1 /*
2 * os-posix.c
3 *
4 * Copyright (c) 2003-2008 Fabrice Bellard
5 * Copyright (c) 2010 Red Hat, Inc.
6 *
7 * Permission is hereby granted, free of charge, to any person obtaining a copy
8 * of this software and associated documentation files (the "Software"), to deal
9 * in the Software without restriction, including without limitation the rights
10 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
11 * copies of the Software, and to permit persons to whom the Software is
12 * furnished to do so, subject to the following conditions:
13 *
14 * The above copyright notice and this permission notice shall be included in
15 * all copies or substantial portions of the Software.
16 *
17 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
18 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
19 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
20 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
21 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
22 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
23 * THE SOFTWARE.
24 */
25
26 #include "qemu/osdep.h"
27 #include <sys/resource.h>
28 #include <sys/wait.h>
29 #include <pwd.h>
30 #include <grp.h>
31 #include <libgen.h>
32
33 #include "qemu/error-report.h"
34 #include "qemu/log.h"
35 #include "sysemu/runstate.h"
36 #include "qemu/cutils.h"
37
38 #ifdef CONFIG_LINUX
39 #include <sys/prctl.h>
40 #endif
41
42
os_setup_early_signal_handling(void)43 void os_setup_early_signal_handling(void)
44 {
45 struct sigaction act;
46 sigfillset(&act.sa_mask);
47 act.sa_flags = 0;
48 act.sa_handler = SIG_IGN;
49 sigaction(SIGPIPE, &act, NULL);
50 }
51
termsig_handler(int signal,siginfo_t * info,void * c)52 static void termsig_handler(int signal, siginfo_t *info, void *c)
53 {
54 qemu_system_killed(info->si_signo, info->si_pid);
55 }
56
os_setup_signal_handling(void)57 void os_setup_signal_handling(void)
58 {
59 struct sigaction act;
60
61 memset(&act, 0, sizeof(act));
62 act.sa_sigaction = termsig_handler;
63 act.sa_flags = SA_SIGINFO;
64 sigaction(SIGINT, &act, NULL);
65 sigaction(SIGHUP, &act, NULL);
66 sigaction(SIGTERM, &act, NULL);
67 }
68
os_set_proc_name(const char * s)69 void os_set_proc_name(const char *s)
70 {
71 #if defined(PR_SET_NAME)
72 char name[16];
73 if (!s)
74 return;
75 pstrcpy(name, sizeof(name), s);
76 /* Could rewrite argv[0] too, but that's a bit more complicated.
77 This simple way is enough for `top'. */
78 if (prctl(PR_SET_NAME, name)) {
79 error_report("unable to change process name: %s", strerror(errno));
80 exit(1);
81 }
82 #else
83 error_report("Change of process name not supported by your OS");
84 exit(1);
85 #endif
86 }
87
88
89 /*
90 * Must set all three of these at once.
91 * Legal combinations are unset by name by uid
92 */
93 static struct passwd *user_pwd; /* NULL non-NULL NULL */
94 static uid_t user_uid = (uid_t)-1; /* -1 -1 >=0 */
95 static gid_t user_gid = (gid_t)-1; /* -1 -1 >=0 */
96
97 /*
98 * Prepare to change user ID. user_id can be one of 3 forms:
99 * - a username, in which case user ID will be changed to its uid,
100 * with primary and supplementary groups set up too;
101 * - a numeric uid, in which case only the uid will be set;
102 * - a pair of numeric uid:gid.
103 */
os_set_runas(const char * user_id)104 bool os_set_runas(const char *user_id)
105 {
106 unsigned long lv;
107 const char *ep;
108 uid_t got_uid;
109 gid_t got_gid;
110 int rc;
111
112 user_pwd = getpwnam(user_id);
113 if (user_pwd) {
114 user_uid = -1;
115 user_gid = -1;
116 return true;
117 }
118
119 rc = qemu_strtoul(user_id, &ep, 0, &lv);
120 got_uid = lv; /* overflow here is ID in C99 */
121 if (rc || *ep != ':' || got_uid != lv || got_uid == (uid_t)-1) {
122 return false;
123 }
124
125 rc = qemu_strtoul(ep + 1, 0, 0, &lv);
126 got_gid = lv; /* overflow here is ID in C99 */
127 if (rc || got_gid != lv || got_gid == (gid_t)-1) {
128 return false;
129 }
130
131 user_pwd = NULL;
132 user_uid = got_uid;
133 user_gid = got_gid;
134 return true;
135 }
136
change_process_uid(void)137 static void change_process_uid(void)
138 {
139 assert((user_uid == (uid_t)-1) || user_pwd == NULL);
140 assert((user_uid == (uid_t)-1) ==
141 (user_gid == (gid_t)-1));
142
143 if (user_pwd || user_uid != (uid_t)-1) {
144 gid_t intended_gid = user_pwd ? user_pwd->pw_gid : user_gid;
145 uid_t intended_uid = user_pwd ? user_pwd->pw_uid : user_uid;
146 if (setgid(intended_gid) < 0) {
147 error_report("Failed to setgid(%d)", intended_gid);
148 exit(1);
149 }
150 if (user_pwd) {
151 if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) {
152 error_report("Failed to initgroups(\"%s\", %d)",
153 user_pwd->pw_name, user_pwd->pw_gid);
154 exit(1);
155 }
156 } else {
157 if (setgroups(1, &user_gid) < 0) {
158 error_report("Failed to setgroups(1, [%d])",
159 user_gid);
160 exit(1);
161 }
162 }
163 if (setuid(intended_uid) < 0) {
164 error_report("Failed to setuid(%d)", intended_uid);
165 exit(1);
166 }
167 if (setuid(0) != -1) {
168 error_report("Dropping privileges failed");
169 exit(1);
170 }
171 }
172 }
173
174
175 static const char *chroot_dir;
176
os_set_chroot(const char * path)177 void os_set_chroot(const char *path)
178 {
179 chroot_dir = path;
180 }
181
change_root(void)182 static void change_root(void)
183 {
184 if (chroot_dir) {
185 if (chroot(chroot_dir) < 0) {
186 error_report("chroot failed");
187 exit(1);
188 }
189 if (chdir("/")) {
190 error_report("not able to chdir to /: %s", strerror(errno));
191 exit(1);
192 }
193 }
194
195 }
196
197
198 static int daemonize;
199 static int daemon_pipe;
200
is_daemonized(void)201 bool is_daemonized(void)
202 {
203 return daemonize;
204 }
205
os_set_daemonize(bool d)206 int os_set_daemonize(bool d)
207 {
208 daemonize = d;
209 return 0;
210 }
211
os_daemonize(void)212 void os_daemonize(void)
213 {
214 if (daemonize) {
215 pid_t pid;
216 int fds[2];
217
218 if (!g_unix_open_pipe(fds, FD_CLOEXEC, NULL)) {
219 exit(1);
220 }
221
222 pid = fork();
223 if (pid > 0) {
224 uint8_t status;
225 ssize_t len;
226
227 close(fds[1]);
228
229 do {
230 len = read(fds[0], &status, 1);
231 } while (len < 0 && errno == EINTR);
232
233 /* only exit successfully if our child actually wrote
234 * a one-byte zero to our pipe, upon successful init */
235 exit(len == 1 && status == 0 ? 0 : 1);
236
237 } else if (pid < 0) {
238 exit(1);
239 }
240
241 close(fds[0]);
242 daemon_pipe = fds[1];
243
244 setsid();
245
246 pid = fork();
247 if (pid > 0) {
248 exit(0);
249 } else if (pid < 0) {
250 exit(1);
251 }
252 umask(027);
253
254 signal(SIGTSTP, SIG_IGN);
255 signal(SIGTTOU, SIG_IGN);
256 signal(SIGTTIN, SIG_IGN);
257 }
258 }
259
os_setup_limits(void)260 void os_setup_limits(void)
261 {
262 struct rlimit nofile;
263
264 if (getrlimit(RLIMIT_NOFILE, &nofile) < 0) {
265 warn_report("unable to query NOFILE limit: %s", strerror(errno));
266 return;
267 }
268
269 if (nofile.rlim_cur == nofile.rlim_max) {
270 return;
271 }
272
273 nofile.rlim_cur = nofile.rlim_max;
274
275 if (setrlimit(RLIMIT_NOFILE, &nofile) < 0) {
276 warn_report("unable to set NOFILE limit: %s", strerror(errno));
277 return;
278 }
279 }
280
os_setup_post(void)281 void os_setup_post(void)
282 {
283 int fd = 0;
284
285 if (daemonize) {
286 if (chdir("/")) {
287 error_report("not able to chdir to /: %s", strerror(errno));
288 exit(1);
289 }
290 fd = RETRY_ON_EINTR(qemu_open_old("/dev/null", O_RDWR));
291 if (fd == -1) {
292 exit(1);
293 }
294 }
295
296 change_root();
297 change_process_uid();
298
299 if (daemonize) {
300 uint8_t status = 0;
301 ssize_t len;
302
303 dup2(fd, 0);
304 dup2(fd, 1);
305 /* In case -D is given do not redirect stderr to /dev/null */
306 if (!qemu_log_enabled()) {
307 dup2(fd, 2);
308 }
309
310 close(fd);
311
312 do {
313 len = write(daemon_pipe, &status, 1);
314 } while (len < 0 && errno == EINTR);
315 if (len != 1) {
316 exit(1);
317 }
318 }
319 }
320
os_set_line_buffering(void)321 void os_set_line_buffering(void)
322 {
323 setvbuf(stdout, NULL, _IOLBF, 0);
324 }
325
os_mlock(void)326 int os_mlock(void)
327 {
328 #ifdef HAVE_MLOCKALL
329 int ret = 0;
330
331 ret = mlockall(MCL_CURRENT | MCL_FUTURE);
332 if (ret < 0) {
333 error_report("mlockall: %s", strerror(errno));
334 }
335
336 return ret;
337 #else
338 return -ENOSYS;
339 #endif
340 }
341