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/error-report.h" 35 #include "qemu/log.h" 36 #include "sysemu/runstate.h" 37 #include "qemu/cutils.h" 38 39 #ifdef CONFIG_LINUX 40 #include <sys/prctl.h> 41 #endif 42 43 44 void os_setup_early_signal_handling(void) 45 { 46 struct sigaction act; 47 sigfillset(&act.sa_mask); 48 act.sa_flags = 0; 49 act.sa_handler = SIG_IGN; 50 sigaction(SIGPIPE, &act, NULL); 51 } 52 53 static void termsig_handler(int signal, siginfo_t *info, void *c) 54 { 55 qemu_system_killed(info->si_signo, info->si_pid); 56 } 57 58 void os_setup_signal_handling(void) 59 { 60 struct sigaction act; 61 62 memset(&act, 0, sizeof(act)); 63 act.sa_sigaction = termsig_handler; 64 act.sa_flags = SA_SIGINFO; 65 sigaction(SIGINT, &act, NULL); 66 sigaction(SIGHUP, &act, NULL); 67 sigaction(SIGTERM, &act, NULL); 68 } 69 70 void os_set_proc_name(const char *s) 71 { 72 #if defined(PR_SET_NAME) 73 char name[16]; 74 if (!s) 75 return; 76 pstrcpy(name, sizeof(name), s); 77 /* Could rewrite argv[0] too, but that's a bit more complicated. 78 This simple way is enough for `top'. */ 79 if (prctl(PR_SET_NAME, name)) { 80 error_report("unable to change process name: %s", strerror(errno)); 81 exit(1); 82 } 83 #else 84 error_report("Change of process name not supported by your OS"); 85 exit(1); 86 #endif 87 } 88 89 90 /* 91 * Must set all three of these at once. 92 * Legal combinations are unset by name by uid 93 */ 94 static struct passwd *user_pwd; /* NULL non-NULL NULL */ 95 static uid_t user_uid = (uid_t)-1; /* -1 -1 >=0 */ 96 static gid_t user_gid = (gid_t)-1; /* -1 -1 >=0 */ 97 98 /* 99 * Prepare to change user ID. optarg can be one of 3 forms: 100 * - a username, in which case user ID will be changed to its uid, 101 * with primary and supplementary groups set up too; 102 * - a numeric uid, in which case only the uid will be set; 103 * - a pair of numeric uid:gid. 104 */ 105 bool os_set_runas(const char *optarg) 106 { 107 unsigned long lv; 108 const char *ep; 109 uid_t got_uid; 110 gid_t got_gid; 111 int rc; 112 113 user_pwd = getpwnam(optarg); 114 if (user_pwd) { 115 user_uid = -1; 116 user_gid = -1; 117 return true; 118 } 119 120 rc = qemu_strtoul(optarg, &ep, 0, &lv); 121 got_uid = lv; /* overflow here is ID in C99 */ 122 if (rc || *ep != ':' || got_uid != lv || got_uid == (uid_t)-1) { 123 return false; 124 } 125 126 rc = qemu_strtoul(ep + 1, 0, 0, &lv); 127 got_gid = lv; /* overflow here is ID in C99 */ 128 if (rc || got_gid != lv || got_gid == (gid_t)-1) { 129 return false; 130 } 131 132 user_pwd = NULL; 133 user_uid = got_uid; 134 user_gid = got_gid; 135 return true; 136 } 137 138 static void change_process_uid(void) 139 { 140 assert((user_uid == (uid_t)-1) || user_pwd == NULL); 141 assert((user_uid == (uid_t)-1) == 142 (user_gid == (gid_t)-1)); 143 144 if (user_pwd || user_uid != (uid_t)-1) { 145 gid_t intended_gid = user_pwd ? user_pwd->pw_gid : user_gid; 146 uid_t intended_uid = user_pwd ? user_pwd->pw_uid : user_uid; 147 if (setgid(intended_gid) < 0) { 148 error_report("Failed to setgid(%d)", intended_gid); 149 exit(1); 150 } 151 if (user_pwd) { 152 if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) { 153 error_report("Failed to initgroups(\"%s\", %d)", 154 user_pwd->pw_name, user_pwd->pw_gid); 155 exit(1); 156 } 157 } else { 158 if (setgroups(1, &user_gid) < 0) { 159 error_report("Failed to setgroups(1, [%d])", 160 user_gid); 161 exit(1); 162 } 163 } 164 if (setuid(intended_uid) < 0) { 165 error_report("Failed to setuid(%d)", intended_uid); 166 exit(1); 167 } 168 if (setuid(0) != -1) { 169 error_report("Dropping privileges failed"); 170 exit(1); 171 } 172 } 173 } 174 175 176 static const char *chroot_dir; 177 178 void os_set_chroot(const char *optarg) 179 { 180 chroot_dir = optarg; 181 } 182 183 static void change_root(void) 184 { 185 if (chroot_dir) { 186 if (chroot(chroot_dir) < 0) { 187 error_report("chroot failed"); 188 exit(1); 189 } 190 if (chdir("/")) { 191 error_report("not able to chdir to /: %s", strerror(errno)); 192 exit(1); 193 } 194 } 195 196 } 197 198 199 static int daemonize; 200 static int daemon_pipe; 201 202 bool is_daemonized(void) 203 { 204 return daemonize; 205 } 206 207 int os_set_daemonize(bool d) 208 { 209 daemonize = d; 210 return 0; 211 } 212 213 void os_daemonize(void) 214 { 215 if (daemonize) { 216 pid_t pid; 217 int fds[2]; 218 219 if (!g_unix_open_pipe(fds, FD_CLOEXEC, NULL)) { 220 exit(1); 221 } 222 223 pid = fork(); 224 if (pid > 0) { 225 uint8_t status; 226 ssize_t len; 227 228 close(fds[1]); 229 230 do { 231 len = read(fds[0], &status, 1); 232 } while (len < 0 && errno == EINTR); 233 234 /* only exit successfully if our child actually wrote 235 * a one-byte zero to our pipe, upon successful init */ 236 exit(len == 1 && status == 0 ? 0 : 1); 237 238 } else if (pid < 0) { 239 exit(1); 240 } 241 242 close(fds[0]); 243 daemon_pipe = fds[1]; 244 245 setsid(); 246 247 pid = fork(); 248 if (pid > 0) { 249 exit(0); 250 } else if (pid < 0) { 251 exit(1); 252 } 253 umask(027); 254 255 signal(SIGTSTP, SIG_IGN); 256 signal(SIGTTOU, SIG_IGN); 257 signal(SIGTTIN, SIG_IGN); 258 } 259 } 260 261 void os_setup_post(void) 262 { 263 int fd = 0; 264 265 if (daemonize) { 266 if (chdir("/")) { 267 error_report("not able to chdir to /: %s", strerror(errno)); 268 exit(1); 269 } 270 fd = RETRY_ON_EINTR(qemu_open_old("/dev/null", O_RDWR)); 271 if (fd == -1) { 272 exit(1); 273 } 274 } 275 276 change_root(); 277 change_process_uid(); 278 279 if (daemonize) { 280 uint8_t status = 0; 281 ssize_t len; 282 283 dup2(fd, 0); 284 dup2(fd, 1); 285 /* In case -D is given do not redirect stderr to /dev/null */ 286 if (!qemu_log_enabled()) { 287 dup2(fd, 2); 288 } 289 290 close(fd); 291 292 do { 293 len = write(daemon_pipe, &status, 1); 294 } while (len < 0 && errno == EINTR); 295 if (len != 1) { 296 exit(1); 297 } 298 } 299 } 300 301 void os_set_line_buffering(void) 302 { 303 setvbuf(stdout, NULL, _IOLBF, 0); 304 } 305 306 int os_mlock(void) 307 { 308 #ifdef HAVE_MLOCKALL 309 int ret = 0; 310 311 ret = mlockall(MCL_CURRENT | MCL_FUTURE); 312 if (ret < 0) { 313 error_report("mlockall: %s", strerror(errno)); 314 } 315 316 return ret; 317 #else 318 return -ENOSYS; 319 #endif 320 } 321