[821] | 1 | /* vi: set sw=4 ts=4: */
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| 2 | /*
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| 3 | * Rexec program for system have fork() as vfork() with foreground option
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| 4 | *
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| 5 | * Copyright (C) Vladimir N. Oleynik <dzo@simtreas.ru>
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| 6 | * Copyright (C) 2003 Russ Dill <Russ.Dill@asu.edu>
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| 7 | *
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| 8 | * daemon() portion taken from uClibc:
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| 9 | *
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| 10 | * Copyright (c) 1991, 1993
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| 11 | * The Regents of the University of California. All rights reserved.
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| 12 | *
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| 13 | * Modified for uClibc by Erik Andersen <andersee@debian.org>
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| 14 | *
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| 15 | * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
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| 16 | */
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| 17 |
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| 18 | #include <paths.h>
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[1770] | 19 | #include "busybox.h" /* for struct bb_applet */
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[821] | 20 |
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[1770] | 21 | /* This does a fork/exec in one call, using vfork(). Returns PID of new child,
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| 22 | * -1 for failure. Runs argv[0], searching path if that has no / in it. */
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| 23 | pid_t spawn(char **argv)
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| 24 | {
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| 25 | /* Compiler should not optimize stores here */
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| 26 | volatile int failed;
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| 27 | pid_t pid;
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[821] | 28 |
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[1770] | 29 | // Ain't it a good place to fflush(NULL)?
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| 30 |
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| 31 | /* Be nice to nommu machines. */
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| 32 | failed = 0;
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| 33 | pid = vfork();
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| 34 | if (pid < 0) /* error */
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| 35 | return pid;
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| 36 | if (!pid) { /* child */
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| 37 | /* This macro is ok - it doesn't do NOEXEC/NOFORK tricks */
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| 38 | BB_EXECVP(argv[0], argv);
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| 39 |
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| 40 | /* We are (maybe) sharing a stack with blocked parent,
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| 41 | * let parent know we failed and then exit to unblock parent
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| 42 | * (but don't run atexit() stuff, which would screw up parent.)
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| 43 | */
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| 44 | failed = errno;
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| 45 | _exit(111);
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| 46 | }
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| 47 | /* parent */
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| 48 | /* Unfortunately, this is not reliable: according to standards
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| 49 | * vfork() can be equivalent to fork() and we won't see value
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| 50 | * of 'failed'.
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| 51 | * Interested party can wait on pid and learn exit code.
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| 52 | * If 111 - then it (most probably) failed to exec */
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| 53 | if (failed) {
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| 54 | errno = failed;
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| 55 | return -1;
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| 56 | }
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| 57 | return pid;
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| 58 | }
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| 59 |
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| 60 | /* Die with an error message if we can't spawn a child process. */
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| 61 | pid_t xspawn(char **argv)
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[821] | 62 | {
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[1770] | 63 | pid_t pid = spawn(argv);
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| 64 | if (pid < 0)
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| 65 | bb_perror_msg_and_die("%s", *argv);
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| 66 | return pid;
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| 67 | }
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[821] | 68 |
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[1770] | 69 | // Wait for the specified child PID to exit, returning child's error return.
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| 70 | int wait4pid(int pid)
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| 71 | {
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| 72 | int status;
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[821] | 73 |
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[1770] | 74 | if (pid <= 0) {
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| 75 | /*errno = ECHILD; -- wrong. */
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| 76 | /* we expect errno to be already set from failed [v]fork/exec */
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| 77 | return -1;
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| 78 | }
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| 79 | if (waitpid(pid, &status, 0) == -1)
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| 80 | return -1;
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| 81 | if (WIFEXITED(status))
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| 82 | return WEXITSTATUS(status);
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| 83 | if (WIFSIGNALED(status))
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| 84 | return WTERMSIG(status) + 1000;
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| 85 | return 0;
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| 86 | }
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[821] | 87 |
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[1770] | 88 | int wait_nohang(int *wstat)
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| 89 | {
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| 90 | return waitpid(-1, wstat, WNOHANG);
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| 91 | }
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| 92 |
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| 93 | int wait_pid(int *wstat, int pid)
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| 94 | {
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| 95 | int r;
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| 96 |
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| 97 | do
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| 98 | r = waitpid(pid, wstat, 0);
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| 99 | while ((r == -1) && (errno == EINTR));
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| 100 | return r;
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| 101 | }
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| 102 |
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| 103 | #if ENABLE_FEATURE_PREFER_APPLETS
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| 104 | void save_nofork_data(struct nofork_save_area *save)
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| 105 | {
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| 106 | memcpy(&save->die_jmp, &die_jmp, sizeof(die_jmp));
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| 107 | save->current_applet = current_applet;
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| 108 | save->xfunc_error_retval = xfunc_error_retval;
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| 109 | save->option_mask32 = option_mask32;
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| 110 | save->die_sleep = die_sleep;
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| 111 | save->saved = 1;
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| 112 | }
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| 113 |
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| 114 | void restore_nofork_data(struct nofork_save_area *save)
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| 115 | {
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| 116 | memcpy(&die_jmp, &save->die_jmp, sizeof(die_jmp));
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| 117 | current_applet = save->current_applet;
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| 118 | xfunc_error_retval = save->xfunc_error_retval;
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| 119 | option_mask32 = save->option_mask32;
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| 120 | die_sleep = save->die_sleep;
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| 121 |
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| 122 | applet_name = current_applet->name;
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| 123 | }
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| 124 |
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| 125 | int run_nofork_applet_prime(struct nofork_save_area *old, const struct bb_applet *a, char **argv)
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| 126 | {
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| 127 | int rc, argc;
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| 128 |
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| 129 | current_applet = a;
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| 130 | applet_name = a->name;
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| 131 | xfunc_error_retval = EXIT_FAILURE;
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| 132 | /*option_mask32 = 0; - not needed */
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| 133 | /* special flag for xfunc_die(). If xfunc will "die"
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| 134 | * in NOFORK applet, xfunc_die() sees negative
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| 135 | * die_sleep and longjmp here instead. */
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| 136 | die_sleep = -1;
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| 137 |
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| 138 | argc = 1;
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| 139 | while (argv[argc])
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| 140 | argc++;
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| 141 |
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| 142 | rc = setjmp(die_jmp);
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| 143 | if (!rc) {
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| 144 | /* Some callers (xargs)
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| 145 | * need argv untouched because they free argv[i]! */
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| 146 | char *tmp_argv[argc+1];
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| 147 | memcpy(tmp_argv, argv, (argc+1) * sizeof(tmp_argv[0]));
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| 148 | /* Finally we can call NOFORK applet's main() */
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| 149 | rc = a->main(argc, tmp_argv);
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| 150 | } else { /* xfunc died in NOFORK applet */
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| 151 | /* in case they meant to return 0... */
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| 152 | if (rc == -2222)
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| 153 | rc = 0;
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[821] | 154 | }
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| 155 |
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[1770] | 156 | /* Restoring globals */
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| 157 | restore_nofork_data(old);
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| 158 | return rc;
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| 159 | }
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| 160 |
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| 161 | int run_nofork_applet(const struct bb_applet *a, char **argv)
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| 162 | {
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| 163 | struct nofork_save_area old;
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| 164 |
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| 165 | /* Saving globals */
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| 166 | save_nofork_data(&old);
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| 167 | return run_nofork_applet_prime(&old, a, argv);
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| 168 | }
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| 169 | #endif /* FEATURE_PREFER_APPLETS */
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| 170 |
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| 171 | int spawn_and_wait(char **argv)
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| 172 | {
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| 173 | int rc;
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| 174 | #if ENABLE_FEATURE_PREFER_APPLETS
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| 175 | const struct bb_applet *a = find_applet_by_name(argv[0]);
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| 176 |
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| 177 | if (a && (a->nofork
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| 178 | #if BB_MMU
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| 179 | || a->noexec /* NOEXEC trick needs fork() */
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| 180 | #endif
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| 181 | )) {
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| 182 | #if BB_MMU
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| 183 | if (a->nofork)
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| 184 | #endif
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| 185 | {
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| 186 | return run_nofork_applet(a, argv);
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| 187 | }
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| 188 | #if BB_MMU
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| 189 | /* MMU only */
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| 190 | /* a->noexec is true */
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| 191 | rc = fork();
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| 192 | if (rc) /* parent or error */
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| 193 | return wait4pid(rc);
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| 194 | /* child */
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| 195 | xfunc_error_retval = EXIT_FAILURE;
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| 196 | current_applet = a;
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| 197 | run_current_applet_and_exit(argv);
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| 198 | #endif
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[821] | 199 | }
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[1770] | 200 | #endif /* FEATURE_PREFER_APPLETS */
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| 201 | rc = spawn(argv);
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| 202 | return wait4pid(rc);
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| 203 | }
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| 204 |
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| 205 | #if !BB_MMU
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| 206 | void re_exec(char **argv)
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| 207 | {
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| 208 | /* high-order bit of first char in argv[0] is a hidden
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| 209 | * "we have (already) re-execed, don't do it again" flag */
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| 210 | argv[0][0] |= 0x80;
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| 211 | execv(bb_busybox_exec_path, argv);
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| 212 | bb_perror_msg_and_die("exec %s", bb_busybox_exec_path);
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| 213 | }
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| 214 |
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| 215 | void forkexit_or_rexec(char **argv)
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| 216 | {
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| 217 | pid_t pid;
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| 218 | /* Maybe we are already re-execed and come here again? */
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| 219 | if (re_execed)
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| 220 | return;
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| 221 |
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| 222 | pid = vfork();
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| 223 | if (pid < 0) /* wtf? */
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[821] | 224 | bb_perror_msg_and_die("vfork");
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[1770] | 225 | if (pid) /* parent */
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[821] | 226 | exit(0);
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[1770] | 227 | /* child - re-exec ourself */
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| 228 | re_exec(argv);
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| 229 | }
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| 230 | #else
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| 231 | /* Dance around (void)...*/
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| 232 | #undef forkexit_or_rexec
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| 233 | void forkexit_or_rexec(void)
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| 234 | {
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| 235 | pid_t pid;
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| 236 | pid = fork();
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| 237 | if (pid < 0) /* wtf? */
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| 238 | bb_perror_msg_and_die("fork");
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| 239 | if (pid) /* parent */
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| 240 | exit(0);
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| 241 | /* child */
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| 242 | }
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| 243 | #define forkexit_or_rexec(argv) forkexit_or_rexec()
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| 244 | #endif
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| 245 |
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| 246 | /* Due to a #define in libbb.h on MMU systems we actually have 1 argument -
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| 247 | * char **argv "vanishes" */
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| 248 | void bb_daemonize_or_rexec(int flags, char **argv)
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| 249 | {
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| 250 | int fd;
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| 251 |
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| 252 | if (flags & DAEMON_CHDIR_ROOT)
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| 253 | xchdir("/");
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| 254 |
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| 255 | if (flags & DAEMON_DEVNULL_STDIO) {
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| 256 | close(0);
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| 257 | close(1);
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| 258 | close(2);
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[821] | 259 | }
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[1770] | 260 |
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| 261 | fd = xopen(bb_dev_null, O_RDWR);
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| 262 |
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| 263 | while ((unsigned)fd < 2)
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| 264 | fd = dup(fd); /* have 0,1,2 open at least to /dev/null */
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| 265 |
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| 266 | if (!(flags & DAEMON_ONLY_SANITIZE)) {
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| 267 | forkexit_or_rexec(argv);
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| 268 | /* if daemonizing, make sure we detach from stdio & ctty */
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| 269 | setsid();
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| 270 | dup2(fd, 0);
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| 271 | dup2(fd, 1);
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| 272 | dup2(fd, 2);
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| 273 | }
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| 274 | while (fd > 2) {
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| 275 | close(fd--);
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| 276 | if (!(flags & DAEMON_CLOSE_EXTRA_FDS))
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| 277 | return;
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| 278 | /* else close everything after fd#2 */
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| 279 | }
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[821] | 280 | }
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[1770] | 281 |
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| 282 | void bb_sanitize_stdio(void)
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| 283 | {
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| 284 | bb_daemonize_or_rexec(DAEMON_ONLY_SANITIZE, NULL);
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| 285 | }
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