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