xref: /qemu/os-posix.c (revision c01196bd) 
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/wait.h>
28 #include <pwd.h>
29 #include <grp.h>
30 #include <libgen.h>
31 
32 /* Needed early for CONFIG_BSD etc. */
33 #include "net/slirp.h"
34 #include "qemu/qemu-options.h"
35 #include "qemu/error-report.h"
36 #include "qemu/log.h"
37 #include "sysemu/runstate.h"
38 #include "qemu/cutils.h"
39 #include "qemu/config-file.h"
40 #include "qemu/option.h"
41 #include "qemu/module.h"
42 
43 #ifdef CONFIG_LINUX
44 #include <sys/prctl.h>
45 #include "qemu/async-teardown.h"
46 #endif
47 
48 /*
49  * Must set all three of these at once.
50  * Legal combinations are              unset   by name   by uid
51  */
52 static struct passwd *user_pwd;    /*   NULL   non-NULL   NULL   */
53 static uid_t user_uid = (uid_t)-1; /*   -1      -1        >=0    */
54 static gid_t user_gid = (gid_t)-1; /*   -1      -1        >=0    */
55 
56 static const char *chroot_dir;
57 static int daemonize;
58 static int daemon_pipe;
59 
60 void os_setup_early_signal_handling(void)
61 {
62     struct sigaction act;
63     sigfillset(&act.sa_mask);
64     act.sa_flags = 0;
65     act.sa_handler = SIG_IGN;
66     sigaction(SIGPIPE, &act, NULL);
67 }
68 
69 static void termsig_handler(int signal, siginfo_t *info, void *c)
70 {
71     qemu_system_killed(info->si_signo, info->si_pid);
72 }
73 
74 void os_setup_signal_handling(void)
75 {
76     struct sigaction act;
77 
78     memset(&act, 0, sizeof(act));
79     act.sa_sigaction = termsig_handler;
80     act.sa_flags = SA_SIGINFO;
81     sigaction(SIGINT,  &act, NULL);
82     sigaction(SIGHUP,  &act, NULL);
83     sigaction(SIGTERM, &act, NULL);
84 }
85 
86 void os_set_proc_name(const char *s)
87 {
88 #if defined(PR_SET_NAME)
89     char name[16];
90     if (!s)
91         return;
92     pstrcpy(name, sizeof(name), s);
93     /* Could rewrite argv[0] too, but that's a bit more complicated.
94        This simple way is enough for `top'. */
95     if (prctl(PR_SET_NAME, name)) {
96         error_report("unable to change process name: %s", strerror(errno));
97         exit(1);
98     }
99 #else
100     error_report("Change of process name not supported by your OS");
101     exit(1);
102 #endif
103 }
104 
105 
106 static bool os_parse_runas_uid_gid(const char *optarg)
107 {
108     unsigned long lv;
109     const char *ep;
110     uid_t got_uid;
111     gid_t got_gid;
112     int rc;
113 
114     rc = qemu_strtoul(optarg, &ep, 0, &lv);
115     got_uid = lv; /* overflow here is ID in C99 */
116     if (rc || *ep != ':' || got_uid != lv || got_uid == (uid_t)-1) {
117         return false;
118     }
119 
120     rc = qemu_strtoul(ep + 1, 0, 0, &lv);
121     got_gid = lv; /* overflow here is ID in C99 */
122     if (rc || got_gid != lv || got_gid == (gid_t)-1) {
123         return false;
124     }
125 
126     user_pwd = NULL;
127     user_uid = got_uid;
128     user_gid = got_gid;
129     return true;
130 }
131 
132 /*
133  * Parse OS specific command line options.
134  * return 0 if option handled, -1 otherwise
135  */
136 int os_parse_cmd_args(int index, const char *optarg)
137 {
138     switch (index) {
139     case QEMU_OPTION_runas:
140         user_pwd = getpwnam(optarg);
141         if (user_pwd) {
142             user_uid = -1;
143             user_gid = -1;
144         } else if (!os_parse_runas_uid_gid(optarg)) {
145             error_report("User \"%s\" doesn't exist"
146                          " (and is not <uid>:<gid>)",
147                          optarg);
148             exit(1);
149         }
150         break;
151     case QEMU_OPTION_chroot:
152         warn_report("option is deprecated, use '-run-with chroot=...' instead");
153         chroot_dir = optarg;
154         break;
155     case QEMU_OPTION_daemonize:
156         daemonize = 1;
157         break;
158 #if defined(CONFIG_LINUX)
159     /* deprecated */
160     case QEMU_OPTION_asyncteardown:
161         init_async_teardown();
162         break;
163 #endif
164     case QEMU_OPTION_run_with: {
165         const char *str;
166         QemuOpts *opts = qemu_opts_parse_noisily(qemu_find_opts("run-with"),
167                                                  optarg, false);
168         if (!opts) {
169             exit(1);
170         }
171 #if defined(CONFIG_LINUX)
172         if (qemu_opt_get_bool(opts, "async-teardown", false)) {
173             init_async_teardown();
174         }
175 #endif
176         str = qemu_opt_get(opts, "chroot");
177         if (str) {
178             chroot_dir = str;
179         }
180         break;
181     }
182     default:
183         return -1;
184     }
185 
186     return 0;
187 }
188 
189 static void change_process_uid(void)
190 {
191     assert((user_uid == (uid_t)-1) || user_pwd == NULL);
192     assert((user_uid == (uid_t)-1) ==
193            (user_gid == (gid_t)-1));
194 
195     if (user_pwd || user_uid != (uid_t)-1) {
196         gid_t intended_gid = user_pwd ? user_pwd->pw_gid : user_gid;
197         uid_t intended_uid = user_pwd ? user_pwd->pw_uid : user_uid;
198         if (setgid(intended_gid) < 0) {
199             error_report("Failed to setgid(%d)", intended_gid);
200             exit(1);
201         }
202         if (user_pwd) {
203             if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) {
204                 error_report("Failed to initgroups(\"%s\", %d)",
205                         user_pwd->pw_name, user_pwd->pw_gid);
206                 exit(1);
207             }
208         } else {
209             if (setgroups(1, &user_gid) < 0) {
210                 error_report("Failed to setgroups(1, [%d])",
211                         user_gid);
212                 exit(1);
213             }
214         }
215         if (setuid(intended_uid) < 0) {
216             error_report("Failed to setuid(%d)", intended_uid);
217             exit(1);
218         }
219         if (setuid(0) != -1) {
220             error_report("Dropping privileges failed");
221             exit(1);
222         }
223     }
224 }
225 
226 static void change_root(void)
227 {
228     if (chroot_dir) {
229         if (chroot(chroot_dir) < 0) {
230             error_report("chroot failed");
231             exit(1);
232         }
233         if (chdir("/")) {
234             error_report("not able to chdir to /: %s", strerror(errno));
235             exit(1);
236         }
237     }
238 
239 }
240 
241 void os_daemonize(void)
242 {
243     if (daemonize) {
244         pid_t pid;
245         int fds[2];
246 
247         if (!g_unix_open_pipe(fds, FD_CLOEXEC, NULL)) {
248             exit(1);
249         }
250 
251         pid = fork();
252         if (pid > 0) {
253             uint8_t status;
254             ssize_t len;
255 
256             close(fds[1]);
257 
258             do {
259                 len = read(fds[0], &status, 1);
260             } while (len < 0 && errno == EINTR);
261 
262             /* only exit successfully if our child actually wrote
263              * a one-byte zero to our pipe, upon successful init */
264             exit(len == 1 && status == 0 ? 0 : 1);
265 
266         } else if (pid < 0) {
267             exit(1);
268         }
269 
270         close(fds[0]);
271         daemon_pipe = fds[1];
272 
273         setsid();
274 
275         pid = fork();
276         if (pid > 0) {
277             exit(0);
278         } else if (pid < 0) {
279             exit(1);
280         }
281         umask(027);
282 
283         signal(SIGTSTP, SIG_IGN);
284         signal(SIGTTOU, SIG_IGN);
285         signal(SIGTTIN, SIG_IGN);
286     }
287 }
288 
289 void os_setup_post(void)
290 {
291     int fd = 0;
292 
293     if (daemonize) {
294         if (chdir("/")) {
295             error_report("not able to chdir to /: %s", strerror(errno));
296             exit(1);
297         }
298         fd = RETRY_ON_EINTR(qemu_open_old("/dev/null", O_RDWR));
299         if (fd == -1) {
300             exit(1);
301         }
302     }
303 
304     change_root();
305     change_process_uid();
306 
307     if (daemonize) {
308         uint8_t status = 0;
309         ssize_t len;
310 
311         dup2(fd, 0);
312         dup2(fd, 1);
313         /* In case -D is given do not redirect stderr to /dev/null */
314         if (!qemu_log_enabled()) {
315             dup2(fd, 2);
316         }
317 
318         close(fd);
319 
320         do {
321             len = write(daemon_pipe, &status, 1);
322         } while (len < 0 && errno == EINTR);
323         if (len != 1) {
324             exit(1);
325         }
326     }
327 }
328 
329 void os_set_line_buffering(void)
330 {
331     setvbuf(stdout, NULL, _IOLBF, 0);
332 }
333 
334 bool is_daemonized(void)
335 {
336     return daemonize;
337 }
338 
339 int os_set_daemonize(bool d)
340 {
341     daemonize = d;
342     return 0;
343 }
344 
345 int os_mlock(void)
346 {
347 #ifdef HAVE_MLOCKALL
348     int ret = 0;
349 
350     ret = mlockall(MCL_CURRENT | MCL_FUTURE);
351     if (ret < 0) {
352         error_report("mlockall: %s", strerror(errno));
353     }
354 
355     return ret;
356 #else
357     return -ENOSYS;
358 #endif
359 }
360 
361 static QemuOptsList qemu_run_with_opts = {
362     .name = "run-with",
363     .head = QTAILQ_HEAD_INITIALIZER(qemu_run_with_opts.head),
364     .desc = {
365 #if defined(CONFIG_LINUX)
366         {
367             .name = "async-teardown",
368             .type = QEMU_OPT_BOOL,
369         },
370 #endif
371         {
372             .name = "chroot",
373             .type = QEMU_OPT_STRING,
374         },
375         { /* end of list */ }
376     },
377 };
378 
379 static void register_runwith(void)
380 {
381     qemu_add_opts(&qemu_run_with_opts);
382 }
383 opts_init(register_runwith);
384