1 /* $NetBSD: system.c,v 1.28 2022/03/14 22:14:19 riastradh Exp $ */
2
3 /*
4 * Copyright (c) 1988, 1993
5 * The Regents of the University of California. All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of the University nor the names of its contributors
16 * may be used to endorse or promote products derived from this software
17 * without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 */
31
32 #include <sys/cdefs.h>
33 #if defined(LIBC_SCCS) && !defined(lint)
34 #if 0
35 static char sccsid[] = "@(#)system.c 8.1 (Berkeley) 6/4/93";
36 #else
37 __RCSID("$NetBSD: system.c,v 1.28 2022/03/14 22:14:19 riastradh Exp $");
38 #endif
39 #endif /* LIBC_SCCS and not lint */
40
41 #include "namespace.h"
42 #include <sys/types.h>
43 #include <sys/wait.h>
44 #include <errno.h>
45 #include <signal.h>
46 #include <stdlib.h>
47 #include <unistd.h>
48 #include <paths.h>
49 #include <spawn.h>
50
51 #include "env.h"
52
53 int
system(const char * command)54 system(const char *command)
55 {
56 pid_t pid;
57 struct sigaction intsa, quitsa, sa;
58 sigset_t nmask, omask, sigdefault;
59 int pstat;
60 const char *argp[] = {"sh", "-c", "--", command, NULL};
61 posix_spawnattr_t attr;
62 int error;
63
64 /*
65 * ISO/IEC 9899:1999 in 7.20.4.6 describes this special case.
66 * We need to check availability of a command interpreter.
67 */
68 if (command == NULL) {
69 if (access(_PATH_BSHELL, X_OK) == 0)
70 return 1;
71 return 0;
72 }
73
74 sa.sa_handler = SIG_IGN;
75 sigemptyset(&sa.sa_mask);
76 sa.sa_flags = 0;
77
78 if (sigaction(SIGINT, &sa, &intsa) == -1)
79 return -1;
80 if (sigaction(SIGQUIT, &sa, &quitsa) == -1) {
81 sigaction(SIGINT, &intsa, NULL);
82 return -1;
83 }
84
85 sigemptyset(&nmask);
86 sigaddset(&nmask, SIGCHLD);
87 if (sigprocmask(SIG_BLOCK, &nmask, &omask) == -1) {
88 sigaction(SIGINT, &intsa, NULL);
89 sigaction(SIGQUIT, &quitsa, NULL);
90 return -1;
91 }
92
93 /*
94 * We arrange to inherit all signal handlers from the caller by
95 * default, except possibly SIGINT and SIGQUIT. These we have
96 * overridden internally for system(3) to be SIG_IGN.
97 *
98 * - If the caller had SIGINT or SIGQUIT at SIG_IGN, then we
99 * inherit them as is -- caller had SIG_IGN, child will too.
100 *
101 * - Otherwise, they are SIG_DFL or a signal handler, and we
102 * must reset them to SIG_DFL in the child, rather than
103 * SIG_IGN in system(3) in the parent, by including them in
104 * the sigdefault set.
105 */
106 sigemptyset(&sigdefault);
107 if (intsa.sa_handler != SIG_IGN)
108 sigaddset(&sigdefault, SIGINT);
109 if (quitsa.sa_handler != SIG_IGN)
110 sigaddset(&sigdefault, SIGQUIT);
111
112 posix_spawnattr_init(&attr);
113 posix_spawnattr_setsigdefault(&attr, &sigdefault);
114 posix_spawnattr_setsigmask(&attr, &omask);
115 posix_spawnattr_setflags(&attr,
116 POSIX_SPAWN_SETSIGDEF|POSIX_SPAWN_SETSIGMASK);
117 (void)__readlockenv();
118 error = posix_spawn(&pid, _PATH_BSHELL, NULL, &attr, __UNCONST(argp),
119 environ);
120 (void)__unlockenv();
121 posix_spawnattr_destroy(&attr);
122
123 if (error) {
124 errno = error;
125 pstat = -1;
126 goto out;
127 }
128
129 while (waitpid(pid, &pstat, 0) == -1) {
130 if (errno != EINTR) {
131 pstat = -1;
132 break;
133 }
134 }
135
136 out: sigaction(SIGINT, &intsa, NULL);
137 sigaction(SIGQUIT, &quitsa, NULL);
138 (void)sigprocmask(SIG_SETMASK, &omask, NULL);
139
140 return (pstat);
141 }
142