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Move SIGCHLD handling into handle_sigchld() functions and move the

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remaining bits of dispatch_signal() into signal_pipe_cb()
This commit is contained in:
Todd C. Miller
2017-03-09 08:36:40 -07:00
parent 78f3f8bb9d
commit 867fd16343
3 changed files with 177 additions and 164 deletions
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236
src/exec_nopty.c
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@@ -301,127 +301,127 @@ exec_nopty(struct command_details *details, struct command_status *cstat)
}
/*
* Forward a signal to the command (non-pty version) or handle
* changes to the command's status (SIGCHLD).
* XXX - separate SIGCHLD code?
* Wait for command status after receiving SIGCHLD.
* If the command exits, fill in cstat and stop the event loop.
* If the command stops, save the tty pgrp, suspend sudo, then restore
* the tty pgrp when sudo resumes.
*/
static void
dispatch_signal(struct exec_closure_nopty *ec, int signo, char *signame)
handle_sigchld_nopty(struct exec_closure_nopty *ec)
{
debug_decl(dispatch_signal, SUDO_DEBUG_EXEC)
pid_t pid;
int status;
char signame[SIG2STR_MAX];
debug_decl(handle_sigchld_nopty, SUDO_DEBUG_EXEC)
sudo_debug_printf(SUDO_DEBUG_INFO,
"%s: evbase %p, child: %d, signo %s(%d), cstat %p",
__func__, ec->evbase, (int)ec->child, signame, signo, ec->cstat);
/* Read command status. */
do {
pid = waitpid(ec->child, &status, WUNTRACED|WNOHANG);
} while (pid == -1 && errno == EINTR);
switch (pid) {
case 0:
/* waitpid() will return 0 for SIGCONT, which we don't care about */
debug_return;
case -1:
sudo_warn(U_("%s: %s"), __func__, "waitpid");
debug_return;
}
if (ec->child == -1)
goto done;
if (signo == SIGCHLD) {
pid_t pid;
int status;
if (WIFSTOPPED(status)) {
/*
* The command stopped or exited.
* Save the controlling terminal's process group so we can restore it
* after we resume, if needed. Most well-behaved shells change the
* pgrp back to its original value before suspending so we must
* not try to restore in that case, lest we race with the child upon
* resume, potentially stopping sudo with SIGTTOU while the command
* continues to run.
*/
do {
pid = waitpid(ec->child, &status, WUNTRACED|WNOHANG);
} while (pid == -1 && errno == EINTR);
if (pid == ec->child) {
if (WIFSTOPPED(status)) {
/*
* Save the controlling terminal's process group
* so we can restore it after we resume, if needed.
* Most well-behaved shells change the pgrp back to
* its original value before suspending so we must
* not try to restore in that case, lest we race with
* the child upon resume, potentially stopping sudo
* with SIGTTOU while the command continues to run.
*/
sigaction_t sa, osa;
pid_t saved_pgrp = -1;
int signo = WSTOPSIG(status);
int fd = open(_PATH_TTY, O_RDWR);
if (fd != -1) {
saved_pgrp = tcgetpgrp(fd);
if (saved_pgrp == -1) {
close(fd);
fd = -1;
}
}
if (saved_pgrp != -1) {
/*
* Child was stopped trying to access controlling
* terminal. If the child has a different pgrp
* and we own the controlling terminal, give it
* to the child's pgrp and let it continue.
*/
if (signo == SIGTTOU || signo == SIGTTIN) {
if (saved_pgrp == ppgrp) {
pid_t child_pgrp = getpgid(ec->child);
if (child_pgrp != ppgrp) {
if (tcsetpgrp(fd, child_pgrp) == 0) {
if (killpg(child_pgrp, SIGCONT) != 0) {
sudo_warn("kill(%d, SIGCONT)",
(int)child_pgrp);
}
close(fd);
goto done;
}
sigaction_t sa, osa;
pid_t saved_pgrp = -1;
int fd, signo = WSTOPSIG(status);
if (sig2str(signo, signame) == -1)
snprintf(signame, sizeof(signame), "%d", signo);
sudo_debug_printf(SUDO_DEBUG_INFO, "%s: command (%d) stopped, SIG%s",
__func__, (int)ec->child, signame);
fd = open(_PATH_TTY, O_RDWR);
if (fd != -1) {
saved_pgrp = tcgetpgrp(fd);
if (saved_pgrp == -1) {
close(fd);
fd = -1;
}
}
if (saved_pgrp != -1) {
/*
* Child was stopped trying to access the controlling terminal.
* If the child has a different pgrp and we own the controlling
* terminal, give it to the child's pgrp and let it continue.
*/
if (signo == SIGTTOU || signo == SIGTTIN) {
if (saved_pgrp == ppgrp) {
pid_t child_pgrp = getpgid(ec->child);
if (child_pgrp != ppgrp) {
if (tcsetpgrp_nobg(fd, child_pgrp) == 0) {
if (killpg(child_pgrp, SIGCONT) != 0) {
sudo_warn("kill(%d, SIGCONT)",
(int)child_pgrp);
}
close(fd);
goto done;
}
}
}
if (signo == SIGTSTP) {
memset(&sa, 0, sizeof(sa));
sigemptyset(&sa.sa_mask);
sa.sa_flags = SA_RESTART;
sa.sa_handler = SIG_DFL;
if (sudo_sigaction(SIGTSTP, &sa, &osa) != 0) {
sudo_warn(U_("unable to set handler for signal %d"),
SIGTSTP);
}
}
if (kill(getpid(), signo) != 0)
sudo_warn("kill(%d, SIG%s)", (int)getpid(), signame);
if (signo == SIGTSTP) {
if (sudo_sigaction(SIGTSTP, &osa, NULL) != 0) {
sudo_warn(U_("unable to restore handler for signal %d"),
SIGTSTP);
}
}
if (saved_pgrp != -1) {
/*
* Restore foreground process group, if different.
* Otherwise, we cannot resume some shells (pdksh).
*
* It is possible that we are no longer the foreground
* process so use tcsetpgrp_nobg() to avoid sudo
* receiving SIGTTOU.
*/
if (saved_pgrp != ppgrp)
tcsetpgrp_nobg(fd, saved_pgrp);
close(fd);
}
} else {
/* Child has exited or been killed, we are done. */
ec->child = -1;
/* Don't overwrite execve() failure with child exit status. */
if (ec->cstat->type != CMD_ERRNO) {
ec->cstat->type = CMD_WSTATUS;
ec->cstat->val = status;
}
sudo_ev_del(ec->evbase, ec->signal_event);
sudo_ev_loopexit(ec->evbase);
goto done;
}
}
} else {
/* Send signal to child. */
if (signo == SIGALRM) {
terminate_command(ec->child, false);
} else if (kill(ec->child, signo) != 0) {
sudo_warn("kill(%d, SIG%s)", (int)ec->child, signame);
if (signo == SIGTSTP) {
memset(&sa, 0, sizeof(sa));
sigemptyset(&sa.sa_mask);
sa.sa_flags = SA_RESTART;
sa.sa_handler = SIG_DFL;
if (sudo_sigaction(SIGTSTP, &sa, &osa) != 0) {
sudo_warn(U_("unable to set handler for signal %d"),
SIGTSTP);
}
}
if (kill(getpid(), signo) != 0)
sudo_warn("kill(%d, SIG%s)", (int)getpid(), signame);
if (signo == SIGTSTP) {
if (sudo_sigaction(SIGTSTP, &osa, NULL) != 0) {
sudo_warn(U_("unable to restore handler for signal %d"),
SIGTSTP);
}
}
if (saved_pgrp != -1) {
/*
* On resume, restore foreground process group, if different.
* Otherwise, we cannot resume some shells (pdksh).
*
* It is possible that we are no longer the foreground process so
* use tcsetpgrp_nobg() to prevent sudo from receiving SIGTTOU.
*/
if (saved_pgrp != ppgrp)
tcsetpgrp_nobg(fd, saved_pgrp);
close(fd);
}
} else {
/* Child has exited or been killed, we are done. */
if (WIFSIGNALED(status)) {
if (sig2str(WTERMSIG(status), signame) == -1)
snprintf(signame, sizeof(signame), "%d", WTERMSIG(status));
sudo_debug_printf(SUDO_DEBUG_INFO, "%s: command (%d) killed, SIG%s",
__func__, (int)ec->child, signame);
} else {
sudo_debug_printf(SUDO_DEBUG_INFO, "%s: command (%d) exited: %d",
__func__, (int)ec->child, WEXITSTATUS(status));
}
/* Don't overwrite execve() failure with child exit status. */
if (ec->cstat->type != CMD_ERRNO) {
ec->cstat->type = CMD_WSTATUS;
ec->cstat->val = status;
}
ec->child = -1;
}
done:
debug_return;
@@ -459,9 +459,25 @@ signal_pipe_cb(int fd, int what, void *v)
}
if (sig2str(signo, signame) == -1)
snprintf(signame, sizeof(signame), "%d", signo);
sudo_debug_printf(SUDO_DEBUG_DIAG, "received SIG%s", signame);
/* XXX - deliver vs. SIGCHLD? */
dispatch_signal(ec, signo, signame);
sudo_debug_printf(SUDO_DEBUG_DIAG,
"%s: evbase %p, child: %d, signo %s(%d), cstat %p",
__func__, ec->evbase, (int)ec->child, signame, signo, ec->cstat);
if (signo == SIGCHLD) {
handle_sigchld_nopty(ec);
if (ec->child == -1) {
/* Command exited or was killed, exit event loop. */
sudo_ev_del(ec->evbase, ec->signal_event);
sudo_ev_loopexit(ec->evbase);
}
} else if (ec->child != -1) {
/* Send signal to child. */
if (signo == SIGALRM) {
terminate_command(ec->child, false);
} else if (kill(ec->child, signo) != 0) {
sudo_warn("kill(%d, SIG%s)", (int)ec->child, signame);
}
}
} while (ec->child != -1);
debug_return;
}