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run_command: back out changes to run editor in its own process group.

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It unnecessarily complicates things to work around bugs in an OS
almost no one runs.
This commit is contained in:
Todd C. Miller
2023-06-04 19:11:48 -06:00
parent 95cd409079
commit 2392ee9d7d
1 changed files with 8 additions and 125 deletions
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133
plugins/sudoers/visudo.c
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@@ -901,36 +901,15 @@ setup_signals(void)
static int
run_command(const char *path, char *const *argv)
{
pid_t pid, visudo_pgrp = getpgrp();
int status, ttyfd;
int ret = -1;
int status;
pid_t pid, rv;
debug_decl(run_command, SUDOERS_DEBUG_UTIL);
/* We may need access to /dev/tty to set the foreground process. */
ttyfd = open(_PATH_TTY, O_RDWR);
if (ttyfd != -1)
(void)fcntl(ttyfd, F_SETFD, FD_CLOEXEC);
switch (pid = sudo_debug_fork()) {
case -1:
sudo_fatal(U_("unable to execute %s"), path);
break; /* NOTREACHED */
case 0:
/*
* Run command in its own process group. If visudo is run
* in the foreground, it will make the editor the foreground
* process. There is a race between the parent's call to
* tcsetpgrp() and the child's execve(). If the parent loses
* the race, the child will be stopped with SIGTTOU or SIGTTIN
* and be restarted immediately.
*/
if (setpgid(0, 0) == -1) {
sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_ERRNO,
"%s: unable to set pgrp to %d (editor)",
__func__, (int)getpid());
}
sudo_debug_printf(SUDO_DEBUG_DEBUG, "%s: executing %s",
__func__, path);
closefrom(STDERR_FILENO + 1);
execv(path, argv);
sudo_warn(U_("unable to run %s"), path);
@@ -938,113 +917,17 @@ run_command(const char *path, char *const *argv)
break; /* NOTREACHED */
}
/* Set child process group in both parent and child to avoid a race. */
if (setpgid(pid, pid) == -1) {
sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_ERRNO,
"%s: unable to set pgrp to %d (editor)",
__func__, (int)pid);
} else if (ttyfd != -1 && tcgetpgrp(ttyfd) == visudo_pgrp) {
/*
* This races with execve() in the child. If we lose the race,
* the child may be stopped by SIGTTOU or SIGTTIN when it tries
* to use the terminal. That is handled by the waitpid() loop.
*/
if (tcsetpgrp(ttyfd, pid) == -1) {
sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_ERRNO,
"%s: unable to set foreground pgrp to %d (editor)",
__func__, (int)pid);
}
}
for (;;) {
if (waitpid(pid, &status, WUNTRACED) == -1) {
if (errno == EINTR)
continue;
rv = waitpid(pid, &status, 0);
if (rv == -1 && errno != EINTR)
break;
}
if (WIFEXITED(status)) {
ret = WEXITSTATUS(status);
sudo_debug_printf(SUDO_DEBUG_DIAG, "%s: %d: exited %d",
__func__, (int)pid, ret);
if (rv != -1 && !WIFSTOPPED(status))
break;
} else if (WIFSIGNALED(status)) {
sudo_debug_printf(SUDO_DEBUG_DIAG, "%s: %d: killed by signal %d",
__func__, (int)pid, WTERMSIG(status));
break;
} else if (WIFSTOPPED(status)) {
const int signo = WSTOPSIG(status);
sudo_debug_printf(SUDO_DEBUG_DIAG, "%s: %d: suspended by signal %d",
__func__, (int)pid, signo);
switch (signo) {
case SIGTTIN:
case SIGTTOU:
/*
* The editor stopped because it needs to be the foreground
* process. Try to make it the foreground process and continue
* (suspending visudo itself if running in the background).
*/
if (ttyfd != -1) {
retry:
if (tcsetpgrp(ttyfd, pid) == 0) {
sudo_debug_printf(SUDO_DEBUG_DIAG, "%s: %d: continuing",
__func__, (int)pid);
killpg(pid, SIGCONT);
break;
} else {
/*
* macOS suffers from a kernel bug where tcsetpgrp()
* is not restarted so we have to do it manually.
*/
if (errno == EINTR && tcgetpgrp(ttyfd) == visudo_pgrp)
goto retry;
sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_ERRNO,
"%s: unable to set foreground pgrp to %d (visudo)",
__func__, (int)visudo_pgrp);
}
}
FALLTHROUGH;
default:
killpg(visudo_pgrp, signo);
sudo_debug_printf(SUDO_DEBUG_DIAG, "%s: %d: continuing",
__func__, (int)pid);
killpg(pid, SIGCONT);
break;
}
} else {
sudo_debug_printf(SUDO_DEBUG_ERROR,
"%d: unknown status 0x%x", (int)pid, status);
}
}
if (ttyfd != -1) {
pid = tcgetpgrp(ttyfd);
if (pid != -1 && pid != visudo_pgrp) {
/*
* If the foreground process does not exist it is usually because
* we made the editor the foreground process and it terminated.
* Change it back to visudo so we can prompt the user as needed.
*/
if (kill(pid, 0) == -1 && errno == ESRCH) {
sigset_t mask, omask;
sigemptyset(&mask);
sigaddset(&mask, SIGTTOU);
sigprocmask(SIG_BLOCK, &mask, &omask);
sudo_debug_printf(SUDO_DEBUG_DEBUG,
"%s: changing foreground pgrp from %d to %d (visudo)",
__func__, (int)pid, (int)visudo_pgrp);
if (tcsetpgrp(ttyfd, visudo_pgrp) == -1) {
/* This should not fail since we block SIGTTOU. */
sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_ERRNO,
"%s: unable to restore foreground pgrp to %d (visudo)",
__func__, (int)visudo_pgrp);
}
sigprocmask(SIG_SETMASK, &omask, NULL);
}
}
close(ttyfd);
}
debug_return_int(ret);
if (rv != -1)
rv = WIFEXITED(status) ? WEXITSTATUS(status) : -1;
debug_return_int(rv);
}
static bool