1 | /* Copyright (C) 1991-2017 Free Software Foundation, Inc. |
2 | This file is part of the GNU C Library. |
3 | |
4 | The GNU C Library is free software; you can redistribute it and/or |
5 | modify it under the terms of the GNU Lesser General Public |
6 | License as published by the Free Software Foundation; either |
7 | version 2.1 of the License, or (at your option) any later version. |
8 | |
9 | The GNU C Library is distributed in the hope that it will be useful, |
10 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
11 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
12 | Lesser General Public License for more details. |
13 | |
14 | You should have received a copy of the GNU Lesser General Public |
15 | License along with the GNU C Library; if not, see |
16 | <http://www.gnu.org/licenses/>. */ |
17 | |
18 | #include <errno.h> |
19 | #include <signal.h> |
20 | #include <stddef.h> |
21 | #include <stdlib.h> |
22 | #include <unistd.h> |
23 | #include <sys/types.h> |
24 | #include <sys/wait.h> |
25 | #include <libc-lock.h> |
26 | #include <sysdep-cancel.h> |
27 | |
28 | |
29 | #define SHELL_PATH "/bin/sh" /* Path of the shell. */ |
30 | #define SHELL_NAME "sh" /* Name to give it. */ |
31 | |
32 | |
33 | #ifdef _LIBC_REENTRANT |
34 | static struct sigaction intr, quit; |
35 | static int sa_refcntr; |
36 | __libc_lock_define_initialized (static, lock); |
37 | |
38 | # define DO_LOCK() __libc_lock_lock (lock) |
39 | # define DO_UNLOCK() __libc_lock_unlock (lock) |
40 | # define INIT_LOCK() ({ __libc_lock_init (lock); sa_refcntr = 0; }) |
41 | # define ADD_REF() sa_refcntr++ |
42 | # define SUB_REF() --sa_refcntr |
43 | #else |
44 | # define DO_LOCK() |
45 | # define DO_UNLOCK() |
46 | # define INIT_LOCK() |
47 | # define ADD_REF() 0 |
48 | # define SUB_REF() 0 |
49 | #endif |
50 | |
51 | |
52 | /* Execute LINE as a shell command, returning its status. */ |
53 | static int |
54 | do_system (const char *line) |
55 | { |
56 | int status, save; |
57 | pid_t pid; |
58 | struct sigaction sa; |
59 | #ifndef _LIBC_REENTRANT |
60 | struct sigaction intr, quit; |
61 | #endif |
62 | sigset_t omask; |
63 | |
64 | sa.sa_handler = SIG_IGN; |
65 | sa.sa_flags = 0; |
66 | __sigemptyset (&sa.sa_mask); |
67 | |
68 | DO_LOCK (); |
69 | if (ADD_REF () == 0) |
70 | { |
71 | if (__sigaction (SIGINT, &sa, &intr) < 0) |
72 | { |
73 | (void) SUB_REF (); |
74 | goto out; |
75 | } |
76 | if (__sigaction (SIGQUIT, &sa, &quit) < 0) |
77 | { |
78 | save = errno; |
79 | (void) SUB_REF (); |
80 | goto out_restore_sigint; |
81 | } |
82 | } |
83 | DO_UNLOCK (); |
84 | |
85 | /* We reuse the bitmap in the 'sa' structure. */ |
86 | __sigaddset (&sa.sa_mask, SIGCHLD); |
87 | save = errno; |
88 | if (__sigprocmask (SIG_BLOCK, &sa.sa_mask, &omask) < 0) |
89 | { |
90 | #ifndef _LIBC |
91 | if (errno == ENOSYS) |
92 | __set_errno (save); |
93 | else |
94 | #endif |
95 | { |
96 | DO_LOCK (); |
97 | if (SUB_REF () == 0) |
98 | { |
99 | save = errno; |
100 | (void) __sigaction (SIGQUIT, &quit, (struct sigaction *) NULL); |
101 | out_restore_sigint: |
102 | (void) __sigaction (SIGINT, &intr, (struct sigaction *) NULL); |
103 | __set_errno (save); |
104 | } |
105 | out: |
106 | DO_UNLOCK (); |
107 | return -1; |
108 | } |
109 | } |
110 | |
111 | #ifdef CLEANUP_HANDLER |
112 | CLEANUP_HANDLER; |
113 | #endif |
114 | |
115 | #ifdef FORK |
116 | pid = FORK (); |
117 | #else |
118 | pid = __fork (); |
119 | #endif |
120 | if (pid == (pid_t) 0) |
121 | { |
122 | /* Child side. */ |
123 | const char *new_argv[4]; |
124 | new_argv[0] = SHELL_NAME; |
125 | new_argv[1] = "-c" ; |
126 | new_argv[2] = line; |
127 | new_argv[3] = NULL; |
128 | |
129 | /* Restore the signals. */ |
130 | (void) __sigaction (SIGINT, &intr, (struct sigaction *) NULL); |
131 | (void) __sigaction (SIGQUIT, &quit, (struct sigaction *) NULL); |
132 | (void) __sigprocmask (SIG_SETMASK, &omask, (sigset_t *) NULL); |
133 | INIT_LOCK (); |
134 | |
135 | /* Exec the shell. */ |
136 | (void) __execve (SHELL_PATH, (char *const *) new_argv, __environ); |
137 | _exit (127); |
138 | } |
139 | else if (pid < (pid_t) 0) |
140 | /* The fork failed. */ |
141 | status = -1; |
142 | else |
143 | /* Parent side. */ |
144 | { |
145 | /* Note the system() is a cancellation point. But since we call |
146 | waitpid() which itself is a cancellation point we do not |
147 | have to do anything here. */ |
148 | if (TEMP_FAILURE_RETRY (__waitpid (pid, &status, 0)) != pid) |
149 | status = -1; |
150 | } |
151 | |
152 | #ifdef CLEANUP_HANDLER |
153 | CLEANUP_RESET; |
154 | #endif |
155 | |
156 | save = errno; |
157 | DO_LOCK (); |
158 | if ((SUB_REF () == 0 |
159 | && (__sigaction (SIGINT, &intr, (struct sigaction *) NULL) |
160 | | __sigaction (SIGQUIT, &quit, (struct sigaction *) NULL)) != 0) |
161 | || __sigprocmask (SIG_SETMASK, &omask, (sigset_t *) NULL) != 0) |
162 | { |
163 | #ifndef _LIBC |
164 | /* glibc cannot be used on systems without waitpid. */ |
165 | if (errno == ENOSYS) |
166 | __set_errno (save); |
167 | else |
168 | #endif |
169 | status = -1; |
170 | } |
171 | DO_UNLOCK (); |
172 | |
173 | return status; |
174 | } |
175 | |
176 | int |
177 | __libc_system (const char *line) |
178 | { |
179 | if (line == NULL) |
180 | /* Check that we have a command processor available. It might |
181 | not be available after a chroot(), for example. */ |
182 | return do_system ("exit 0" ) == 0; |
183 | |
184 | return do_system (line); |
185 | } |
186 | weak_alias (__libc_system, system) |
187 | |