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Diffstat (limited to 'networking')
-rw-r--r--networking/telnetd.c34
1 files changed, 23 insertions, 11 deletions
diff --git a/networking/telnetd.c b/networking/telnetd.c
index cccf03dfd..108bbf44f 100644
--- a/networking/telnetd.c
+++ b/networking/telnetd.c
@@ -279,6 +279,10 @@ make_new_session(
279 /* make new session and process group */ 279 /* make new session and process group */
280 setsid(); 280 setsid();
281 281
282 /* Restore default signal handling */
283 signal(SIGCHLD, SIG_DFL);
284 signal(SIGPIPE, SIG_DFL);
285
282 /* open the child's side of the tty. */ 286 /* open the child's side of the tty. */
283 /* NB: setsid() disconnects from any previous ctty's. Therefore 287 /* NB: setsid() disconnects from any previous ctty's. Therefore
284 * we must open child's side of the tty AFTER setsid! */ 288 * we must open child's side of the tty AFTER setsid! */
@@ -302,14 +306,18 @@ make_new_session(
302 /* Uses FILE-based I/O to stdout, but does fflush(stdout), 306 /* Uses FILE-based I/O to stdout, but does fflush(stdout),
303 * so should be safe with vfork. 307 * so should be safe with vfork.
304 * I fear, though, that some users will have ridiculously big 308 * I fear, though, that some users will have ridiculously big
305 * issue files, and they may block writing to fd 1. */ 309 * issue files, and they may block writing to fd 1,
310 * (parent is supposed to read it, but parent waits
311 * for vforked child to exec!) */
306 print_login_issue(issuefile, NULL); 312 print_login_issue(issuefile, NULL);
307 313
308 /* Exec shell / login / whatever */ 314 /* Exec shell / login / whatever */
309 login_argv[0] = loginpath; 315 login_argv[0] = loginpath;
310 login_argv[1] = NULL; 316 login_argv[1] = NULL;
311 execvp(loginpath, (char **)login_argv); 317 /* exec busybox applet (if PREFER_APPLETS=y), if that fails,
312 /* Safer with vfork, and we shouldn't send message 318 * exec external program */
319 BB_EXECVP(loginpath, (char **)login_argv);
320 /* _exit is safer with vfork, and we shouldn't send message
313 * to remote clients anyway */ 321 * to remote clients anyway */
314 _exit(1); /*bb_perror_msg_and_die("execv %s", loginpath);*/ 322 _exit(1); /*bb_perror_msg_and_die("execv %s", loginpath);*/
315} 323}
@@ -374,7 +382,7 @@ free_session(struct tsession *ts)
374 382
375#else /* !FEATURE_TELNETD_STANDALONE */ 383#else /* !FEATURE_TELNETD_STANDALONE */
376 384
377/* Used in main() only, thus exits. */ 385/* Used in main() only, thus "return 0" actually is exit(0). */
378#define free_session(ts) return 0 386#define free_session(ts) return 0
379 387
380#endif 388#endif
@@ -384,20 +392,22 @@ static void handle_sigchld(int sig)
384 pid_t pid; 392 pid_t pid;
385 struct tsession *ts; 393 struct tsession *ts;
386 394
387 pid = waitpid(-1, &sig, WNOHANG); 395 /* Looping: more than one child may have exited */
388 if (pid > 0) { 396 while (1) {
397 pid = waitpid(-1, NULL, WNOHANG);
398 if (pid <= 0)
399 break;
389 ts = sessions; 400 ts = sessions;
390 while (ts) { 401 while (ts) {
391 if (ts->shell_pid == pid) { 402 if (ts->shell_pid == pid) {
392 ts->shell_pid = -1; 403 ts->shell_pid = -1;
393 return; 404 break;
394 } 405 }
395 ts = ts->next; 406 ts = ts->next;
396 } 407 }
397 } 408 }
398} 409}
399 410
400
401int telnetd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; 411int telnetd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
402int telnetd_main(int argc, char **argv) 412int telnetd_main(int argc, char **argv)
403{ 413{
@@ -430,7 +440,7 @@ int telnetd_main(int argc, char **argv)
430 if (!(opt & OPT_FOREGROUND)) { 440 if (!(opt & OPT_FOREGROUND)) {
431 /* DAEMON_CHDIR_ROOT was giving inconsistent 441 /* DAEMON_CHDIR_ROOT was giving inconsistent
432 * behavior with/without -F, -i */ 442 * behavior with/without -F, -i */
433 bb_daemonize_or_rexec(0 /*DAEMON_CHDIR_ROOT*/, argv); 443 bb_daemonize_or_rexec(0 /*was DAEMON_CHDIR_ROOT*/, argv);
434 } 444 }
435 } 445 }
436 /* Redirect log to syslog early, if needed */ 446 /* Redirect log to syslog early, if needed */
@@ -466,6 +476,8 @@ int telnetd_main(int argc, char **argv)
466 476
467 if (opt & OPT_WATCHCHILD) 477 if (opt & OPT_WATCHCHILD)
468 signal(SIGCHLD, handle_sigchld); 478 signal(SIGCHLD, handle_sigchld);
479 else /* prevent dead children from becoming zombies */
480 signal(SIGCHLD, SIG_IGN);
469 481
470/* 482/*
471 This is how the buffers are used. The arrows indicate the movement 483 This is how the buffers are used. The arrows indicate the movement
@@ -497,7 +509,7 @@ int telnetd_main(int argc, char **argv)
497 while (ts) { 509 while (ts) {
498 struct tsession *next = ts->next; /* in case we free ts. */ 510 struct tsession *next = ts->next; /* in case we free ts. */
499 if (ts->shell_pid == -1) { 511 if (ts->shell_pid == -1) {
500 /* Child died ad we detected that */ 512 /* Child died and we detected that */
501 free_session(ts); 513 free_session(ts);
502 } else { 514 } else {
503 if (ts->size1 > 0) /* can write to pty */ 515 if (ts->size1 > 0) /* can write to pty */
@@ -514,7 +526,7 @@ int telnetd_main(int argc, char **argv)
514 if (!IS_INETD) { 526 if (!IS_INETD) {
515 FD_SET(master_fd, &rdfdset); 527 FD_SET(master_fd, &rdfdset);
516 /* This is needed because free_session() does not 528 /* This is needed because free_session() does not
517 * take into account master_fd when it finds new 529 * take master_fd into account when it finds new
518 * maxfd among remaining fd's */ 530 * maxfd among remaining fd's */
519 if (master_fd > maxfd) 531 if (master_fd > maxfd)
520 maxfd = master_fd; 532 maxfd = master_fd;