os-posix.c

   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);