0,
89 (char *const[]){ (char*) "sh", (char*) "-c",
90 (char *) command, NULL }, __environ) != 0)
91 return false;
92
93 __close_nocancel (pipe_fds[child_end]);
94
95 if (!do_cloexec)
96 /* Undo the effects of the pipe2 call which set the
97 close-on-exec flag. */
98 __fcntl (pipe_fds[parent_end], F_SETFD, 0);
99
100 _IO_fileno (fp) = pipe_fds[parent_end];
101
102 ((_IO_proc_file *) fp)->next = proc_file_chain;
103 proc_file_chain = (_IO_proc_file *) fp;
104
105 return true;
106}
107
108FILE *
109_IO_new_proc_open (FILE *fp, const char *command, const char *mode)
110{
111 int read_or_write;
112 /* These are indexes for pipe_fds. */
113 int parent_end, child_end;
114 int pipe_fds[2];
115 int child_pipe_fd;
116 bool spawn_ok;
117
118 int do_read = 0;
119 int do_write = 0;
120 int do_cloexec = 0;
121 while (*mode != '\0')
122 switch (*mode++)
123 {
124 case 'r':
125 do_read = 1;
126 break;
127 case 'w':
128 do_write = 1;
129 break;
130 case 'e':
131 do_cloexec = 1;
132 break;
133 default:
134 errout:
135 __set_errno (EINVAL);
136 return NULL;
137 }
138
139 if ((do_read ^ do_write) == 0)
140 goto errout;
141
142 if (_IO_file_is_open (fp))
143 return NULL;
144
145 /* Atomically set the O_CLOEXEC flag for the pipe end used by the
146 child process (to avoid leaking the file descriptor in case of a
147 concurrent fork). This is later reverted in the child process.
148 When popen returns, the parent pipe end can be O_CLOEXEC or not,
149 depending on the 'e' open mode, but there is only one flag which
150 controls both descriptors. The parent end is adjusted below,
151 after creating the child process. (In the child process, the
152 parent end should be closed on execve, so O_CLOEXEC remains set
153 there.) */
154 if (__pipe2 (pipe_fds, O_CLOEXEC) < 0)
155 return NULL;
156
157 if (do_read)
158 {
159 parent_end = 0;
160 child_end = 1;
161 read_or_write = _IO_NO_WRITES;
162 child_pipe_fd = 1;
163 }
164 else
165 {
166 parent_end = 1;
167 child_end = 0;
168 read_or_write = _IO_NO_READS;
169 child_pipe_fd = 0;
170 }
171
172 posix_spawn_file_actions_t fa;
173 /* posix_spawn_file_actions_init does not fail. */
174 __posix_spawn_file_actions_init (&fa);
175
176 /* The descriptor is already the one the child will use. In this case
177 it must be moved to another one otherwise, there is no safe way to
178 remove the close-on-exec flag in the child without creating a FD leak
179 race in the parent. */
180 if (pipe_fds[child_end] == child_pipe_fd)
181 {
182 int tmp = __fcntl (child_pipe_fd, F_DUPFD_CLOEXEC, 0);
183 if (tmp < 0)
184 goto spawn_failure;
185 __close_nocancel (pipe_fds[child_end]);
186 pipe_fds[child_end] = tmp;
187 }
188
189 if (__posix_spawn_file_actions_adddup2 (&fa, pipe_fds[child_end],
190 child_pipe_fd) != 0)
191 goto spawn_failure;
192
193#ifdef _IO_MTSAFE_IO
194 _IO_cleanup_region_start_noarg (unlock);
195 _IO_lock_lock (proc_file_chain_lock);
196#endif
197 spawn_ok = spawn_process (&fa, fp, command, do_cloexec, pipe_fds,
198 parent_end, child_end, child_pipe_fd);
199#ifdef _IO_MTSAFE_IO
200 _IO_lock_unlock (proc_file_chain_lock);
201 _IO_cleanup_region_end (0);
202#endif
203
204 __posix_spawn_file_actions_destroy (&fa);
205
206 if (!spawn_ok)
207 {
208 spawn_failure:
209 __close_nocancel (pipe_fds[child_end]);
210 __close_nocancel (pipe_fds[parent_end]);
211 __set_errno (ENOMEM);
212 return NULL;
213 }
214
215 _IO_mask_flags (fp, read_or_write, _IO_NO_READS|_IO_NO_WRITES);
216 return fp;
217}
218
219FILE *
220_IO_new_popen (const char *command, const char *mode)
221{
222 struct locked_FILE
223 {
224 struct _IO_proc_file fpx;
225#ifdef _IO_MTSAFE_IO
226 _IO_lock_t lock;
227#endif
228 } *new_f;
229 FILE *fp;
230
231 new_f = (struct locked_FILE *) malloc (sizeof (struct locked_FILE));
232 if (new_f == NULL)
233 return NULL;
234#ifdef _IO_MTSAFE_IO
235 new_f->fpx.file.file._lock = &new_f->lock;
236#endif
237 fp = &new_f->fpx.file.file;
238 _IO_init_internal (fp, 0);
239 _IO_JUMPS (&new_f->fpx.file) = &_IO_proc_jumps;
240 _IO_new_file_init_internal (&new_f->fpx.file);
241 if (_IO_new_proc_open (fp, command, mode) != NULL)
242 return (FILE *) &new_f->fpx.file;
243 _IO_un_link (&new_f->fpx.file);
244 free (new_f);
245 return NULL;
246}
247
248int
249_IO_new_proc_close (FILE *fp)
250{
251 /* This is not name-space clean. FIXME! */
252 int wstatus;
253 _IO_proc_file **ptr = &proc_file_chain;
254 pid_t wait_pid;
255 int status = -1;
256
257 /* Unlink from proc_file_chain. */
258#ifdef _IO_MTSAFE_IO
259 _IO_cleanup_region_start_noarg (unlock);
260 _IO_lock_lock (proc_file_chain_lock);
261#endif
262 for ( ; *ptr != NULL; ptr = &(*ptr)->next)
263 {
264 if (*ptr == (_IO_proc_file *) fp)
265 {
266 *ptr = (*ptr)->next;
267 status = 0;
268 break;
269 }
270 }
271#ifdef _IO_MTSAFE_IO
272 _IO_lock_unlock (proc_file_chain_lock);
273 _IO_cleanup_region_end (0);
274#endif
275
276 if (status < 0 || __close_nocancel (_IO_fileno(fp)) < 0)
277 return -1;
278 /* POSIX.2 Rationale: "Some historical implementations either block
279 or ignore the signals SIGINT, SIGQUIT, and SIGHUP while waiting
280 for the child process to terminate. Since this behavior is not
281 described in POSIX.2, such implementations are not conforming." */
282 do
283 {
284 wait_pid = __waitpid_nocancel (((_IO_proc_file *) fp)->pid, &wstatus, 0);
285 }
286 while (wait_pid == -1 && errno == EINTR);
287 if (wait_pid == -1)
288 return -1;
289 return wstatus;
290}
291
292static const struct _IO_jump_t _IO_proc_jumps libio_vtable = {
293 JUMP_INIT_DUMMY,
294 JUMP_INIT(finish, _IO_new_file_finish),
295 JUMP_INIT(overflow, _IO_new_file_overflow),
296 JUMP_INIT(underflow, _IO_new_file_underflow),
297 JUMP_INIT(uflow, _IO_default_uflow),
298 JUMP_INIT(pbackfail, _IO_default_pbackfail),
299 JUMP_INIT(xsputn, _IO_new_file_xsputn),
300 JUMP_INIT(xsgetn, _IO_default_xsgetn),
301 JUMP_INIT(seekoff, _IO_new_file_seekoff),
302 JUMP_INIT(seekpos, _IO_default_seekpos),
303 JUMP_INIT(setbuf, _IO_new_file_setbuf),
304 JUMP_INIT(sync, _IO_new_file_sync),
305 JUMP_INIT(doallocate, _IO_file_doallocate),
306 JUMP_INIT(read, _IO_file_read),
307 JUMP_INIT(write, _IO_new_file_write),
308 JUMP_INIT(seek, _IO_file_seek),
309 JUMP_INIT(close, _IO_new_proc_close),
310 JUMP_INIT(stat, _IO_file_stat),
311 JUMP_INIT(showmanyc, _IO_default_showmanyc),
312 JUMP_INIT(imbue, _IO_default_imbue)
313};
314
315strong_alias (_IO_new_popen, __new_popen)
316versioned_symbol (libc, _IO_new_popen, _IO_popen, GLIBC_2_1);
317versioned_symbol (libc, __new_popen, popen, GLIBC_2_1);
318versioned_symbol (libc, _IO_new_proc_open, _IO_proc_open, GLIBC_2_1);
319versioned_symbol (libc, _IO_new_proc_close, _IO_proc_close, GLIBC_2_1);
320