1 /* $NetBSD: pidfile.c,v 1.16 2021/08/01 15:29:29 andvar Exp $ */
2
3 /*-
4 * Copyright (c) 1999, 2016 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Jason R. Thorpe, Matthias Scheler, Julio Merino and Roy Marples.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29 * POSSIBILITY OF SUCH DAMAGE.
30 */
31
32 #include <sys/param.h>
33
34 #include <errno.h>
35 #include <fcntl.h>
36 #include <inttypes.h>
37 #include <limits.h>
38 #include <paths.h>
39 #include <stdbool.h>
40 #include <stdlib.h>
41 #include <stdio.h>
42 #include <string.h>
43 #include <unistd.h>
44
45 #include <sys/file.h> /* for flock(2) */
46 #include "config.h"
47 #include "defs.h"
48
49 static pid_t pidfile_pid;
50 static char pidfile_path[PATH_MAX];
51 static int pidfile_fd = -1;
52
53 /* Closes pidfile resources.
54 *
55 * Returns 0 on success, otherwise -1. */
56 static int
pidfile_close(void)57 pidfile_close(void)
58 {
59 int error;
60
61 pidfile_pid = 0;
62 error = close(pidfile_fd);
63 pidfile_fd = -1;
64 pidfile_path[0] = '\0';
65 return error;
66 }
67
68 /* Truncate, close and unlink an existent pidfile,
69 * if and only if it was created by this process.
70 * The pidfile is truncated because we may have dropped permissions
71 * or entered a chroot and thus unable to unlink it.
72 *
73 * Returns 0 on truncation success, otherwise -1. */
74 int
pidfile_clean(void)75 pidfile_clean(void)
76 {
77 int error;
78
79 if (pidfile_fd == -1) {
80 errno = EBADF;
81 return -1;
82 }
83
84 if (pidfile_pid != getpid())
85 error = EPERM;
86 else if (ftruncate(pidfile_fd, 0) == -1)
87 error = errno;
88 else {
89 #ifndef HAVE_PLEDGE /* Avoid a pledge violating segfault. */
90 (void)unlink(pidfile_path);
91 #endif
92 error = 0;
93 }
94
95 (void) pidfile_close();
96
97 if (error != 0) {
98 errno = error;
99 return -1;
100 }
101 return 0;
102 }
103
104 /* atexit shim for pidfile_clean */
105 static void
pidfile_cleanup(void)106 pidfile_cleanup(void)
107 {
108
109 pidfile_clean();
110 }
111
112 /* Constructs a name for a pidfile in the default location (/var/run).
113 * If 'bname' is NULL, uses the name of the current program for the name of
114 * the pidfile.
115 *
116 * Returns 0 on success, otherwise -1. */
117 static int
pidfile_varrun_path(char * path,size_t len,const char * bname)118 pidfile_varrun_path(char *path, size_t len, const char *bname)
119 {
120
121 if (bname == NULL)
122 bname = PACKAGE;
123
124 /* _PATH_VARRUN includes trailing / */
125 if ((size_t)snprintf(path, len, "%s%s.pid", _PATH_VARRUN, bname) >= len)
126 {
127 errno = ENAMETOOLONG;
128 return -1;
129 }
130 return 0;
131 }
132
133 /* Returns the process ID inside path on success, otherwise -1.
134 * If no path is given, use the last pidfile path, otherwise the default one. */
135 pid_t
pidfile_read(const char * path)136 pidfile_read(const char *path)
137 {
138 char dpath[PATH_MAX], buf[16], *eptr;
139 int fd, error;
140 ssize_t n;
141 pid_t pid;
142
143 if (path == NULL && pidfile_path[0] != '\0')
144 path = pidfile_path;
145 if (path == NULL || strchr(path, '/') == NULL) {
146 if (pidfile_varrun_path(dpath, sizeof(dpath), path) == -1)
147 return -1;
148 path = dpath;
149 }
150
151 if ((fd = open(path, O_RDONLY | O_NONBLOCK)) == -1)
152 return -1;
153 n = read(fd, buf, sizeof(buf) - 1);
154 error = errno;
155 (void) close(fd);
156 if (n == -1) {
157 errno = error;
158 return -1;
159 }
160 buf[n] = '\0';
161 pid = (pid_t)strtoi(buf, &eptr, 10, 1, INT_MAX, &error);
162 if (error && !(error == ENOTSUP && *eptr == '\n')) {
163 errno = error;
164 return -1;
165 }
166 return pid;
167 }
168
169 /* Locks the pidfile specified by path and writes the process pid to it.
170 * The new pidfile is "registered" in the global variables pidfile_fd,
171 * pidfile_path and pidfile_pid so that any further call to pidfile_lock(3)
172 * can check if we are recreating the same file or a new one.
173 *
174 * Returns 0 on success, otherwise the pid of the process who owns the
175 * lock if it can be read, otherwise -1. */
176 pid_t
pidfile_lock(const char * path)177 pidfile_lock(const char *path)
178 {
179 char dpath[PATH_MAX];
180 static bool registered_atexit = false;
181
182 /* Register for cleanup with atexit. */
183 if (!registered_atexit) {
184 if (atexit(pidfile_cleanup) == -1)
185 return -1;
186 registered_atexit = true;
187 }
188
189 if (path == NULL || strchr(path, '/') == NULL) {
190 if (pidfile_varrun_path(dpath, sizeof(dpath), path) == -1)
191 return -1;
192 path = dpath;
193 }
194
195 /* If path has changed (no good reason), clean up the old pidfile. */
196 if (pidfile_fd != -1 && strcmp(pidfile_path, path) != 0)
197 pidfile_clean();
198
199 if (pidfile_fd == -1) {
200 int fd, opts;
201
202 opts = O_WRONLY | O_CREAT | O_NONBLOCK;
203 #ifdef O_CLOEXEC
204 opts |= O_CLOEXEC;
205 #endif
206 #ifdef O_EXLOCK
207 opts |= O_EXLOCK;
208 #endif
209 if ((fd = open(path, opts, 0644)) == -1)
210 goto return_pid;
211 #ifndef O_CLOEXEC
212 if ((opts = fcntl(fd, F_GETFD)) == -1 ||
213 fcntl(fd, F_SETFL, opts | FD_CLOEXEC) == -1)
214 {
215 int error = errno;
216
217 (void) close(fd);
218 errno = error;
219 return -1;
220 }
221 #endif
222 #ifndef O_EXLOCK
223 if (flock(fd, LOCK_EX | LOCK_NB) == -1) {
224 int error = errno;
225
226 (void) close(fd);
227 if (error != EAGAIN) {
228 errno = error;
229 return -1;
230 }
231 fd = -1;
232 }
233 #endif
234
235 return_pid:
236 if (fd == -1) {
237 pid_t pid;
238
239 if (errno == EAGAIN) {
240 /* The pidfile is locked, return the process ID
241 * it contains.
242 * If successful, set errno to EEXIST. */
243 if ((pid = pidfile_read(path)) != -1)
244 errno = EEXIST;
245 } else
246 pid = -1;
247
248 return pid;
249 }
250 pidfile_fd = fd;
251 strlcpy(pidfile_path, path, sizeof(pidfile_path));
252 }
253
254 pidfile_pid = getpid();
255
256 /* Truncate the file, as we could be re-writing it.
257 * Then write the process ID. */
258 if (ftruncate(pidfile_fd, 0) == -1 ||
259 lseek(pidfile_fd, 0, SEEK_SET) == -1 ||
260 dprintf(pidfile_fd, "%d\n", pidfile_pid) == -1)
261 {
262 int error = errno;
263
264 pidfile_cleanup();
265 errno = error;
266 return -1;
267 }
268
269 /* Hold the fd open to persist the lock. */
270 return 0;
271 }
272